Question

Which of the following hydrocarbons are unsaturated? (This question has multiple correct answers)
A. ${{H}_{3}}C-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
B. ${{H}_{2}}C=C-C{{H}_{3}}$
C. ${{(C{{H}_{3}})}_{2}}-C=C{{H}_{2}}$
D. ${{(C{{H}_{3}})}_{3}}C-C{{H}_{3}}$

Answer 1

Hint: Remember that an unsaturated hydrocarbon is one which contains double or triple covalent bonds between some of its atoms. For instance, ethene ($C{{H}_{2}}=C{{H}_{2}}$) and but-2-yne (${{H}_{3}}C-C\equiv C-C{{H}_{3}}$) are examples of unsaturated hydrocarbons whereas propane (${{H}_{3}}C-C{{H}_{2}}-C{{H}_{3}}$) is a saturated hydrocarbon.

Step-by-step Solution:
Now that we know what exactly unsaturated and unsaturated hydrocarbons are, let us now go through all the options one at a time,
${{H}_{3}}C-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
The IUPAC name of this structure is butane. Since this structure contains no doubly or triply bonded atoms in its structure, therefore by definition this is a saturated hydrocarbon.
${{H}_{2}}C=C-C{{H}_{3}}$
The IUPAC name of this structure is propene. Since this structure contains one double bond in its structure, therefore by definition this is an unsaturated hydrocarbon.
${{(C{{H}_{3}})}_{2}}-C=C{{H}_{2}}$
The IUPAC name of this structure is 2-dimethylethene. Since this structure contains one double bond in its structure, therefore by definition this is an unsaturated hydrocarbon.
${{(C{{H}_{3}})}_{3}}C-C{{H}_{3}}$
The IUPAC name of this structure is 2,2-dimethylpropane (more commonly known as neopentane). Since this structure contains no double or triple bonds in its structure, therefore by definition this is a saturated hydrocarbon.
Therefore, by this analysis of ours, we can conclude that the answers to this question are options b) and c).

Note: Please remember that it is important to know the properties of hydrocarbons to be able to answer this question properly. Also please note that this question has multiple correct answers and you have to read both the questions and options thoroughly before coming to a conclusion.