Which of the following compounds is oxidised to prepare methyl ethyl ketone?

Which of the following alcohols shows the fastest reaction with $HI$?

What is obtained by the oxidation of ethyl alcohol with $K_2Cr_2O_7$?

The major product of the following reaction is: $CH_3CH(OH)CH_3 \xrightarrow{Cu, 573 \ K} ?$

$A$ on heating isomerizes to $B$. What is the structure of $B$?

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