
%0 Journal Article
%A Beecham, AF 
%A Collins, DJ 
%T The circular dichroism of a,b-unsaturated ketones. I. Circular dichroism in the singlet-singlet and singlet-triplet n «p* transitions of steroidal 4-en-3-ones
%J Australian Journal of Chemistry
%D 1980/10/01
%V 33
%N 10
%P 2189-2197
%K 
%R https://doi.org/10.1071/CH9802189
%U https://www.publish.csiro.au/paper/CH9802189 
%X The circular dichroism from 22 steroidal 4-en-3-ones in cyclohexane solution has been recorded through the wavelength range 400-265 nm. It is shown that both the singlet-triplet and the singlet-singlet n &#8594; &#960;* electronic transitions contribute. Through examination of evidence from c.d. and X-ray structure analysis, it is concluded that the conformation of the chromophore and its immediate environment remains constant under the conditions of measurement. In three of the 6&#946;- substituted compounds the normal, highly structured, negative Cotton effect from the singlet-singlet n &#8594; &#960;* transition is modified by positive c.d. with the same vibrational structuring. The origin of the positive contribution is discussed. 
