Question

The first member of alkene series is

• A. $\left({CH}_4\right)$
• B. $\left(C_2{H}_4\right)$
• C. $\left(C_2{H}_2\right)$
• D. $\left(C_3{H}_6\right)$

Answer 1

The correct option is B

$\left({\mathrm{C}}_2{\mathrm{H}}_4\right)$

Step 1: Introduction

The organic compounds consisting of Carbon $\left(\mathrm{C}\right)$ and Hydrogen $\left(\mathrm{H}\right)$ atoms are known as hydrocarbons.

The compounds containing Carbon atoms have multiple bonds between two Carbon-Carbon atoms are called unsaturated hydrocarbons.

The multiple bonds are either double or triple bonds.

They are of two types depending upon the kind of bonds formed between Carbon-Carbon atoms:

Saturated hydrocarbons

Unsaturated hydrocarbons

Step 2: The explanation for the correct option:

Alkenes and alkynes contain double and triple bonds between Carbon-Carbon atoms. So these are known as unsaturated hydrocarbons.

The general formula of alkenes is $\left({\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}\right)$.

The first member of the alkene series is Ethene $\left({\mathrm{C}}_2{\mathrm{H}}_4\right)$.

The explanation for the incorrect option:

Methane $\left({\mathrm{CH}}_4\right)$ is a saturated hydrocarbon. It follows the general formula of alkanes.

Propene $\left({\mathrm{C}}_3{\mathrm{H}}_6\right)$ is an unsaturated hydrocarbon. It follows the general formula of alkenes but it is not the first member of alkene series.

Ethyne $\left({\mathrm{C}}_2{\mathrm{H}}_2\right)$ is an unsaturated hydrocarbon. It follows the general formula of alkynes.

Final answer:

Hence, option (B) is the correct option.