Electronic Spectra of Carbonium Ions by Internal Reflection Spectroscopy

Abstract

Problems are frequently encountered in using conventional transmission spectrophotometry for obtaining the electronic spectra of unstable reaction intermediates such as carbonium ions. Hence, an investigation of the use of internal reflection spectroscopy (IRS) was conducted. A comparison was made of the transmission and internal reflection spectra of triphenyl carbonium and methylbenzenonium ions. The internal reflection technique was also used to obtain the spectrum of organic ions formed by the reaction of ethylbenzene with aluminum chloride and hydrogen chloride. The reaction of ethylbenzene with methylene chloride in the presence of aluminum chloride—hydrogen chloride catalyst was followed by IRS. The results showed that IRS is a valuable technique for investigating certain unstable reaction intermediates.

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