Reduction of the lactol $S$ with sodium borohydride $(NaBH_4)$ gives:

An organic compound $A$ on reaction with $PCC$ $(\text{Pyridinium chlorochromate})$ gives a compound $B$. $B$ on further reaction with $I_2$ and $NaOH$ forms tri-iodomethane. Identify the compound $A$.

Consider the reaction:
$RCHO + NH_2NH_2 \rightarrow RCH=NNH_2 + H_2O$
What sort of reaction is it?

In the following reaction,
$CH_3-C \equiv CH$ $\xrightarrow[H_3O^+]{Hg^{2+}} X$ $\xrightarrow[PhCHO]{dil. NaOH} Y$
$X$ and $Y$,respectively,are

The products formed in the following reaction,$A$ and $B$ are

Identify the organic compound which,on heating with a strong solution of $NaOH$,is partly converted into an acid salt and partly into an alcohol.