Knowledge Bank

The methine stretching VCD spectra of a number of hydroxy acids and substituted hydroxy acids have been investigated. Deuterium substitution was used to remove overlapping absorption features when possible. For L-lactide, (S)-methyl-d$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ lactate, (S)-methyl-d$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ mandelate, di(methyl-d$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$) L-tartrate, methyl-d$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ (2S)-methoxy-d$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$-propionate, and (S)-O-acetylmandelic acid in nonaqueous solution, anisotropy ratios equal to $\sim +2.5$X$10-4$ were measured. Salts of hydroxy acids in aqueous solution exhibited similar large anisotropy ratios. In dimethyl-d$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$-2,3-O-benzylidine-C-d$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$-L-tartrate and (S)-methyl 2-chloropropionate, the methine stretching VCD intensity is quite small. The factors leading to a large methine VCD anisotropy ratio will be assessed.""