Question

How do we make propanoic acid from ethyl chloride?

Answer 1

Make the Grignard, and drop it onto dry ice.

Explanation:

You want to extend the carbon-chain by one carbon. A Grignard plus dry ice is the obvious (and most facile) standby....

`i.` `H_3C-CH_2Br+Mgstackrel("dry ether")rarrH_3C-CH_2MgBr`

`ii.` `Et-MgBr + CO_2(s) rarr Et-CO_2^(-)""^(+)MgBr`

`iii.` `EtCO_2^(-)""^(+)MgBrstackrel(H_3O^+)rarrunderbrace(EtCO_2H)_"propanoic acid" + MgBrOH`