Analysis of Rotatory Dispersion Curves of Configurationally Related Fatty Acids

The dispersion curves of fatty acids of the type $$\begin{array}{c}\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}{\mathrm{CH}}_3\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}|}\\ \mathrm{H}–\mathrm{C}\mathrm{–(}{\mathrm{CH}}_2{)}_{\mathrm{x}}\mathrm{COOH}\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}|}\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}\mathrm{R}\end{array}$$ have been measured in the visible and in the ultraviolet regions with a view to establishing the sign and the magnitude of the contribution of the radicals $$\begin{array}{c}\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}{\mathrm{CH}}_3\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}|}\\ \mathrm{H}–\mathrm{C}\mathrm{–(}{\mathrm{CH}}_2{)}_{\mathrm{x}}-\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}|}\\ \mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}\mathrm{R}\end{array}$$ and —COOH to the total rotation. The variables were R and x, the latter varying from 0 to 2. It was found that the increase of the chain of R had no effect on the sign of the contributions. The change of x from 0 to 1 or 2 resulted in a change of sign of the contribution of —COOH, leaving the sign of the other contribution unchanged. For 4 of the compounds it was possible to determine with precision the values of each of the two contributions.