Question

The alternative path for radical chain reactions of $B{r}_2$ with ethane may be represented as follows:
1) $C{H}_3-C{H}_3+B{r}_2\to C{H}_3-C{H}_2-Br+HBr$
2) $C{H}_3-C{H}_3+B{r}_2\to 2C{H}_{3}Br$

• A. Reaction (1) is more likely because it is more exothermic
• B. Reaction (1) is more likely because it is more endothermic
• C. Reaction (2) is more likely because it is more exothermic
• D. Reaction (2) is more likely because it is more endothermic

Answer 1

The correct option is A Reaction (1) is more likely because it is more exothermic

Reaction (1) is more likely because it is more exothermic and thermodynamically more favoured. The product of first reaction, ethyl bromide is further brominated till all $H$ atoms are replaced with $Br$ atoms to form hexa bromo ethane $C_{2}B{r}_6$.