Kerr constants of amides and peptides

Abstract Molar Kerr contants m K have been determined for N ‐methylacetamide, N ‐ethyl‐acatamide, N ‐methylpropionamide, N ‐acetylglycine‐ N ′‐methylamide, N ‐acetyl‐ L ‐ala‐nine‐ N ′‐methylamide, and N ‐acetyl‐ L ‐leucine‐ N ′‐methylamide from electric birefringence measurements on dilute solutions in dioxane. The resultes are compared with configurational averatges 〈 m K 〉 calculated on the basis of conformational energies. Values of m K calculated for various fixed confromations on the peptides vary over a wide range depending on the choice of conformation; hece, the configurational averages 〈 m K 〉 are sensitive to smalll changes in the conformational enerey. Kerr constants are calculated for random coiled oligoglycine and oligoalanine peptides as functions of chain length. The Kerr constant is an especially acute index of the average conformation.