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AB initio and semi‐empirical investigation of gas‐phase carbon acidity
Author(s) -
Saunders William H.
Publication year - 1994
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610070509
Subject(s) - chemistry , gas phase , ab initio , computational chemistry , carbon fibers , phase (matter) , ab initio quantum chemistry methods , thermodynamics , organic chemistry , molecule , materials science , physics , composite number , composite material
Acidities of a representative range of carbon acids were calculated by various levels of ab initio theory and by the semi‐empirical methods AM1 and PM3 in order to ascertain what level is necessary in order to obtain consistently reliable results. The semi‐empirical methods give good agreement with experiment in about a third of the cases, but are significantly, and sometimes seriously, in error for the rest. The 3–21G ab initio method consistently underestimates acidities by a substantial amount. The best results were obtained at the MP2/6–31 + G*//6–31 + G* level. Higher level Møller–Plesset corrections worsened the agreement with experiment.