Alcohol, Phenols and Ethers

Metamerism arises due to different alkyl chains on either side of the functional group in the molecule pair of molecules $\mathrm{CH}_3 \mathrm{OCH}_2 \mathrm{CH}_2 \mathrm{CH}_3$ and $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OCH}_2 \mathrm{CH}_3$ are metamers of each other.

$ \text { } \begin{aligned}So,\,\, \mathrm{X} & =\mathrm{POCl}_3 \\ \mathrm{Z} & =\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{Br} \end{aligned} $

Phthalein Dye test: Phenol on heating with phthalic anhydride in presence of concentrated sulphuric acid forms a colourless condensation compound called phenolphthalein. On further reaction with NaOH it gives pink colour.

So phenolic group is correct answer.

Tertiary alcohols react instantaneously with Lucas reagent and gives immediate turbidity. In case of tertiary alcohols, they form halides easily with Lucas reagent (conc. $\mathrm{HCl}$ and $\mathrm{ZnCl}_2$)

Let's analyze the given reactions and determine the products $\mathrm{A}$ and $\mathrm{B}$.

Reaction with PCl₃:

When an alcohol ($\mathrm{ROH}$) reacts with phosphorus trichloride ($\mathrm{PCl}_3$), the hydroxyl group ($\mathrm{OH}$) of the alcohol is replaced by a chloro group ($\mathrm{Cl}$), resulting in the formation of an alkyl chloride ($\mathrm{RCl}$). Additionally, the reaction produces phosphorous acid as a byproduct. This can be represented as:

$3 \mathrm{ROH} + \mathrm{PCl}_3 \rightarrow 3 \mathrm{RCl} + \mathrm{H}_3\mathrm{PO}_3$

Here, $\mathrm{A}$ is $\mathrm{H}_3\mathrm{PO}_3$ (phosphorous acid).

Reaction with PCl₅:

When an alcohol reacts with phosphorus pentachloride ($\mathrm{PCl}_5$), it also replaces the hydroxyl group with a chloro group. The reaction differs slightly in the byproducts; phosphorus oxychloride ($\mathrm{POCl}_3$) and hydrogen chloride ($\mathrm{HCl}$) are produced:

$\mathrm{ROH} + \mathrm{PCl}_5 \rightarrow \mathrm{RCl} + \mathrm{HCl} + \mathrm{POCl}_3$

Here, $\mathrm{B}$ is $\mathrm{POCl}_3$ (phosphorus oxychloride).

Thus, in the reactions provided:

• $\mathrm{A} = \mathrm{H}_3\mathrm{PO}_3$
• $\mathrm{B} = \mathrm{POCl}_3$

Matching these findings against the provided options, we see that Option D correctly identifies $\mathrm{A}$ as $\mathrm{H}_3\mathrm{PO}_3$ and $\mathrm{B}$ as $\mathrm{POCl}_3$:

Option D: $\mathrm{H}_3 \mathrm{PO}_3$ and $\mathrm{POCl}_3$

This is the correct answer.

Due to presence of conjugation in product.

At STP condition substitution at sp² carbon atom is not feasible.

$\bullet$ Nitro group has electron withdrawing tendency. It can withdraw electrons both by $-$I effect and $-$R effect. Thus the acidic strength of monosubstituted nitrophenol is higher than phenol.

$\bullet$ Nitro group present at o- and p-positions will have strong $-$R effect while nitro group present at m-position will influence only $-$I effect hence acidity or o/p isomer will be more meta isomer.

Primary, secondary and tertiary alcohols can be differentiated by their reaction with (HCl + anhy ZnCl₂) Lucas reagent

$\bullet$ 3$^\circ$ alcohol $\buildrel {ZnC{l_2} + HCl} \over \longrightarrow $ Immediate turbidity at room temperature

$\bullet$ 2$^\circ$ alcohol $\buildrel {ZnC{l_2} + HCl} \over \longrightarrow $ Turbidity after 5 minutes at room temperature

$\bullet$ 1$^\circ$ alcohol $\buildrel {ZnC{l_2} + HCl} \over \longrightarrow $ Do not gives turbidity at room temperature

Ethers are readily cleaved by halogen acids at $373 \mathrm{~K}$ to form an alcohol and an alkyl halide.

$\underset{\text { Tert-butyl methylether }}{\left(\mathrm{CH}_3\right)_3 \mathrm{COCH}_3}+\mathrm{HBr} \longrightarrow \underset{\text { Tert-butyl bromide }}{\left(\mathrm{CH}_3\right)_3 \mathrm{CBr}}+\underset{\text { Methanol }}{\mathrm{CH}_3 \mathrm{OH}}$

$\mathrm{S}_{\mathrm{N}} 1$ mechanism is followed as $(\mathrm{CH}_3)_3 \mathrm{C}^{+}(s)$ is most stable carbocation and $\mathrm{I}^{-}$ is attached to it.

When phenol reacts with $\mathrm{CH}_3 \mathrm{I}$ in presence of $\mathrm{NaOH}$, it gives methoxybenzene due to formation of phenoxide ion, which is a better nucleophile than phenol.

The reaction takes place as follows :

Thus given assertion and reason, both are correct and given reason is the correct answer of the given assertion.

Hence, option (a) is the correct.

IUPAC name of the above given compound is correct, i.e. 1-(2-propoxy) propane. In this compound, hydrogen atom is replaced by—OR group and thus named ether.

Therefore, both assertion and reason is correct and reason is the correct explanation of the assertion.

Haloform test is used to identify the compound (alcohol or carbonyl compound). In this reaction, alcohols (aldehydes and ketones) on heating with $X_2\left(\mathrm{Cl}_2, \mathrm{Br}_2\right.$ and $\left.\mathrm{I}_2\right)$ and $\mathrm{OH}^{-}$ form $\mathrm{CH} X_3$ (haloform). This test is given by $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH}$,

Therefore, both assertion and reason is correct but reason in not the correct explanation of the assertion.