(a) A neutral organic compound $X'$ (Molecular formula $\mathrm{C_2H_6O}$) on reacting with acidified $\mathrm{K_2Cr_2O_7}$ gives an organic compound $Y'$ which is acidic in nature. $X'$ reacts with $Y'$ on warming in the presence of conc. $\mathrm{H_2SO_4}$ to give a sweet smelling compound $Z'$. (i) Identify $X'$, $Y'$ and $Z'$. (ii) Write the chemical equations for the reactions in the conversion of (1) $X'$ to $Y'$ and (2) $X'$ to $Z'$. (iii) State the role of (1) acidified $\mathrm{K_2Cr_2O_7}$ in the conversion of $X'$ to $Y'$ and (2) conc. $\mathrm{H_2SO_4}$ in the reaction of $X'$ and $Y'$. (iv) Name the reaction which occurs when $Z'$ reacts with an alkali. OR (b) Carry out the following conversions, stating the condition(s) for each : (i) Ethanol Ethene (ii) Ethene Ethane (iii) Ethane Chloroethane (iv) Ethanol Ethanoic acid (v) Ethanoic acid Ethyl ethanoate

Part (a)

(i) Identification:

• $X'$ is Ethanol ($\mathrm{CH_3CH_2OH}$ or $\mathrm{C_2H_5OH}$).
• $Y'$ is Ethanoic acid ($\mathrm{CH_3COOH}$).
• $Z'$ is Ethyl ethanoate ($\mathrm{CH_3COOCH_2CH_3}$), which is a sweet-smelling ester.

(ii) Chemical Equations:

1. Conversion of $X'$ to $Y'$ (Oxidation):

$$\mathrm{CH_3CH_2OH \xrightarrow{Acidified\ K_2Cr_2O_7,\ Heat} CH_3COOH + H_2O}$$

1. Conversion of $X'$ and $Y'$ to $Z'$ (Esterification):

$$\mathrm{CH_3COOH + CH_3CH_2OH \xrightarrow{Conc.\ H_2SO_4,\ Warm} CH_3COOCH_2CH_3 + H_2O}$$

(iii) Role of Reagents:

1. Acidified $\mathrm{K_2Cr_2O_7}$: It acts as an oxidizing agent that provides nascent oxygen to oxidize ethanol to ethanoic acid.
2. Concentrated $\mathrm{H_2SO_4}$: It acts as a catalyst to speed up the reaction and as a dehydrating agent to remove the water formed, shifting the equilibrium in the forward direction to maximize the yield of ester.

(iv) Name of the reaction:

When ester $Z'$ reacts with an alkali, the reaction is called Saponification (alkaline hydrolysis of an ester).

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Part (b) (OR Part)

(i) Ethanol to Ethene:

• Condition: Heating ethanol at $443\ \mathrm{K}$ with excess concentrated $\mathrm{H_2SO_4}$.
• Equation:

$$\mathrm{CH_3CH_2OH \xrightarrow{Conc.\ H_2SO_4,\ 443\ K} CH_2=CH_2 + H_2O}$$

(ii) Ethene to Ethane:

• Condition: Heating ethene with hydrogen gas in the presence of a nickel ($\mathrm{Ni}$) or palladium ($\mathrm{Pd}$) catalyst.
• Equation:

$$\mathrm{CH_2=CH_2 + H_2 \xrightarrow{Ni,\ \Delta} CH_3-CH_3}$$

(iii) Ethane to Chloroethane:

• Condition: Reaction of ethane with chlorine gas in the presence of sunlight.
• Equation:

$$\mathrm{CH_3-CH_3 + Cl_2 \xrightarrow{Sunlight} CH_3-CH_2Cl + HCl}$$

(iv) Ethanol to Ethanoic acid:

• Condition: Heating ethanol with alkaline potassium permanganate ($\mathrm{KMnO_4}$) or acidified potassium dichromate ($\mathrm{K_2Cr_2O_7}$).
• Equation:

$$\mathrm{CH_3CH_2OH \xrightarrow{Acidified\ K_2Cr_2O_7,\ Heat} CH_3COOH + H_2O}$$

(v) Ethanoic acid to Ethyl ethanoate:

• Condition: Warming ethanoic acid with ethanol in the presence of a few drops of concentrated sulphuric acid.
• Equation:

$$\mathrm{CH_3COOH + CH_3CH_2OH \xrightarrow{Conc.\ H_2SO_4,\ Warm} CH_3COOCH_2CH_3 + H_2O}$$