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Durham e-Theses
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Substituent and neighbouring group effects in the bromination of olefins

Hooley, Stephen Roger (1973) Substituent and neighbouring group effects in the bromination of olefins. Doctoral thesis, Durham University.



Second-order rate constants have been determined for the bromination of the series CH(_2)C(X)CH(_2)C1 (for -X = -H, -F, -CI and -Br) in 50% by volume methanol-water and trifluoroacetic acid solvents. 2-Halo substitution caused deactivation with respect to the unsubstituted allyl chloride, but enhanced reactivity was observed for the 2-fluoro substituted olefin compared to the 2-chloro and 2-bromo substituted compounds. The above data were compared with the rate coefficients for the addition of trifluoroacetic acid to a series of 2-halopropenes. The difference in the scale of rate enhancement for the 2-fluoro substituted olefins in the two reactions is discussed in terms of the relative contributions of the cyclic bromonium ion structure and of the classical open carbonium ion structure to the transition state for electrophilic addition to olefins. Second-order rate constants have been measured for the addition of bromine to allyl chloride and bromide and benzyl chloride and bromide in acetic acid-water and trifluoroacetic acid solvents. The relative rate enhancement for addition to allyl bromide in trifluoroacetic acid compared to allyl chloride was discussed in terms of solvent enhancement of the inductive effects of the halo substituents by hydrogen bonding, and compared to the rates of electrophilic substitution of bromine into the analogous aromatic compounds. The second-order rate constants for bromination of the two series CH(_2)=CH(CH(_2))(_n-2)OH and CH(_2)=CH(CH(_2))(_n-2)Br (where n = 3 to 6) were measured in acetic acid-water and trifluoroacetic acid solvents, Neighbouring group participation was not observed in the bromo-substituted series of olefins.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Thesis Date:1973
Copyright:Copyright of this thesis is held by the author
Deposited On:13 Nov 2013 15:40

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