Research in the pyrimidine series

Abstract

The frequencies and forms of the normal vibrations of thymine, 5-amino-, 5-fluoro-, 5- and 6-chloro-, 5-bromo-, and 5-nitrouracils and their 1,3-dideutero analogs were calculated, and their force constants were determined. The calculated and observed frequencies were assigned with respect to the types of vibrations. The introduction of substituents into the 5 and 6 positions of the uracil ring leads to a change in a whole series of force constants and to redistribution of the forms of the normal vibrations with respect to natural coordinates. Despite this, one can isolate those structural fragments of the investigated molecules whose normal vibrations remain characteristic in form. A linear dependence of theνN(1)H andνN(3)H frequencies on the force constants of the corresponding bonds was observed.