The correct order of $\mathrm{p} K_a$ of the following is

$$ \underset{\mathrm{I}}{\mathrm{CCl}_3 \mathrm{COOH}} \quad \underset{\mathrm{II}}{\mathrm{CF}_3 \mathrm{COOH}} $$

$$ \underset{\text { III }}{\mathrm{NO}_2 \mathrm{CH}_2 \mathrm{COOH}} \underset{\text { IV }}{\mathrm{NCCH}_2 \mathrm{COOH}} $$

The major product of the following reactions

Which of the following set of compounds react with $\mathrm{NaHCO}_3$ ?

$n$ - propanol on treatment with concentrated HBr gives $P$. The product $P$ on reaction with KCN gave the product $Q$. The product $Q$ on heating with aqueous acidic solution, furnished the product $R$. The product ' $R$ ' is