Circular dichroism of dissymmetric αβ-unsaturated ketones

1963 ◽  
Vol 35 (0) ◽  
pp. 43-47 ◽  
Author(s):  
R. E. Ballard ◽  
S. F. Mason ◽  
G. W. Vane
Keyword(s):  
Circular Dichroism ◽  
Unsaturated Ketones ◽  
Circular Dichroïsm

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

1980 ◽  
Vol 33 (10) ◽  
pp. 2189 ◽  
Author(s):  
AF Beecham ◽  
DJ Collins
Keyword(s):  
Circular Dichroism ◽  
Structure Analysis ◽  
Wavelength Range ◽  
Cotton Effect ◽  
Electronic Transitions ◽  
Positive Contribution ◽  
X Ray ◽  
Unsaturated Ketones ◽  
Negative Cotton Effect ◽  
Circular Dichroïsm

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 → π* 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 6β- substituted compounds the normal, highly structured, negative Cotton effect from the singlet-singlet n → π* transition is modified by positive c.d. with the same vibrational structuring. The origin of the positive contribution is discussed.

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