Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

¹³C, ¹⁵N, and ¹⁹F NMR spectra of the azo coupling products obtained from 4-X-benzenediazonium salts (X = H, F, NO₂) and propanedinitrile (I) or methyl cyanoacetate (II) and of their ¹⁵N isotopomers have been measured. The ¹³C chemical shifts of cyano groups have been assigned unambiguously on the basis of the ²J(¹⁵N_β¹³C) coupling constants, and mutual comparison of the ¹⁵N chemical shifts in compounds I and II enabled also the assignment of the¹⁵N chemical shifts of these groups. The ¹³C chemical shifts of cyano groups in cis position with respect to free electron pair at N_β nitrogen atom are shifted downfield, whereas δ(¹⁵N) of the same groups exhibit upfield shifts as compared with the cyano in trans position. The azo coupling products of benzenediazonium salts and methyl cyanoacetate contain predominantly the E isomer even after long-term standing in hexadeuteriodimethyl sulphoxide.