Reaction of 2-methyl-2-phenylprop-1-yl magnesium chloride(90) with benzaldehyde in tetrahydrofuran gives a 1:2 mixture of meso-and dl-2,7-dimethyl-2,4 ,5,7-tetraphenyl octane-4,5-diol(91), 1,3-diphenyl-3-methylbutan-1-one(92a), benzyl alcohol(93), 2-methyl-2-phenylpropane(94) and 1,3-diphenyl-3-methylbutan-1-ol(97a). The mechanism involved in the formation of the products of the Grignard reaction is examined. The substituted 1-aryl-3-methyl-3- phenylbutan-1-ols(97b: para-methoxy, c: para-methyl, d: para-chloro, e: meta-chloro, f: 3',4'-dichloro) are prepared. Dehydration of the alcohols(97) with p-toluene-sulphonic acid and a short reaction time gives the trans-1-aryl-3-methyl-3-phenylbut-1-enes(88) but longer reaction times afford the 1-aryl-3,3-dimethylindanes(102) in a reaction involving intramolecular electrophilic substitution. Short term photolyses of the trans-1-aryl-3-methyl-3- phenylbut-1-enes(88) give cis-1-aryl-3-methyl-3-phenylbut-lenes(109) and trans-1-aryl-3,3-dimethyl-2-phenylcyclopropanes (112). Long term photolyses of the trans-alkenes(88) give 4-aryl-2-methyl-3-phenylbut-1-enes(115) in addition to the cis-alkenes(109) and tram-cyclopropanes(112). Deuterium labelling studies show that the secondary photoproducts(115) are formed by C1-C3 cyclopropyl bond cleavage. Photolyses of the trans-1-aryl-1,2-epoxy-3-methyl-3-phenylbutanes(89) give the 1-aryl-3-methyl-3-phenylbutan-2-ones(139),2-aryl-3- methyl-3-phenylbutanals(140) and secondary photoproduct hydrocarbons(141, 142, 143). Photolysis of 1,2-epoxy-3- methyl-1,1,3-triphenylbutane(144) gives benzophenone(46) and secondary photoproduct hydrocarbons(141, 145). Photolysis of 2,3-diphenyl-1,2-epoxy-3-methylbutane(l49) gives 2,3-diphenyl-3-methylbutanal(140) ,2,3-diphenyl-3- methylbutan-1-ol(153), 3,3-diphenyl-4-hydroxyl-2-methylbut-lene(152) and 2,2-dimethyl-3,3-diphenyloxetane(151). Photolyses of a series of 1,2-unsaturated epoxides show both c-o and c-c bond cleavage of the epoxide ring. The interaction between the epoxide and vinyl moieties is discussed. Reaction of the trans-1-aryl-1,2-epoxy-3-methyl-3- phenylbutanes(89) with BF₃-etherate in benzene give 2-aryl-3-methyl-3-phenylbutanals(140) shown by deuterium labelling experiments to be formed by Cl-0 bond cleavage and alkyl migration, and the 1R*, 2R*-1-aryl-1-ethanoxy-3- methyl-3-phenylbutan-2-ols(189) in a process involving retention of configuration at Cl. In ether as solvent the epoxides(89) give in addition to the aldehydes(140) and ethanoxyalcohols(189), 1-aryl-3-methyl-3-phenylbutan-2-ones (139), vinyl ethers(207) and dimers(208). The cis-1-aryl-1, 2-epoxy-3-methyl-3-phenylbutanes(216) react with BF₃-etherate in benzene to give the aldehydes(140) and ketones(139). 1,2-Epoxy-3-methyl-1,1,3-triphenylbutane(144) reacts with BF₃-etherate in benzene to give 2-phenylpropyl-2-(2,2-diphenylethylene) ether(217), 3-methyl-1,1,3-triphenylbutan-2-one(146), 2-phenylpropyl-2-ethylether(218) and benzophenone as primary products and 4-phenylpentan-2-ol(226) and 2,4-diphenyl- 4-methylpent-1-ene(227) as secondary products. The chlorosubstituted epoxide(230) gives 2-phenylpropyl-2-(2,2-bis( 4'-chlorophenyl)ethylene) ether(238) and bis-(4'-chlorophenyl)ketone(235) as primary products and 2,4-diphenyl-4-methylpentl-ene(227) as a secondary product on reaction with BF ₃-etherate in benzene. The complexity of the BF3 -etherate catalysed reactions of these systems(89, 144, 216, 230) is discussed.