Induction Studies in Several Groups of Halogen-Containing Organic Compounds by Their Cl35, Br79, or Br81 Pure Quadrupole Resonance Spectra

Abstract

Induction studies have been carried out in several groups of halogen-containing organic compounds by means of the halogen pure quadrupole spectra. In several straight-chain compounds inductive effects have been examined as a function of the length of the chain in some monohalogenated-paraffin hydrocarbons and as a function of the number of carbon atoms separating halogen atoms attached to either end of dihalogenated-paraffin hydrocarbons. The effects of the hybridization of the carbon atom have also been examined in some aliphatic hydrocarbons. Chlorine pure quadrupole resonance frequencies from chlorine atoms bonded to atoms other than carbon, such as silicon, nitrogen, and sulfur, have been measured, and the effects of these different atoms upon the Cl35 resonance frequencies are qualitatively discussed. Inductive effects have also been examined in different groups of aromatic compounds. The inductive effect in several chlorobenzyl compounds is found to be about ¾ of what it is in the corresponding chlorobenzene compounds as determined from a comparison of the Cl35 resonance frequencies. Definite discrepancies have been observed between the Cl35 spectra obtained from several aromatic compounds which have molecular structures similar to anthraquinone and the Cl35 frequencies that can be predicted from data obtained from chlorobenzene compounds and Hammett σ values. Employing the linear relationship between Cl35 resonance frequency and Hammett σ values, several Cl35 frequencies were predicted and compared to the measured frequencies in some chlorobenzene compounds. Some unknown σ values have also been predicted. A linear relationship between Br81 resonance frequencies and Hammett σ values has been developed from measured bromine quadrupole frequencies. Several halogen frequencies from some unrelated compounds have been measured and are tabulated in this paper.