Poly(2-methylbut-1-en-3-one) was prepared by bulk polymerisation with azobisisobutyronitrile as initiator. Six copolymers of 2-methylbut-l-en-3-one and styrene in various ratios were prepared similarly. The homopolymer on treatment in solution with hydrogen chloride gave a product in which water had been condensed from neighbouring acetyl side-chains to give a polymer containing series of conjugated double bonds. The homopolymer was oxidised with aqueous alkaline potassium permanganate to give a copolymer of methacrylic acid and 3-niethylbut-3-en-2-oxo-1-oic acid. The homopolymer was reduced with lithium aluminium hydride in tetrahydrofuran to give a product containing 70% of secondary alcohol groups. The homopolymer was treated with hydroxylamine hydrochloride in pyridine to give a product containing oxime groups, oxime anhydride groups and unreacted ketone groups. The 1:2-copolymer was brominated to give a product in which all the methyl ketone side-chains had been converted to bromomethyl ketone side-chains. The brominated 1:2-copolymer was reacted with thiourea to give a copolymer in which all the bromine had been replaced by isothiourea groups. Where possible low molecular weight analogues of the polymers were prepared, based on 2,2-dimethylbutan-3-one. The infra-red spectra of the polymers and polymeric derivatives were compared with those of the low molecular weight analogues. The reactivities of the above polymeric compounds are discussed in relation to the characteristics of the corresponding molecular models
