Details
| Original language | English |
|---|---|
| Pages (from-to) | 55-61 |
| Number of pages | 7 |
| Journal | Journal of molecular spectroscopy |
| Volume | 351 |
| Early online date | 11 Jul 2018 |
| Publication status | Published - Sept 2018 |
Abstract
The rotational spectrum of para-tolualdehyde (CH3-C6H4-CHO) has been measured using three different microwave spectrometers, with the goal of quantifying the influence of the aldehyde group at the top of the benzene ring on the internal rotation barrier seen by the methyl group at the bottom of the ring. This barrier consists of a six-fold component, which results from the local C2v symmetry of the benzene ring seen by the methyl top (as in toluene), and an additional three-fold component, which results from information on the non-C2v symmetry at the aldehyde site at the top of the ring being transmitted to the methyl-group site at the bottom of the ring. The nearly-free internal rotation of the methyl group splits each of the rotational transitions into two components, one of A and one of E symmetry. Assignment and fit of 786 A-state and E-state transitions to an internal rotation Hamiltonian containing barrier terms of three-fold (V3 = 28.111(1) cm−1) and six-fold (V6 = −4.768(7) cm−1) symmetry with respect to the internal rotation angle, as well as the three rotational constants and a number of higher-order torsion-rotation interaction terms, resulted in residuals equal to experimental measurement uncertainty. Isotopic data from all eight mono-substituted 13C species and the one 18O species were obtained in natural abundance and used to determine an rs substitution structure. Various chemical and physical implications of this structure and the two barrier parameters are discussed.
Keywords
- Equilibrium structure, Internal rotation barriers, Intramolecular information transmission, Microwave spectrum, P-tolualdehyde
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Atomic and Molecular Physics, and Optics
- Chemistry(all)
- Spectroscopy
- Chemistry(all)
- Physical and Theoretical Chemistry
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In: Journal of molecular spectroscopy, Vol. 351, 09.2018, p. 55-61.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Microwave study of internal rotation in para-tolualdehyde
T2 - Local versus global symmetry effects at the methyl-rotor site
AU - Saal, Hilkka
AU - Grabow, J. U.
AU - Hight Walker, A. R.
AU - Hougen, J. T.
AU - Kleiner, I.
AU - Caminati, W.
N1 - Publisher Copyright: © 2018 Elsevier Inc. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/9
Y1 - 2018/9
N2 - The rotational spectrum of para-tolualdehyde (CH3-C6H4-CHO) has been measured using three different microwave spectrometers, with the goal of quantifying the influence of the aldehyde group at the top of the benzene ring on the internal rotation barrier seen by the methyl group at the bottom of the ring. This barrier consists of a six-fold component, which results from the local C2v symmetry of the benzene ring seen by the methyl top (as in toluene), and an additional three-fold component, which results from information on the non-C2v symmetry at the aldehyde site at the top of the ring being transmitted to the methyl-group site at the bottom of the ring. The nearly-free internal rotation of the methyl group splits each of the rotational transitions into two components, one of A and one of E symmetry. Assignment and fit of 786 A-state and E-state transitions to an internal rotation Hamiltonian containing barrier terms of three-fold (V3 = 28.111(1) cm−1) and six-fold (V6 = −4.768(7) cm−1) symmetry with respect to the internal rotation angle, as well as the three rotational constants and a number of higher-order torsion-rotation interaction terms, resulted in residuals equal to experimental measurement uncertainty. Isotopic data from all eight mono-substituted 13C species and the one 18O species were obtained in natural abundance and used to determine an rs substitution structure. Various chemical and physical implications of this structure and the two barrier parameters are discussed.
AB - The rotational spectrum of para-tolualdehyde (CH3-C6H4-CHO) has been measured using three different microwave spectrometers, with the goal of quantifying the influence of the aldehyde group at the top of the benzene ring on the internal rotation barrier seen by the methyl group at the bottom of the ring. This barrier consists of a six-fold component, which results from the local C2v symmetry of the benzene ring seen by the methyl top (as in toluene), and an additional three-fold component, which results from information on the non-C2v symmetry at the aldehyde site at the top of the ring being transmitted to the methyl-group site at the bottom of the ring. The nearly-free internal rotation of the methyl group splits each of the rotational transitions into two components, one of A and one of E symmetry. Assignment and fit of 786 A-state and E-state transitions to an internal rotation Hamiltonian containing barrier terms of three-fold (V3 = 28.111(1) cm−1) and six-fold (V6 = −4.768(7) cm−1) symmetry with respect to the internal rotation angle, as well as the three rotational constants and a number of higher-order torsion-rotation interaction terms, resulted in residuals equal to experimental measurement uncertainty. Isotopic data from all eight mono-substituted 13C species and the one 18O species were obtained in natural abundance and used to determine an rs substitution structure. Various chemical and physical implications of this structure and the two barrier parameters are discussed.
KW - Equilibrium structure
KW - Internal rotation barriers
KW - Intramolecular information transmission
KW - Microwave spectrum
KW - P-tolualdehyde
UR - http://www.scopus.com/inward/record.url?scp=85050506052&partnerID=8YFLogxK
U2 - 10.1016/j.jms.2018.07.004
DO - 10.1016/j.jms.2018.07.004
M3 - Article
AN - SCOPUS:85050506052
VL - 351
SP - 55
EP - 61
JO - Journal of molecular spectroscopy
JF - Journal of molecular spectroscopy
SN - 0022-2852
ER -