Formation and reactions of ipso adducts of 2-X-p-xylenes

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dc.contributor.authorXi, Danen_US
dc.date.accessioned2024-08-15T20:18:53Z
dc.date.available2024-08-15T20:18:53Z
dc.date.copyright1991en_US
dc.date.issued1991
dc.degree.departmentDepartment of Chemistry
dc.degree.levelMaster of Science M.Sc.en
dc.description.abstractThe low temperature nitration of 2-X-p-xylenes (X = Cl, Br, COCH3 , COC 6H5 ) in acetic anhydride has been studied in detail. The nitration of 2-bromo- and 2-chloro-X-p-xylene and 2,5-dimethylacetophenone gives 1,4 adducts exclusively while the nitration of 2,5-dimethylbenzophenone leads to 1,2 adducts only. The yield of these adducts range from moderate to good. The regioselectivity of acetic acid capture appears to be more sensitive to steric effects than to electronic effects. The principle of additivity can qualitatively predict the isomer distribution in the nitration reactions. Reactions of the 1,4 adducts (X = Cl, Br, COCH3 ) in different media have been studied. Strong to moderate acid conditions favor the formation of the nitrocyclohexadienyl cation and the competition among three possible pathways (1,2 nitro shift, 1,3 nitro shift and the triene process) is affected by the substituents (X), the acidity and the solvent. In methanol the nitrocyclohexadienyl cation is captured by the solvent to form the dienyl methyl ether. The dominant reaction of the nitrocyclohexadienyl cation in acetic anhydride is deprotonation to give triene and ultimately, side chain aromatics, while the 1,2 nitre shift process dominates in more strongly acidic media. It is also observed that the more strongly electron withdrawing acetyl group facilitates the 1,2 nitre shift process and, to a lesser extent, the 1,3 nitre shift process. Side chain products are not observed with this substituent. Finally the reactions of 1,4 ipso adducts with methanol in the absence of acid give dienols stereospecifically.
dc.format.extent101 pages
dc.identifier.urihttps://hdl.handle.net/1828/20214
dc.rightsAvailable to the World Wide Weben_US
dc.titleFormation and reactions of ipso adducts of 2-X-p-xylenesen_US
dc.typeThesisen_US

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