This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Alcohols, Phenols and Ethers Classification”.
1. What is the general formula for an aliphatic alcohol? (R=alkyl group)
Explanation: Alcohols are compounds having OH group attached to an alkyl group and are hence hydroxy derivatives of hydrocarbons.
2. Which of the following is true regarding polyhydric alcohols?
a) It should have one or more OH groups
b) It should have two or more OH groups
c) It should have three or more OH groups
d) It should have more than four OH groups
Explanation: Alcohols may be classified as mono-, di- tri- or polyhydric depending on whether it has one, two, three or more OH groups in its structure. Di- and trihydric alcohols are also classified as polyhydric.
3. Which of the following types of alcohol contain a bond between sp2 hybridised carbon and OH group?
a) Primary allylic alcohols
b) Secondary allylic alcohols
c) Tertiary allylic alcohols
d) Vinylic alcohols
Explanation: Allylic alcohols are those in which OH group is attached to a sp3 hybridised carbon adjacent to a C-C double bond, i.e., an allylic carbon. Whereas, vinylic alcohols contain OH group attached directly to a C-C double bond.
4. Which of the following terms does not describe CH2=CH-CH2OH?
Explanation: The given compound contains a sp3 hybridised C-OH bond and is allylic. Ince it has only one alkyl group attached to the C bonded to the OH group, it is primary and the presence of only one OH group makes it monohydric.
5. Choose the most suitable classification for the shown compound?
a) Secondary alcohol
b) Allylic alcohol
c) Dihydric alcohol
d) Benzylic alcohol
Explanation: The compound shown is a monohydric, tertiary alcohol in which the OH group is attached to the C next to a C-C double bond, hence make it allylic.
6. Primary alcohols van be benzylic in nature.
Explanation: Benzylic alcohols contain a sp3 C-OH bond next to an aromatic ring, which means that the C atom can have zero or two alkyl groups attached to it along with the ring and OH group.
7. Which of the following is not a vinylic alcohol?
Explanation: Vinylic alcohols contain an OH group bonded to a sp2 hybridised carbon of a double bond. CH2=CH-CH2-OH is an allylic alcohol.
8. Which of the following compounds contain an aryl carbon?
b) Benzyl alcohol
c) Vinyl alcohol
Explanation: The sp2 hybridised carbon of an aromatic ring to which the hydroxyl group is attached is called an aryl carbon. In phenol, the OH group is attached to an aryl carbon.
9. R-O-R, where R represent an alkyl or aryl group is the general formula of which compound?
Explanation: Ethers are compounds where the hydrogen of a hydrocarbon is replaced by an alkoxy or aryloxy group. It may also be thought of as compounds formed when the hydrogen of the OH group of an alcohol is replaced by an alkyl or aryl group.
10. When the alkyl groups attached to either side of the oxygen atom of an ether id different, it is known as _______ ether.
Explanation: If the alkyl or aryl groups on either side of O atom is different, it is known as a mixed or unsymmetrical ether.
11. Identify the simple ether from the following.
Explanation: Since C6H5OC6H5 has the same aromatic ring on both sides of the oxygen atom, it a simple or symmetrical ether.
12. Which of the following is not an aromatic ether?
Explanation: Aromatic ethers are those in which at least one of the groups on either side of O atom is an aryl group. In CH3-O-CH2CH3, both the groups are alkyl and is hence an aliphatic ether.
13. Diethyl ether is a mixed ether.
Explanation: Diethyl ether consists of ethyl (C2H5) groups on either side of O, hence it is a simple symmetrical ether.
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