Case Based Questions Test: Alcohols, Phenols & Ethers


17 Questions MCQ Test Topic-wise MCQ Tests for NEET | Case Based Questions Test: Alcohols, Phenols & Ethers


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Attempt Case Based Questions Test: Alcohols, Phenols & Ethers | 17 questions in 34 minutes | Mock test for NEET preparation | Free important questions MCQ to study Topic-wise MCQ Tests for NEET for NEET Exam | Download free PDF with solutions
QUESTION: 1

Read the passage given below and answer the following questions:

A compound (X) containing C, H and O is unreactive towards sodium. It also does not react with Schiff’s reagent. On refluxing with an excess of hydroiodic acid, (X) yields only one organic product (Y). On hydrolysis, (Y) yields a new compound (Z) which can be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight of this acid is 60.

Q. The IUPAC name of the acid formed is
 

Solution:

Formic Acid is HCOOH 
IUPAC name is methanoic acid

QUESTION: 2

Read the passage given below and answer the following questions:

A compound (X) containing C, H and O is unreactive towards sodium. It also does not react with Schiff’s reagent. On refluxing with an excess of hydroiodic acid, (X) yields only one organic product (Y). On hydrolysis, (Y) yields a new compound (Z) which can be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight of this acid is 60.

Q. Compound (X) on treatment with excess of Cl2 in presence of light gives

Solution:
QUESTION: 3

Read the passage given below and answer the following questions:

A compound (X) containing C, H and O is unreactive towards sodium. It also does not react with Schiff’s reagent. On refluxing with an excess of hydroiodic acid, (X) yields only one organic product (Y). On hydrolysis, (Y) yields a new compound (Z) which can be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight of this acid is 60.

Q. The compound (X) is an

Solution:
QUESTION: 4

Read the passage given below and answer the following questions:

A compound (X) containing C, H and O is unreactive towards sodium. It also does not react with Schiff’s reagent. On refluxing with an excess of hydroiodic acid, (X) yields only one organic product (Y). On hydrolysis, (Y) yields a new compound (Z) which can be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight of this acid is 60.

Q. Compound (Y) is

Solution:
QUESTION: 5

Read the passage given below and answer the following questions:

A compound (X) containing C, H and O is unreactive towards sodium. It also does not react with Schiff’s reagent. On refluxing with an excess of hydroiodic acid, (X) yields only one organic product (Y). On hydrolysis, (Y) yields a new compound (Z) which can be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight of this acid is 60.

Q. Compound (Z) is

Solution:
QUESTION: 6

Read the passage given below and answer the following questions:

Alcohols are versatile compounds. They act both as nucleophiles and electrophiles. The bond between O-H is broken when alcohols act as nucleophiles.
(i) Alcohols as nucleophiles

(ii) The bond between C-O is broken when they act as, electrophiles. Protonated alcohols react in this manner.
Protonated alcohols as electrophiles
R-CH2-OH+H→R-CH2+OH2
Based on the cleavage of O-H and C-O bonds, the reaction of alcohols and phenols may be divided into two groups :
(a) Reactions involving cleavage of O-H bond
(b) Reactions involving cleavage of C-O bond
Acidity of alcohols and phenols
(i) Reaction with metals :Alcohols and phenols react with active metals such as sodium, potassium and aluminium to yield corresponding alkoxide/ phenoxides and hydrogen.

 

Q. Name the following reaction:

Solution:
QUESTION: 7

Read the passage given below and answer the following questions:

Alcohols are versatile compounds. They act both as nucleophiles and electrophiles. The bond between O-H is broken when alcohols act as nucleophiles.
(i) Alcohols as nucleophiles

(ii) The bond between C-O is broken when they act as, electrophiles. Protonated alcohols react in this manner.
Protonated alcohols as electrophiles
R-CH2-OH+H→R-CH2+OH2
Based on the cleavage of O-H and C-O bonds, the reaction of alcohols and phenols may be divided into two groups :
(a) Reactions involving cleavage of O-H bond
(b) Reactions involving cleavage of C-O bond
Acidity of alcohols and phenols
(i) Reaction with metals :Alcohols and phenols react with active metals such as sodium, potassium and aluminium to yield corresponding alkoxide/ phenoxides and hydrogen.

 

Q. Write the IUPAC name of the following compound:

 

Solution:

QUESTION: 8

Read the passage given below and answer the following questions:

Alcohols are versatile compounds. They act both as nucleophiles and electrophiles. The bond between O-H is broken when alcohols act as nucleophiles.
(i) Alcohols as nucleophiles

(ii) The bond between C-O is broken when they act as, electrophiles. Protonated alcohols react in this manner.
Protonated alcohols as electrophiles
R-CH2-OH+H→R-CH2+OH2
Based on the cleavage of O-H and C-O bonds, the reaction of alcohols and phenols may be divided into two groups :
(a) Reactions involving cleavage of O-H bond
(b) Reactions involving cleavage of C-O bond
Acidity of alcohols and phenols
(i) Reaction with metals :Alcohols and phenols react with active metals such as sodium, potassium and aluminium to yield corresponding alkoxide/ phenoxides and hydrogen.

