Answer: The correct answer is Option 2.
Explanation:
Hydrocarbons are defined as the compounds which have a covalent bond present between hydrogen and carbon atoms. For Example: [tex]CH_4[/tex] is a hydrocarbon. [tex]H_2O,CO_2[/tex] are not considered as hydrocarbons.
For the given options:
Option 1: butanal
The chemical formula for this compound is [tex]CH_3CH_2CH_2CHO[/tex]
This is not considered as a hydrocarbon because a covalent bond is present between carbon and oxygen atom.
Option 2: butyne
The chemical formula for this compound is [tex]CH\equiv CCH_2CH_3[/tex]
This is considered as a hydrocarbon because covalent bonds are present between carbon and hydrogen atoms only.
Option 3: 2-butanol
The chemical formula for this compound is [tex]CH_3CH(OH)-CH_2CH_3[/tex]
This is not considered as a hydrocarbon because a covalent bond is present between carbon and oxygen atom.
Option 4: 2-butanone
The chemical formula for this compound is [tex]CH_3C(O)-CH_2CH_3[/tex]
This is not considered as a hydrocarbon because a covalent bond is present between carbon and oxygen atom.
From the above information, the correct answer is Option 2.