Question

Alkenes and Alkynes are:
A) saturated aliphatic hydrocarbons
B) unsaturated aliphatic hydrocarbons
C) unsaturated aromatic hydrocarbons
D) cyclic hydrocarbons

Answer 1

Hint: Alkene contains a double bond between the adjacent carbon and alkynes contain the single bond between the adjacent carbons in their structure which means more hydrogen can be added in the alkene and alkynes to make it saturated.

Complete step by step answer:
The unsaturated hydrocarbons have a double or triple bond between the two adjacent carbon atoms.
If the unsaturated hydrocarbon consists of straight-chain and branched chains of carbons then it is termed as unsaturated aliphatic hydrocarbons.
An example of unsaturated aliphatic hydrocarbon is Alkene and Alkyne.
And if the unsaturated hydrocarbon is consisting of the aromatic compound then it is termed as unsaturated aromatic hydrocarbons
Let us see the general representation of alkynes is:
\[{C_n}{H_{2n - 2}}\]
Let us see the general representation of alkenes:
\[{C_n}{H_{2n}}\]

Therefore, we can conclude that the correct answer to this question is option B.

Additional information: -Alkene is also known as olefins since the first member ethylene was found to form an oily liquid on reaction with chlorine. As alkene has a double bond which consists of one sigma strong bond formed by the head on head overlapping of \[{\text{s}}{{\text{p}}^{\text{2}}}\] hybrid orbital and one weak pi bond formed by the sideways overlapping of two \[2{\text{p}}\] orbitals.
-The first stable member of the alkyne is acetylenes. Acetylene in the presence of oxygen gas is given an oxyacetylene flame. Two types of isomerism shown by alkynes are position isomerism and chain isomerism.

Note:
In these questions, we can get confused between an unsaturated aliphatic hydrocarbon and unsaturated aromatic hydrocarbon. But, we know that alkenes and alkynes do not contain any aromatic properties as the pi electrons do not undergo resonance.