The formation of diethyl ether from ethanol is based on:

$Ethanol \xrightarrow{H_2SO_4, 413 K} \text{diethyl ether}$. The above reaction is which type?

What is produced when glycerol is heated with oxalic acid at $110\,^{\circ}C$?

Find the major product for the following reaction.

Consider the following alcohols. The order of decreasing reactivities of these alcohols towards substitution with $HBr$ is:
$(I)$ $C_6H_5CH_2OH$
$(II)$ $p-NO_2-C_6H_4CH_2OH$
$(III)$ $p-CH_3O-C_6H_4CH_2OH$
$(IV)$ $p-Br-C_6H_4CH_2OH$

Identify the product formed when vapours of $2-$methylpropan$-2-$ol are passed over hot copper.