Acta Crystallographica Section B

Structural Science

Volume 57, Part 1 (February 2001)

research papers

 

X-ray investigations of sulfur-containing fungicides. II. Intramolecular forces governing the conformation of four novel -phenylazo- and -phenylhydrazono--ketosulfones

W. M. Wolf

Abstract: The crystal and molecular structures of four novel -ketosulfones, phenyl benzoyl(phenylhydrazono)methyl sulfone (I), phenyl benzoyl(4-nitrophenylhydrazono)methyl sulfone (II), (benzoyl)(phenyl)(phenylazo)methyl phenyl sulfone (III) and (benzoyl)(phenyl)(3-chlorophenylazo)methyl 4-tolyl sulfone (IV), have been investigated using X-ray analysis and density functional theory supplemented by ab initio Hartree-Fock calculations. The conformations of (I) and (II) are stabilized by strong intramolecular resonance-assisted hydrogen bonds formed between the sulfonyl and the -hydrazono moieties. The following increase of a positive charge on the S atoms is compensated via -conjugation and stereoelectronic back-donation from the nearby -carbonyl group. Compounds (III) and (IV) adopt a strongly distorted propeller shape with pivotal tetrahedral C1 atoms. Distortion mostly follows from the approximate coplanarity of the -azophenyl and -phenyl moieties opposite each other. The main stereoelectronic interactions involve the donation of electron density from the -azo N2 towards the sulfonyl S and the -carbonyl C2 atoms.

Keywords: fungicides; sulfones; conformation.

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