ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The radical cation of dimethyl ether has been studied by ESR in the temperature region of 6–140 K focusing on the internal rotation of the methyl groups. The methyl groups rotate almost freely at above ∼70 K to give a septet ESR spectrum. At temperatures below 40 K there emerge extra lines due to the tunneling rotation of the methyl groups. From the analysis of the line shape, the interaction potential for the rotation of the two methyl groups, if any, should be approximated as proportional to cos 3θ1 cos 3θ2, where θ1 and θ2 denote the rotational angles of the methyl groups measured from the potential minima of the internal rotation of the methyl groups. The activation energy for the thermally induced internal rotation is determined to be ∼100 cal/mol at temperatures above 25 K, whereas at lower temperatures the apparent activation energy drops sharply, which is consistent with the quantum tunneling of the methyl protons. The small activation energy of 100 cal/mol for the radical cation is compatible with the result of ab initio MO calculation for the potential barrier.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.458560
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