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A theoretical study of C 4 H 5 N isomers: Comparison of cyano and isocyano as substituents
Author(s) -
Lien Min H.,
Hopkinson Alan C.
Publication year - 1985
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560270102
Subject(s) - chemistry , isocyanide , carbanion , ab initio , computational chemistry , basis set , ring strain , ab initio quantum chemistry methods , molecular orbital , hydrocarbon , ring (chemistry) , pyrrole , medicinal chemistry , molecule , density functional theory , organic chemistry
Ab initio molecular orbital calculations using a 3‐21G basis set have been used to optimize geometries for pyrrole, CH 3 (X)CCH 2 , CH 3 (H)CCHX (both cis and trans), c ‐C 3 H 5 X, and CH 2 CHCH 2 X, where X is CN and NC. In all the alkenyl derivatives methyl groups are found to adopt the conformation in which the methyl hydrogen eclipses the double bond. 6‐31G*∥3‐21G level calculations show the alkenyl cyanides to be of similar energy to pyrrole, but the isocyanides are ∼20 kcal mol −1 higher in energy. For both substituents the cyclopropyl derivatives are higher in energy by ∼10 kcal mol −1 . At the 6‐31G* level ring strain is 27.7 kcal mol −1 for the cyanide and 30.6 kcal mol −1 for the isocyanide. Data on the relative energies of RCN and RNC are compared when R is (i) a saturated hydrocarbon, (ii) an unsaturated hydrocarbon, (iii) an α‐carbenium ion, (iv) an allyl cation, and (v) an α‐carbanion.