Degree Type

Dissertation

Date of Award

1986

Degree Name

Doctor of Philosophy

Department

Chemistry

Abstract

As part of our efforts to understand the chemistry of cyclopropylidenes in solution, the reactions of norcaranylidene in alcohols and nitriles have been studied;In alcohols (methanol or t-butanol), the partitioning of norcaranylidene between intramolecular insertion and intermolecular reaction with alcohols is a function of alcohol concentration. In methanol, an ylide intermediate is transformed into the product ether in a stepwise manner. However, in t-butanol, the corresponding ylide intermediate releases the t-butanol molecule to give the intramolecular insertion product, in competition with protonation to form the ether product;Methanol was found to react with norcaranylidene 2.5 times faster than t-butanol, irrespective of the total alcohol concentrations. A reasonable interpretation of the activation parameters is that norcaranylidene is solvated preferentially by t-butanol monomers at "high" alcohol concentration, but is solvated essentially equally by either methanol or t-butanol at "low" alcohol concentration. Thus at either "low" or "high" alcohol concentrations, the "starting carbene" is a single, albeit differently, solvated species;When nitriles are present in methanol, the nitrile ylide intermediate from the reaction norcaranylidene with nitriles reacts with methanol to yield a mixture of epimeric methanol insertion products. In acrylonitrile, the ylide is also captured by another molecule of acrylonitrile to give a 3 + 2 cycloadduct. And dipolarophiles also capture the diazo-precursor to norcaranylidene in acrylonitrile and methacrylonitrile;Pyrolysis of anti-7-bromo-syn-7-trimethylstannylbicyclo 4.1.0 heptane also generates norcaranylidene. This allows the high temperature study of the kinetic deuterium isotope effects for the reaction of norcaranylidene with methanol and t-butanol. Mechanisms to account for the isotope effects at low (diazo-precursor) and high (tin bromide precursor) temperatures are discussed. Two changes in mechanism are seen as the temperature is changed from -78(DEGREES) to 160(DEGREES)C.

DOI

https://doi.org/10.31274/rtd-180813-13108

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

I-Shan Chu

Language

en

Proquest ID

AAI8627099

File Format

application/pdf

File Size

271 pages

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