The conformations of aromatic ethers as determined from their ultraviolet absorption spectra
- 1 January 1967
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society B: Physical Organic
- p. 859-866
- https://doi.org/10.1039/j29670000859
Abstract
A number of heterocyclic analogues of choline phenyl ether have been synthesised in order to investigate the relationship between conformation and biological activity in choline aryl ethers. The intensity of the Ph–O π→π* transition has been used to determine the angle (θ) between the plane of the benzene ring and the plane containing the oxygen bonds. The calculated angles increase in the order 2,3-dihydrobenzofuran < 2,3-dihydro-7-methylbenzofuran < chroman < homochroman; but the value of θ obtained for the 2,3-dihydro-7-methyl benzofuran is anomalously high and is explained on the basis of steric inhibition to sp2 hybridisation of oxygen. Two β-methylated derivatives of choline phenyl ether bromide have also been investigated and the time-averaged values for θ calculated. It is deduced that unlike choline phenyl ether bromide these molecules are unable to adopt a conformation in which θ= 0°.Keywords
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