85818-62-8Relevant academic research and scientific papers
Substituent Effects on the C-C-Bond Strength, 12. - Thermolysis of Aromatic Pinacol Dimethyl Ethers and Stabilisation Energies of α-Methoxybenzyl Radicals
Birkhofer, Hermann,Beckhaus, Hans-Dieter,Peters, Karl,Schnering, Hans-Georg von,Ruechardt, Christoph
, p. 1693 - 1700 (2007/10/02)
The phenyl-substituted pinacol dimethylethers meso- and DL- 5a-d have been prepared by reductive dimerisation of the dimethyl acetals 7a-d of the ketones 8a-d. (1)H NMR spectra and GC-retention times are used to distinguish between the diastereomers, and an X-ray structure analysis of meso-5a confirms these distinctive criteria.The products and the kinetics of the thermolysis reaction of 5a-d have been studied.A linear correlation between ΔG(excit.) (300 deg C) of thermolysis and strain enthalpies HS of 5, or its release DS during the dissoziation into radicals 6, is observed.These correlations do not differ from those of the thermolysis of tetraalkyl-diphenylethanes (1, R = alkyl, S = phenyl).Hence, the methoxy group does not influence the homolysis reaction of the C-C bond in 5 compared to an alkyl group.It is concluded that any stabilisation of the radicals 6 by the alkoxy group is canceled by an extra stabilisation of 5 by the geminal phenyl/methoxy pairs. Key Words: C-C Bond homolysis/ Thermolysis/ Kinetics/ Radical stabilisation
