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MECHANISMS OF ELIMINATION REACTIONS AND CONDENSATION REACTIONS IN GAS-PHASE RADICAL CATIONS
Abstract
The elimination of water and acetic acid occurring in substituted tetralin and indan radical cations has been investigated by using isotopic labeling, high resolution mass spectrometry and metastable techniques. cis-1-Tetralol-4-d(,1) and trans-1-tetralol-4-d(,1) were synthesized and characterized in order to investigate the stereochemistry of the highly regiospecific 1,4-elimination of water and acetic acid from 1-tetralol and its corresponding acetate, respectively. The water and acetic acid eliminations occurring in the source were approximately 33% cis-1,4- stereospecific, and this value decreased in the longer-lived metastable ions. The elimination of H(,2)O and DOH occurring from four deuterated 1-indanols were interpreted in terms of competing 1,2- and 1,3- mechanisms. In contrast, the acetate was found to eliminate acetic acid predominantly via a 1,3- mechanism. Water and acetic acid are eliminated from 2-indanol and 2-acetoxyindan, respectively, via specific 1,2- mechanisms. Water elimination occurring from 1-tetralol, 1-indanol and 2-indanol is accompanied by the release of large amounts of kinetic energy. Conversely, very little kinetic energy is released in the elimination of acetic acid eliminations occurring in the substituted indans and tetralins experience considerable deuterium-hydrogen isotope effects. The structures of the radical cation products resulting from the ion-molecule reactions of 1,3-butadiene plus 1,3-butadiene, 1,3-butadiene plus vinyl methyl ether and styrene plus styrene have been investigated by performing the reactions and stabilizing the products inside a high pressure chemical ionization source. The stabilized ion-molecule adducts are isolated by MS-I of a tandem mass spectrometer, and a collision activated decomposition (CAD) spectrum is acquired by MS-II. The structures of the adducts are assigned by comparing their CAD spectra to the spectra of isomeric reference compounds. Under conditions of rapid collisional stabilization (high source pressure), all three reactions produce acyclic intermediates. Conversely, under conditions of slow collisional stabilization, evidence for cyclic intermediates is observed. These observations are best interpreted in terms of a single, two-step cyclization mechanism.
Subject Area
Organic chemistry
Recommended Citation
GROENEWOLD, GARY STEVEN, "MECHANISMS OF ELIMINATION REACTIONS AND CONDENSATION REACTIONS IN GAS-PHASE RADICAL CATIONS" (1983). ETD collection for University of Nebraska-Lincoln. AAI8318657.
https://digitalcommons.unl.edu/dissertations/AAI8318657