The selective oxidation of toluenes to benzaldehydes by cerium(III), hydrogen peroxide and bromide ion

✍ Scribed by Kevin Auty; Bruce C. Gilbert; C.Barry Thomas; Scott W. Brown; Craig W. Jones; William R. Sanderson

• Book ID: 104423180
• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 734 KB
• Volume: 117
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(96)00255-5

✦ Synopsis

4-t-Butyltoluene

can be oxidised in acetic acid to 4-r-butylbenzaldehyde by hydrogen peroxide in a process catalyzed by cerium(II1) and bromide ions. The conversion proceeds via benzylic bromination, hydrolysis of the bromide to alcohol and the rapid oxidation of the alcohol to the aldehyde by bromine. The reaction is ineffective in the absence of bromide but is also inhibited by significant quantities of the ion, apparently because the hydrolysis step is reversible. The role of the cerium has not been clearly established. Cerium(IV) is formed in the system but the first step appears not to involve electron transfer from the aromatic ring. Nor can simple radical bromination explain the rate of formation of benzylic bromide.