Structure of Molecules and Internal Rotation reviews early studies on dihalogenoethanes. This book is organized into two parts encompassing 8 chapters that evaluate the Raman effect in ethane derivatives, the energy difference between rotational isomers, and the infrared absorption of ethane derivatives. Some of the topics covered in the book are the potential barrier to internal rotation; nature of the hindering potential; entropy difference between the rotational isomers; internal rotation in butane, pentane, and hexane; and internal rotation in long chain n-paraffins. Other chapters deal with the configuration of a polypeptide chain, as well as the sum rule and the product rule for rotational isomers. The normal vibrations of the 1,2-dihalogenoethanes are presented. The last chapters are devoted to the examination of the Raman effect, dielectric constant, and electron diffraction. The book can provide useful information to chemists, physicists, students, and researchers.