Question

Identify the unsaturated compounds from the following $\left(\mathrm{i}\right)$ Propane $\left(\mathrm{ii}\right)$ Propene $\left(\mathrm{iii}\right)$ Propyne $\left(\mathrm{iv}\right)$ Chloropropane

• A. $\left(\mathrm{i}\right),\left(\mathrm{ii}\right)$
• B. $\left(\mathrm{ii}\right),\left(\mathrm{iv}\right)$
• C. $\left(\mathrm{iii}\right),\left(\mathrm{iv}\right)$
• D. $\left(\mathrm{ii}\right),\left(\mathrm{iii}\right)$

Answer 1

The correct option is D

$\left(\mathrm{ii}\right),\left(\mathrm{iii}\right)$

The explanation for the correct option:

Option D: $\left(\mathrm{ii}\right),\left(\mathrm{iii}\right)$

1. Organic substances made entirely of carbon and hydrogen atoms with a double or triple bond between two carbon atoms close to each other are known as unsaturated hydrocarbons.
2. Hydrocarbons with one double bond between two carbon atoms are known as alkenes.
3. Alkynes are hydrocarbons that have a triple bond between carbon and carbon.
4. Propene is an alkene having a double bond at the position$1$. Its chemical formula is ${\mathrm{CH}}_3\mathrm{CH}={\mathrm{CH}}_2$
5. Propyne is an alkyne having a triple bond at first carbon. Its chemical formula is ${\mathrm{CH}}_3\mathrm{C}\equiv \mathrm{CH}$
6. Hence it is the correct option.

The explanation for incorrect options:

Option A: $\left(\mathrm{i}\right),\left(\mathrm{ii}\right)$

1. Propane is a saturated three-carbon alkane. Its chemical formula is ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_3$
2. Propene is an unsaturated hydrocarbon because it contains a double bond between carbon atoms.
3. Hence, it is an incorrect option.

Option B: $\left(\mathrm{ii}\right),\left(\mathrm{iv}\right)$

1. Propene is an unsaturated hydrocarbon containing a carbon-carbon double bond.
2. Chloropropane is not an unsaturated hydrocarbon because it contains no unsaturations i.e no double or triple bonds and it has chlorine as its functional group.
3. Hence, it is an incorrect option.

Option C: $\left(\mathrm{iii}\right),\left(\mathrm{iv}\right)$

1. Propyne isn't a saturated hydrocarbon because it contains a carbon-carbon triple bond at first carbon.
2. Chloropropane is not an unsaturated hydrocarbon as it contains a halogen group i.e. chlorine.
3. Hence, it is an incorrect option.

Therefore, only $\left(\mathrm{ii}\right),\left(\mathrm{iii}\right)$ i.e. propene and propyne are unsaturated hydrocarbons.