Question

What is the mechanism for a fischer esterification reaction between acetic acid and ethyl alcohol catalyzed by acid?

Answer 1

This is essentially a nucleophilic substitution in which the ethanol adds as the nucleophile, and the acid acts as the electrophile.....

Explanation:

The leaving group is water (i.e. the carboxyl hydroxide that is protonated off as water...)

`"H"_3"CCO"_2"H" + "HOCH"_2"CH"_3 stackrel("H"^+)rarr"H"_3"CCO"_2"CH"_2"CH"_3 + "H"_2"O"`

And this will be explained in much greater detail, and with much greater nuance in you organic text. Get to it!

If you had a less common acid (i.e. one that was expensive or one that you synthesized), you might make the acid halide, by treating the acid with thionyl chloride. Subsequent treatment with alcohol in the presence of a non-nucleophilic base (e.g `NEt_3` or `"DBU"`) delivers the ester......i.e.

`RCO_2H + SOCl_2 stackrel(Et_3N)rarr RCO_2Cl + Et_3N*HCl`

`RCO_2Cl + HOR' +DBU rarrRCO_2R' + DBU*HCl`