Question

Hi! Can someone summarize what the reaction article is saying? I am having trouble understanding it.

The purpose of this experiment was to investigate the catalytic performance of solid acid catalyst developed from modification of coal combustion fly ash to synthesize methyl 4-aminobenzoate (MAB) by Fischer esterification between 4-aminobenzoic acid and methanol. Upon acid modification of fly ash, surface acidity of solid acid catalyst (SAC) is greatly enhanced as a result of increased surface area, augmented silica content, and fabricated phosphates. The proposed mechanism, similar to our lab, demonstrates that the surface acid sites of solid acid catalyst (SAC) initiate the reaction by donating proton to 4-aminobenzoic acid, resulting in the formation of carbocation, which is then attacked by the electron-rich oxygen atom of methanol. Subsequent loss of water and deprotonation resulted in the formation of the desired product, MAB. Recyclability study reveals that the solid acid catalyst (SAC) retains similar catalytic activity till the fifth reaction cycle furnishing the yield of methyl 4-aminobenzoate in the range 82–98% This unveils that the acidity remains unaffected during regeneration of the catalyst. This eco-friendly, highly efficient, and low-cost solid acid catalyst system may be used as a replacement of harmful traditional liquid acids for important reactions in pharmaceutical industries to synthesize indispensable drugs.

Answer 1

first of all we will understand the solidacid catalyst ,these are heterogeneous catalyst i.e they are not soluble in the reaction they are insoluble in the reaction medium it function as Lewis acids including silico-aluminates (zeolites, alumina, silico-alumino-phosphate), and sulfated zirconia. Many transition metal oxides are acidic, including titania, zirconia, and niobia.

above mentioned explanation is tells taht it is a esterification reaction,generally esterification is done in presnce of acid like H2SO4 dehydrating agent s nad the acid which is used is not recovered ,

in above mention reactin between 4-aminobenzoic acid and methanol solid acid catalyst in this process the solid acid catalyst donates proton and forms carbocation ,the lone pai of electron in O of methanol attcks to the carbocation and forrms estes and catalyst is generated once again as the solid catalyst is solid it is then filterd and used for esterification once agin and the efficiency of catalyst remains as such and can be used for 5 times with same yields