Resonance (chemistry) - Knowledge (XXG)

846: 1022: 502: 2322:(Now I assume that in the case of substances to which a double bond is attributed, actually two affinities of each of the participating atoms are used for their bond; however, on account of the capacity for addition of double bonds, the power of affinity is not completely consumed, and in each of the atoms a remnant of affinity or a "partial valence" exists – an assumption that can also be substantiated thermally .) On p. 90, Thiele coined the term "conjugated": 818: 1043: 894: 31: 1316: 1354: 138:. However, in some cases, more than one Lewis structure could be drawn, and experimental properties are inconsistent with any one structure. In order to address this type of situation, several contributing structures are considered together as an average, and the molecule is said to be represented by a resonance hybrid in which several Lewis structures are used collectively to describe its true structure. 1254:; that of a C=C double bond is 133 pm. In localized cyclohexatriene, the carbon–carbon bonds should be alternating 154 and 133 pm. Instead, all carbon–carbon bonds in benzene are found to be about 139 pm, a bond length intermediate between single and double bond. This mixed single and double bond (or triple bond) character is typical for all molecules in which bonds have a different 1416: 518: 1066: 367:, a large, whale-like creature. The narwhal is not a creature that goes back and forth between being a unicorn and being a leviathan, nor do the unicorn and leviathan have any physical existence outside the collective human imagination. Nevertheless, describing the narwhal in terms of these imaginary creatures provides a reasonably good description of its physical characteristics. 1138:. When 1 mole of HCl adds to 1 mole of 1,3-butadiene, in addition to the ordinarily expected product 3-chloro-1-butene, we also find 1-chloro-2-butene. Isotope labelling experiments have shown that what happens here is that the additional double bond shifts from 1,2 position to 2,3 position in some of the product. This and other evidence (such as 1232: 142: 675:

One contributing structure may resemble the actual molecule more than another (in the sense of energy and stability). Structures with a low value of potential energy are more stable than those with high values and resemble the actual structure more. The most stable contributing structures are called

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Equivalent contributors contribute equally to the actual structure, while the importance of nonequivalent contributors is determined by the extent to which they conform to the properties listed above. A larger number of significant contributing structures and a more voluminous space available for

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group, wherein the negative charge is centered equally on the two oxygen atoms. Charge delocalization in anions is an important factor determining their reactivity (generally: the higher the extent of delocalization the lower the reactivity) and, specifically, the acid strength of their conjugate

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an MO will be delocalized over the whole molecule. This MO interpretation has inspired the picture of the benzene ring as a hexagon with a circle inside. When describing benzene, the VB concept of localized σ bonds and the MO concept of delocalized π orbitals are frequently combined in elementary

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as a linear superposition of the wave functions representing the two structures. As both Kekulé structures have equal energy, they are equal contributors to the overall structure – the superposition is an equally weighted average, or a 1:1 linear combination of the two in the case of benzene. The

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Practicing chemists familiar with the concepts of resonance and delocalization will often draw just one major contributing structure to implicitly represent a molecule whose structure should be described by invoking a resonance hybrid. For example, a chemist might arbitrarily choose to draw the

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or delocalization energy. The magnitude of the resonance energy depends on assumptions made about the hypothetical "non-stabilized" species and the computational methods used and does not represent a measurable physical quantity, although comparisons of resonance energies computed under similar

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as well, leading to a higher coordination number for lithium.) Thus, in principle, up to an octet can be accommodated. Nevertheless, the formal number of valence electrons around Li never exceeds two, unless weak donor-acceptor interactions with neutral ligands (e.g., solvent molecules, often

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Because electron delocalization lowers the potential energy of a system, any species represented by a resonance hybrid is more stable than any of the (hypothetical) contributing structures. Electron delocalization stabilizes a molecule because the electrons are more evenly spread out over the

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Hydrogenation of one mole of double bonds delivers 119.7 kJ (28.6 kcal), as can be deduced from the last step, the hydrogenation of cyclohexene. In benzene, however, 23.4 kJ (5.6 kcal) are needed to hydrogenate one mole of double bonds. The difference, being 143.1 kJ

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Be, B, C, N, O, and F, as is a maximum of two for H and He and effectively for Li as well. The issue of expansion of the valence shell of third period and heavier main group elements is controversial. A Lewis structure in which a central atom has a valence electron count greater than eight

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isomers with the brominated carbon atoms joined by either a single or a double bond. In reality there are only three dibromobenzene isomers and only one is ortho, in agreement with the idea that there is only one type of carbon-carbon bond, intermediate between a single and a double bond.

1322:(34.2 kcal), is the empirical resonance energy of benzene. Because 1,3-cyclohexadiene also has a small delocalization energy (7.6 kJ or 1.8 kcal/mol) the net resonance energy, relative to the localized cyclohexatriene, is a bit higher: 151 kJ or 36 kcal/mol. 237:

are molecules with the same chemical formula but are distinct chemical species with different arrangements of atomic nuclei in space. Resonance contributors of a molecule, on the other hand, can only differ in the way electrons are formally assigned to atoms in the Lewis structure

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to find the lowest possible energy for the given set of basis wave functions. When more contributing structures are included, the molecular wave function becomes more accurate and more excited states can be derived from different combinations of the contributing structures.

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solutions) shows that the intermediate carbocation must have a highly delocalized structure, different from its mostly classical (delocalization exists but is small) parent molecule. This cation (an allylic cation) can be represented using resonance, as shown above.

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Delocalized electrons are important for several reasons; a major one is that an expected chemical reaction may not occur because the electrons delocalize to a more stable configuration, resulting in a reaction that happens at a different location. An example is the

251:(a weighted average of the contributors), with a single, well-defined geometry and distribution of electrons. It is incorrect to regard resonance hybrids as rapidly interconverting isomers, even though the term "resonance" might evoke such an image. (As described 2080:

shown on the left, with the understanding that the reader is aware of the other contributor, shown on the right, as well as the implication that the N–O bonds are actually equivalent. This practice is especially prevalent in organic chemistry, where one of the

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that are involved in resonance are usually pictured as curves or dashed lines, indicating that these are partial rather than normal complete pi bonds. In benzene and other aromatic rings, the delocalized pi-electrons are sometimes pictured as a solid circle.

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value of −10. The extent of charge delocalization in an anion can be quantitatively expressed via the WAPS (weighted average positive sigma) parameter parameter and an analogous WANS (weighted average negative sigma) parameter is used for cations.

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Raamat, E.; Kaupmees, K.; Ovsjannikov, G.; Trummal, A.; Kütt, A.; Saame, J.; Koppel, I.; Kaljurand, I.; Lipping, L.; Rodima, T.; Pihl, V.; Koppel, I. A.; Leito, I. (2013). "Acidities of strong neutral Brønsted acids in different media".

