13 C n.m.r. spectra of some polychloroalkenes

13 C n.m.r. spectra have been measured for thirty‐two polychloroalkenes including (i) monosubstituted compounds CH 2 CHCCl n H 2− n X, where X stands for H, Cl, alkyl, and trisubstituted alkenes CCl 2 CHAlk, none of which form geometric isomers; (ii) disubstituted compounds RCHCHR′; (iii) and (iv) trisubstituted compounds of the types RCClCHR′ and CHClCClR, respectively. Compounds (ii) to (iv) represent either individual isomers or mixtures of the Z and E forms. In the case of compounds (ii) and (iii), the ordering of chemical shifts is δ E > δ Z for the sp 2 ‐carbon atoms and δ E < δ z for the adjacent tetrahedral ones. On the contrary, the signals of the sp 2 ‐carbon atoms of compounds (iv) obey the rule δ E < δ z . The effect of vinyl and allyl groups as substituents on the 13 C chemical shifts of chlorine‐containing groups is discussed. The dependence of the sp 2 ‐carbon spin–spin coupling constants J ( 13 C 1 H) on the number of chlorinated substituents in the molecule is also considered.