The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones

A rationalization of the known difference between the 3,4J C4H1 and 3,4JC1H4 couplings transmitted mainly through the 7-bridge in norbomanone is presented in terms of the effects of hyperconjugative interactions involving the carbonyl group. Theoretical and experimental studies of 3,4JCH couplings w...

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Detalles Bibliográficos
Publicado: 2008
Materias:
3,4JCH
Carbonyl group
NMR
Norbornanones
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07491581_v46_n2_p107_DosSantos
http://hdl.handle.net/20.500.12110/paper_07491581_v46_n2_p107_DosSantos
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_07491581_v46_n2_p107_DosSantos
record_format dspace
spelling paper:paper_07491581_v46_n2_p107_DosSantos2023-06-08T15:45:37Z The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones 3,4JCH Carbonyl group NMR Norbornanones A rationalization of the known difference between the 3,4J C4H1 and 3,4JC1H4 couplings transmitted mainly through the 7-bridge in norbomanone is presented in terms of the effects of hyperconjugative interactions involving the carbonyl group. Theoretical and experimental studies of 3,4JCH couplings were carried out in 3-endo- and 3-exo-X-2-norbornanone derivatives (X = Cl, Br) and in exo- and endo-2-noborneol compounds. Hyperconjugative interactions were studied with the natural bond orbital (NBO) method. Hyperconjugative interactions involving the carbonyl π*C2 = O and σ*C2=O antibonding orbitais produce a decrease of three-bond contribution to both 3,4JC4H1 and 3,4JC1H4 couplings. However, the latter antibonding orbital also undergoes a strong σC3-C4 → σC2=O interaction, which defines an additional coupling pathway for 3,4JC4H1 but not for 3,4JC1H4. This pathway is similar to that known for homoallylic couplings, the only difference being the nature of the intermediate antibonding orbital; i.e. for 3,4JC4H1 it is of σ*-type, while in homoallylic couplings it is of π*-type. Copyright © 2007 John Wiley & Sons, Ltd. 2008 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07491581_v46_n2_p107_DosSantos http://hdl.handle.net/20.500.12110/paper_07491581_v46_n2_p107_DosSantos
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic 3,4JCH
Carbonyl group
NMR
Norbornanones
spellingShingle 3,4JCH
Carbonyl group
NMR
Norbornanones
The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones
topic_facet 3,4JCH
Carbonyl group
NMR
Norbornanones
description A rationalization of the known difference between the 3,4J C4H1 and 3,4JC1H4 couplings transmitted mainly through the 7-bridge in norbomanone is presented in terms of the effects of hyperconjugative interactions involving the carbonyl group. Theoretical and experimental studies of 3,4JCH couplings were carried out in 3-endo- and 3-exo-X-2-norbornanone derivatives (X = Cl, Br) and in exo- and endo-2-noborneol compounds. Hyperconjugative interactions were studied with the natural bond orbital (NBO) method. Hyperconjugative interactions involving the carbonyl π*C2 = O and σ*C2=O antibonding orbitais produce a decrease of three-bond contribution to both 3,4JC4H1 and 3,4JC1H4 couplings. However, the latter antibonding orbital also undergoes a strong σC3-C4 → σC2=O interaction, which defines an additional coupling pathway for 3,4JC4H1 but not for 3,4JC1H4. This pathway is similar to that known for homoallylic couplings, the only difference being the nature of the intermediate antibonding orbital; i.e. for 3,4JC4H1 it is of σ*-type, while in homoallylic couplings it is of π*-type. Copyright © 2007 John Wiley & Sons, Ltd.
title The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones
title_short The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones
title_full The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones
title_fullStr The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones
title_full_unstemmed The effect of carbonyl group in the asymmetry of3,4J CH coupling constants in norbornanones
title_sort effect of carbonyl group in the asymmetry of3,4j ch coupling constants in norbornanones
publishDate 2008
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07491581_v46_n2_p107_DosSantos
http://hdl.handle.net/20.500.12110/paper_07491581_v46_n2_p107_DosSantos
_version_ 1768543853139197952

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