Question

Propyne is formed by heating 1,2-dibromopropane with :

• A. $C_2{H}_{5}ONa$
• B. Alc. KOH and sodamide
• C. Aqueous $KMn{O}_4$
• D. dil. $H_{2}S{O}_4$ and then $KMn{O}_4/H^{+}$

Answer 1

The correct option is B Alc. KOH and sodamide

1,2-dibromo propane is a vicinal halide since bomine attached to adjacent carbon atoms. Vicinal dihalides on treatment with alcoholic KOH undergo dehydrohalogenation to form alkenyl halide which on treatment with sodamide gives alkyne.

1,2-dibromo propane undergoes dehydrohalogenation to give 2-bromoprop-1-ene which on on further tratment with $NaN{H}_2$ gives prop-1-yne.