Which one of the following compounds is resistant to nucleophilic attack by hydroxyl $(OH^{-})$ ions?

Consider the following reaction: $CH_3-C(CH_3)_2-O-CH_3 \xrightarrow{HI (1 \text{ mole})} \text{Products}$. The main products of the reaction will be:

Ethers are prepared from alcohols by Williamson synthesis. Heating ethanol with sulfuric acid at $413 \ K$ gives ethoxyethane. Match the ether compounds in Column-$I$ with the products formed upon heating with $HI$ in Column-$II$.

Column-$I$ (Ether)	Column-$II$ (Product)
$(A)$ $CH_3CH_2-CH(CH_3)-CH_2-OCH_2CH_3$	$(i)$ $CH_3OH + CH_3-C(CH_3)_2-I$
$(B)$ $CH_3CH_2CH_2-O-C(CH_3)_2CH_2CH_3$	(ii) $C_6H_5OH + C_6H_5CH_2I$
$(C)$ $C_6H_5CH_2-O-C_6H_5$	(iii) $CH_3CH_2CH_2OH + CH_3CH_2-C(CH_3)_2-I$
$(D)$ $CH_3-C(CH_3)_2-O-CH_3$	(iv) $CH_3CH_2-CH(CH_3)-CH_2OH + CH_3CH_2I$

The major products formed in the reaction of $t$-butyl methyl ether with $HI$ are

Write a note on Williamson's ether synthesis.

What is the product formed when acetic anhydride reacts with diethyl ether in the presence of anhydrous $AlCl_3$?