Abstract
The determination of uniform scaling factors for force constants calculated at the STO‐3G and 4‐31G levels of ab initio SCF MO theory is described; scaled 4‐31G force constants provide reasonable estimates of reduced partition function ratios for deuteriated/protiated molecules. Gas‐phase deuterium fractionation factors relative to methane calculated using scaled 4‐31G force constants are, however, consistently too high, whereas those obtained by the MP2/6‐31G* and scaled STO‐3G methods are inconsistent. Scaled 4‐31G deuterium fractionation factors relative to water for a range of structural moieties correlate linearly with experimental aqueous‐phase values, but are also consistently overestimated. Substitution at a hydrogen‐bearing carbon atom affects the deuterium fractionation factor through the combined effect of changes in reduced mass and changes in force constants other than for CH stretching.
Original language | English |
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Pages (from-to) | 181-189 |
Number of pages | 9 |
Journal | Journal of Physical Organic Chemistry |
Volume | 3 |
Issue number | 3 |
DOIs | |
Publication status | Published - 1 Mar 1990 |
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry