Comment on: Accuracy ofabinitioCndash;H bond length differences and their correlation with isolated Cndash;H stretching frequencies

摘要

Relative Cndash;H bond distances innhyphen;alkanes, obtained fromabinitiogeometry optimizations with the 4hyphen;31G, 4hyphen;21G, and 5hyphen;31Gast;ast; basis sets, are compared with experimental isolated Cndash;H stretching frequency data. It is found that results from different calculations all give essentially linear frequencyhyphen;bond length correlations, but with different slopes. For each of the sets of calculated Cndash;H bonds investigated, the slope of the frequencyhyphen;bond correlation is too small compared to the equation given by McKean lsqb;J. Mol. Struct.116, 313 (1984)rsqb; for correlations between isolated Cndash;H stretching frequencies and experimentalr0bonds. Thus it is concluded that, in contrast to work previously published by Aljiburyetal. lsqb;J. Chem. Phys.84, 6872 (1986)rsqb; and Snyderetal. lsqb;J. Chem. Phys.81, 5352 (1984)rsqb;, precise correlation between calculated bond lengths and isolated Cndash;H stretching frequencies does not determine the relative differences between the various Cndash;H bonds innhyphen;alkanes to plusmn;0.0001 Aring;.