Benzamide on reaction with $POCl_3$ gives

Acetamide is

Explain hydrogen bonding in carboxylic acids and its effect on their boiling points.

Toluene on reaction with the reagent $X$ gives $Y$,which dissolves in $NaHCO_3$ and when reacted with $Br_2 / Fe$ gives $Z$. What are $X$ and $Z$?

Which one of the following is not an intermediate in the generally accepted mechanism for the reaction shown below?
$CF_3C(O)OH + CH_3CH(OH)CH_3 \xrightarrow{H_2SO_4} CF_3C(O)OCH(CH_3)_2 + H_2O$

Which of the following carboxylic acids is difficult to decarboxylate?