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Title: Anharmonic modeling of the conformation-specific IR spectra of ethyl, n-propyl, and n-butylbenzene

Journal Article · · Journal of Chemical Physics
DOI:https://doi.org/10.1063/1.4953181· OSTI ID:1471526

In this paper, conformation-specific UV-IR double resonance spectra are presented for ethyl, n-propyl, and n-butylbenzene. With the aid of a local mode Hamiltonian that includes the effects of stretch-scissor Fermi resonance, the spectra can be accurately modeled for specific conformers. These molecules allow for further development of a first principles method for calculating alkyl stretch spectra. Across all chain lengths, certain dihedral patterns impart particular spectral motifs at the quadratic level. However, the anharmonic contributions are consistent from molecule to molecule and conformer to conformer. This transferability of anharmonicities allows for the Hamiltonian to be constructed from only a harmonic frequency calculation, reducing the cost of the model. Finally, the phenyl ring alters the frequencies of the CH2 stretches by about 15 cm-1 compared to their n-alkane counterparts in trans configurations. Conformational changes in the chain can lead to shifts in frequency of up to 30 cm-1.

Research Organization:
Purdue Univ., West Lafayette, IN (United States); Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF); German Research Foundation (DFG)
Grant/Contract Number:
FG02-96ER14656; CHE-1213449; SU 121/6-1
OSTI ID:
1471526
Alternate ID(s):
OSTI ID: 1257004
Journal Information:
Journal of Chemical Physics, Vol. 144, Issue 22; ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 28 works
Citation information provided by
Web of Science

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Anharmonic interstellar PAH molecules: CANDIAN AND MACKIE journal September 2016
Halocarbons as hydrogen bond acceptors: a spectroscopic study of haloethylbenzenes (PhCH 2 CH 2 X, X = F, Cl, Br) and their hydrate clusters journal January 2018
Fermi resonance in solvated H 3 O + : a counter-intuitive trend confirmed via a joint experimental and theoretical investigation journal January 2018
Conformational explosion: Understanding the complexity of short chain para -dialkylbenzene potential energy surfaces journal May 2018
Modeling vibrational anharmonicity in infrared spectra of high frequency vibrations of polyatomic molecules journal March 2019