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Anti addition is in direct contrast to syn addition. In anti addition, two substituents are added to opposite sides (or faces) of a double bond or triple bond, once again resulting in a decrease in bond order and increase in number of substituents. The classical example of this is
591:
reaction, disiamylborane is added to one face of the triple bond. The boron atom attaches to the less substituted carbon, and later forms a bond between the more substituted carbon and the OH group. This reaction utilizes syn addition.
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for the orientation of a reaction, which refers to the bonding preference of different substituents for different carbons on an alkene or alkyne. In order for a reaction to follow
Markovnikov's rule, the intermediate
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or the specific absolute orientation of the substituents needs to be taken into account, knowing the type of addition is significant. Unlike straight-chain alkenes,
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316:). Thus whether substituents are added to the same side (syn) or opposite sides (anti) of a double can usually be ignored due to free rotation. However, if
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The type of addition that occurs depends on multiple different factors of a reaction, and is defined by the final orientation of the substituents on the
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into a ketone. This process utilizes anti addition of an OH group to the more substituted carbon, making this reaction a
Markovnikov reaction.
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286:) of alkenes. An anti addition reaction results in a trans-isomer of the products, as the substituents are on opposite faces of the bond.
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must be on the more-substituted carbon, allowing the substituent to bond to the more-stable carbocation and the more-substituted carbon.
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The reaction is considered
Markovnikov as it results in water addition with same regiospecificity as a direct hydration reaction.
72:
171:). The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the
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syn addition allows stable addition of substituents to the same side of the ring, where they remain together. The cyclic locked
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Stereospecific: Can only be anti addition – water kicks out the mercury from underneath the intermediate three-membered ring.
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This reaction is considered
Markovnikov because the halogen substituent attaches to the more substituted carbon.
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Depending on the substrate double bond, addition can have different effects on the molecule. After addition to a
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Can occur either in syn or anti addition fashion, depending on the solution it is in; 50% of each orientation.
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Can occur either in syn or anti addition fashion, depending on the solution it is in; 50% of each orientation.
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This reaction is considered
Markovnikov because the hydroxyl group attaches to the more substituted carbon.
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Stereospecific: Can only be syn addition – hydrogen and hydroxyl (-OH) are added to the same face.
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Classification notes (type of addition, molecule location, regiochemistry, stereochemistry, etc.)
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are the reverse processes of syn and anti addition. These result in a new double bond, such as in
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Can occur either in syn or anti addition fashion depending on the specific mechanism followed.
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Stereospecific: Can only be anti-addition – both halogen molecules are on different planes.
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reacts with an alkyne in a
Markovnikov regioselective manner to form an enol that is
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The reaction is anti-Markovnikov. Hydroxyl attaches to the less substituted carbon.
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Terms for the placement of chemical substituents relative to a double or triple bond
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When alkenes undergo hydrobromination, the alkyl bromides are formed
Markovnikov.
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Neither
Markovnikov or anti-Markovnikov because the substituents are the same.
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Neither
Markovnikov or anti-Markovnikov because the substituents are the same.
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747:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
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308:), the resulting alkane will rapidly and freely rotate around its single
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If osmium tetroxide is used, hydroxide groups are added in syn fashion.
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Syn addition is the addition of two substituents to the same side (or
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Stereospecific: Can be syn or anti addition, depending on situation.
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mechanism is followed, hydroxide groups are added in an anti fashion.
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687:"Illustrated Glossary of Organic Chemistry - Syn addition"
248:. An example of syn addition would be the oxidation of an
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but an increase in number of substituents. Generally the
613:"17.2: Markovnikov Orientation vs. Syn or Anti Addition"
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to a diol by way of a suitable oxidizing agent such as
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60:. Unsourced material may be challenged and removed.
355:Common reactions and respective addition types
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193:. Syn and anti addition are related to
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58:adding citations to reliable sources
744:Compendium of Chemical Terminology
25:
350:Reactions and their addition type
34:
45:needs additional citations for
312:under normal conditions (i.e.
