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DOI: 10.1039/A800621K (Paper) Reference Section for: J. Chem. Soc., Perkin Trans. 2, 1998, 1159-1162

Structure and molecular interactions of anti-thyroid drugs. Part 1. Dipole moments of carbimazole and methimazole, and conformation of carbimazole

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Christian Laurence, Mohamed J. El Ghomari and Maryvonne Luçon

Abstract

The dipole moments of carbimazole and methimazole are respectively 4.30 D (in benzene) and 5.43 D (in dioxane). The 4.30 D value and the solvent variation of the two carbonyl bands of carbimazole in the IR spectrum are consistent with a Z⇌E conformational equilibrium. Polar solvents stabilize the more polar Z conformer and, whereas carbimazole exists about 90% in the E form in heptane and CCl4, it is almost entirely in the Z form in water. In CCl4 the energy difference between the Z and E isomers, determined from the ratio of the intensities of the two carbonyl bands, is found to be 9.6 kJ mol–1, and is in good agreement with 6-31G** calculations.

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