Optical Activity of Symmetric Compounds in Chiral Media. I. Induced Circular Dichroism of Unbound Substrates

Abstract

In the presence of chiral environment compounds, C, optical rotation is induced in symmetric substrates, S, and may be detected as circular dichroism in the electronic spectra of the solutions. Thus the n-?I* transitions of symmetric and racemic carbonyl compounds, and of symmetric nitro and azo compounds, become optically active when these S are dissolved in chiral hydrocarbons, ketones, or carbinols, or in solutions of these C in achiral solvents. The rotational strengths of the induced circular dichroism bands of S are solvent, temperature, and concentration dependent. Only limited correlation of the sign and magnitude of the induced bands with the stereochemistry of C and S is evident on the data so far accumulated. Halogenated achiral solvents enhance the intensity, and, in some cases reverse the sign of the induced bands.A new mechanism of asymmetric induction is proposed in which specific bonding of C with S is not prerequisite.

Circular Dichroism of Nitrate Esters: A Planar Symmetry Rule for the Nitrato Chromophore

“…Low temperature measurements (21) were corrected for volume contraction from published solvent data (22). Ultraviolet spectra were run on a Cary 15 spectrophotometer with slit widths less than 1 mm and absorbance below 1 .O.…”

“…Band I was even more sensitive to changes in temperature and solvent polarity for [19][20][21][22][23][24][25] (Table 3). There was no clear correlation of the molecular ellipticity of band I with the usual solvent parameters (33), and, as noted above, it increased linearly in magnitude with decreasing temperature.…”

Chirality transfer from chiral solvents and its memory in an azobenzene derivative exhibiting photo-switchable racemization

“…a Research Institute for electronic Science, Hokkaido University, Sapporo,[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]Japan. Fax: +81 11 706 9357;Tel: +81 11 706 9356; The chirality is trasferred form a chiral solvent and memorized as a well defined planar chirality of the single small molecule.…”

Insect Pheromones: A Critical Review of Recent Advances in Their Chemistry, Biology, and Application

“…In a lengthy sequence starting from azaleic acid, BUTLER (348). In a relatively high yield synthesis, SISIDO et al (167) oxidized iodoalkyne (349), chain extended and transformed the terminal alkyne to the methyl ketone (Scheme 63).…”

“…It has been demonstrated experimentally that when an achiral molecule approaches a chiral one, chirality may be induced in the previously achiral molecule (348)(349)(350)(351). This molecular twisting occurs before the two molecules are close enough together to be bound by the formation of a donor-acceptor complex or by hydrogen bonding (348)(349)(350)(351) and has been demonstrated by observing the induced circular dichroism of the n-n* transition of various achiral substances in chiral solvents (348)(349)(350)(351)(352).…”