... A carbon atom of a C~N~ moiety is expected however, to absorb in a region about 100 ppm upfield from 219.4 ppm [10]; the carbon atom of the C1C=N moiety in Xb, in which the carbon-chlorine bond probably is polarised by the Cl-l interaction, may account better for the observed low field resonance. It may, of course, be that both isomeric species Xa and Xb are present in solution. ... 12(a). RR Holmes, RO Day, AC Sau, W. Althoff, S. Husebye, R. Brown, T. Clark. ...