At which value of $n$ does the formation of a six-membered ring take place in the following reaction?
$Br-(CH_2)_n-CH_2-Br + CH_2(CO_2Et)_2 \xrightarrow{NaOEt, EtOH} \text{cyclic product}$

The products $A$ and $B$ in the following reaction sequence are:

Which of the following compounds will undergo decarboxylation on heating?

Draw the structures of the following compounds:
$(i)$ $3-$Methylbutanal
$(ii)$ $p-$Nitropropiophenone
$(iii)$ $p-$Methylbenzaldehyde
$(iv)$ $4-$Methylpent$-3-$en$-2-$one
$(v)$ $4-$Chloropentan$-2-$one
$(vi)$ $3-$Bromo$-4-$phenylpentanoic acid
$(vii)$ $p, p^{\prime}-$Dihydroxybenzophenone
$(viii)$ Hex$-2-$en$-4-$ynoic acid

Product $(X)$ is

$CH_3-CH_2-CH=O$ $\xrightarrow[(2) H^{+}]{(1) \text{Tollen's reagent}} X$ $\xrightarrow[(2) \text{dry distillation}]{(1) Ca(OH)_2} Y$; $Y$ is