Ketones MCQ Quiz - Objective Question with Answer for Ketones - Download Free PDF

Explanation:-

NaBH₄ can reduce aldehyde and ketone functional groups into primary and secondary alcohol respectively.

Explanation:

First, it is important to understand each reaction :

This reaction is known as Rosenmund reduction. It involves the conversion of acyl chlorides into an aldehyde. It is a hydrogenation process where H₂ reacts with an acyl chloride in presence of a catalyst ( Pd-BaSO₄).

This reaction is known as the Hell-Volhard Zelinsky reaction. Carboxylic acids with one or more alpha-hydrogen atoms react with Cl₂ /Br₂ in presence of Red P resulting in the formation of alpha-halocarboxylic acids.

This reaction is known as the Hofmann bromamide degradation reaction. This method is used for the preparation of primary amine from amide by treating it with bromine in an aqueous ethanolic solution of NaOH.

This reaction is known as Clemmensen's reduction. It involves the reduction of carbonyl compounds to alkanes using Zn-Hg amalgam and conc.HCl.

Answer: According to all these reactions, option (4)  : (a) - (ii), (b) - (iv), (c) - (i), (d) - (iii) , is correct.

Concept:

Wolf-Kischner reduction - 

• It is used to reduce the carbonyl group into alkane.
• In this reaction, hydrazine (- NH₂-NH₂) in presence of a strong base is used as a reducing agent.
• The reaction occurs in the high protic solvent.

,

• N₂ is released in the reaction.
• Hydrazine is converted into nitrogen gas.

Explanation:

In the given reaction -

The reaction follows Wolf Kischner's reduction as -CO reduced into corresponding alkane without harming the other double bonds.

Hence, hydrazine in presence of a strong base is used a reducing agent.

∴ NH2 – NH2 / \(\rm C_2H_5 \overset{\ominus}{O}\overset{\oplus}{N}a\) is a reducing agent that works in the given reaction.

The complete reaction will be- 

Hence, the correct answer is option 2.

CONCEPT:

Asymmetric Carbon

• An asymmetric carbon is a carbon atom that is attached to four different groups, making the molecule chiral.
• In organic synthesis, identifying asymmetric carbons in the final product helps in determining its chirality and properties.

EXPLANATION:

• P: The compound contains a carbon atom bonded to four different groups (CH₃, C₂H₅, OH, and Ph). Hence, P has an asymmetric carbon.
• Q: The product contains a phenyl ring attached to a carbon with OH, CH₃, and Ph. This makes the carbon asymmetric.
• R: The product contains a central carbon bonded to four different groups (CH₂CH₃, OH, Ph, and another phenyl group), making it asymmetric.
• S: The product is an alkyne with no asymmetric carbon as the triple bond and surrounding groups are symmetrical.

Conclusion: P and R have asymmetric carbons.

CONCEPT:

Organic Reactions and Product Analysis

• Oxidation of compounds with KMnO₄ and KOH yields carboxylic acids.
• Hydrolysis of esters under alkaline or acidic conditions produces carboxylic acids.
• Grignard reagents react with CO₂ followed by hydrolysis to give carboxylic acids.
• Cannizzaro reaction occurs only in aldehydes without α-hydrogen atoms.

EXPLANATION:

• Identify products P, Q, R, and S:
  • P: Formed by oxidation of the side chain in the given compound to carboxylic acid using KMnO₄.
  • Q: Ester hydrolysis results in the formation of a carboxylic acid.
  • R: Hydrolysis of the cyanide group and subsequent oxidation produces a carboxylic acid.
  • S: Grignard reagent reacts with CO₂ followed by hydrolysis to yield a carboxylic acid, and ammoniacal AgNO₃ confirms the absence of Cannizzaro reaction in S.
• Analyze statements:
  • Statement 1: P and Q are monomers of polymers Dacron and Glyptal.
    The monomers for Dacron are ethylene glycol and terephthalic acid, while the monomers for Glyptal are ethylene glycol and phthalic acid
    This is incorrect.
  • Statement 2: P, Q, and R are dicarboxylic acids. This is incorrect, as only Q and R are dicarboxylic acids.
  • Statement 3: Q and R are the same compounds. This is correct.
  • Statement 4: R does not undergo aldol condensation, and S does not undergo Cannizzaro reaction. This is correct.

Conclusion: The correct statements are  3 and 4.

Explanation:-

NaBH₄ can reduce aldehyde and ketone functional groups into primary and secondary alcohol respectively.

The correct answer is option 3 .

Concept:

• Ammonia is diluted with silver ions to create Tollens' reagent. Since the silver ion is reduced to metallic silver and the aldehyde is oxidized to carboxylic acids, this reagent is used to separate aldehydes from ketones.
• This is frequently observed as a "silver mirror" developing inside the test tube.

