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

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Abstract
13C n.m.r. spectra have been measured for thirty‐two polychloroalkenes including (i) monosubstituted compounds CH2CHCClnH2−nX, where X stands for H, Cl, alkyl, and trisubstituted alkenes CCl2CHAlk, none of which form geometric isomers; (ii) disubstituted compounds RCHCHR′; (iii) and (iv) trisubstituted compounds of the types RCClCHR′ and CHClCClR, 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 δE > δZ for the sp2‐carbon atoms and δE < δz for the adjacent tetrahedral ones. On the contrary, the signals of the sp2‐carbon atoms of compounds (iv) obey the rule δE < δz. The effect of vinyl and allyl groups as substituents on the 13C chemical shifts of chlorine‐containing groups is discussed. The dependence of the sp2‐carbon spin–spin coupling constants J(13C1H) on the number of chlorinated substituents in the molecule is also considered.