1.

a. Prepare the following ethers via Willamson's syntesis. I. Di-n- propyl ether (A0) II. Benzyl methyl ether (B) III. Phenylethyl ehter (C) IV. t- Butyl ethyl ether (D) b. Which compound in the above problem, can be prepared by alternative Williamson's reaction? c. Explain teh inabiliity of (A),(C), (D) in the above problem to be preaparedvia alternate Williamson's syntesis. d. Give six typesof ethers that cannot be syntesised by the typicalwilliamson's synthesis. e. Rank the following alkyl halides in the decreasing order of reactivity in Willamson's reaction. (CH_(3))C - CH_(2) Br (A), ClCH_(2) CH + CH_(2) (B), ClCH_(2) CH_(2) (C), Br CH_(2) CH_(2) CH_(3)(D)

Answer»

Solution :a.
I. `n-PrOH overset(Na)(rarr) n-PrO overset(n-PrBr)(rarr)PROPR (A)`
IIgt `MeOH overset(Na)(rarr) MeO overset(PhCH_(2)Br)(rarr)PhCH_(2) OMe (B)`
III. `PHOH overset(NAOH)(rarr) PhO overset(ErBr)(rarr) PhOEt (C)`
IV. `t- BuOH overset(Na)(rarr) t-BuOoverset(EtBr)(rarr) t-Bu - OEt (D)`
b. Only (B): `PhCH_(2) OH overset(Na)(rarr) PhCH_(2)O`
`overset(MeBr)(rarr) Ph-CH_(2)OMe (B)`
c. I.`(A)` is a simple ether.
III. Aryl halides do not undergo nuclephilicdisplacement`(SN)` reaction.
III. `ErO` is a strong base as well as a nucleophile and dehydohalogenates `t-` butylchloride in completing `E2` reaction, givingalkeneand littleor no ether.
d. i. `R_(2) CH - O - CHR_(2)`, both `C` atoms are `2^(@)`.
ii. `R_(2)CH - O - CR_(3)`, one `C` is `2^(@)` and one is `3^(@)`.
iii. `R_(3)C - O - CR_(3)`, both `C` atoms are `3^(@)`.
iv. `Ar-O-Ar`, both diarly ethers.
v. `R-CH=CH-O-CH=CH-R'`: vinyl halides do not undergo `SN` reaction
vi. `R - underset(R) underset(||)overset(R) overset(|)(C) - CH_(2) - O - CH_(2) - underset(R') underset(|)overset(R')overset(|)(C) - R'`
e. `(B) gt (D) gt (C) gt (A)`. Alliylic gt bromidic gt chloride gt neopentyl (too hindered).


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