601:
Each of the two terminal carbons in the backbone chain needs one extra hydrogen – that is why "1" is added to the formula. (A branch's terminal doesn't need an H added in the calculation because the H replaced by the branch can be counted as the H added to the branch terminal. This is also true for a
597:
Except for the terminal carbons, every carbon chained to the structure with two single bonds requires a pair of hydrogen atoms attached to it. The number of carbons in the formula actually represents the number of hydrogen pairs required for that number of carbons to form a saturated structure. (This
650:
represents the number of hydrogen pairs because it gives a value of 1 for every two hydrogen atoms. It is subtracted in the formula to count how many pairs of hydrogen atoms are missing in the unsaturated structure, which tells us the degree of hydrogen deficiency. (No hydrogen pair is missing if
478:
that are required to make the structure saturated, simply because joining two elements to form a ring or adding one extra bond (e.g., a single bond changed to a double bond) in a structure reduces the need for two H's. For non-hydrocarbons, the elements in a pair can include any elements in the
626:
is in the formula, which gives a value of 1 for every two nitrogens. (This is also true if nitrogen is added into the structure, whether it is inserted into a backbone chain, attached to a terminal to replace an H, or branched out from a C to replace an
438:
825:
556:
293:
920:
702:
Adding an oxygen atom to the structure requires no hydrogen added, which is why the number of oxygen atoms does not appear in the formula. Furthermore, the formula can be generalised to include all elements of
184:
598:
is also true if a carbon is added to the structure, whether it is inserted into a backbone chain, attached to a terminal to replace a hydrogen, or branched out from a carbon to replace a hydrogen.)
333:
729:
977:
Badertscher, M.; Bischofberger, K.; Munk, M.E.; Pretsch, E. (2001). "A Novel
Formalism To Characterize the Degree of Unsaturation of Organic Molecules".
85:, as well as qualitative inspection. It is based on comparing the actual molecular formula to what would be a possible formula if the structure were
488:
231:
20:
605:
Except the terminal nitrogens, each nitrogen in the chain only requires one H attached to it, which is half a pair of hydrogens—that is why
474:
For hydrocarbons, the DBE (or IHD) tells us the number of rings and/or extra bonds in a non-saturated structure, which equals the number of
65:
to help draw chemical structures. It does not give any information about those components individually—the specific number of rings, or of
836:
86:
1031:
961:
111:
27:
1054:
1078:
1073:
225:
For certain classes of molecules, the general formula can be simplified or rewritten more clearly. For example:
197:
94:
433:{\displaystyle \mathrm {rings+\pi \ bonds} =C-{\frac {H}{2}}-{\frac {X}{2}}+{\frac {N}{2}}+1\,}
1027:
994:
957:
593:
atoms, respectively. Each of the terms on the RHS can be explained, respectively, as follows:
78:
62:
34:
820:{\displaystyle {\text{IHD}}=G_{4}+1+{\frac {G_{5}}{2}}-{\frac {G_{1}}{2}}-{\frac {G_{7}}{2}}}
986:
217: − 2 to the degree of unsaturation. The result is then halved and increased by 1.
38:
1058:
82:
466:
atoms do not contribute to the degree of unsaturation, as 2 − 2 = 0.
720:
479:
lithium family and the fluorine family in the periodic table, not necessarily all H's.
1067:
931:
704:
1046:
1051:
70:
66:
90:
551:{\displaystyle {\text{IHD}}=C+1+{\frac {N}{2}}-{\frac {H}{2}}-{\frac {X}{2}}}
998:
708:
586:
582:
463:
288:{\displaystyle {\text{Double bond equivalent}}=(a+1)-{\frac {b-c+f}{2}}}
716:
712:
590:
58:
990:
578:
915:{\displaystyle {\text{IHD}}=G_{4}+1+{\frac {G_{5}-G_{1}-G_{7}}{2}}}
26:
57:) is a calculation that determines the total number of rings and
73:(two π bonds each). The final structure is verified with use of
74:
179:{\displaystyle \mathrm {DU} ={\sum n_{i}(v_{i}-2) \over 2}+1}
25:
934:- practical measure of number of double bonds in a sample
16:
Term which determines total number of rings and π bonds
1047:
Molecular weight and degree of unsaturation calculator
839:
732:
491:
336:
234:
114:
459:= number of nitrogens, gives an equivalent result.
914:
819:
550:
432:
287:
178:
655:, which corresponds to no hydrogen deficiency.)
482:A popular form of the formula is as follows:
8:
979:Journal of Chemical Information and Modeling
719:(the fluorine family) of CAS A group in the
956:. Pittsburgh: Global View Pub. p. 54.
