Synthesis Of P-tert-butylbenzoic Acid

p-tert-Butylbenzoic acid (PTBA) is a colourless crystal and an important organic intermediate, which can be used for the preparition of fine chemicals, cosmetics, compound essence, resin additives, cutting oil, annexing agent, anticorrosive additives, polyethylene stabilization additive, etc. Nowadays, it is widely used as commericall product in developed countries. Howerer, there has no pratical process in our country. So it is important to develop a process of practical value for the preparation of PTBA.Up to now, PTBA is generally synthesized from p-tert-butyltoluene via oxidation, including solvent-free method, HNO3 oxidation, liquid-phase catalytic oxidation, KMnO4 oxidation, microwave promoted oxidation, high-temperature gas phase oxidation, etc.A novel method to prepare PTBA from tert-butylbenzene was developed in this work via Friedel-Crafts acylation and haloform reaction. Some reaction conditions such as reaction temperature, reaction time, catalyst loading were investigated to result in some conclusions as follows:(1) The optimal reaction conditions for the preparation of 1-(4-tert-butylphenyl)-2-chloroethanone:1.5 g aluminum chloride was dissovled in 50 mL tert-butylbenzene, and 21 mL 2-chloroacetyl chloride was added at 80℃in 50 min, then the mixture was stirred at 100℃for 8 h to afford the intermediate in high yields up to 85.6%.(2) The optimal reaction conditions for the preparation of PTBA:A mixture of 80 mL sodium hypochlorite solution (5.5%) and 15 mL benzalkonium bromide was heated to 50℃and 10 g 1-(4-tert-butylphenyl)-2-chloroethanone was added then stirred at 90℃for 8 h. PTBA was abtained in high yields up to 90.4%.(3) PTBA was abtained in a total yield of 75% from tert-butylbenzene after purification.The innovation of this article is the appliction of acylation and haloform reaction to prepare PTBA. Benzalkonium bromide was used as phase-transfer catalyst in the haloform reaction and chloroacetyl chloride was used as acylating reagent in this process. The reaction coniditions were optimized to forward a experimental basis for further industrial pratice.