ION STRUCTURES OF 2,4-HEXADIENE ISOMERS
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Date
1978
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Ohio State University
Abstract
Ion cyclotron resonance spectroscopy has proven to be an effective method to determine structural information about radical cations formed by electron impact from different isomers. Photodissociation spectra are often characteristic for each isomer, as is the case for the isomers of 2,4-hexadlene, The trans-trans and the cis-cis forma each have two distinct photodissociation peaks; one in the UV (300-340 nm); the other in the visible (440-540 nm). Each of the cis-cis peaks, however, fall significantly to the red of the corresponding peaks of the trans-trans ions, These spectral shifts indicate that the isomers form ions which retain structural differences and do not isomerize. Photo-dissociation occurs because of an electronic transition in the ion, where the light energy corresponds to the energy difference of the ion’s molecular orbitals. In this case the UV peak, corresponds to a $\Pi \rightarrow \Pi^{*}$ transition, while the visible peak corresponds to a $\Pi \rightarrow \Pi$ transition. The molecular orbital energy spacings have been theoretically determined and these calculations are compared to the experimental results.
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Author Institution: Department of Chemistry, Case Western Reserve University