Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites

Photochemistry in organized assemblies has attracted considerable attention because of their potential use in controlling photophysical and photochemical behaviour of organic molecules in a confined space. Conversion of a starting material to product in a photoreaction involves selectivity by the re...

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Main Author:	Yeoh, Kar Kheng
Format:	Thesis
Language:	English
Published:	2005
Subjects:	QD Chemistry
Online Access:	http://eprints.utm.my/id/eprint/4451/1/YeohKarKhengMFS2005.pdf
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spelling	my-utm-ep.44512018-01-28T08:27:16Z Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites 2005-05 Yeoh, Kar Kheng QD Chemistry Photochemistry in organized assemblies has attracted considerable attention because of their potential use in controlling photophysical and photochemical behaviour of organic molecules in a confined space. Conversion of a starting material to product in a photoreaction involves selectivity by the reaction cavity to the specified product. For solid and rigid media like zeolite, the size of the reaction cavity plays an important role in products selectivity. The surface of NaY zeolite was first studied with paramagnetic probe using Electron Spin Resonance spectroscopy (ESR). Two favourable active sites were identified. The study of a confine space reaction was first studied in the photosensitization of triethylamine by acetophenone in NaY zeolite. ESR result showed that radical cation of amine dimer was formed inside zeolite resulted from the confinement effect of the zeolite Y supercage. Ultraviolet (UV) irradiation of acetophenone in toluene solution results in photochemical hydrogen abstraction and yielded a mixture of both symmetric (1,2-diphenylethane and 1,2-diphenylethyl alcohol) and asymmetric (1,2-diphenylpinacol) coupling products. These were identified and characterized by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR). With the introduction of NaY zeolite, high yield of asymmetric product, 1,2-diphenylpinacol was observed. It further proved the confinement effect played by the zeolite produced a drastic change in product selectivity compared to homogenous reaction. Photodimerization of 2-cyclohexenone in various cation-exchanged Y zeolites were also studied in solid state and zeolite-solvent slurries. Both the reactions showed a great reversal of head-to-tail (HT) cyclohexenone dimer, to head-to-head (HH) cyclohexenone dimer with increasing pattern from LiY to CsY zeolite. The study of regioselectivity in the photocycloaddition of 2-cyclohexenone to vinyl acetate was also carried out in zeolite slurries, in which the result showed a drastically change of product yield compared to the homogeneous reaction. However, the cationexchanged zeolites failed to control the selectivity. This is explained by the passive cavity effect of zeolite. 2005-05 Thesis http://eprints.utm.my/id/eprint/4451/ http://eprints.utm.my/id/eprint/4451/1/YeohKarKhengMFS2005.pdf application/pdf en public masters Universiti Teknologi Malaysia, Faculty of Science Faculty of Science
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	QD Chemistry
spellingShingle	QD Chemistry Yeoh, Kar Kheng Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites
description	Photochemistry in organized assemblies has attracted considerable attention because of their potential use in controlling photophysical and photochemical behaviour of organic molecules in a confined space. Conversion of a starting material to product in a photoreaction involves selectivity by the reaction cavity to the specified product. For solid and rigid media like zeolite, the size of the reaction cavity plays an important role in products selectivity. The surface of NaY zeolite was first studied with paramagnetic probe using Electron Spin Resonance spectroscopy (ESR). Two favourable active sites were identified. The study of a confine space reaction was first studied in the photosensitization of triethylamine by acetophenone in NaY zeolite. ESR result showed that radical cation of amine dimer was formed inside zeolite resulted from the confinement effect of the zeolite Y supercage. Ultraviolet (UV) irradiation of acetophenone in toluene solution results in photochemical hydrogen abstraction and yielded a mixture of both symmetric (1,2-diphenylethane and 1,2-diphenylethyl alcohol) and asymmetric (1,2-diphenylpinacol) coupling products. These were identified and characterized by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR). With the introduction of NaY zeolite, high yield of asymmetric product, 1,2-diphenylpinacol was observed. It further proved the confinement effect played by the zeolite produced a drastic change in product selectivity compared to homogenous reaction. Photodimerization of 2-cyclohexenone in various cation-exchanged Y zeolites were also studied in solid state and zeolite-solvent slurries. Both the reactions showed a great reversal of head-to-tail (HT) cyclohexenone dimer, to head-to-head (HH) cyclohexenone dimer with increasing pattern from LiY to CsY zeolite. The study of regioselectivity in the photocycloaddition of 2-cyclohexenone to vinyl acetate was also carried out in zeolite slurries, in which the result showed a drastically change of product yield compared to the homogeneous reaction. However, the cationexchanged zeolites failed to control the selectivity. This is explained by the passive cavity effect of zeolite.
format	Thesis
qualification_level	Master's degree
author	Yeoh, Kar Kheng
author_facet	Yeoh, Kar Kheng
author_sort	Yeoh, Kar Kheng
title	Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites
title_short	Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites
title_full	Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites
title_fullStr	Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites
title_full_unstemmed	Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites
title_sort	intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites
granting_institution	Universiti Teknologi Malaysia, Faculty of Science
granting_department	Faculty of Science
publishDate	2005
url	http://eprints.utm.my/id/eprint/4451/1/YeohKarKhengMFS2005.pdf
_version_	1747814531160080384

Intermolecular photoreactions and selectivity studies in confined space of cation-exchanged y zeolites

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