Question

How to get formic acid from acetic acid?

Answer 1

Formic acid is the methanoic acid i.e. first carboxylic acid having chemical formula HCOOH whereas, acetic acid is the ethanoic acid i.e. second and most important carboxylic acid with chemical formula $C{{H}_{3}}COOH$ . There are many steps to eliminate methyl groups from acetic acid to form formic acid.

Complete step-by-step answer: Let us learn about the steps involved in the conversion of acetic acid to formic acid;
In short, we can describe the needed point as $HCOOH\Rightarrow C{{H}_{3}}COOH$ . Thus, we have;
Reaction of acetic acid with $Na{{N}_{3}}$ giving methylamine which further reacts with $HN{{O}_{2}}$ to give methanol. Further methanol is oxidised to give formic acid by ${{K}_{2}}C{{r}_{2}}{{O}_{7}}+{{H}^{+}}$ .
Reaction of acetic acid with soda lime giving methane which then reacts with chlorine in presence of sunlight to give chloromethane. This then reacts with KOH to give methanol which on oxidation gives formic acid.
From the above two methods we can see that we just need a way to chop out the methyl group present in acetic acid which is simple. Thus, considering first statement and mechanism;
Step I-
$C{{H}_{3}}COOH+Na{{N}_{3}}\to C{{H}_{3}}N{{H}_{2}}+{{N}_{2}}+C{{O}_{2}}$ ; this is Schmidt reaction.
Step II-
$C{{H}_{3}}N{{H}_{2}}+HN{{O}_{2}}\to C{{H}_{3}}OH$
Step III-
$C{{H}_{3}}OH+{{K}_{2}}C{{r}_{2}}{{O}_{7}}+{{H}^{+}}\to HCOOH$

Note: For the conversion of acetic acid to formic acid there are many reactions i.e. many ways for this process. But when it comes for the industrial application, we need to find the most suitable and cheaper method to be applied with higher amounts of product.