equation of when we change ethanoic …

Following steps / reactions would convert ethanoic acid to  methanoic acid .

1.Reaction  of ethanoic acid with  NH₃  to form  ethanamide ,   C H3 CO  NH₂

CH₃ COOH ---------------NH₃ +  H₂ O----------> CH₃ COONH₄ ---- {tex}\Delta{/tex}---------->  CH₃ CO NH₂   

or, CH₃ COOH    +    NH₃ ----------Al₂O₃ /{tex}\Delta{/tex}-----> CH₃ CO NH₂ 

2.  Treat  ethanamide  with ( alcoholic KOH  +   Br₂ ) to get methanamine CH₃ NH₂  .....(  ie.Hoffmann's Bromamide reaction )

CH₃ CO NH₂  ------  KOH _{(alcoholic)  +}  Br₂   ------------->   CH₃ NH₂     +  K₂ CO₃   +   H₂ O 

3.  Reduction   of  CH₃ NH₂   with  HNO₂  to get methanol  .  

CH₃ NH₂ -------------[H] /  HNO_{2----------->}   CH₃OH   +  N₂    +    H₂ O

4. Oxidation of methanol with ( K₂ Cr₂ O₇ +  dil.  H₂ S O₄) yields  methanoic acid.

CH₃ OH  -------[2 O ] /  ( K ₂ Cr ₂ O₇  +  dil. H ₂SO₄ ) -------- HCOOH