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molecule is described by contributing structures, each with electron-deficiency on different atoms. This reduces the electron-deficiency on each atom and stabilizes the molecule. Below are the contributing structures of an individual

2745: 1658:) is evenly distributed among the symmetrically oriented oxygen atoms (and a part of it is also kept by the central chlorine atom). This excellent charge delocalization combined with the high number of oxygen atoms (four) and high 741:

traditionally implies the participation of d orbitals in bonding. However, the consensus opinion is that while they may make a marginal contribution, the participation of d orbitals is unimportant, and the bonding of so-called

181:, ). According to the contributing structures, each N–O bond is an average of a formal single and formal double bond, leading to a true bond order of 1.5. By virtue of this averaging, the Lewis description of the bonding in NO 246:

mean that electrons of the molecule are "resonating" or shifting back and forth between several sets of positions, each one represented by a Lewis structure. Rather, it means that the set of contributing structures

800:, are taken together as contributing structures to represent the total structure. In the hybrid structure on the right, the dashed hexagon replaces three double bonds, and represents six electrons in a set of three 209:

molecule, decreasing electron-electron repulsion. The difference in potential energy between the actual species and the (computed) energy of the contributing structure with the lowest potential energy is called the

761:, for example. Regarded as a formalism that does not necessarily reflect the true electronic structure, such depictions are preferred by the IUPAC over structures featuring partial bonds, charge separation, or 192:

taking on intermediate values compared to those expected for the individual Lewis structures of the contributors, were they to exist as "real" chemical entities. The contributing structures differ only in the

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apportionment of electrons to the atoms, and not in the actual physically and chemically significant electron or spin density. While contributing structures may differ in formal bond orders and in

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Li with some degree of covalency, bonding is achieved primarily with the 2s orbital, with some contribution from a 2p orbital. (This bonding scheme is used in condensed phase aggregates like (CH

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For example, in benzene, valence bond theory begins with the two Kekulé structures which do not individually possess the sixfold symmetry of the real molecule. The theory constructs the actual

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in different contributing structures. Bond lengths can be compared using bond orders. For example, in cyclohexane the bond order is 1 while that in benzene is 1 + (3 ÷ 6) =

255:, the term "resonance" originated as a classical physics analogy for a quantum mechanical phenomenon, so it should not be construed too literally.) Symbolically, the double headed arrow 1345:

are, respectively, 88, 121, and 67 kJ/mol (21, 29, and 16 kcal/mol). Thus, these heterocycles are far less aromatic than benzene, as is manifested in the lability of these rings.

904:, the rationalization described above can be applied to generate contributing structures to explain the bonding in such molecules. Shown below are the contributing structures of a 346: 2330:(Such a system of adjacent double bonds with equalized inner partial valences shall be termed "conjugated".) Thiele discussed the conjugated structure of benzene on pp. 125–129: 281: 1384:(VB). Quantum mechanics requires that the wavefunction of a molecule obey its observed symmetry. If a single contributing structure does not achieve this, resonance is invoked. 861:

molecule is represented by two contributing structures. In reality the two terminal oxygen atoms are equivalent and the hybrid structure is drawn on the right with a charge of −

2402: 126:, and connected by bonds of positive integer order, is sufficient for describing the chemical bonding and rationalizing experimentally determined molecular properties like 1185:

and are represented either by contributing structures involving rearrangement of σ electrons or by a special notation, a Y that has the three nuclei at its three points.

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Resonance (or delocalization) energy is the amount of energy needed to convert the true delocalized structure into that of the most stable contributing structure. The

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Molecules with an extended π system such as linear polyenes and polyaromatic compounds are well described by resonance hybrids as well as by delocalised orbitals in

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This measured resonance energy is also the difference between the hydrogenation energy of three 'non-resonance' double bonds and the measured hydrogenation energy:

390:. The double headed arrows would be replaced by commas to illustrate a set of structures, as arrows of any type may suggest that a chemical change is taking place. 2802: 636:

for two decades thanks to being relatively easier to understand for chemists without fundamental physics background, even if they couldn't grasp the concept of

566:'s structure proposed in 1865 with alternating single and double bonds. Benzene undergoes substitution reactions, rather than addition reactions as typical for 593:

in 1926 in a discussion of the quantum states of the helium atom. He compared the structure of the helium atom with the classical system of resonating coupled

149:, shown on the right, is best rationalized by describing its structure as a resonance hybrid consisting of two major and equally important contributing forms. 1780: 655:

In the Soviet Union, resonance theory – especially as developed by Pauling – was attacked in the early 1950s as being contrary to the Marxist principles of

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In diagrams, contributing structures are typically separated by double-headed arrows (↔). The arrow should not be confused with the right and left pointing

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Kaupmees, K.; Kaljurand, I.; Leito, I. (2010). "Influence of Water Content on the Acidities in Acetonitrile. Quantifying Charge Delocalization in Anions".

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used this mechanism to explain the partial valence of molecules in 1928, and developed it further in a series of papers in 1931-1933. The alternative term

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on benzene. The utility of MO theory is that a quantitative indication of the charge from the π system on an atom can be obtained from the squares of the

165:. However, its measured structure is consistent with a description as a resonance hybrid of the two major contributing structures shown above: it has two 1633:

In the case of ions it is common to speak about delocalized charge (charge delocalization). An example of delocalized charge in ions can be found in the

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do not deviate substantially from idealized bond lengths and angles (e.g., the relative unimportance of Dewar-type resonance contributors for benzene);

538:(⇌). All structures together may be enclosed in large square brackets, to indicate they picture one single molecule or ion, not different species in a 102:. The resonance hybrid is the accurate structure for a molecule or ion; it is an average of the theoretical (or hypothetical) contributing structures. 797: 3465: 3436: 1333:

Regardless of their exact values, resonance energies of various related compounds provide insights into their bonding. The resonance energies for

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that indicates the AO's contribution to a particular MO. For example, in benzene, the MO model gives us 6 π MOs which are combinations of the 2p

1621:, or finally from empirical calculations based on the Hückel method. A Hückel method-based software for teaching resonance is available on the 1087: 3617: 3368: 3123: 2916: 2891: 2859: 2136: 2108: 1432: 3472: 1602:

Weighting of the contributing structures in terms of their contribution to the overall structure can be calculated in multiple ways, using

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convened a conference on the chemical structure of organic compounds, attended by 400 physicists, chemists, and philosophers, where "the

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The resonance proposal also helped explain the number of isomers of benzene derivatives. For example, Kekulé's structure would predict

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is used to indicate that A and B are contributing forms of a single chemical species (as opposed to an equilibrium arrow, e.g.,

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has two contributing structures with a positive charge on the terminal carbon atoms. In the hybrid structure their charge is +

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can be described by a Lewis structure. For many chemical species, a single Lewis structure, consisting of atoms obeying the

1516:. The reason for squaring the coefficient is that if an electron is described by an AO, then the square of the AO gives the 2388: 188:

The resonance hybrid represents the actual molecule as the "average" of the contributing structures, with bond lengths and

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have more delocalized structure than their parent reactants, giving rise to unexpected products. The classical example is

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Alternatively to the use of contributing structures in diagrams, a hybrid structure can be used. In a hybrid structure,

374:, as no entities actually physically "resonate", it has been suggested that the term resonance be abandoned in favor of 161:

anion, the two N–O bond lengths are equal, even though no single Lewis structure has two N–O bonds with the same formal

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This observation of greater delocalization in less stable molecules is quite general. The excited states of conjugated

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than either of the uncoupled vibrations; quantum mechanically, this lower frequency is interpreted as a lower energy.

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of the molecule. Specifically, when a molecular structure is said to be represented by a resonance hybrid, it does

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Pauling, Linus. (1931). "The Nature of the Chemical Bond. Ii. The One-Electron Bond and the Three-Electron Bond".

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Sellers, Kathleen; Weeks, Katherine; Alsop, William R.; Clough, Stephen R.; Hoyt, Marilyn; Pugh, Barbara (2006).

893: 649: 559: 3348: 1591: 1475: 1424: 762: 684:. With rules listed in rough order of diminishing importance, major contributors are generally structures that 218: 202: 1458:

AOs on each of the 6 C atoms. Thus, each π MO is delocalized over the whole benzene molecule and any electron

2293: 2181: 1614: 1272:. Consequently, benzene has more double bond character and hence has a shorter bond length than cyclohexane. 749:. Nevertheless, by tradition, expanded octet structures are still commonly drawn for functional groups like 562:'s "Partial Valence Hypothesis" to explain the unusual stability of benzene which would not be expected from 3534: 664: 656: 610: 3001:

Kaupmees, K.; Kaljurand, I.; Leito, I. (2014). "Influence of Water Content on Basicities in Acetonitrile".

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has taken on a related but different meaning. The double headed arrow was introduced by the German chemist

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assignments, all contributing structures must have the same number of valence electrons and the same spin

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molecules are, for the most part, better explained by charge-separated contributing forms that depict

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sent him a friendly request, he responded arrogantly that he is not interested in organic chemistry.

