Structure and conformation of bis(methylthio)methane, (MeS)(2)CH2, determined by gas-phase electron diffractiom and ab initio methods

Structure and conformation of bis(methylthio)methane, (MeS)(2)CH2, determined by gas-phase electron diffractiom and ab initio methods

The gas-phase structure and conformational properties of bis(methylthio)methane, (MeS)(2)CH2, have been determined by electron diffraction, augmented by results from ab initio molecular orbital calculations. The molecule was found to exist in the gas phase at similar to 100 degrees C, predominantly in the G(+)G(+) form (70(18)%), where the CH3 groups an on opposite sides of the SCS plane, with a smaller contribution from the GA form in the conformational mixture. The main conformer possesses C-2 symmetry with a dihedral angle phi(CSCS) of 54(6)degrees, The second conformer has C-1 symmetry with CSCS dihedral angles of 74 degrees and 186 degrees (ab initio values). Assuming entropy differences between the two conformers as obtained from MP3/6-311+G(d) calculations (Delta S = R In 2 + 2.72 cal mol(-1) K-1), this composition corresponds to an enthalpy difference of Delta H = 2.2(6) kcal mol(-1). The corresponding ab initio/DFT enthalpy difference values at 373 K are 1.49 kcal mol(-1) (HF), 2.38 kcal mol(-1) (MP2), and 2.15 kcal mol(-1) (B3LYP). The results for the main distances (r(g)) and angles (angle(alpha)) from the combined GED/ab initio (HF/6-311+G(d)) study of the G(+)G(+) form of (MeS)(2)CH2 (with estimated 2 sigma uncertainties) are r(C-CH3-S) = 1.805(2) Angstrom, r(C-CH2-S) 1.806(2) Angstrom, r(C-CH3-H) = 1.108(5) Angstrom, r(C-CH2-H) = 1.098(5) Angstrom, angle(C-S-C)= 102.8(24)degrees, angle(S-C-S)= 115.9(3)degrees, angle(H-C-CH2-H) = 107.5 degrees (ab initio), and angle(S-C-CH3-H) = 108.9 degrees (ab initio).

molecular-orbital calculations

6672-6676

Page, E. M.

9845d5cd-9846-4a80-b3ff-c68f3564e93b

Rice, D. A.

bbf21d42-a4d6-44ce-943a-af5d8cb212b2

Aarset, K.

2f82c2c0-77d0-4030-83d2-781b832bc216

Hagen, K.

2cb4071b-5a19-4834-b958-831e2606c5b0

Genge, A. R. J.

f327b0d2-6b94-4684-a9ec-0af5444bc884

20 July 2000

Page, E. M.

9845d5cd-9846-4a80-b3ff-c68f3564e93b

Rice, D. A.

bbf21d42-a4d6-44ce-943a-af5d8cb212b2

Aarset, K.

2f82c2c0-77d0-4030-83d2-781b832bc216

Hagen, K.

2cb4071b-5a19-4834-b958-831e2606c5b0

Genge, A. R. J.

f327b0d2-6b94-4684-a9ec-0af5444bc884

Page, E. M., Rice, D. A., Aarset, K., Hagen, K. and Genge, A. R. J.
(2000)
Structure and conformation of bis(methylthio)methane, (MeS)(2)CH2, determined by gas-phase electron diffractiom and ab initio methods.
*Journal of Physical Chemistry A*, 104 (28), .
(doi:10.1021/jp001561f).

## Abstract

The gas-phase structure and conformational properties of bis(methylthio)methane, (MeS)(2)CH2, have been determined by electron diffraction, augmented by results from ab initio molecular orbital calculations. The molecule was found to exist in the gas phase at similar to 100 degrees C, predominantly in the G(+)G(+) form (70(18)%), where the CH3 groups an on opposite sides of the SCS plane, with a smaller contribution from the GA form in the conformational mixture. The main conformer possesses C-2 symmetry with a dihedral angle phi(CSCS) of 54(6)degrees, The second conformer has C-1 symmetry with CSCS dihedral angles of 74 degrees and 186 degrees (ab initio values). Assuming entropy differences between the two conformers as obtained from MP3/6-311+G(d) calculations (Delta S = R In 2 + 2.72 cal mol(-1) K-1), this composition corresponds to an enthalpy difference of Delta H = 2.2(6) kcal mol(-1). The corresponding ab initio/DFT enthalpy difference values at 373 K are 1.49 kcal mol(-1) (HF), 2.38 kcal mol(-1) (MP2), and 2.15 kcal mol(-1) (B3LYP). The results for the main distances (r(g)) and angles (angle(alpha)) from the combined GED/ab initio (HF/6-311+G(d)) study of the G(+)G(+) form of (MeS)(2)CH2 (with estimated 2 sigma uncertainties) are r(C-CH3-S) = 1.805(2) Angstrom, r(C-CH2-S) 1.806(2) Angstrom, r(C-CH3-H) = 1.108(5) Angstrom, r(C-CH2-H) = 1.098(5) Angstrom, angle(C-S-C)= 102.8(24)degrees, angle(S-C-S)= 115.9(3)degrees, angle(H-C-CH2-H) = 107.5 degrees (ab initio), and angle(S-C-CH3-H) = 108.9 degrees (ab initio).

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## More information

Published date: 20 July 2000

Keywords:
molecular-orbital calculations

## Identifiers

Local EPrints ID: 18903

URI: http://eprints.soton.ac.uk/id/eprint/18903

ISSN: 1089-5639

PURE UUID: a87e8436-14a0-497b-86f0-7e981ecfc8a0

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Date deposited: 05 Jan 2006

Last modified: 17 Jul 2017 16:34

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## Contributors

Author:
E. M. Page

Author:
D. A. Rice

Author:
K. Aarset

Author:
K. Hagen

Author:
A. R. J. Genge

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