Лако-красочные материалы — производство

IR spectroscopy has been utilized to demonstrate the existence of isomers for 2,3,5-triaryl-substituted tetrazolium salts.203 In a systematic study, Arnold and Schiele list and assign all of the vibrational frequencies of 33 triaryl tetrazolium perchlorates.221 Of particular interest are the ring frequencies. Only one of the carbon—nitrogen frequencies is dependent on substitution. For example, C=N1 in triaryl tetrazoliums shifts from 1530cm-1 in the triphenyl derivative to 1527cm-1 in the 5-(4-chloro — phenyl), to 1523cm-1 in the 2-(4-chlorophenyl), and to 1544cm-1 in the 5-(4-methoxyphenyl) derivatives. By contrast, the C=N4 frequency, ranging between 1146 and 1149 cm-1, is insensitive to substitution for the mesoionic thiolate series.222 The assignment is refined by using nitrogen-15 in posi­tions 1 and 4 of the tetrazolium ring.223