539: 95: 2324:"Ein solches System benachbarter Doppelbindungen mit ausgeglichenen inneren Partialvalenzen sei als 2267: 2242: 1242:

Comparing the two contributing structures of benzene, all single and double bonds are interchanged.

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A non-chemical analogy is illustrative: one can describe the characteristics of a real animal, the

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symmetric combination gives the ground state, while the antisymmetric combination gives the first

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are stabilised more by conjugation than their ground states, causing them to become organic dyes.

570:. He proposed that the carbon-carbon bond in benzene is intermediate of a single and double bond. 3561: 3018: 2822: 2587:"Graphical representation standards for chemical structure diagrams (IUPAC Recommendations 2008)" 2527: 2519: 1938: 1719: 1373: 1300: 1162: 135: 3518: 1466:

The contributing structures in the VB model are particularly useful in predicting the effect of

648:'s approach as "cumbersome" at the time, and his lack of communication skills contributed: when 1638:

acids. As a general rule, the better delocalized is the charge in an anion the stronger is its

3555: 3513: 3363: 3156: 2968: 2912: 2887: 2855: 2727: 2608: 2426: 2396: 2351: 2132: 2104: 2056: 1933: 1912: 1892: 1771: 1659: 1247: 801: 710: 590: 586: 2048: 918: 402: 3095: 3056: 3010: 2960: 2875: 2814: 2783: 2719: 2598: 2511: 2482: 2450: 2305: 2224: 2165: 2028: 1999: 1943: 1874: 1517: 1209: 1158: 909: 737: 693: 633: 614: 563: 115: 30: 3313: 1958:"HuLiS : Java Applet − Simple Hückel Theory and Mesomery − program logiciel software" 1856: 1839: 1663: 1618: 1285: 758: 488: 99: 63: 2876: 2550:

Terror and Progress USSR: Some Sources of Change and Stability in the Soviet Dictatorship

2436: 1016:. The full positive charge can also be depicted as delocalized among three carbon atoms. 645: 169:

N–O bonds of 125 pm, intermediate in length between a typical N–O single bond (145 pm in

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on π systems such as benzene. They lead to the models of contributing structures for an

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In general, the superposition is written with undetermined coefficients, which are then

706:, with the separation for unlike and like charges minimized and maximized, respectively; 3256: 3240: 3235: 3151: 2707: 2432: 1916: 1761: 1639: 809: 723: 189: 1315: 769:

delocalized electrons lead to stabilization (lowering of the energy) of the molecule.

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Lithium is always found as Li (1s), a duet, in ionic compounds. In compounds like CH

2531: 2419: 1393: 1388: 1289: 1131: 602: 597:. In the classical system, the coupling produces two modes, one of which is lower in 198: 178: 170: 123: 55: 3022: 2826: 2478: 2161: 2024: 1995: 3586: 2500:"The Technology: Science Interaction: Walter Reppe and Cyclooctatetraene Chemistry" 1791: 1467: 1127: 1003: 833: 17: 1415: 1353: 609:

popular in German and French publications with the same meaning was introduced by

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is reconciled with the experimental fact that the anion has equivalent N–O bonds.

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Morris, Peter J. T.; Hornix, Willem J.; Bud, Robert; Morris, Peter J. T. (1992).

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WAPS values of anions of common acids and WANS values of cations of common bases

3230: 3225: 3220: 2845: 2746:"4.10: Alkylation and Acylation of Aromatic Rings - The Friedel-Crafts Reaction" 2473: 2156: 2082: 2053:

The Nature of the Chemical Bond – An Introduction to Modern Structural Chemistry

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in 1938, but did not catch on in the English literature. The current concept of

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is frequently chosen to depict the regular hexagonal structure of the molecule.

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on both oxygen atoms and partial double bonds with a full and dashed line and

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Description of a molecule's true bond structure as a combination of structures

2731: 2612: 2477:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) " 2309: 2160:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) " 2023:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) " 1994:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) " 3334: 2603: 2586: 2486: 2169: 2115:

The resonance hybrid is more stable than any of the contributing structures.

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A well-studied example of delocalization that does not involve π electrons (

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maintain aromatic substructures locally while avoiding anti-aromatic ones (

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of the real substance with that estimated for the contributing structure.

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of the oxygen atom interacts with the π orbitals of the carbon atoms. The

659:, and in June 1951 the Soviet Academy of Sciences under the leadership of 3201: 1919:. Larger values indicate more localized charge in the corresponding ion. 1864: 1029: 680:. Energetically unfavourable and therefore less favorable structures are 546: 2787: 2454: 3191: 2818: 2523: 2499: 2086: 1882: 1334: 1236: 1221: 789: 754: 524: 508: 360: 356: 158: 2964: 2320:

vorhanden ist, eine Annahme, die sich auch thermisch begründen lässt."

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Goudard, N.; Carissan, Y.; Hagebaum-Reignier, D.; Humbel, S. (2008).

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Resonance has a deeper significance in the mathematical formalism of

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Kerber, Robert C. (2006). "If It's Resonance, What Is Resonating?".

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labels define the symmetries of the two states, as defined by the

1352: 1342: 1230: 1205: 1151: 858: 825: 1611: 359:, in terms of the characteristics of two mythical creatures: the 3414: 2851:

Advanced Organic Chemistry: Reactions, Mechanisms, and Structure

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On p. 89, Thiele introduced the concept of "partial valence":

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atoms and positive charge, if any, on the most electropositive;

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essence of the theory of resonance was exposed and unmasked".

114:, resonance is an extension of the idea that the bonding in a 1435:(AOs) on all the atoms; there are as many MOs as AOs. Each AO 1311:; 1 mole of benzene delivers 208.4 kJ (49.8 kcal). 3045:"Basicities of Strong Bases in Water: A Computational Study" 2770:

Wiberg; Nakaji; Morgan (1993). "Heat of hydrogenation of a

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Advanced Organic Chemistry Part A: Structure and Mechanisms

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methods derived from Valence Bond theory, or else from the

2854:(6th ed.), New York: Wiley-Interscience, p. 62, 2268:"Graphical representation for chemical structure diagrams" 2243:"Graphical representation for chemical structure diagrams" 2055:(3rd ed.). Cornell University Press. pp. 10–13. 1349:

Quantum mechanical description in valence bond (VB) theory

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In this source, Pauling first mentions related papers by

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assumptions and conditions may be chemically meaningful.

2803:"The heats of hydrogenation of unsaturated hydrocarbons" 1329:(3 × 119.7) − 208.4 = 150.7 kJ/mol (36 kcal). 736:

A maximum of eight valence electrons is strict for the

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Due to confusion with the physical meaning of the word

2296:[ to our knowledge of unsaturated compounds]. 315: 2103:(5th ed.). Prentice Hall of India. p. 372. 2099:

Morrison, Robert; Boyd, Robert (1989). "Chapter 10".

