Microwave spectra of monohalogenated allenes. Chloroallene and iodoallene

Abstract

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.