Rhodium (Chief Bee)
12-01-01 20:15
No 243048
      P2P from alpha-methylstyrene  Bookmark   

118g alpha-methylstyrene was added to a mixture of 160g of bromine and 1200ml 15% H2SO4, and the mixture was heated at 80C for 8h. The mixture was cooled to room temperature and the organic layer separated, and the aqueous layer extracted with benzene. The extracts and organic layer was mixed and dried over Na2SO4. The benzene was evaporated under vacuo, and the residue was vacuum distilled, and the fraction boiling at 75-85C/8 mmHg weighed 75g and was purified via its bisulfite adduct to give a product mixture boiling at 78-81C/4 mmHg in 57% yield, consisting of 48.5% 2-phenylpropanal and 51.5% phenyl-2-propanone.

Ref: Chem. Abs. 71, 61016x (1969)

Any ideas on how to separate the two, or should the mixture be further processed as in ../rhodium/chemistry /phenylacetone.html#phenylpropanal to give pure P2P?
 
 
 
 
    Scooby_Doo
(Hive Bee)
12-02-01 05:36
No 243165
      Re: P2P from alpha-methylstyrene  Bookmark   

The aldehyde is a little bugger to separate off. However the addition of a sodium hydroxide solution (from memory 10%) causses the aldehyde to form some sort of white gooey mess leaving the ketone to be poured off.

Alternatively run the mixture through a tube furnace filled with a zeolite catalyst (I'll dig out the US patent) to get a 95+% conversion of the aldehyde to ketone. Therefore getting a larger yield and no separation headaches.
 
 
 
 
    Rhodium
(Chief Bee)
12-02-01 06:14
No 243173
      Re: P2P from alpha-methylstyrene  Bookmark   

I believe that is US Patent 4,694,107 if I remember correctly.