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35
Subjective

Alcohols react with active metals e.g., $\mathrm{Na}, \mathrm{K}$ etc., to give corresponding alkoxides. Write down the decreasing order of reactivity of sodium metal towards primary, secondary and tertiary alcohols.

Explanation

An electron releasing group produces $+I$ effect so it increases the electron density on oxygen and decreases the polarity of O - H bond. As the number of alkyl group increases from $1^{\circ}$ to $3^{\circ}$ alcohols, the electron density on the O - H bond increases. It will finally decrease the polarity and increase the strength of $\mathrm{O}-\mathrm{H}$ bond in going from $1^{\circ}$ to $3^{\circ}$ alcohols. Thus, acidic strength decreases in the following order

As we know that, sodium metal is basic in nature and alcohols are acidic in nature. Thus, reactivity of alcohol with sodium metal decreases with decrease in acidic strength. Therefore, the correct order is $1^{\circ}>2^{\circ}>3^{\circ}.$

36
Subjective

What happens when benzene diazonium chloride is heated with water?

Explanation

When benzene diazonium chloride is heated with water then phenol is formed.

37
Subjective

Arrange the following compounds in decreasing order of acidity.

$$\mathrm{H}_2 \mathrm{O}, \mathrm{ROH}, \mathrm{HC} \equiv \mathrm{CH}$$

Explanation

A stronger acid displaces a weaker acid from its salt. When $R \mathrm{ONa}$ is treated with $\mathrm{H}_2 \mathrm{O}$, it forms ROH . So, water is a stronger acid than ROH .

$$\underset{\text { Stronger acid }}{\mathrm{HOH}}+\mathrm{RONa} \longrightarrow \mathrm{NaOH} \underset{\text { Weaker acid }}{+\mathrm{ROH}}$$

Similarly, when sodium ethynide is treated with water and alcohol, then acetylene is obtained.

$\underset{\substack{\text { Stronger } \\ \text { acid }}}{\mathrm{HOH}}+\mathrm{CH} \equiv \mathrm{CNa} \longrightarrow \underset{\text { Weak acid }}{\mathrm{HC} \equiv \mathrm{CH}}+\mathrm{NaOH}$

$\underset{\substack{\text { Stronger } \\ \text { acid }}}{\mathrm{ROH}}+\mathrm{HC} \equiv \mathrm{CNa} \longrightarrow \underset{\text { Weak acid }}{\mathrm{HC} \equiv \mathrm{CH}}+\mathrm{RONa}$

Thus, water and alcohol are stronger acid than ethyne and the decreasing order of acidity of given compounds are

$\mathrm{HOH > ROH > HC \equiv CH}$

38
Subjective

Name the enzymes and write the reactions involved in the preparation of ethanol from sucrose by fermentation.

Explanation

Sucrose is converted to glucose and fructose in the presence of an enzyme, invertase or sucrase. Glucose and fructose undergo fermentation in the presence of another enzyme, zymase. Both these enzymes are present in yeast.

$\underset{\text { Sucrose }}{\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}}+\mathrm{H}_2 \mathrm{O} \xrightarrow{\text { Invertase/sucrose }} \underset{\text { Glucose }}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6}+\underset{\text { Fructose }}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6}$

$\underset{\substack{\text { Glucose /Fructose }}}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6} \xrightarrow{\text { Zymase }} \underset{\substack{\text { Ethanol }}}{2 \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH}}+2 \mathrm{CO}_2$

39
Subjective

How can propan-2-one be converted into tert-butyl alcohol?

Explanation

Propan-2-one is a ketone. Its structural formula is ketones when treated with Grignard reagent give tertiary alcohols.