I. Walden Inversions Involving the Isomeric 2,3-Butanediamenes and Related Compounds. II. An Experimental Test of Kirkwood's Theory of Optical Rotatory Power. III. Zero-Point Vibrational Contributions to the Optical Activity of Isotopically Asymmetric Molecules

Abstract

It has been demonstrated that reaction of ammonia with 1,2-dimethylethyleneimine is attended by single Walden inversion and that the analogous reaction of ammonia with 2,3-epoxybutane very probably proceeds in the same way. This result and other evidence have been used to assign configurations to the 3-amino-2-butanols and to draw certain conclusions about the courses of the reactions in which they are involved. Optically active 1,2-dichloropropane has been prepared and its relative configuration determined. Measurements of its optical rotatory power in different solvents and at different temperatures permit an approximate determination of the optical rotations of the two forms of the molecule corresponding to the two lowest potential minima for internal rotation about the 1,2-carbon-carbon bond. These values are compared with the results of a theoretical calculation; the resulting assignment of absolute configuration is consistent with a previous result for 2,3-epoxybutane. Kirkwood's theory of optical rotation has been modified so as to take into account contributions arising from zero-point vibrational effects. The theory is used to calculate the optical rotations of compounds of the type R1R2CHD. The result for α-deuteroethylbenzene is found to be comparable in magnitude with an experimental value and consistent in sign with previous assignments of absolute configuration.