The chapter ‘Ethers’ is a very important part of Chemistry in the syllabus of UPSEE 2018. About 1-2 questions have always been asked from this chapter in the examination. The levels of the questions asked in this examination are bit low as compared to JEE Main.
Students can study the following topics here:
1. Preparation of Ethers
- By dehydration of alcohols
- Williamson synthesis
2. Physical properties of Ether
About the notes:
1. These notes are prepared by Subject Experts of Chemistry.
2. It will provide you the complete overview of the chapter “Ethers”.
3. Some solved questions are also included here to explain the concept in an easier manner.
4. It contains the crux of the chapter “Ethers”.
5. Students can use these notes to save their precious before the examination.
6. The mechanism of each name reaction is explained in an easiest possible way.
UPSEE/UPTU Chemistry Syllabus: 2017 - 2018
Important Concepts:
Ethers are organic compounds in which an oxygen atom is bonded to two alkyl groups or aryl groups. Therefore, ethers can be represented as R – O – R’ where R and R' may be alkyl or aryl groups.
When the two substituent groups (R and R’) are identical, then the ether is called a symmetrical ether, otherwise if these two groups are different, then the ether is known as an unsymmetrical ether.
Preparation of Ether:
- By dehydration of alcohols
- Williamson synthesis
By dehydration of alcohols
- On dehydration of alcohols in the presence of protic acid H2SO4. H3PO4 alkene or ether is formed depending on the reaction conditions
Williamson synthesis
- This is used for the synthesis of ether.
- Alkyl halide reacts with sodium alkoxide to produce ether.
- The reaction involves SN2 mechanism.
- Primary alkyl halide gives best result.
- In case of tertiary halides elimination competes over substitution and no ether is formed
Physical Properties of ether:
- Ethers are more water-soluble than alkanes, because water molecules have H-bond with them.
- The boiling point of ether are high comparable to the alkanes.
Some important solved questions are given below:
Question 1:
Which of the following alkyl halides is least reactive in the Williamson synthesis of ether?
(a) CH3CH2CH2Br
(b) CH3CH2CH2Cl
(c) (CH3)3CCH2Br
(d) CH2= CH - CH2Cl
Solution 1:
(CH3)3CCH2Br is less reactive in the Williamson synthesis of ether.
Hence, the correct option is (c).
Question 2:
Hydrogen bonding is maximum in
(a) Ethanol
(b) Diethyl ether
(c) Ethyl chloride
(d) Ethyl amine
Solution 2:
Ethers and halides do not form H-bonding whereas oxygen being more electronegative forms excessive H-bonding
Hence, the correct option is (a).
Question 3:
The acidic hydrolysis of ether (X) shown below is fastest when
(a) One phenyl group is replaced by a methyl group
(b) One phenyl group is replaced by a para - methoxylphenyl group
(c) Two phenyl groups are replaced by two para - methoxylphenyl groups
(d) No structural change is made to X
Solution 3:
The more stable is carbocation formed during SN1 reaction faster is the reaction.
Para - methoxylphenyl group is electron donating which stablises the carbocation.
Hence, the correct option is (c).
Conclusion:
These notes will help you to grasp all the important concepts related to chapter Ethers. With the help of solved questions given here aspirants can get easily familiar with the difficulty level of the question paper. It will also help you to score full marks in the questions asked from this chapter.
Mathematics all chapters complete notes for UPSEE/UPTU 2018
Physics all chapters complete notes for UPSEE/UPTU 2018
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