 

Q. Write down the decreasing order of reactivity of sodium metal towards primary, secondary and tertiary alcohols.

Solution:

Na metal is basic and alcohols are acidic in nature. Hence, reactivity of Na metal towards alcohols decreases as the acidic strength of alcohols decreases due to steric hinderance of alkyl groups in tertiary alcohol and increase in electron density on an oxygen atom in the hydroxyl bond.

QUESTION: 9

Read the passage given below and answer the following questions:

Alcohols are versatile compounds. They act both as nucleophiles and electrophiles. The bond between O-H is broken when alcohols act as nucleophiles.
(i) Alcohols as nucleophiles

(ii) The bond between C-O is broken when they act as, electrophiles. Protonated alcohols react in this manner.
Protonated alcohols as electrophiles
R-CH2-OH+H→R-CH2+OH2
Based on the cleavage of O-H and C-O bonds, the reaction of alcohols and phenols may be divided into two groups :
(a) Reactions involving cleavage of O-H bond
(b) Reactions involving cleavage of C-O bond
Acidity of alcohols and phenols
(i) Reaction with metals :Alcohols and phenols react with active metals such as sodium, potassium and aluminium to yield corresponding alkoxide/ phenoxides and hydrogen.

 

Q. Given the descending order of acid strength of alcohols.

Solution:

The more stable the alkoxide ion, the more acidic is the alcohol. Electron releasing effect (+I effect ) of alkyl group in secondary and tertiary alcohols makes the alkoxide ion less stable.

QUESTION: 10

Read the passage given below and answer the following questions:

Oxidation of alcohols involves the formation of a carbon-oxygen double bond with cleavage of an O-H and C-H bonds.

Such a cleavage and formation of bonds occur in oxidation reactions. These are also known as dehydrogenation reactions as these involve loss of dihydrogen from an alcohol molecule. Depending on the oxidising agent used, a primary alcohol is oxidised to an aldehyde which in turn is oxidised to a carboxylic acid.
Strong oxidising agents such as acidified potassium permanganate are used for getting carboxylic acids from alcohols directly. CrO3 in anhydrous medium is used as the oxidising agent for the isolation of aldehydes.

Assertion (A): CH3CH2OH can be converted into CH3CHO by treatment with pyridinium chlorochromate.
Reason (R): PCC is a better reagent for oxidation of primary alcohols to aldehydes

Solution:

PCC (Pyridinium chlorochromate) is a better reagent for converting ethyl alcohol into acetaldehyde.

QUESTION: 11

Read the passage given below and answer the following questions:

Oxidation of alcohols involves the formation of a carbon-oxygen double bond with cleavage of an O-H and C-H bonds.

Such a cleavage and formation of bonds occur in oxidation reactions. These are also known as dehydrogenation reactions as these involve loss of dihydrogen from an alcohol molecule. Depending on the oxidising agent used, a primary alcohol is oxidised to an aldehyde which in turn is oxidised to a carboxylic acid.
Strong oxidising agents such as acidified potassium permanganate are used for getting carboxylic acids from alcohols directly. CrO3 in anhydrous medium is used as the oxidising agent for the isolation of aldehydes.

Assertion (A): Vapours of primary and secondary alcohols are passed through heated copper an aldehyde and ketone are formed.
Reason (R): It’s a dehydration reaction.

Solution:

Vapours of primary and secondary alcohols are passed through heated copper an aldehyde and ketone are formed. It’s a dehydrogenation reaction

QUESTION: 12

Read the passage given below and answer the following questions:

Oxidation of alcohols involves the formation of a carbon-oxygen double bond with cleavage of an O-H and C-H bonds.

Such a cleavage and formation of bonds occur in oxidation reactions. These are also known as dehydrogenation reactions as these involve loss of dihydrogen from an alcohol molecule. Depending on the oxidising agent used, a primary alcohol is oxidised to an aldehyde which in turn is oxidised to a carboxylic acid.
Strong oxidising agents such as acidified potassium permanganate are used for getting carboxylic acids from alcohols directly. CrO3 in anhydrous medium is used as the oxidising agent for the isolation of aldehydes.

Assertion (A): Dehydrogenation reaction of alcohols is an oxidising reaction.
Reason (R): It involves loss of dihydrogen from alcohol.

