250+ TOP MCQs on Classification of Organic Compounds and Answers

Chemistry Multiple Choice Questions on “Classification of Organic Compounds”.

1. What is the other name for acyclic compounds?
a) Aliphatic
b) Aromatic
c) Heterocyclic
d) Alicyclic
Answer: a
Clarification: Acyclic or open chain compounds are also called as aliphatic compounds as they consist of straight or branched chain compounds. Aromatic, heterocyclic and alicyclic compounds are closed chain or ring compounds.

2. The successive members of a homologous series differ by an unit of which of the following?
a) –CH₃
b) CH₃CH₃
c) –CH₂
d) –CH₂CH₃
Answer: c
Clarification: The successive members of a homologous series differ by a CH₂ unit. Taking, methanol (CH₃OH), ethanol (CH₃CH₂OH), and propanol (CH₃CH₂CH₂OH) as examples. From this, we clearly understand that as the series progresses, the difference between each successive member is a CH₂ unit.

3. Tropolone is a benzenoid compound.
a) True
b) False
Answer: b
Clarification: Tropolone is a non-benzenoid compound. It does not have a benzene ring and hence, not a benzenoid compound. Benzenoid compounds are the compounds that include benzene rings. For example: Benzene, Aniline, Naphthalene, etc.

4. Which of these is not an aliphatic compound?
a) Acetic acid
b) Acetaldehyde
c) Ethane
d) Tetrahydrofuran
Answer: d
Clarification: Tetrahydrofuran is a closed chain or a ring compound. Acetic acid, acetaldehyde, and ethane are open chain compounds, thereby, making them aliphatic compounds. Tetrahydrofuran is an organic compound with the formula (CH₂)₄O.

5. Pick out the option that is not a functional group from the following.
a) Hydroxyl group
b) Benzene group
c) Aldehyde group
d) Carboxylic acid group
Answer: b
Clarification: Benzene group is not a functional group. Functional groups can be defined as an atom or group of atoms joined in a specified manner which is responsible for the characteristic chemical properties of the organic compound. Hydroxyl group (-OH), aldehyde group (-CHO), and carboxylic acid group (-COOH), all cause changes in chemical properties when attached to the hydrocarbon chains.