Question

How will you prepare bromopropane from butanoic acid?

Answer 1

Bromopropane (C₃H₇Br) can be prepared from butanoic acid (C₄H₈O₂) using a two-step process:

1. Decarboxylation of Butanoic Acid to Propane: Butanoic acid is heated with soda lime (a mixture of NaOH and CaO) to remove the carboxyl group (-COOH) as carbon dioxide. This produces propane (C₃H₈) as the main product and sodium carbonate (Na₂CO₃) as a by-product.
   \[\ce{\underset{Butanoic acid}{C3H7 - COOH} + \underset{Sodium hydroxide}{NaOH} →[Δ, CaO][] \underset{Propane}{C3H8} + \underset{Sodium carbonate}{Na2CO3}}\]
2. Bromination of Propane to Form Bromopropane: Propane is then treated with bromine (Br₂) in the presence of UV light, which initiates a free radical substitution reaction. In this reaction, one hydrogen atom of propane is replaced by a bromine atom, forming bromopropane (C₃H₇Br) and hydrogen bromide (HBr) as a by-product.
   \[\ce{\underset{Propane}{C3H8} + \underset{Bromine}{Br2} →[UV light][] \underset{Bromopropane}{C3H7Br} + \underset{Hydrogen bromide}{HBr}}\]