921: 405: 363:, a creature with a single horn on its head, and the 289: 261: 98:

where the bonding cannot be expressed by one single

3548: 3527: 3489: 3452: 3382: 3356: 3347: 3322: 3296: 3287: 3254: 3210: 3179: 3172: 1676: 1431:, the molecular orbitals (MOs) are approximated as 2418: 2350:(2nd ed.). Thomson Learning. pp. 470–1. 2332:VIII. Die aromatischen Verbindungen. Das Benzol. 980: 477: 340: 275: 145:The experimental geometry of the nitrite anion, NO 2909:Perchlorate: Environmental problems and solutions 2425:(3rd ed.). Oxford University Press. p. 1250:. The average length of a C–C single bond is 154 450: 323: 322: 305: 304: 2401:: CS1 maint: bot: original URL status unknown ( 2127:Carey, Francis A.; Sundberg, Richard J. (2007). 3038: 3036: 3034: 3032: 2996: 2994: 2992: 2990: 2988: 2986: 2984: 2982: 2774:imine. An experimental and theoretical study". 1666:being one of the strongest known acids with a p 644:. Pauling and Wheland themselves characterized 585:The mechanism of resonance was introduced into 349: 2874:Shaik, Sason S.; Hiberty, Phillipe C. (2008). 2504:The British Journal for the History of Science 1196:of benzene with 1-chloro-2-methylpropane; the 3430: 3124: 3043:Kaupmees, K.; Trummal, A.; Leito, I. (2014). 2294:"Zur Kenntnis der ungesättigten Verbindungen" 1411:Comparison with molecular orbital (MO) theory 8: 2575:omitted from Lewis structures) are included. 2439:in 1931, and then cites his own key papers: 2938: 2936: 2934: 2932: 2930: 2928: 2882:. New Jersey: Wiley-Interscience. pp. 2391:. Archived from the original on 2012-03-31. 2389:"The Science and Humanism of Linus Pauling" 1094:. Unsourced material may be challenged and 840:, which results in different contributors. 709:place negative charge, if any, on the most 378:and resonance energy abandoned in favor of 3437: 3423: 3415: 3353: 3293: 3176: 3131: 3117: 3109: 2334:(VIII. The aromatic compounds. Benzene.) 632:Resonance theory dominated over competing 3080: 3078: 3076: 3074: 3072: 3060: 2708:"The 2-norbornyl cation: a retrospective" 2602: 2042: 2040: 1295:The complete hydrogenation of benzene to 1114:Learn how and when to remove this message 968: 963: 960: 954: 951: 941: 938: 932: 929: 928: 927: 923: 922: 920: 462: 454: 444: 431: 422: 414: 407: 406: 404: 324: 317: 316: 314: 306: 299: 297: 296: 294: 290: 288: 262: 260: 2878:A Chemist's Guide to Valence Bond Theory 699:have a maximum number of covalent bonds; 140: 94:. It has particular value for analyzing 29: 3466:Sickle Cell Anemia, a Molecular Disease 1978: 1565: = 1 on each C atom. With an 1212:, a particular form of delocalization. 1161:) can be observed in the non-classical 298: 2682:"16.12 Conjugated Dienes and UV Light" 2394: 1662:of the central chlorine atom leads to 1642:. For example, the negative charge in 1126:Often, reactive intermediates such as 964: 955: 942: 933: 577:dibromobenzene isomers, including two 558:The concept first appeared in 1899 in 229:Resonance is to be distinguished from 2712:Journal of Physical Organic Chemistry 2658:"Bonus Topic: Allylic Rearrangements" 1181:). These can be viewed as containing 386:and the resonance hybrid becomes the 341:{\displaystyle {\ce {A <=> B}}} 177:N–OH) and N–O double bond (115 pm in 7: 1092:adding citations to reliable sources 249:represents an intermediate structure 2706:Moss, Robert A. (4 February 2014). 1357:VB mixing diagram of benzene. The A 1246:can be measured, for example using 276:{\displaystyle {\ce {A<->B}}} 3480:How to Live Longer and Feel Better 2474:Compendium of Chemical Terminology 2298:Justus Liebig's Annalen der Chemie 2157:Compendium of Chemical Terminology 2020:Compendium of Chemical Terminology 1991:Compendium of Chemical Terminology 1911:WAPS and WANS values are given in 1284:can be estimated by comparing the 747:three-center four-electron bonding 382:. A resonance structure becomes a 25: 3540:International League of Humanists 3162:Introduction to quantum mechanics 2734:– via Wiley Online Library. 2459:and subsequent papers in 1932–33. 704:minimum of formally charged atoms 2656:Ashenhurst, James (2013-12-02). 2585:Brecher, Jonathan (2008-01-01). 2407:See last paragraph of section 1. 1524:) so that AO = 1, and 1314: 1064: 1041: 1020: 892: 844: 816: 621:who preferred the German phrase 516: 500: 3514:Pauling Electronegativity Scale 3460:The Nature of the Chemical Bond 2421:The Nature of the Chemical Bond 1929:Hückel molecular orbital theory 1433:sums of all the atomic orbitals 1419:π molecular orbitals of benzene 1183:three-center two-electron bonds 487:Contributing structures of the 34:Contributing structures of the 973: 947: 924: 812:in the plane of the molecule. 796:structures, first proposed by 491:, enclosed in square brackets. 470: 437: 408: 325: 300: 266: 66:by the combination of several 1: 3473:Vitamin C and the Common Cold 2801:Sherman, J. (February 1939). 1610:(NBO) approaches of Weinhold 688:obey as much as possible the 3618:Electronic structure methods 2344:Hornback, Joseph M. (2006). 2316:"Ich nehme nun an, ... eine 1781:7-Methyl-triazabicyclodecene 1745:Phenyl tetramethylguanidine 992:Electron-deficient molecules 671:Major and minor contributors 252: 2076:resonance contributor of NO 1801:1,8-Diazabicycloundec-7-ene 1235:Contributing structures of 3634: 2591:Pure and Applied Chemistry 2275:IUPAC Recommendations 2008 2250:IUPAC Recommendations 2008 2049:"The Concept of Resonance" 1567:electron-withdrawing group 1472:electron-withdrawing group 1427:, the main alternative to 1282:empirical resonance energy 1219: 1053: 995: 836:depict the permutation of 781: 394:Representation in diagrams 74:, also variously known as 3572:Intravenous ascorbic acid 3147: 3015:10.1007/s10953-014-0201-4 2911:. CRC Press. p. 16. 