Paper Info
Title
Enthalpies of formation of monoderivatives of hydrocarbons: Interaction of polar groups with an alkyl group.
Abstract
Energies of hydrocarbon monoderivatives CH3X, C2H5X, n-C4H9X, and n-C5H11X with 16 different substituents X were calculated at the levels B3LYP/6-311 +G(d,p) and B3LYP/AUG-cc-pVTZ//B3LYP/6-31 I +G(d,p). The results were used to test the validity of the additive rule that has served commonly for estimating the enthalpies of formation Delta(f)H(T). The exact additivity corresponds to zero reaction energy DeltaE of the isodesmic reaction, in which the substituent X is transferred from one alkyl group R to another. Additivity is approximately fulfilled for butyl and pentyl derivatives with the differences less than 0.3 kJ mol(- 1) (except charged groups X). Methyl derivatives deviated from the additive rule up to 22 U mol(-1) for dipolar groups X and 45 U mol(-1) for charged group, in agreement with the available experiments and with the anticipation of all suggested empirical schemes. In addition, smaller deviations of ethyl derivatives Q or 20 U mol(-1), respectively) were observed here for the first time. There is no correlation between the deviations of methyl and ethyl derivatives; they are also not related to steric effects, and only partly to polarization. Deviations of methyl derivatives are proportional to the electronegativity of the first atom of the substituent; even when the definition of electronegativity is somewhat questionable, one can say in any case that it is controlled by the first atom. (C) 2004 Wiley Periodicals, Inc.
Year
DOI
Venue
2004
10.1002/jcc.20124
JOURNAL OF COMPUTATIONAL CHEMISTRY
Keywords
DocType
Volume
additive properties,B3LYP,electronegativity,isodesmic reaction,substituent effects
Journal
25.0
Issue
ISSN
Citations 
16
0192-8651
1
PageRank 
References 
Authors
0.43
3
2
Name
Order
Citations
PageRank
O. Exner153.49
Stanislav Böhm2508.69