$n$ - 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

The reagent that can reduce the carboxylic acid group to the corresponding alcohol is

$$ \text { Predict } A \text { and } B \text { in the following reaction sequence : } $$

$$ \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{COOH} $$

$$ \xrightarrow[\text { Red phosphorus }]{\mathrm{Br}_2} A \xrightarrow{\mathrm{KOH} \text { (alc.) }} B$$

$$ \text { The major product in the following reaction is } $$