Aldehydes Ketones And Carboxylic Acids

The correct answer is option (b): Sodium butanoate

Positive 2,4-Dinitrophenylhydrazine ( ) test: Compound 'A' gives a positive test, indicating the presence of a carbonyl group, which could be either an aldehyde or a ketone.

Negative Tollen's test: Compound 'A' does not give a positive Tollen's test, which suggests it is not an aldehyde.

Reaction with sodium hypochlorite ( ): Compound 'A' reacts with sodium hypochlorite to give chloroform ( ) and compound 'B'.

Based on the information provided, compound 'A' has a molecular formula of and contains a carbonyl group. One possible structure for compound 'A' is the ketone "2-pentanone" ( ).

Now, let's consider the formation of compound 'B' upon treatment with sodium hypochlorite:

(compound 'A') + → CHCl3 + compound 'B'

The reaction between 2-pentanone (compound 'A') and sodium hypochlorite yields chloroform ( ) and compound 'B'. Given the options provided, "Sodium propanoate," "Sodium butanoate," "Sodium acetate," and "n-Butane," the most likely choice for compound 'B' would be "Sodium acetate" ( ).

So, compound 'B' is likely to be "Sodium acetate" ( ) based on the given information.

A research scholar had four compounds labeled as P, Q, R and S. The compounds were: acetone, benzaldehyde, acetaldehyde, and diethyl ketone.

Based on the test results:

• P and R give the iodoform test → Indicates the presence of either CH₃CO- or CH₃CH(OH)- groups → Could be acetone or acetaldehyde
• R alone gives a reddish brown precipitate with Fehling’s reagent → This confirms R is acetaldehyde, as only aldehydes with alpha-hydrogens give this test
• Q and R give Tollen’s test → Indicates presence of aldehydes. So Q is also an aldehyde → benzaldehyde
• S does not give any test → So it must be diethyl ketone, which doesn’t respond to any of the above tests

Now match the data:

• P = Benzaldehyde
• Q = Diethyl ketone
• R = Acetaldehyde
• S = Acetone

Correct Answer:

Correct Answer: (E) P - benzaldehyde; Q - diethyl ketone; R - acetone; S - acetaldehyde

The conversion of benzene diazonium chloride to bromobenzene by treating with HBr in the presence of copper powder is known as the Gattermann reaction.

The Gattermann reaction is used for the introduction of a formyl group (-CHO) into an aromatic ring, not the formation of aryl halides from diazonium salts. The correct reaction for converting a diazonium salt to an aryl halide, like bromobenzene from benzene diazonium chloride, is the Sandmeyer reaction.
- Sandmeyer reaction involves the substitution of a diazonium group with a halogen (such as bromine or chlorine) using copper salts.
- Gattermann reaction is used for formylation of aromatic rings (introducing the -CHO group).
- Wurtz reaction is used for the formation of alkanes from alkyl halides.
- Hoffmann reaction is used for the degradation of amides to amines. - Gabriel synthesis is used to synthesize primary amines from phthalimide.

Correct Answer: (B) Gattermann reaction

The acid strength of carboxylic acids depends on the electron-withdrawing nature of substituents near the –COOH group. Electron-withdrawing groups (EWGs) stabilize the carboxylate ion formed after losing a proton, thereby increasing acidity.

Let’s analyze the given acids:

• : The chlorine is two carbons away, so the inductive effect is weak → least acidic
• : Has two chlorine atoms directly attached to the α-carbon → strong EWG → very acidic
• : One chlorine on α-carbon → moderate EWG → more acidic than first
• : Nitrile is a strong EWG and stabilizes the carboxylate ion effectively → most acidic

So, the increasing order of acid strength is:

Correct Answer: (C)

Cannizzaro Reaction: This reaction involves the disproportionation of aldehydes lacking alpha-hydrogens in the presence of a strong base. One aldehyde is reduced to an alcohol, and the other is oxidized to a carboxylic acid. No new C-C bond is formed.

Aldol Condensation: This reaction involves the nucleophilic addition of an enolate ion to a carbonyl group (aldehyde or ketone), forming a beta-hydroxyaldehyde or beta-hydroxyketone (aldol). This is followed by dehydration to form an alpha, beta-unsaturated carbonyl compound. A new C-C bond is formed between the alpha carbon of one molecule and the carbonyl carbon of the other.

Sandmeyer's Reaction: This is a method for synthesizing aryl halides from aryl diazonium salts, which are obtained from aromatic amines. The diazonium salt is replaced by a halide (Cl, Br) or other group (CN) in the presence of a copper(I) salt. No new C-C bond is formed directly in this step.

Friedel-Crafts Reaction: This reaction involves the alkylation or acylation of aromatic compounds. An alkyl or acyl group is attached to the aromatic ring. A new C-C bond is formed between the aromatic ring and the alkyl/acyl group.

Gattermann-Koch Reaction: This is a variation of the Friedel-Crafts acylation, used to form aromatic aldehydes using CO and HCl in the presence of a Lewis acid catalyst (e.g., AlCl3). A new C-C bond is formed (although it is converted to a C=O bond in the aldehyde).

Reimer-Tiemann Reaction: This reaction is used to form ortho-hydroxybenzaldehydes from phenols, using chloroform, base, and heat. A new C-C bond is formed in adding the -CHO group to the ring.

Thus, the correct option is (C): Friedel-Crafts reaction and Gattermann-Koch reaction