Question 1

The addition of HCN to carbonyl compounds is an example of ……….

Accepted Answer

The addition of HCN to carbonyl compounds is an example of nucleophilic addition, where the nucleophile (CN-) attacks the electrophilic carbon atom of the carbonyl group, leading to the formation of a cyanohydrin.

Question 2

Which of the following reagents is used to distinguish acetone and Acetophenone?

Accepted Answer

Sodium bisulfite (NaHSO₃) reacts with acetone to form a bisulfite addition compound, but it does not react with acetophenone, allowing for differentiation between the two.

Question 3

The product formed by the reaction of chlorine with benzaldehyde in the absence of a catalyst is…………..

Accepted Answer

Benzaldehyde reacts with chlorine in the absence of a catalyst to form benzoyl chloride. This reaction is a part of the halogenation of aldehydes under substitution conditions, where the chlorine replaces the aldehyde's hydrogen in the formyl group, leading to the formation of an acyl chloride.

Question 4

Enol content is highest in…………..

Accepted Answer

Acetyl acetone has the highest enol content due to the presence of two keto groups which stabilize the enol form through intramolecular hydrogen bonding, making the enol form more favorable.

Question 5

Which one of the following reacts with HCN and Tollen's reagent, but is not oxidised by Fehling's solution……………

Accepted Answer

Benzaldehyde reacts with HCN to form cyanohydrins and with Tollen's reagent to give a silver mirror, but it is not oxidized by Fehling's solution because it lacks the necessary hydroxyl group adjacent to the carbonyl group that is required for oxidation by Fehling's solution.

Question 6

During reaction of benzaldehyde with alkali one of the product is…………

Accepted Answer

The reaction of benzaldehyde with alkali (such as sodium hydroxide) typically involves a Cannizzaro reaction, where benzaldehyde is disproportionated into benzyl alcohol and benzoic acid. Benzyl alcohol is one of the products formed.

Question 7

Cannizzaro reaction is given by…………

Accepted Answer

The Cannizzaro reaction is a redox reaction that occurs with aldehydes that do not have an alpha hydrogen. Formaldehyde (HCHO) is the only option without an alpha hydrogen, making it suitable for the Cannizzaro reaction.

Question 8

When two molecules of acetaldehyde condense in the presence of dilute alkali, it forms………….

Accepted Answer

When two molecules of acetaldehyde condense in the presence of dilute alkali, they undergo an aldol condensation to form an aldol. This reaction involves the formation of a β-hydroxy aldehyde.

Question 9

Acetaldehyde and acetone can be distinguished by……………

Accepted Answer

Tollen's test can distinguish between acetaldehyde and acetone because acetaldehyde is an aldehyde and will give a positive result (silver mirror), while acetone, a ketone, will not react.

Question 10

Aldehyde turns pink with ………….

Accepted Answer

Schiff reagent is specifically designed to react with aldehydes, causing a color change to pink, indicating the presence of an aldehyde group.

Question 11

Boiling point of acetone is…………..

Accepted Answer

The boiling point of acetone is 56°C.

Question 12

The reagent with which both aldehyde and acetone react easily is…………….

Accepted Answer

Grignard reagent reacts with both aldehydes and ketones like acetone to form alcohols, while the other reagents are specific for aldehydes.

Question 13

Acetal is obtained by reacting in the presence of dry HCl and alcohol with…………..

Accepted Answer

Acetal formation typically involves the reaction of an aldehyde with an alcohol in the presence of an acid catalyst, such as dry HCl, leading to the formation of an acetal.

Question 14

Which of the following is used to detect aldehydes…………..

Accepted Answer

Tollen's reagent, which is a solution of silver nitrate in ammonia, is used to detect aldehydes. When an aldehyde is present, it reduces the silver ion to metallic silver, creating a mirror-like coating on the test tube, which is a positive result.

Question 15

Which of the following aldehydes give red precipitate with Fehling solution ?

Accepted Answer

Acetaldehyde is an aliphatic aldehyde, which can be oxidized by Fehling's solution to give a red precipitate of copper(I) oxide. Benzaldehyde and salicylaldehyde are aromatic aldehydes and do not react with Fehling's solution.

Question 16

Acetaldehyde and Acetone can be distinguished by………..

Accepted Answer

The answer of Acetaldehyde and Acetone can be distinguished by………..
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Question 17

Which of the following will fail to react with potassium dichromate and dilute sulphuric acid……………

Accepted Answer

Acetone (propanone) will not react with potassium dichromate and dilute sulphuric acid because it is a ketone, and ketones do not undergo oxidation under these conditions, unlike primary and secondary alcohols and aldehydes.

Question 18

The key step in cannizzaro's reaction is the intermolecular shift of ……….

Accepted Answer

The key step in Cannizzaro's reaction involves the intermolecular transfer of a hydride ion from one aldehyde molecule to another, leading to the formation of an alcohol and a carboxylic acid salt.

Question 19

A compound, containing only carbon, hydrogen and oxygen, has a molecular weight of 44. On complete oxidation it is converted into a compound of molecular weight 60. The original compound is ?

Accepted Answer

The original compound is an aldehyde. On complete oxidation, an aldehyde is converted into a carboxylic acid, which has a molecular weight 16 more than the aldehyde.

Question 20

Which of the following has the most acidic hydrogen?

Accepted Answer

2,4-hexanedione has the most acidic hydrogen due to the presence of two carbonyl groups separated by a methylene group, which allows for resonance stabilization of the enolate ion formed after deprotonation.

Quiz 11: Carboxylic Acids Properties