Microwave spectra of monohalogenated allenes. Chloroallene and iodoallene
The microwave spectra of chloroallene, ClHCCCH2 and ClDCCCH2(35/37Cl), and iodoallene, IHCCCH2 and IDCCCH2, have been studied from 7 to 40 GHz. A least-squares analysis of the observed a- and b-type transition frequencies gave rotational constants and components of the halogen nuclear quadrupole coupling constant tensor in the principal axes systems. The structural parameters for chloroallene and iodoallene are calculated from the rotational constants. The C—X bond lengths in chloroallene and iodoallene were found to be a little longer than those in chloroethene and iodoethene, respectively, in accordance with a slightly lower π character for the carbon–halogen bonds in the haloallenes than those in the haloethenes.