DETECTION OF SHAPE AND CONFORMATIONAL CHANGE IN CARBONYL COMPOUNDS BY THE COMPARISON OF THE VARIATION OF $n \rightarrow \pi^{*}$ TRANSITIONS WITH THE SOLVENT POLARITY STANDARD, Z

Abstract

“Cyclic ketones (I) with $n=5$ or 6 possess $n \rightarrow \pi^{*}$ transitions which vary in a linear fashion [FIGURE] with the polarity of the solvent as measured by Z, the position of the charge-transfer band for 1-ethyl-4-carbomethoxy pyridinium iodide. [E. M. kosower. Jour. Am. Chem. Soc., 80, 3253 (1958).] Ketones with $n = 7, 8, 9, 10$ give reasonably good correlations with the same parameter. Cyclopentadecanone $(n = 15)$ is less responsive to solvent change than could be expected on the basis of the other cyclic ketones and it is concluded that the non-polar portion of the molecule is folded so as to reduce the net polarity of the cybotactic region (solvent molecule group) around the carbonyl bond. Conformational change in 2-chlorocyclohexanone is easily detected by the same technique and is confirmed by infrared studies.”