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The shape of gaseous n ‐butylbenzene: Assessment of computational methods and comparison with experiments
Author(s) -
Halbert Stéphanie,
Clavaguéra Carine,
Bouchoux Guy
Publication year - 2011
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.21733
Subject(s) - conformational isomerism , ionization , basis set , computational chemistry , ionization energy , chemistry , thermodynamics , molecule , atomic physics , density functional theory , ion , physics , organic chemistry
Conformational landscape of neutral and ionized n ‐butylbenzene has been examined. Geometries have been optimized at the B3LYP/6‐31G(d), B3LYP/6‐31+G(d,p), B3LYP‐D/6‐31+G(d,p), B2PLYP/6‐31+G(d,p), B2PLYP‐D/6‐31+G(d,p), B97‐D/6‐31+G(d,p), and M06‐2X/6‐31+G(d,p) levels. This study is complemented by energy computations using 6‐311++G(3df,2p) basis set and CBS‐QB3 and G3MP2B3 composite methods to obtain accurate relative enthalpies. Five distinguishable conformers have been identified for both the neutral and ionized systems. Comparison with experimentally determined rotational constants shows that the best geometrical parameters are provided by B3LYP‐D and M06‐2X functionals, which include an explicit treatment of dispersion effects. Composite G3MP2B3 and CBS‐QB3 methods, and B2PLYP‐D, B3LYP‐D, B97‐D, and M06‐2X functionals, provide comparable relative energies for the two sets of neutral and ionized conformers of butyl benzene. An exception is noted however for conformer V + the stability of which being overestimated by the B3LYP‐D and B97‐D functionals. The better stability of neutral conformers I , III, and IV , and of cation I + , demonstrated by our computations, is in perfect agreement with conclusions based on micro wave, fluorescence, and multiphoton ionization experiments. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011