2516:10.1017/S0007087400045374 2292:Thiele, Johannes (1899). 2281:, pp. 379–382 (GR–6) 1590: > 1 for an 1575: < 1 on the 54:, is a way of describing 3349:Molecular orbital theory 2662:Master Organic Chemistry 2310:10.1002/jlac.18993060107 2131:. Springer. p. 19. 1592:electron-releasing group 1520:. The AOs are adjusted ( 1476:electron-releasing group 1425:molecular orbital theory 981:{\displaystyle {\ce {}}} 792:the two cyclohexatriene 507:Hybrid structure of the 478:{\displaystyle {\ce {}}} 219:molecular orbital theory 3535:Linus Pauling Institute 2604:10.1351/pac200880020277 2487:10.1351/goldbook.M03845 2170:10.1351/goldbook.R05333 2047:Pauling, Linus (1960). 2033:10.1351/goldbook.C01309 2004:10.1351/goldbook.R05326 853:Electron-rich molecules 838:delocalized π electrons 657:dialectical materialism 352:for details on usage). 110:Under the framework of 68:contributing structures 2025:contributing structure 1420: 1377: 1239: 1050:Reactive intermediates 982: 479: 384:contributing structure 342: 277: 225:Resonance vs isomerism 150: 39: 3502:Orbital hybridisation 2546:Moore, Barrington Jr. 2188:. UCDavis. 2013-10-02 1629:Charge delocalization 1608:Natural Bond Orbitals 1418: 1356: 1234: 1136:allylic rearrangement 1056:Reactive intermediate 983: 902:hypervalent molecules 640:and confused it with 638:quantum superposition 480: 380:delocalization energy 343: 278: 144: 96:delocalized electrons 33: 3567:Vitamin C megadosage 2807:J. Am. Oil Chem. Soc 2750:Chemistry LibreTexts 2686:Chemistry LibreTexts 2417:Pauling, L. (1960). 2256:, p. 387 (GR–8) 1692:WANS × 10 1686:WAPS × 10 1208:group stabilized by 1088:improve this section 919: 661:Alexander Nesmeyanov 595:harmonic oscillators 540:chemical equilibrium 523:Hybrid structure of 403: 287: 259: 80:canonical structures 76:resonance structures 3577:Linus Pauling Award 3497:Valence bond theory 3289:Valence bond theory 2957:2010JPCA..11411788K 2951:(43): 11788–11793. 2844:Smith, Michael B.; 2788:10.1021/ja00062a017 2552:. pp. 142–143. 2455:10.1021/ja01360a004 2221:2006JChEd..83..223K 1821:Triazabicyclodecene 1679: 1463:chemistry courses. 1429:valence bond theory 1382:valence bond theory 1165:Another example is 998:Electron deficiency 311: 153:For instance, in NO 122:, possibly bearing 112:valence bond theory 92:valence bond theory 18:Resonance structure 3613:Physical chemistry 3562:Molecular medicine 3088:J. Phys. Org. Chem 2819:10.1007/BF02543208 1939:Fluxional molecule 1720:Triphenylphosphine 1677: 1617:2008-02-08 at the 1421: 1378: 1301:1,3-cyclohexadiene 1240: 1163:2-Norbornyl cation 1037:bond in diborane. 978: 802:molecular orbitals 778:Aromatic molecules 682:minor contributors 678:major contributors 627:intermediate stage 475: 338: 330: 273: 151: 40: 3595: 3594: 3556:Ava Helen Pauling 3412: 3411: 3408: 3407: 3383:Constituent units 3364:Molecular orbital 3343: 3342: 3323:Constituent units 3283: 3282: 3157:Quantum mechanics 3049:Croat. Chem. Acta 2965:10.1021/jp105670t 2918:978-0-8493-8081-5 2893:978-0-470-03735-5 2861:978-0-471-72091-1 2643:Organic Chemistry 2641:Bruice, Paula Y. 2628:Organic Chemistry 2347:Organic Chemistry 2229:10.1021/ed083p223 2186:UCDavis Chem Wiki 2182:"Resonance Forms" 2138:978-0-387-68346-1 2110:978-0-87692-560-7 2101:Organic Chemistry 2083:Kekulé structures 1934:Conjugated system 1909: 1908: 1772:2,4-Dinitrophenol 1660:electronegativity 1248:X-ray diffraction 1124: 1123: 1116: 970: 962: 953: 940: 931: 808:symmetry, with a 759:phosphorus ylides 738:Period 2 elements 694:Period 1 elements 665:pseudo-scientific 591:Werner Heisenberg 587:quantum mechanics 536:equilibrium arrow 469: 461: 453: 443: 430: 421: 413: 336: 332: 293: 271: 265: 16:(Redirected from 3625: 3608:Chemical bonding 3439: 3432: 3425: 3416: 3354: 3294: 3275:Exchange-coupled 3177: 3140:Chemical bonding 3133: 3126: 3119: 3110: 3104: 3103: 3100:10.1002/poc.2946 3082: 3067: 3066: 3064: 3040: 3027: 3026: 3009:(7): 1270–1281. 2998: 2977: 2976: 2945:J. Phys. Chem. A 2940: 2923: 2922: 2904: 2898: 2897: 2881: 2871: 2865: 2864: 2841: 2835: 2834: 2829:. Archived from 2798: 2792: 2791: 2782:(9): 3527–3532. 2776:J. Am. Chem. Soc 2767: 2761: 2760: 2758: 2757: 2742: 2736: 2735: 2724:10.1002/poc.3290 2703: 2697: 2696: 2694: 2693: 2678: 2672: 2671: 2669: 2668: 2653: 2647: 2646: 2638: 2632: 2631: 2623: 2617: 2616: 2606: 2582: 2576: 2560: 2554: 2553: 2542: 2536: 2535: 2495: 2489: 2466: 2460: 2458: 2443:J. Am. Chem. Soc 2430: 2424: 2414: 2408: 2406: 2400: 2392: 2385: 2379: 2378: 2371:Pauling, Linus, 2368: 2362: 2361: 2341: 2335: 2313: 2289: 2283: 2282: 2272: 2264: 2258: 2257: 2247: 2239: 2233: 2232: 2204: 2198: 2197: 2195: 2193: 2178: 2172: 2162:resonance energy 2149: 2143: 2142: 2124: 2118: 2117: 2096: 2090: 2073: 2067: 2066: 2044: 2035: 2012: 2006: 1983: 1969: 1967: 1965: 1944:Avoided crossing 1847:-Dimethylaniline 1680: 1657: 1656: 1655: 1557: 1556: 1518:electron density 1515: 1514: 1318: 1276:Resonance energy 1271: 1270: 1266: 1263: 1210:hyperconjugation 1200:rearranges to a 1180: 1179: 1178: 1159:hyperconjugation 1119: 1112: 1108: 1105: 1099: 1068: 1060: 1045: 1024: 1015: 1014: 1010: 987: 985: 984: 979: 977: 976: 972: 971: 967: 959: 958: 946: 945: 936: 910:xenon difluoride 896: 887: 886: 882: 879: 870: 869: 865: 848: 820: 615:mesomeric effect 520: 504: 484: 482: 481: 476: 474: 473: 467: 466: 459: 458: 451: 449: 448: 441: 436: 435: 428: 426: 419: 418: 411: 388:hybrid structure 347: 345: 344: 339: 337: 334: 333: 331: 329: 328: 321: 313: 312: 310: 303: 295: 291: 282: 280: 279: 274: 272: 269: 263: 211:resonance energy 116:chemical species 88:hybrid structure 84:resonance hybrid 21: 3633: 3632: 3628: 3627: 3626: 3624: 3623: 3622: 3598: 3597: 3596: 3591: 3544: 3523: 3519:Pauling's rules 3485: 3448: 3443: 3413: 3404: 3378: 3339: 3318: 3314:Lewis structure 3279: 3250: 3206: 3168: 3143: 3137: 3107: 3084: 3083: 3070: 3062:10.5562/cca2472 3042: 3041: 3030: 3000: 2999: 2980: 2942: 2941: 2926: 2919: 2906: 2905: 2901: 2894: 2873: 2872: 2868: 2862: 2843: 2842: 2838: 2800: 2799: 2795: 2769: 2768: 2764: 2755: 2753: 2744: 2743: 2739: 2705: 2704: 2700: 2691: 2689: 2680: 2679: 2675: 2666: 2664: 2655: 2654: 2650: 2645:(4th ed.). 