Alcohols, Phenols and Ethers

NEET Chemistry · 67 questions · Page 5 of 7 · Click an option or "Show Solution" to reveal answer

Q41

Match with . th, (Reactants) (Product)

List - I		List - II
(A)	Phenol, Zn/Δ	(I)	Salicylaldehyde
(B)	Phenol, CHCl3, NaOH, HCl	(II)	Salicylic acid
(C)	Phenol, CO2, NaOH, HCl	(III)	Benzene
(D)	Phenol, Conc. HNO3	(IV)	Picric acid

A (A)-(IV), (B)-(I), (C)-(II), (D)-(III)

B (A)-(III), (B)-(I), (C)-(II), (D)-(IV)

C (A)-(IV), (B)-(II), (C)-(I), (D)-(III)

D (A)-(III), (B)-(IV), (C)-(I), (D)-(II)

Correct Answer

Option B

Solution

Let's analyze each reaction given in List I to identify the correct product from List II.

(A) Phenol, Zn/Δ: When phenol is reacted with zinc dust (Zn) upon heating (Δ), it undergoes a reduction reaction known as the Clemmensen reduction, which results in the removal of the oxygen from the hydroxyl group (-OH) attached to the benzene ring, thus forming benzene.

Hence, (A) corresponds to (III) Benzene.

(B) Phenol, CHCl3, NaOH, HCl: This reaction is known as the Reimer-Tiemann reaction.

Phenol, when reacted with chloroform (CHCl3) in the presence of an aqueous base (NaOH), followed by acidification with HCl, forms salicylaldehyde.

Therefore, (B) corresponds to (I) Salicylaldehyde.

In this reaction, phenol reacts with carbon dioxide (CO2) under pressure at high temperatures in the presence of sodium hydroxide (NaOH), followed by acidification with HCl, to yield salicylic acid.

Thus, (C) corresponds to (II) Salicylic acid.

(D) Phenol, Conc.

HNO3: The nitration of phenol with concentrated nitric acid (HNO3) produces picric acid (2,4,6-trinitrophenol).

So, (D) corresponds to (IV) Picric acid.

Based on the above reactions, the correct matching would be: (A)-(III) Benzene (B)-(I) Salicylaldehyde (C)-(II) Salicylic acid (D)-(IV) Picric acid Therefore, the correct answer is Option B: (A)-(III), (B)-(I), (C)-(II), (D)-(IV).

Q42

Given below are two statements : Statement I : o-Nitrophenol is steam volatile due to intramolecular hydrogen bonding. Statement II : o-Nitrophenol has high melting due to hydrogen bonding. In the light of the above statements, choose the most appropriate answer from the options given below :

A Both Statement I and Statement II are true

B Statement I is true but Statement II is false

C Statement I is false but Statement II is true

D Both Statement I and Statement II are false

Correct Answer

Option B

Solution

So it is more volatile due to intramolecular H-bonding.

Melting point depends on packing efficiency not on H-bonding thus statement II is false.

Q43

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Butan -1- ol has higher boiling point than ethoxyethane. Reason R: Extensive hydrogen bonding leads to stronger association of molecules. In the light of the above statements, choose the correct answer from the options given below:

A A is false but R is true

B Both A and R are true but R is not the correct explanation of A

C Both A and R are true and R is the correct explanation of A

D A is true but R is false

Correct Answer

Option C

Solution

The boiling point of a substance is dependent on the strength of the intermolecular forces between its molecules.

Stronger intermolecular forces require more energy to overcome, thus resulting in a higher boiling point.

In the case of butan-1-ol and ethoxyethane (diethyl ether), they are both composed of similar numbers of similar atoms, but the type of intermolecular force between the molecules differs due to their functional groups.

Butan-1-ol is an alcohol and has a -OH group, which allows for hydrogen bonding, a strong type of dipole-dipole interaction.

This happens when the hydrogen atom in a polar bond (especially -OH, -NH, -HF) is attracted to some electronegative atom (like O, N, or F) in another molecule.

Because of this, butan-1-ol molecules "stick together" more strongly, requiring more heat energy to separate them and thus exhibiting a higher boiling point.

On the other hand, ethoxyethane, being an ether, does not have the ability to form hydrogen bonds since it lacks the -OH group.