105:The formula for degree of unsaturation is:
317:= number of nitrogen atoms in the compound
311:= number of hydrogen atoms in the compound
900:
887:
874:
867:
852:
840:
838:
806:
800:
786:
780:
766:
760:
745:
733:
731:
538:
525:
512:
492:
490:
429:
413:
400:
387:
337:
335:
323:= number of halogen atoms in the compound
261:
235:
233:
149:
136:
126:
115:
113:
305:= number of carbon atoms in the compound
944:
209:That is, an atom that has a valence of
93:—with all atoms having their standard
89:—having no rings and containing only
7:
602:branch terminated with any element.)
707:(the hydrogen and lithium family),
374:
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365:
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350:
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344:
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119:
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47:index of hydrogen deficiency (IHD)
14:
462:In either case, oxygen and other
954:Mass Spectrometry Desk Reference
1012:Organic structural spectroscopy
255:
243:
161:
142:
1:
51:double bond equivalents (DBE)
196:is the number of atoms with
952:Sparkman, David O. (2006).
678:is for a reason similar to
43:degree of unsaturation (DU)
1095:
715:(the nitrogen family) and
18:
455:= number of halogens and
69:(one π bond each), or of
577:represent the number of
1022:Young, Paul R. (2000).
451:= number of hydrogens,
213:contributes a total of
61:. A formula is used in
33:In the analysis of the
1052:Degree of Unsaturation
1024:Practical Spectroscopy
916:
821:
552:
434:
289:
237:Double bond equivalent
180:
30:
917:
822:
711:(the carbon family),
553:
447:= number of carbons,
435:
290:
181:
29:
1079:Edible oil chemistry
837:
730:
489:
334:
232:
112:
21:Degree of saturation
19:For other uses, see
221:Simplified formulae
45:(also known as the
1057:2014-01-04 at the
912:
817:
548:
430:
285:
176:
55:unsaturation index
31:
1074:Organic chemistry
991:10.1021/ci000135o
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79:mass spectrometry
63:organic chemistry
39:organic molecules
35:molecular formula
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721:periodic table
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985:(4): 889–93.
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963:0-9660813-9-0
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28:
22:
1023:
1020:
1014:, chapter 1.
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1007:
982:
978:
972:
953:
947:
829:
723:as follows:
701:
684:
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612:
560:
481:
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473:
461:
456:
452:
448:
444:
442:
326:
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208:
200:
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188:
104:
71:triple bonds
67:double bonds
54:
50:
46:
42:
32:
830:Or simply,
470:Explanation
1068:Categories
939:References
894:−
881:−
798:−
778:−
717:Group VII
536:−
523:−
398:−
385:−
357:π
268:−
259:−
156:−
130:∑
87:saturated
1055:Archived
999:11500105
926:See also
709:Group IV
587:hydrogen
583:nitrogen
464:divalent
713:Group V
705:Group I
695:
681:
675:
661:
653:IHD = 0
647:
633:
623:
609:
591:halogen
198:valence
95:valence
91:σ bonds
59:π bonds
1030:
997:
960:
579:carbon
561:where
443:where
360:
298:where
189:where
41:, the
53:, or
1028:ISBN
995:PMID
958:ISBN
630:The
589:and
573:and
81:and
987:doi
842:IHD
735:IHD
627:H.)
494:IHD
327:or
75:NMR
37:of
1070::
1026:.
993:.
983:41
981:.
607:+
585:,
581:,
569:,
565:,
206:.
97:.
77:,
49:,
1036:.
1001:.
989::
966:.
908:2
902:7
898:G
889:1
885:G
876:5
872:G
865:+
862:1
859:+
854:4
850:G
846:=
813:2
808:7
804:G
793:2
788:1
784:G
773:2
768:5
764:G
758:+
755:1
752:+
747:4
743:G
739:=
698:.
692:2
689:/
685:H
672:2
669:/
665:X
644:2
641:/
637:H
620:2
617:/
613:N
575:X
571:H
567:N
563:C
544:2
541:X
531:2
528:H
518:2
515:N
510:+
507:1
504:+
501:C
498:=
457:N
453:X
449:H
445:C
427:1
424:+
419:2
416:N
411:+
406:2
403:X
393:2
390:H
382:C
379:=
375:s
372:d
369:n
366:o
363:b
354:+
351:s
348:g
345:n
342:i
339:r
321:f
315:c
309:b
303:a
281:2
277:f
274:+
271:c
265:b
256:)
253:1
250:+
247:a
244:(
241:=
215:x
211:x
203:i
201:v
193:i
191:n
174:1
171:+
166:2
162:)
159:2
151:i
147:v
143:(
138:i
134:n
124:=
120:U
117:D
23:.
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