2640: 2639: 2635: 2630:(6th ed.). 2625: 2624: 2620: 2584: 2583: 2579: 2573: 2569: 2565: 2561: 2557: 2544: 2543: 2539: 2497: 2496: 2492: 2467: 2463: 2440: 2416: 2415: 2411: 2393: 2387: 2386: 2382: 2370: 2369: 2365: 2358: 2343: 2342: 2338: 2291: 2290: 2286: 2270: 2266: 2265: 2261: 2245: 2241: 2240: 2236: 2206: 2205: 2201: 2191: 2189: 2180: 2179: 2175: 2150: 2146: 2139: 2126: 2125: 2121: 2111: 2098: 2097: 2093: 2079: 2074: 2070: 2063: 2046: 2045: 2038: 2013: 2009: 1984: 1980: 1976: 1963: 1961: 1955: 1952: 1925: 1737: 1733: 1712: 1708: 1704: 1700: 1672: 1664:perchloric acid 1654: 1651: 1650: 1649: 1647: 1631: 1619:Wayback Machine 1600: 1588: 1573: 1563: 1555: 1550: 1549: 1548: 1543: 1536: 1529: 1513: 1508: 1507: 1506: 1500: 1494: 1487: 1457: 1450: 1440: 1413: 1372: 1367:character table 1364: 1360: 1351: 1286:enthalpy change 1278: 1268: 1264: 1261: 1259: 1229: 1224: 1218: 1177: 1174: 1173: 1172: 1170: 1120: 1109: 1103: 1100: 1085: 1069: 1058: 1052: 1012: 1008: 1007: 1000: 994: 950: 937: 917: 916: 884: 880: 877: 875: 867: 863: 862: 855: 786: 780: 775: 711:electronegative 673: 650:Robert Robinson 560:Johannes Thiele 556: 532: 531: 530: 529: 528: 521: 513: 512: 505: 494: 493: 492: 489:thiocyanate ion 485: 440: 427: 401: 400: 396: 285: 284: 257: 256: 227: 190:partial charges 184: 176: 156: 148: 108: 100:Lewis structure 64:polyatomic ions 28: 23: 22: 15: 12: 11: 5: 3631: 3629: 3621: 3620: 3615: 3610: 3600: 3599: 3593: 3592: 3590: 3589: 3584: 3579: 3574: 3569: 3564: 3559: 3552: 3550: 3546: 3545: 3543: 3542: 3537: 3531: 3529: 3525: 3524: 3522: 3521: 3516: 3511: 3510: 3509: 3504: 3493: 3491: 3487: 3486: 3484: 3483: 3477: 3469: 3463: 3456: 3454: 3450: 3449: 3444: 3442: 3441: 3434: 3427: 3419: 3410: 3409: 3406: 3405: 3403: 3402: 3400:Antibonding MO 3397: 3395:Non-bonding MO 3392: 3386: 3384: 3380: 3379: 3377: 3376: 3371: 3366: 3360: 3358: 3351: 3345: 3344: 3341: 3340: 3338: 3337: 3332: 3326: 3324: 3320: 3319: 3317: 3316: 3311: 3306: 3304:Hybrid orbital 3300: 3298: 3291: 3285: 3284: 3281: 3280: 3278: 3277: 3272: 3267: 3261: 3259: 3252: 3251: 3249: 3248: 3243: 3238: 3233: 3228: 3223: 3217: 3215: 3208: 3207: 3205: 3204: 3199: 3194: 3189: 3183: 3181: 3174: 3173:Types of bonds 3170: 3169: 3167: 3166: 3165: 3164: 3154: 3152:Atomic orbital 3148: 3145: 3144: 3138: 3136: 3135: 3128: 3121: 3113: 3106: 3105: 3094:(2): 162–170. 3068: 3055:(4): 385–395. 3028: 3003:J. Solut. Chem 2978: 2924: 2917: 2899: 2892: 2866: 2860: 2836: 2833:on 2011-07-14. 2793: 2762: 2737: 2718:(5): 374–379. 2698: 2673: 2648: 2633: 2618: 2597:(2): 277–410. 2577: 2571: 2567: 2563: 2555: 2537: 2510:(1): 145–167. 2490: 2461: 2449:(1367): 3225. 2409: 2380: 2363: 2356: 2336: 2284: 2259: 2234: 2199: 2173: 2144: 2137: 2119: 2109: 2091: 2077: 2068: 2062:978-0801403330 2061: 2036: 2007: 1977: 1975: 1972: 1971: 1970: 1951: 1950:External links 1948: 1947: 1946: 1941: 1936: 1931: 1924: 1921: 1907: 1906: 1903: 1898: 1895: 1889: 1888: 1885: 1880: 1877: 1871: 1870: 1867: 1862: 1859: 1853: 1852: 1849: 1837: 1834: 1828: 1827: 1824: 1817: 1814: 1808: 1807: 1804: 1797: 1794: 1788: 1787: 1784: 1777: 1774: 1768: 1767: 1764: 1762:Tripropylamine 1759: 1756: 1750: 1749: 1746: 1743: 1740: 1735: 1731: 1726: 1725: 1722: 1717: 1714: 1710: 1706: 1702: 1698: 1694: 1693: 1690: 1687: 1684: 1670: 1652: 1640:conjugate acid 1630: 1627: 1599: 1596: 1586: 1571: 1561: 1558:. In benzene, 1551: 1539: 1534: 1531: ≈ ( 1527: 1509: 1498: 1490: 1485: 1453: 1448: 1436: 1412: 1409: 1370: 1362: 1358: 1350: 1347: 1331: 1330: 1277: 1274: 1228: 1225: 1220:Main article: 1217: 1214: 1191:Friedel–Crafts 1175: 1122: 1121: 1072: 1070: 1063: 1054:Main article: 1051: 1048: 1047: 1046: 1026: 1025: 996:Main article: 993: 990: 989: 988: 975: 966: 957: 949: 944: 935: 926: 898: 897: 854: 851: 850: 849: 822: 821: 782:Main article: 779: 776: 774: 771: 734: 733: 717: 714: 707: 700: 697: 672: 669: 555: 552: 522: 515: 514: 506: 499: 498: 497: 496: 495: 486: 472: 465: 457: 447: 439: 434: 425: 417: 410: 399: 398: 397: 395: 392: 376:delocalization 327: 320: 309: 302: 268: 226: 223: 182: 174: 154: 146: 124:formal charges 107: 104: 50:, also called 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 3630: 3619: 3616: 3614: 3611: 3609: 3606: 3605: 3603: 3588: 3585: 3583: 3582:Pauling Field 3580: 3578: 3575: 3573: 3570: 3568: 3565: 3563: 3560: 3557: 3554: 3553: 3551: 3547: 3541: 3538: 3536: 3533: 3532: 3530: 3526: 3520: 3517: 3515: 3512: 3508: 3505: 3503: 3500: 3499: 3498: 3495: 3494: 3492: 3488: 3481: 3478: 3475: 3474: 3470: 3467: 3464: 3461: 3458: 3457: 3455: 3451: 3447: 3446:Linus Pauling 3440: 3435: 3433: 3428: 3426: 3421: 3420: 3417: 3401: 3398: 3396: 3393: 3391: 3388: 3387: 3385: 3381: 3375: 3372: 3370: 3367: 3365: 3362: 3361: 3359: 3355: 3352: 3350: 3346: 3336: 3333: 3331: 3330:Covalent bond 3328: 3327: 3325: 3321: 3315: 3312: 3310: 3307: 3305: 3302: 3301: 3299: 3295: 3292: 3290: 3286: 3276: 3273: 3271: 3268: 3266: 3263: 3262: 3260: 3258: 3253: 3247: 3244: 3242: 3241:5 (quintuple) 3239: 3237: 3236:4 (quadruple) 3234: 3232: 3229: 3227: 3224: 