Question

How will you convert propan-1-ol to 2-bromopropane?

Answer 1

To convert propan-1-ol to 2-bromopropane, you must first dehydrate propan-1-ol with concentrated sulfuric acid (H₂SO₄) and heat to form propene (CH₃CH = CH₂). Then, treat the propene with hydrogen bromide (HBr), which will add across the double bond via Markovnikov’s rule to yield 2-bromopropane (CH₃CHBrCH₃).

1. Dehydration of Propan-1-ol to Propene: Propan-1-ol (CH₃ – CH₂CH₂OH) is heated with concentrated H₂SO₄. It undergoes dehydration, giving propene (CH₃ – CH = CH₂).
   \[\ce{\underset{propan-1-ol}{CH3 - CH2 - CH2OH} + HBr ->[conc. H2SO4][Heat] \underset{propene}{CH3 - CH = CH2} + H2O}\]
2. Addition of Hydrogen Bromide to Propene: Propene is treated with HBr in the presence of organic peroxide. Due to the peroxide effect (anti-Markovnikov’s rule), Br attaches to the terminal carbon.
   \[\ce{\underset{prop-1-ene}{CH3 - CH = CH2} + HBr ->[peroxide][] \underset{2-bromopropane}{CH3 - CHBr - CH3}}\]