Solution:

Dehydrogenation means loss of dihydrogen from a molecule.

QUESTION: 13

Read the passage given below and answer the following questions:

Oxidation of alcohols involves the formation of a carbon-oxygen double bond with cleavage of an O-H and C-H bonds.

Such a cleavage and formation of bonds occur in oxidation reactions. These are also known as dehydrogenation reactions as these involve loss of dihydrogen from an alcohol molecule. Depending on the oxidising agent used, a primary alcohol is oxidised to an aldehyde which in turn is oxidised to a carboxylic acid.
Strong oxidising agents such as acidified potassium permanganate are used for getting carboxylic acids from alcohols directly. CrO3 in anhydrous medium is used as the oxidising agent for the isolation of aldehydes.

Assertion (A): Tertiary alcohols do not undergo oxidation reactions.
Reason (R): They do not have the required C-H bond.

Solution:

Tertiary alcohols do not undergo oxidation reactions because the carbon atom that carries the -OH group does not have a hydrogen atom.

QUESTION: 14

Read the passage given below and answer the following questions:

The reaction of phenol with aqueous sodium hydroxide indicates that phenols are stronger acids than alcohols and water. Due to the higher electronegativity of sp2 hybridised carbon of phenol to which –OH is attached, electron density decreases on oxygen. This increases the polarity of O–H bond and results in an increase in ionisation of phenols than that of alcohols. Now let us examine the stabilities of alkoxide and phenoxide ions. In alkoxide ion, the negative charge is localised on oxygen while in phenoxide ion, the charge is delocalised. The delocalisation of negative charge makes phenoxide ion more stable and favours the ionisation of phenol.

Q. Which of the following is most acidic?

Solution:

m-chlorophenol is most acidic as electron withdrawing (−Cl )group increases the acidity of phenols.

QUESTION: 15

Read the passage given below and answer the following questions:

The reaction of phenol with aqueous sodium hydroxide indicates that phenols are stronger acids than alcohols and water. Due to the higher electronegativity of sp2 hybridised carbon of phenol to which –OH is attached, electron density decreases on oxygen. This increases the polarity of O–H bond and results in an increase in ionisation of phenols than that of alcohols. Now let us examine the stabilities of alkoxide and phenoxide ions. In alkoxide ion, the negative charge is localised on oxygen while in phenoxide ion, the charge is delocalised. The delocalisation of negative charge makes phenoxide ion more stable and favours the ionisation of phenol.

Q. Phenol can be distinguished from ethanol by the reaction with _____

Solution:

Phenol decolourises bromine water to form white precipitate of 2,4,6-tribromophenol whereas ethanol does not precipitate.

QUESTION: 16

Read the passage given below and answer the following questions:

The reaction of phenol with aqueous sodium hydroxide indicates that phenols are stronger acids than alcohols and water. Due to the higher electronegativity of sp2 hybridised carbon of phenol to which –OH is attached, electron density decreases on oxygen. This increases the polarity of O–H bond and results in an increase in ionisation of phenols than that of alcohols. Now let us examine the stabilities of alkoxide and phenoxide ions. In alkoxide ion, the negative charge is localised on oxygen while in phenoxide ion, the charge is delocalised. The delocalisation of negative charge makes phenoxide ion more stable and favours the ionisation of phenol.

Q. Phenol is less acidic than_________.

Solution:

Phenol is less acidic than o-nitrophenol as electron withdrawing (−NO2) group increases the acidity of phenols.

QUESTION: 17

Read the passage given below and answer the following questions:

The reaction of phenol with aqueous sodium hydroxide indicates that phenols are stronger acids than alcohols and water. Due to the higher electronegativity of sp2 hybridised carbon of phenol to which –OH is attached, electron density decreases on oxygen. This increases the polarity of O–H bond and results in an increase in ionisation of phenols than that of alcohols. Now let us examine the stabilities of alkoxide and phenoxide ions. In alkoxide ion, the negative charge is localised on oxygen while in phenoxide ion, the charge is delocalised. The delocalisation of negative charge makes phenoxide ion more stable and favours the ionisation of phenol.

Q. Mark the correct order of decreasing acid strength of the following compounds.

 

Solution:

The correct order of decreasing acid strength is b>d>a>c>e p-nitrophenol is most acidic and p-methoxy phenol is least acidic. When an electron withdrawing group is para to OH group, the acidity is maximum. When an electron releasing group is para to OH group, the acidity is minimum.

The presence of electron withdrawing group viz. −NO2 group increases the acidity of phenol due to −I effect and electron releasing group viz. −OCH3 group decreases the acidity of phenol due to +I effect. Moreover, p-nitrophenol is more acidic than m-nitrophenol. While, p-methoxyphenol is less acidic than m-methoxyphenol.

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