3222: 3219: 3218: 3216: 3214: 3209: 3203: 3200: 3198: 3195: 3193: 3190: 3188: 3185: 3184: 3182: 3178: 3175: 3171: 3163: 3160: 3159: 3158: 3155: 3153: 3150: 3149: 3146: 3141: 3134: 3129: 3127: 3122: 3120: 3115: 3114: 3111: 3101: 3097: 3093: 3089: 3081: 3079: 3077: 3075: 3073: 3069: 3063: 3058: 3054: 3050: 3046: 3039: 3037: 3035: 3033: 3029: 3024: 3020: 3016: 3012: 3008: 3004: 2997: 2995: 2993: 2991: 2989: 2987: 2985: 2983: 2979: 2974: 2970: 2966: 2962: 2958: 2954: 2950: 2946: 2939: 2937: 2935: 2933: 2931: 2929: 2925: 2920: 2914: 2910: 2903: 2900: 2895: 2889: 2885: 2880: 2879: 2870: 2867: 2863: 2857: 2853: 2852: 2847: 2840: 2837: 2832: 2828: 2824: 2820: 2816: 2812: 2808: 2804: 2797: 2794: 2789: 2785: 2781: 2777: 2773: 2766: 2763: 2751: 2747: 2741: 2738: 2733: 2729: 2725: 2721: 2717: 2713: 2709: 2702: 2699: 2687: 2683: 2677: 2674: 2663: 2659: 2652: 2649: 2644: 2637: 2634: 2629: 2622: 2619: 2614: 2610: 2605: 2600: 2596: 2592: 2588: 2581: 2578: 2559: 2556: 2551: 2547: 2541: 2538: 2533: 2529: 2525: 2521: 2517: 2513: 2509: 2505: 2501: 2494: 2491: 2488: 2484: 2480: 2476: 2475: 2470: 2465: 2462: 2456: 2452: 2448: 2444: 2438: 2434: 2428: 2423: 2422: 2413: 2410: 2404: 2398: 2390: 2384: 2381: 2376: 2375: 2367: 2364: 2359: 2357:9780534389512 2353: 2349: 2348: 2340: 2337: 2333: 2329: 2325: 2321: 2318:Partialvalens 2317: 2311: 2307: 2303: 2300:(in German). 2299: 2295: 2288: 2285: 2280: 2276: 2269: 2263: 2260: 2255: 2251: 2244: 2238: 2235: 2230: 2226: 2222: 2218: 2214: 2210: 2209:J. Chem. Educ 2203: 2200: 2187: 2183: 2177: 2174: 2171: 2167: 2163: 2159: 2158: 2153: 2148: 2145: 2140: 2134: 2130: 2123: 2120: 2116: 2112: 2106: 2102: 2095: 2092: 2088: 2084: 2072: 2069: 2064: 2058: 2054: 2050: 2043: 2041: 2037: 2034: 2030: 2026: 2022: 2021: 2016: 2011: 2008: 2005: 2001: 1997: 1993: 1992: 1987: 1982: 1979: 1973: 1959: 1954: 1953: 1949: 1945: 1942: 1940: 1937: 1935: 1932: 1930: 1927: 1926: 1922: 1920: 1918: 1914: 1904: 1902: 1899: 1896: 1894: 1891: 1890: 1886: 1884: 1881: 1878: 1876: 1873: 1872: 1868: 1866: 1863: 1860: 1858: 1855: 1854: 1850: 1848: 1846: 1842: 1838: 1835: 1833: 1830: 1829: 1825: 1822: 1818: 1815: 1813: 1810: 1809: 1805: 1802: 1798: 1795: 1793: 1790: 1789: 1785: 1782: 1778: 1775: 1773: 1770: 1769: 1765: 1763: 1760: 1757: 1755: 1752: 1751: 1747: 1744: 1741: 1739: 1728: 1727: 1723: 1721: 1718: 1715: 1696: 1695: 1691: 1688: 1685: 1682: 1681: 1675: 1669: 1665: 1661: 1645: 1641: 1636: 1628: 1626: 1624: 1620: 1616: 1613: 1609: 1605: 1597: 1595: 1593: 1589: 1582: 1578: 1574: 1568: 1564: 1554: 1547: 1542: 1537: 1530: 1523: 1519: 1512: 1505: 1502: ≈ 1501: 1493: 1488: 1481: 1477: 1473: 1469: 1464: 1461: 1456: 1451: 1444: 1439: 1434: 1430: 1426: 1417: 1410: 1408: 1405: 1402: 1401:variationally 1397: 1395: 1394:excited state 1390: 1389:wave function 1385: 1383: 1375: 1368: 1355: 1348: 1346: 1344: 1340: 1336: 1328: 1327: 1326: 1323: 1319: 1317: 1312: 1310: 1306: 1302: 1298: 1293: 1291: 1290:hydrogenation 1287: 1283: 1275: 1273: 1257: 1253: 1249: 1245: 1238: 1233: 1226: 1223: 1215: 1213: 1211: 1207: 1203: 1199: 1195: 1192: 1186: 1184: 1168: 1164: 1160: 1155: 1153: 1148: 1145: 1141: 1137: 1133: 1132:free radicals 1129: 1118: 1115: 1107: 1097: 1093: 1089: 1083: 1082: 1078: 1073:This section 1071: 1067: 1062: 1061: 1057: 1049: 1044: 1040: 1039: 1038: 1036: 1031: 1023: 1019: 1018: 1017: 1005: 999: 991: 915: 914: 913: 911: 907: 903: 895: 891: 890: 889: 874: 860: 852: 847: 843: 842: 841: 839: 835: 834:curved arrows 831: 827: 819: 815: 814: 813: 811: 807: 803: 799: 795: 791: 785: 777: 772: 770: 766: 764: 760: 756: 752: 748: 744: 739: 731: 728: 725: 722: 718: 715: 712: 708: 705: 701: 698: 695: 691: 687: 686: 685: 683: 679: 670: 668: 666: 662: 658: 653: 651: 647: 643: 639: 635: 634:Hückel method 630: 628: 624: 623:zwischenstufe 620: 616: 612: 608: 604: 603:Linus Pauling 600: 596: 592: 588: 583: 580: 576: 571: 569: 565: 564:August Kekulé 561: 553: 551: 548: 543: 541: 537: 526: 519: 510: 503: 490: 463: 455: 445: 432: 423: 415: 393: 391: 389: 385: 381: 377: 373: 368: 366: 362: 358: 353: 351: 318: 307: 254: 250: 245: 241: 236: 232: 224: 222: 220: 215: 212: 206: 204: 200: 199:formal charge 196: 191: 186: 180: 179:nitronium ion 172: 171:hydroxylamine 168: 164: 160: 143: 139: 137: 136:dipole moment 133: 129: 125: 121: 117: 113: 105: 103: 101: 97: 93: 89: 85: 81: 77: 73: 69: 65: 61: 57: 53: 49: 45: 37: 32: 19: 3587:4674 Pauling 3506: 3479: 3471: 3468:(1949 paper) 3459: 3453:Publications 3308: 3246:6 (sextuple) 3213:multiplicity 3091: 3087: 3052: 3048: 3006: 3002: 2948: 2944: 2908: 2902: 2877: 2869: 2850: 2846:March, Jerry 2839: 2831:the original 2810: 2806: 2796: 2779: 2775: 2771: 2765: 2754:. Retrieved 2752:. 2020-06-21 2749: 2740: 2715: 2711: 2701: 2690:. Retrieved 2688:. 2015-04-01 2685: 2676: 2665:. Retrieved 2661: 2651: 2642: 2636: 2627: 2621: 2594: 2590: 2580: 2558: 2549: 2540: 2507: 2503: 2493: 2472: 2464: 2446: 2442: 2420: 2412: 2383: 2373: 2366: 2346: 2339: 2331: 2328:bezeichnet." 2327: 2323: 2319: 2315: 2301: 2297: 2287: 2274: 2262: 2249: 2237: 2212: 2208: 2202: 2190:. Retrieved 2185: 2176: 2155: 2147: 2128: 2122: 2114: 2100: 2094: 2071: 2052: 2018: 2010: 1989: 1981: 1962:. Retrieved 1910: 1844: 1840: 1792:Benzoic acid 1667: 1632: 1603: 1601: 1598:Coefficients 1584: 1583:C atoms and 1580: 1576: 1569: 1559: 1552: 1545: 1540: 1532: 1525: 1510: 1503: 1496: 1491: 1483: 1482:coefficient 1479: 1468:substituents 1465: 1459: 1454: 1446: 1445:coefficient 1442: 1437: 1422: 1398: 1396:, as shown. 