
%0 Journal Article
%A Le Fevre, RJW 
%A Sousa, JB 
%A Werner, RL 
%T The stretching frequency of the Azo-group in Formazans
%J Australian Journal of Chemistry
%D 1956/06/01
%V 9
%N 2
%P 151-159
%K 
%R https://doi.org/10.1071/CH9560151
%U https://www.publish.csiro.au/paper/CH9560151 
%X Infra-red spectra between 680 and 1600 cm-1 are recorded for 10 formazans and five copper complexes derived therefrom. A common feature at c. 1450 cm-1 in the formazans is removed by chelation ; it is therefore suggested that 1450 cm-l is the stretching frequency of -N:N- as modified by conjugation and hydrogen-bonding in a system Ar.N:N.CAr:N-. Analogies with keto-enol systems indicate that azo- groups in simpler environments would absorb a&quot; higher frequencies, so that of the two alternatives left open by Le Fèvre, O'Dwyer, and Werner (1953), namely, 1579 or 1406 cm-1, the larger is to be preferred. 
