THE REACTION-MECHANISM OF ALKYL-HALIDES WITH CARBON-DIOXIDE CATALYZEDBY 5,10,15,20-TETRAPHENYL PORPHYRIN COBALT (COTPP)

Benzyl chloride and butyl halide each react with CO2 catalyzed by 5,10 ,15,20-tetraphenylporphyrin cobalt (CoTPP) to form phenylacetic acid ( in the form of benzyl phenylacetate, the product of electrocarboxylati on) or oxalic acid (the direct reduction product of CO2, in the form o f dibutyl oxalate), respectively. The data show that electrocarboxylat ion of benzyl chloride reacting with CO2 can occur, but butyl halide i n the presence of CO2 cannot produce the electrocarboxylation product amylic acid. The reasons for the different mechanisms are examined thr ough the reaction of alkyl halide with CoTPP studied by electrochemist ry and spectroelectrochemistry. The intermediate N-alkyl CoTPP is dete cted by spectroelectrochemistry in situ. The reasons that they form di fferent products with different N-alkyl CoTPP are discussed in detail.