In the given reaction sequence,$Z$ is a mixture of alcohol and acid. The reaction for the conversion of $Y$ to $Z$ is:
$CH_3CH_2OH$ $\xrightarrow[443 \ K]{\text{Conc. } H_2SO_4} X$ $\xrightarrow[(2) \ Zn/H_2O]{(1) \ O_3} Y$ $\xrightarrow[(ii) \ H^+]{(i) \ \text{Conc. } NaOH} Z$

$A$ carbonyl compound $P$,which gives a positive iodoform test,undergoes reaction with $MeMgBr$ followed by dehydration to give an olefin $Q$. Ozonolysis of $Q$ leads to a dicarbonyl compound $R$,which undergoes intramolecular aldol reaction to give predominantly $S$.
$P$ $\xrightarrow[\substack{2. H^{+}, H_2 O \\ 3. H_2 SO_4, \Delta}]{1. MeMgBr} Q$ $\xrightarrow[2. Zn, H_2 O]{1. O_3} R$ $\xrightarrow[2. \Delta]{1. OH^{-}} S$
$1.$ The structure of the carbonyl compound $P$ is
$2.$ The structures of the products $Q$ and $R$,respectively,are
$3.$ The structure of the product $S$ is
Give the answer for questions $1, 2$ and $3.$

The reaction shown below is:
$CH_3CH_2COCH_2CH_3 \xrightarrow{Zn-Hg/HCl} CH_3CH_2CH_2CH_2CH_3$

Compound $A$ $(C_3H_6O)$ undergoes the following reactions to form $B$ and $C$. Identify $A, B$ and $C$.

Arrange the following compounds in order of decreasing reactivity for nucleophilic addition reaction:
$(I)$ $CH_3COCH_2Cl$
$(II)$ $ClCH_2CHO$
$(III)$ $HCHO$
$(IV)$ $CH_3COCH_3$

The compound $A$ in the following reaction is:
$A$ $\xrightarrow[(ii) Conc. H_2SO_4 / \Delta]{(i) CH_3MgBr / H_2O} B$ $\xrightarrow[(ii) Zn / H_2O]{(i) O_3} C + D$
$D \xrightarrow[Ba(OH)_2, \Delta]{} CH_3-C(CH_3)=CH-CO-CH_3$