1:
236:, resulting in a decrease in
148:molecules can be added to an
543:oxymercuration-demercuration
417:oxymercuration-demercuration
144:are different ways in which
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1150:Octahedral propeller twist
886:Arene substitution pattern
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824:Configuration descriptors
642:www.organic-chemistry.org
1167:Category:Stereochemistry
328:prevents free rotation.
1059:Absolute configurations
964:Three identical ligands
757:10.1351/goldbook.E02094
574:hydroboration-oxidation
440:hydroboration-oxidation
204:mechanism of a reaction
69:"Syn and anti addition"
1127:Relative configuration
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715:Chemistry LibreTexts
666:Chemistry LibreTexts
638:"Markovnikov's Rule"
617:Chemistry LibreTexts
587:In this reaction, a
54:improve this article
983:In carbon skeletons
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217:undergoing syn and
1186:Addition reactions
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556:In this reaction,
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711:"Syn Addition"
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662:"Syn Addition"
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110:November 2022
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71: –
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43:This article
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18:Anti addition
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719:. Retrieved
717:. 2015-10-05
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694:. Retrieved
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670:. Retrieved
668:. 2015-10-05
665:
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645:. Retrieved
641:
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621:. Retrieved
619:. 2020-05-21
616:
607:
565:tautomerized
534:
512:
476:
462:Halogenation
454:
431:
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335:
331:
330:
288:
284:halogenation
276:
225:
223:
188:
141:
137:
131:
116:
107:
97:
90:
83:
76:
64:
52:Please help
47:verification
44:
344:elimination
322:cycloalkene
280:bromination
234:triple bond
230:double bond
215:Cycloalkene
200:carbocation
146:substituent
1180:Categories
721:2022-11-17
696:2022-11-17
672:2022-11-17
647:2022-11-17
623:2022-11-17
599:References
310:sigma bond
238:bond order
80:newspapers
1006:Secondary
928:isomerism
840:isomerism
808:Chirality
394:Hydration
318:chirality
242:substrate
1041:Catenane
1010:tertiary
866:notation
363:Example
177:products
999:, cyclo
862:–
572:Alkyne
541:Alkyne
507:epoxide
438:Alkene
415:Alkene
228:) of a
202:of the
175:of the
94:scholar
1155:Λ-, Δ-
1047:catena
800:Topics
505:If an
295:ethene
250:alkene
246:alkyne
165:alkyne
150:alkene
96:
89:
82:
75:
67:
1034:spiro
904:ortho
875:)-, (
850:trans
838:trans
739:IUPAC
360:Name
282:(any
263:, or
169:RC≡CR
163:) or
101:JSTOR
87:books
1097:), (
1077:), (
1020:tert
1008:and
956:anti
934:endo
922:Endo
912:para
908:meta
558:HgSO
334:and
269:KMnO
226:face
158:C=CR
140:and
138:syn-
73:news
1137:-,
1018:-,
1016:sec
997:neo
993:iso
974:mer
970:fac
952:syn
938:exo
936:,
926:exo
902:- (
898:-,
894:-,
848:-,
846:cis
834:cis
753:doi
751:".
258:OsO
232:or
132:In
56:by
1182::
1119:l-
1117:,
1115:d-
995:,
991:,
972:,
954:,
910:,
906:,
879:)-
741:,
713:.
689:.
664:.
640:.
615:.
346:.
274:.
267:,
256:,
136:,
1143:-
1140:L
1134:D
1101:)
1099:s
1095:r
1093:(
1081:)
1079:S
1075:R
1073:(
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989:n
924:-
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900:p
896:m
892:o
877:Z
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871:(
864:Z
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836:–
785:e
778:t
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724:.
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301:2
299:C
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156:2
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152:(
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117:(
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108:(
98:·
91:·
84:·
77:·
50:.
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