Explanation:

• To check if aldehydes are present, use Tollens' reagent. It contains silver ions, which, in the presence of an aldehyde, are converted to metallic silver.
• Sucrose, often known as cane sugar, hydrolyzes when heated with diluted acid to produce glucose and fructose, both of which are reducing sugars, although it does not directly reduce Tollens' reagent.
• Starch: Tollen's reagent will not be reduced by starch because it is not a reducing sugar.
• glucose: Tollens' reagent will be reduced by glucose, a reducing sugar, creating a silver mirror.

Explanation:-

NaBH₄ can reduce aldehyde and ketone functional groups into primary and secondary alcohol respectively.

CONCEPT:

Acid-Catalyzed Rearrangement of Cyclic Ketones

• The starting compound is a bicyclic compound with two ketone functional groups.
• When treated with acid (H⁺), cyclic ketones can undergo rearrangement reactions due to the protonation of the carbonyl group, making it more susceptible to ring opening or reorganization.
• This reaction typically results in the formation of a new, more stable cyclic structure by rearranging the bonds in the molecule.

REACTION EXPLANATION:

• The given bicyclic compound is treated with an acid (H⁺), which protonates one of the carbonyl groups, making the structure more reactive.
• This leads to a rearrangement, potentially involving a ring contraction or expansion, to form a new cyclic structure with stabilized keto groups.
• 

CONCLUSION:

The correct option is: Option 4

CONCEPT:

Clemmensen Reduction

• The Clemmensen reduction is a chemical reaction used to reduce ketones or aldehydes to alkanes using zinc amalgam (Zn-Hg) and concentrated hydrochloric acid (HCl).
• This reaction effectively removes the carbonyl group (C=O) and replaces it with hydrogen atoms (H).
• 

Mechanism:-

• The given compound is a diketone with two carbonyl groups attached to a benzene ring and a cyclohexane ring.
• Under Clemmensen reduction conditions, both carbonyl groups are reduced to methylene groups (CH₂).
• The resulting product is a compound where the benzene ring is directly attached to the cyclohexane ring via a CH₂ group.

​Explanation:-

• The correct structure of the product (A) should have no carbonyl groups and should have two methylene (CH₂) groups connecting the benzene ring and the cyclohexane ring.
• Among the given options, Option 1 matches this structure.

The correct answer is Option 1.

Explanation:

A. The reaction is Clemmenson reduction,

• Reaction of aldehyde and ketones in zinc amalgam in concn. HCl will reduce the aldehyde or ketone to the corresponding hydrocarbon.

The reaction is shown as - 

The product formed here is toluene.

B. The reaction is Rosenmund reaction,

• Pd-BaSO₄  is known as the Rosenmund catalyst.
• The reaction used to reduce acyl chloride to their corresponding aldehyde using Rosenmund catalyst and H₂.

The reaction is shown as - 

The product of the reaction is benzaldehyde.

C. The reaction is Wolf-Kischner reduction,

• The carbonyl group of aldehydes and ketones is reduced to corresponding hydrocarbon on treatment with hydrazine(NH₂NH₂) followed by heatingwith sodium or potassium hydroxide.
• The reaction proceed through hydrazine intermediate.

The reaction is shown as - 

The product formed is cyclohexane.

Conclusion:

Matching the given reaction with the product obtained we get, (A - III), (B - IV), (C - V) .

Therefore, the correct answer is option 1.

Explanation:

First, it is important to understand each reaction :

This reaction is known as Rosenmund reduction. It involves the conversion of acyl chlorides into an aldehyde. It is a hydrogenation process where H₂ reacts with an acyl chloride in presence of a catalyst ( Pd-BaSO₄).

This reaction is known as the Hell-Volhard Zelinsky reaction. Carboxylic acids with one or more alpha-hydrogen atoms react with Cl₂ /Br₂ in presence of Red P resulting in the formation of alpha-halocarboxylic acids.

This reaction is known as the Hofmann bromamide degradation reaction. This method is used for the preparation of primary amine from amide by treating it with bromine in an aqueous ethanolic solution of NaOH.

This reaction is known as Clemmensen's reduction. It involves the reduction of carbonyl compounds to alkanes using Zn-Hg amalgam and conc.HCl.

Answer: According to all these reactions, option (4)  : (a) - (ii), (b) - (iv), (c) - (i), (d) - (iii) , is correct.

Concept:

Wolf-Kischner reduction - 

• It is used to reduce the carbonyl group into alkane.
• In this reaction, hydrazine (- NH₂-NH₂) in presence of a strong base is used as a reducing agent.
• The reaction occurs in the high protic solvent.

,

• N₂ is released in the reaction.
• Hydrazine is converted into nitrogen gas.

Explanation:

In the given reaction -

The reaction follows Wolf Kischner's reduction as -CO reduced into corresponding alkane without harming the other double bonds.

Hence, hydrazine in presence of a strong base is used a reducing agent.

∴ NH2 – NH2 / \(\rm C_2H_5 \overset{\ominus}{O}\overset{\oplus}{N}a\) is a reducing agent that works in the given reaction.

The complete reaction will be- 

Hence, the correct answer is option 2.