Lone-pair orientation effect of an α-oxygen atom on 1JCC NMR spin-spin coupling constants in o-substituted phenols. Experimental and DFT study
The well-known N lone-pair orientation effect on 1JCC spin-spin coupling constants (SSCCs) in oximes and their derivatives was used to study how negative hyperconjugative interactions of type LP1(O) → σ*CC depend on ortho interactions involving the OH group. This study demanded the following analyse...
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| Autores principales: | , , , , |
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| Formato: | JOUR |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_15499618_v3_n4_p1284_Taurian |
| Aporte de: |
| Sumario: | The well-known N lone-pair orientation effect on 1JCC spin-spin coupling constants (SSCCs) in oximes and their derivatives was used to study how negative hyperconjugative interactions of type LP1(O) → σ*CC depend on ortho interactions involving the OH group. This study demanded the following analyses: (i) a qualitative estimation of how 1JCC SSCCs are affected by hyperconjugative interactions, (ii) a study of similar stereochemical effects to those in oximes, but in 1JCC and 1JC1C6 in a series of 2-substituted phenols, and (iii) a quantitative estimation, with the natural bond order approach, of some key electron derealization interactions. A few unexpected results are quoted. LP1(O) → σ* CC interactions are affected by proximity interactions as follows: (a) they are enhanced by hydrogen bonds transferring charge into the (O-H)* antibonding orbital; (b) they are enhanced by proximity interactions of type LP1(O)⋯H-C; (c) they are inhibited by interactions of type LP(O1)⋯H-O. Consequences of these observations are discussed. © 2007 American Chemical Society. |
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