The primary intermolecular forces in ethers are relatively weaker van der Waals forces.

Therefore, it requires less heat energy to break these forces, resulting in a lower boiling point compared to butan-1-ol.

So, both A and R are true and R is indeed the correct explanation for A.

Q44

Given below are two statement : Statements I : Bromination of phenol in solvent with low polarity such as

\mathrm{CHCl}_3

\mathrm{CS}_2

requires Lewis acid catalyst. Statements II : The Lewis acid catalyst polarises the bromine to generate

\mathrm{Br}^{+}

. In the light of the above statements, choose the correct answer from the options given below :

A Statement I is true but Statement II is false

B Both Statement I and Statement II are true

C Statement I is false but Statement II is true

D Both Statement I and Statement II are false

Correct Answer

Option C

Solution

Presence of Lewis acid promotes the reaction due to ease in formation of electrophile.

Q45

The most suitable reagent for the conversion of R - CH2 - OH

\to

R - CHO is:

A CrO3

B PCC (Pyridinium Chlorochromate)

C KMnO4

D K2Cr2O7

Correct Answer

Option B

Solution

An excellent reagent for oxidation of

{1^ \circ }

alcohols to aldehydes is

PCC.

Q46

A solution of

\mathrm{Cr O_5}

in amyl alcohol has a __________ colour.

A Yellow

B Orange-Red

C Green

D Blue

Correct Answer

Option D

Solution

CrO

_5

is blue in colour in amyl alcohol.

Q47

Ortho–Nitrophenol is less soluble in water than p– and m– Nitrophenols because :

A o–Nitrophenol is more volatile in steam than those of m – and p–isomers

B o–Nitrophenol shows Intramolecular H–bonding

C o–Nitrophenol shows Intermolecular H–bonding

D Melting point of o–Nitrophenol is lower than those of m–and p–isomers.

Correct Answer

Option B

Solution

As in ortho-Nitrophenol H of -OH is already in Intra-moleculer H Bond and become stable so it will not perticipate in H bonding with H2O by breaking this H bonding.

That is why solublity of Ortho–Nitrophenol is less in water. para– and meta– Nitrophenols both shows inter-moleculer H bonding with H2O.

That is why both are more soluble in water.

Q48

An unknown alcohol is treated with the “Lucas reagent” to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism:

A tertiary alcohol by SN1

B secondary alcohol by SN2

C tertiary alcohol by SN2

D secondary alcohol by SN1

Correct Answer

Option A

Solution

Tertiary alcohols reacts fastest with lucas reagnet as the rate of reaction is directly proportional to the stability of carbocation formed in the reaction.

Since most stable

{3^ \circ }

carbocation is formed in the reaction hence it will react fastest further tetriary alcohols appears to react by

{S_N}1

mechanism.

Q49

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Treatment of bromine water with propene yields 1-bromopropan-2-ol. Reason (R) : Attack of water on bromonium ion follows Markovnikov rule and results in 1-bromopropan-2-ol. In the light of the above statements, choose the most appropriate answer from the options given below :

A Both (A) and (R) are true but (R) is not the correct explanation of (A)

B (A) is false but (R) is true

C Both (A) and (R) are true and (R) is the correct explanation of (A)

D (A) is true but (R) is false

Correct Answer

Option C

Solution

Its IUPAC name 1-bromopropan-2-ol A and R are true and (R) is the correct explanation of (A).

Q50

Given below are two statements : Statement I : On heating with

\mathrm{KHSO}_{4}

, glycerol is dehydrated and acrolein is formed. Statement II : Acrolein has fruity odour and can be used to test glycerol's presence. Choose the correct option.

A Both Statement I and Statement II are correct.

B Both Statement I and Statement II are incorrect.

C Statement I is correct but Statement II is incorrect.

D Statement I is incorrect but Statement II is correct.

Correct Answer

Option C

Solution

Glycerol, on heating with KHSO4, undergoes dehydration to give unsaturated aldehyde called acrolein.

So, the statement I is correct.

Acrolein has a piercing unpleasant smell.

So, statement II is incorrect.

Ready for a full NEET mock test? Timed · full syllabus · instant results

Take a Mock Test →