Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636191
Title: Organic reactions utilizing shape-selective microporous solids
Author: Butters, M.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1986
Availability of Full Text:
Access from EThOS:
Abstract:
Chapters one, two and three provide some introductory information including a detailed review of supported reagents (from 1978 to mid-1986). Chapter four describes the electrophilic activation of a series of different chlorine-containing compounds by the presence of silica gel, these include tert-butylhypochlorite, N, N-dichloramine-T, N, N-dichlorourethane and calcium hypochlorite. Their ability to chlorinate toluene in the ring is comparable to more traditional reagents (like Cl2 in acetic acid). Optimal results are obtained with silica which is significantly acidic and which has been dried at 120oC. The application of such reagents extends from anisole to more deactivated substrates like biphenyl. Chapter five involves the utilization of a variety of aluminosilicate (zeolite) supports. Thus by careful consideration of structural parameters (Al/Si ratio, counter cations, pore and cavity size/shape, and conditions of activation) it is shown that tert-butylhypochlorite in the presence of H+, Na+ Faujasite X produces highly para-selective monochlorinations (> 90% para) of monosubstituted benzenes. For example, chlorobenzene in acetonitrile (at 40oC) produces dichlorobenzene (92% isolated yield) with an isomer ratio of 97% para/3% ortho. Similarly, toluene is chlorinated at 25oC in dichloromethane/diethyl ether (1/3) to give monochlorotoluenes quantitatively with a p:o ratio of 91:9. Proton-exchanged forms of Faujasite with a low aluminium content (Si/Al > 2.4) give by-products resulting from Friedel-Crafts type alkylation reactions. Presence of the stronger acid sites responsible for this reaction change is confirmed by ammonia-temperature programmed desorption experiments. Chapter six deals with the evaluation of different N-chlorodialkylamines in the presence of silica gel as ortho-selective chlorinating reagents for phenols. For example, N-chloro bis (2-chloroethyl) amine in the presence of silica gel in tetrachloromethane solvent gives good mono- to di-chlorination ratios with high selectivity for the ortho- position in phenol (o/p ~ atop = 12.75). Chapter seven outlines some preliminary attempts to control the exo-endo isomer ratio in the 4π + 2π cycloaddition reaction between cyclopentadiene and acrylonitrile.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.636191  DOI: Not available
Share: