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

In the following reaction sequence, the amount of $D$ (in $g$) formed from $10$ moles of acetophenone is. . . . . . (Atomic weights in $g \ mol^{-1}: H = 1, C = 12, N = 14, O = 16, Br = 80$. The yield (%) corresponding to the product in each step is given in the parenthesis)

Identify the major product obtained in the following reaction:

The product$(s)$ formed when $m$-chlorobenzaldehyde is heated with concentrated $NaOH$ is/are:

Benzaldehyde can be converted to benzonitrile by treatment with

An organic compound $X$ is oxidised by using acidified $K_2Cr_2O_7$ solution. The product obtained reacts with phenyl hydrazine but does not give the silver mirror test. The compound $X$ is,