Patent GB-708565-A (GB)
Title: Improvements in or relating to acylstyrenes
Filed: 1951-12-11
Abstract: Acyl-styrene derivatives of the formula <FORM:0708565/IV (a)/1> where R is hydrogen or a methyl group, X is a methyl group, n is 0, 1 or 2, and R1 is an alkyl group containing less than 4 carbon atoms and where nuclear carbon atoms ortho to that directly carrying the unsaturated side chain are directly connected to hydrogen when R is methyl are homo- or co-polymerized to give resins.  The acetylstyrenes are polymerizable and co-polymerizable with, e.g. styrene, butadiene, 3, 4-dichloro-2-methylstyrene and methylmethacrylate.  The acetyl-2-methylstyrenes having the substituents in the 3-, 4-and/or 5-nuclear positions copolymerize with e.g. butadiene, styrene, dichloro-styrene and methylmethacrylate.  The polymers, particularly when rubbers, are curable with formaldehyde and formaldehyde-liberating substances, e.g. hexamethylene tetramine.  Copolymers of a di-olefin with the acetyl substituted styrenes and a -methyl styrene are compatible with high melting point vinyl resins which contain polar groups such as chlorine and cyanogen groups in the molecule.  The preparation of the acyl styrenes is described (see Group IV (b)).ALSO:The invention comprises compounds of the formula <FORM:0708565/IV (b)/1> where R is hydrogen or a methyl group, X is a methyl group, n is 0, 1 or 2, R1 is an alkyl group containing less than 4 carbon atoms, and where nuclear carbon atoms ortho to that directly carrying the unsaturated side chain are directly connected to hydrogen when R is methyl.  Such compounds when R is methyl may be prepared commercially by reacting the corresponding isopropyl-benzene with an acylating agent such as acetic anhydride or acetyl chloride in the presence of a Friedel-Crafts catalyst, e.g. aluminium chloride or boron trifluoride and then dehydrogenating the product.  Thus p-acetyl-cumene (from cumene and acetyl chloride in presence of aluminium chloride) gives on dehydrogenation p-acetyl-a -methyl styrene.  In the laboratory bromobenzene may be reacted with acetic or other acid anhydride in the presence of aluminium chloride to give p-bromo-acetophenone or the corresponding homologue.  The product, e.g. p-bromo-acetophenone, may be reacted with methyl magnesium bromide to give di-methyl-(p-bromophenyl)-carbinol, which on dehydration with, e.g., fused potassium bisulphate, gives p-bromoisopropylbenzene.  The latter on reaction with cuprous cyanide gives p-cyanoisopropylbenzene which on reaction with methyl magnesium bromide gives p-acetylisopropenylbenzene.  The compounds where R is hydrogen may be prepared from the corresponding di-acetylbenzene with about 40 mol. per cent of aluminium isopropoxide to form a p-acetophenylmethylcarbinol with some p-di-(a -hydroxyethyl) benzene. Dehydration of the p-acetoxyphenylmethyl carbinol gives p-acetyl-styrene.  In examples: (1) p-diacetylbenzene is reacted with aluminium propoxide with distillation of acetone to give p-di-(a -hydroxyethylbenzene (by-product) and p-acetophenylmethylcarbinol. The latter is flash-dehydrated to p-acetylstyrene by dropping it on to a heated mixture of tert.-butylcatechol and potassium bisulphate; (2) p-acetylcumene, prepared by reacting isopropylbenzene and acetic anhydride with an aluminium chloride catalyst is converted to p-acetylstyrene by passage as vapour at 500 DEG  C. with 8 times its volume of carbon dioxide through a heated tube containing a dehydrogenation catalyst, e.g. alumina, alumina-zinc, chromate, zinc-chrom-alumina or zinc oxide base dehydrogenation catalyst, or through a heated iron tube.  A catalyst containing zinc and chromium deposited on alumina is preferred.  In place of p-acetyl cumene, m-acetylcumene may be used.  Some cumene is also found in the product.  In general dehydrogenation may be effected at about 400 DEG to 650 DEG  C.  The products are useful in the preparation of polymers (see Group IV (a)).