1386: 1379: 1332: 1324: 1320: 1313: 1294: 1281: 1279: 1244:Bond lengths 1241: 1227:Bond lengths 1201: 1187: 1156: 1149: 1128:carbocations 1125: 1110: 1104:January 2017 1101: 1086:Please help 1074: 1027: 1004:allyl cation 1001: 899: 856: 823: 793: 787: 767: 763:dative bonds 735: 726: 720: 681: 677: 674: 654: 646:Erich Hückel 631: 626: 622: 611:C. K. Ingold 606: 584: 574: 572: 557: 544: 535: 533: 387: 383: 379: 375: 369: 354: 248: 243: 239: 228: 216: 210: 207: 203:multiplicity 194: 187: 166: 152: 128:bond lengths 109: 87: 83: 79: 75: 71: 67: 51: 47: 41: 3476:(1970 book) 3462:(1939 book) 3180:By symmetry 2377:, p. 1 1960:(in French) 1901:Propylamine 1832:Acetic acid 1754:Picric acid 1644:perchlorate 1635:carboxylate 1604:"Ab initio" 1305:cyclohexene 1297:cyclohexane 1198:carbocation 810:nodal plane 784:Aromaticity 743:hypervalent 730:biphenylene 724:Clar sextet 642:tautomerism 619:Fritz Arndt 58:in certain 3602:Categories 3390:Bonding MO 3374:MO diagram 3231:3 (triple) 3226:2 (double) 3221:1 (single) 2756:2024-02-07 2692:2024-02-07 2667:2024-02-07 2479:Mesomerism 2304:: 87–142. 2215:(2): 223. 1974:References 1964:29 October 1625:Web site. 1522:normalized 1309:exothermic 1256:bond order 1194:alkylation 873:bond order 751:sulfoxides 690:octet rule 607:mesomerism 240:depictions 163:bond order 120:octet rule 52:mesomerism 3507:Resonance 3335:Lone pair 3309:Resonance 3197:Delta (δ) 3187:Sigma (σ) 2813:(2): 28. 2732:0894-3230 2626:Wade, G. 2613:1365-3075 2532:145124799 2374:Resonance 2326:conjugirt 2192:7 October 1996:Resonance 1689:Compound 1683:Compound 1544:) ≈ 1495:. Charge 1489:on atom C 1480:weighting 1460:occupying 1443:weighting 1404:optimized 1369:for the D 1339:thiophene 1167:methanium 1144:superacid 1075:does not 965:− 956:− 948:⟷ 943:− 934:− 830:lone pair 599:frequency 464:≡ 456:− 446:⊖ 438:⟷ 433:⊖ 372:resonance 365:leviathan 326:⇀ 319:− 308:− 301:↽ 267:⟷ 231:isomerism 82:) into a 60:molecules 48:resonance 44:chemistry 36:carbonate 3490:Concepts 3357:Concepts 3297:Concepts 3023:95538780 2973:20919704 2848:(2007), 2827:96029597 2548:(1954). 2397:cite web 1923:See also 1865:Pyridine 1615:Archived 1374:symmetry 1030:diborane 908:bond in 773:Examples 755:sulfones 702:carry a 547:pi bonds 106:Overview 3549:Related 3528:Founded 3270:Singlet 3265:Triplet 3202:Phi (φ) 2953:Bibcode 2524:4027009 2217:Bibcode 2087:benzene 1883:Aniline 1646:anion ( 1335:pyrrole 1267:⁄ 1237:benzene 1222:Benzene 1216:Benzene 1096:removed 1081:sources 1011:⁄ 883:⁄ 866:⁄ 790:benzene 568:alkenes 554:History 525:benzene 509:nitrate 361:unicorn 357:narwhal 235:Isomers 159:nitrite 56:bonding 3558:(wife) 3482:(1986) 3192:Pi (π) 3142:theory 3021: 2971: 2915: 2890: 2886:–203. 2858: 2825: 2730: 2611: 2530: 2522: 2437:Hückel 2433:Slater 2354: 2135: 2107: 2059: 1812:Phenol 1779:MTBD ( 1441:has a 1376:group. 1341:, and 1152:dienes 798:Kekulé 794:Kekulé 757:, and 442: 348:; see 195:formal 134:, and 132:angles 3019:S2CID 2823:S2CID 2528:S2CID 2520:JSTOR 2469:IUPAC 2279:IUPAC 2271:(PDF) 2254:IUPAC 2246:(PDF) 2152:IUPAC 2015:IUPAC 1986:IUPAC 1897:35.9 1879:29.1 1861:21.9 1836:16.1 1819:TBD ( 1799:DBU ( 1623:HuLiS 1577:ortho 1361:and B 1343:furan 1206:butyl 1035:3c-2e 906:3c-4e 859:ozone 826:furan 579:ortho 350:below 253:below 167:equal 90:) in 72:forms 3369:LCAO 3257:spin 2969:PMID 2913:ISBN 2888:ISBN 2856:ISBN 2728:ISSN 2609:ISSN 2435:and 2403:link 2352:ISBN 2194:2015 2133:ISBN 2105:ISBN 2057:ISBN 1966:2010 1905:8.9 1887:8.2 1869:7.2 1851:4.7 1826:3.5 1816:8.8 1806:3.0 1796:7.1 1786:2.9 1776:4.9 1766:2.6 1758:4.3 1748:2.5 1742:3.6 1724:2.1 1716:2.0 1612:NBO5 1581:para 1579:and 1474:and 1303:and 1299:via 1202:tert 1130:and 1079:any 1077:cite 1028:The 1002:The 900:For 857:The 575:four 86:(or 70:(or 3255:By 3211:By 3096:doi 3057:doi 3011:doi 2961:doi 2949:114 2884:200 2815:doi 2784:doi 2780:115 2772:cis 2720:doi 2599:doi 2570:Li) 2512:doi 2483:doi 2481:". 2451:doi 2427:184 2306:doi 2302:306 2225:doi 2166:doi 2164:". 2085:of 2029:doi 2027:". 2000:doi 1998:". 1893:HCl 1875:HBr 1738:COH 1730:(CF 1713:NH 1648:ClO 1423:In 1307:is 1288:of 1142:in 1140:NMR 1090:by 939:XeF 824:In 804:of 788:In 727:and 721:see 625:or 589:by 511:ion 244:not 173:, H 78:or 62:or 42:In 38:ion 3604:: 3092:26 3090:. 3071:^ 3053:87 3051:. 3047:. 3031:^ 3017:. 3007:43 3005:. 2981:^ 2967:. 2959:. 2947:. 2927:^ 2821:. 2811:16 2809:. 2805:. 2778:. 2748:. 2726:. 2716:27 2714:. 2710:. 2684:. 2660:. 2607:. 2595:80 2593:. 2589:. 2526:. 2518:. 2508:25 2506:. 2502:. 2471:, 2447:53 2445:. 2399:}} 2395:{{ 2277:, 2273:, 2252:, 2248:, 2223:. 2213:83 2211:. 2184:. 2154:, 2113:. 2051:. 2039:^ 2017:, 1988:, 1857:HI 1823:) 1803:) 1783:) 1705:SO 1697:(C 1594:. 1538:AO 1371:6h 1363:2u 1359:1g 1337:, 1252:pm 1171:CH 961:Xe 912:. 888:. 828:a 765:. 753:, 732:). 696:); 629:. 542:. 233:. 221:. 205:. 157:, 130:, 46:, 3438:e 3431:t 3424:v 3132:e 3125:t 3118:v 3102:. 3098:: 3065:. 3059:: 3025:. 3013:: 2975:. 2963:: 2955:: 2921:. 2896:. 2817:: 2790:. 2786:: 2759:. 2722:: 2695:. 2670:. 2615:. 2601:: 2572:4 2568:3 2564:3 2534:. 2514:: 2485:: 2457:. 2453:: 2429:. 2405:) 2360:. 2312:. 2308:: 2231:. 2227:: 2219:: 2196:. 2168:: 2141:. 2078:2 2065:. 2031:: 2002:: 1968:. 1917:Å 1915:/ 1913:e 1845:N 1843:, 1841:N 1736:3 1734:) 1732:3 1711:2 1709:) 1707:2 1703:5 1701:F 1699:2 1671:a 1668:K 1653:4 1587:i 1585:q 1572:i 1570:q 1562:i 1560:q 1553:i 1546:c 1541:i 1535:i 1533:c 1528:i 1526:q 1511:i 1504:c 1499:i 1497:q 1492:i 1486:i 1484:c 1455:z 1449:i 1447:c 1438:i 1269:2 1265:1 1262:+ 1260:1 1204:- 1176:5 1169:( 1117:) 1111:( 1106:) 1102:( 1098:. 1084:. 1013:2 1009:1 974:] 969:F 952:F 930:F 925:[ 885:2 881:1 878:+ 876:1 868:2 864:1 806:π 527:. 471:] 468:N 460:C 452:S 429:N 424:= 420:C 416:= 412:S 409:[ 335:B 292:A 270:B 264:A 183:2 175:2 155:2 147:2 20:)

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