# Which of the following hydrocarbons undergo addition reaction: C_2H_6, C_3H_8, C_3H_6, C_2H_2 and CH_4?

Apr 9, 2016

${\text{C"_3"H}}_{6}$ and ${\text{C"_2"H}}_{2}$ undergo addition reactions.

#### Explanation:

Unsaturated compounds having one or more carbon-carbon double bonds or triple bonds or both type of bonds undergo addition reactions .

For open chain hydrocarbons, the general molecular formula of a saturated compound (alkane category) is ${C}_{n} {H}_{2 n + 2}$.

The general molecular formula of an aliphatic hydrocarbon with one double bond is ${C}_{n} {H}_{2 n}$, and the general molecular formula of a hydrocarbon having one triple bond or two double bonds is ${C}_{n} {H}_{2 n - 2}$.

Matching with these formulas, we can decide whether the the compound is unsaturated or not.

Here, ${C}_{3} {H}_{8} = {C}_{3} {H}_{2 \times 3 + 2}$, ${C}_{2} {H}_{6} = {C}_{2} {H}_{2 \times 2 + 2}$, and $C {H}_{4} = C {H}_{2 \times 1 + 2}$.

All three follow the general formula of a saturated compound, i.e.$C n {H}_{2 n + 2}$, so they will not undergo addition reaction

${C}_{3} {H}_{6} = {C}_{3} {H}_{2 \times 3}$ follows the general formula ${C}_{n} {H}_{2 n}$,
and ${C}_{2} {H}_{2} = {C}_{2} {H}_{2 \times 2 - 2}$ follows the general formula ${C}_{n} {H}_{2 n - 2}$, so they are unsaturated and undergo addition reactions.