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

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 CH 2 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.
Authors:
 [1] ; ORCiD logo [2] ;  [2] ; ORCiD logo [2] ;  [2] ;  [2] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Chemistry. Theoretical Chemistry Inst.
  2. Purdue Univ., West Lafayette, IN (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
FG02-96ER14656; CHE-1213449; SU 121/6-1
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 22; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Purdue Univ., West Lafayette, IN (United States); Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); German Research Foundation (DFG)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; chemical compounds and components; Becke, three-parameter, Lee-Yang-Parr; Fermi resonance; electronic structure methods; chemical elements; organic compounds; electronic-structure theory; spectroscopy; correlation-consistent basis sets; conformational dynamics
OSTI Identifier:
1471526
Alternate Identifier(s):
OSTI ID: 1257004

Tabor, Daniel P., Hewett, Daniel M., Bocklitz, Sebastian, Korn, Joseph A., Tomaine, Anthony J., Ghosh, Arun K., Zwier, Timothy S., and Sibert, Edwin L.. Anharmonic modeling of the conformation-specific IR spectra of ethyl, n-propyl, and n-butylbenzene. United States: N. p., Web. doi:10.1063/1.4953181.
Tabor, Daniel P., Hewett, Daniel M., Bocklitz, Sebastian, Korn, Joseph A., Tomaine, Anthony J., Ghosh, Arun K., Zwier, Timothy S., & Sibert, Edwin L.. Anharmonic modeling of the conformation-specific IR spectra of ethyl, n-propyl, and n-butylbenzene. United States. doi:10.1063/1.4953181.
Tabor, Daniel P., Hewett, Daniel M., Bocklitz, Sebastian, Korn, Joseph A., Tomaine, Anthony J., Ghosh, Arun K., Zwier, Timothy S., and Sibert, Edwin L.. 2016. "Anharmonic modeling of the conformation-specific IR spectra of ethyl, n-propyl, and n-butylbenzene". United States. doi:10.1063/1.4953181. https://www.osti.gov/servlets/purl/1471526.
@article{osti_1471526,
title = {Anharmonic modeling of the conformation-specific IR spectra of ethyl, n-propyl, and n-butylbenzene},
author = {Tabor, Daniel P. and Hewett, Daniel M. and Bocklitz, Sebastian and Korn, Joseph A. and Tomaine, Anthony J. and Ghosh, Arun K. and Zwier, Timothy S. and Sibert, Edwin L.},
abstractNote = {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.},
doi = {10.1063/1.4953181},
journal = {Journal of Chemical Physics},
number = 22,
volume = 144,
place = {United States},
year = {2016},
month = {6}
}