How to convert propyne to butanoic acid?

Question

How to convert propyne to butanoic acid?

Answer 1

Hello Israel

Propyne is a 3-carbon chain alkyne with a structural formula of CH3CCH. (There is triple bond between C and CH, which I am unable to indicate here because Wyzant has removed the ability to add some functional fonts and symbols in their text editor, which all tutors use!!)

Butanoic acid is a 4-carbon carboxylic acid with a structural formula of CH3CH2CH2COOH.

Listed below are a sequence of reactions that can be used to convert propyne to butanoic acid.

1) React propyne with sodium amide (NaNH2) to form an acetylide ion.

CH3CCH + NaNH2 --> CH3CC^-

2) React the acetylide ion with formaldehyde (HCHO) followed by adding dilute aqueous acid (H+). This reaction adds one carbon to the 3-carbon propyne chain to give a 4-carbon alkynol (compound containing both an alkyne and a primary alcohol functional group).

CH3CC^- + HCHO --> CH3CC-CH2O^- + H^+ --> CH3CC-CH2OH

3) Reduce the C-C triple bond to C-C single bond with excess H2 and platinum (Pt) catalyst. This will form butan-1-ol (a primary alcohol).

CH3CC-CH2OH + excess H2, Pt catalyst --> CH3CH2CH2CH2OH

4) Oxidize the primary alcohol with KMnO4, KOH and heat to form a carboxylate salt intermediate followed by acidifying with HCl to give butanoic acid.

CH3CH2CH2CH2OH + KMnO4 + KOH + heat --> CH3CH2CH2COO^- K^+ + HCl --> CH3CH2CH2COOH