Aldehydes Ketones And Carboxylic Acids

Step 1: Acidity is determined by the stability of the conjugate base formed after losing a proton. Phenol ( ) is more acidic than water and ethanol due to resonance stabilization of its conjugate base ( ). Ether ( ) does not release protons easily and is least acidic.

Step 1: Reduction of Nitro Compounds Step 2: Reduction of Amides Step 3: Hoffmann Bromamide Degradation Step 4: Gabriel Phthalimide Synthesis Step 5: Alkylation of Ammonia

Step 1: Given Data Step 2: Using Osmotic Pressure Formula Step 3: Substituting Values

Step 1: Preparation of Diazonium Salt Diazonium salts are prepared by diazotization, where an aromatic primary amine reacts with sodium nitrite ( ) and hydrochloric acid (HCl) at low temperatures (0–5°C). Step 2: Reactions of Diazonium Salt \begin{enumerate} \item Sandmeyer Reaction (Halogenation) \item Gattermann Reaction (Aryl Halide Formation) \item Coupling Reaction (Formation of Azo Compounds) \item Reduction to Phenylhydrazine \end{enumerate}

(i) Oxidation of primary alcohol: (ii) Rosenmund reduction: (iii) Stephen reaction: (iv) Hydrolysis of geminal dihalides: (v) Gattermann-Koch reaction:

Cerium ( ) has an atomic number of 58, with the electronic configuration: The state is stable due to the removal of outer electrons ( ), while the state achieves a stable configuration.

(i) 2-methylbenzaldehyde \;(o-methylbenzaldehyde).
(ii) 2,4-dimethylpentan-3-one.
(iii) 2-methoxypropanal.
(iv) hexane-1,6-dioic acid \;(hexanedioic acid, adipic acid).
(v) 2-phenylethanoic acid \;(phenylacetic acid).

Definition: Clemmensen reduction converts aldehydes and ketones to the corresponding methylene compounds using zinc amalgam and concentrated hydrochloric acid.
Example: Acetophenone to ethylbenzene
Note: Works best for acid-stable substrates; for base-sensitive substrates use Wolff–Kishner instead.

i) Tischenko Reaction:
- It is the disproportionation of aldehydes (without -hydrogen) in the presence of an alkoxide catalyst to give esters.
Example:
(Product: ethyl acetate)
ii) Cannizzaro's Reaction:
- This is the base-induced disproportionation of aldehydes without -hydrogen into alcohol and carboxylate salt.
Example:
iii) Clemmensen Reduction:
- It is the reduction of carbonyl compounds (aldehydes and ketones) to hydrocarbons using zinc amalgam and concentrated HCl.
Example:
(Product: toluene)
Thus, these three reactions are important methods: Tischenko (ester formation), Cannizzaro (disproportionation), and Clemmensen (reduction).

i) Acetone + conc.\ (distillation):
Self-condensation and aromatization give mesitylene.

Mesitylene (1,3,5-trimethylbenzene), formula .
ii) Iodoform reaction of acetone (NaOH, , heat):

Iodoform, formula (yellow ppt.).
iii) Aldol reaction of acetaldehyde then dehydration:


3-Hydroxybutanal (aldol), formula .
Crotonaldehyde (but-2-enal), formula .
iv) Formaldehyde with (Cannizzaro):

Calcium formate, formula .

(i) Aldol
An Aldol reaction is a type of organic reaction where an enolate ion (or sometimes an aldehyde or ketone) reacts with a carbonyl compound to form a β-hydroxy aldehyde or ketone, also called an aldol. The reaction occurs due to the nucleophilic attack of the enolate or aldehyde carbonyl carbon. The general form of the aldol reaction is: Example: The reaction between acetaldehyde (CH₃CHO) and acetaldehyde gives 4-hydroxybutanal (a β-hydroxy aldehyde), which is an aldol addition product.

Structural formula of benzaldehyde:

(i) With hydrazine (formation of hydrazone):

(ii) With Tollen's reagent (silver mirror test; oxidation to benzoate/benzoic acid):

(On acidification ).
(iii) Nitration (HNO /H SO ; meta directing):

(Product: -nitrobenzaldehyde).
(iv) With NaOH (Cannizzaro reaction; no -H):
(On acidification of benzoate ).

IUPAC name:
Acetaldehyde ethanal .
(i) With sodium bisulfite (NaHSO ): addition product
(Product: sodium 1-hydroxyethanesulfonate; bisulfite addition compound.)
(ii) With NaOH (aldol reaction)
Cold, dilute NaOH (aldol):
(3-hydroxybutanal)
On warming (dehydration to unsaturated aldehyde):
(crotonaldehyde)
(iii) With hydroxylamine (oxime formation)
(acetaldoxime)
(iv) With methanol in presence of dry HCl (acetal formation)
Via hemiacetal, then acetal:
(Product: acetal, 1,1-dimethoxyethane)

(i) Longest chain contains 7 carbons including the carbonyl carbon; the C=O is at C-2.

(ii) Parent chain includes the group hexanal; substituents: bromo at C-4 and methyl at C-2.

(i) Identification and equations:
Dry distillation of calcium formate gives formaldehyde.

Formaldehyde undergoes Cannizzaro reaction with NaOH to give sodium formate and methanol.

Therefore:
Formaldehyde, formula .
Sodium formate, formula .
(ii) Identification and equations:
Dry distillation of mixed calcium acetate and calcium formate gives acetaldehyde.

Addition of HCN to acetaldehyde gives its cyanohydrin (lactonitrile).

Hydrolysis of the nitrile yields lactic acid (2-hydroxypropanoic acid).

Therefore:
Acetaldehyde, formula .
Acetaldehyde cyanohydrin (lactonitrile), formula .
Lactic acid (2-hydroxypropanoic acid), formula .

1. Oxidation of secondary alcohols:

2. Ozonolysis of alkenes:

3. Friedel–Crafts acylation of aromatic compounds:

4. From calcium salts of carboxylic acids (dry distillation):

5. From nitriles (using dialkyl cadmium):

Thus, ketones can be prepared by oxidation, ozonolysis, acylation, dry distillation, and nitrile methods.

Methods of Preparation:
1. Oxidation of primary alcohols/aldehydes:

2. Hydrolysis of nitriles:

--- Chemical Properties:
1. Acidic nature:

2. Reaction with alcohols (esterification):

3. Decarboxylation:

Thus, carboxylic acids are prepared by oxidation and hydrolysis, and show acidic, esterification, and decarboxylation reactions.

Carbonyl group (C=O):
- The carbonyl group consists of a carbon atom double-bonded to an oxygen atom.
- The C=O bond is polar because oxygen is more electronegative than carbon.
- The carbon atom has a partial positive charge ( ) and oxygen a partial negative charge ( ).
- This polarity makes the carbonyl carbon susceptible to nucleophilic attack and the oxygen capable of hydrogen bonding.
- Hence, aldehydes and ketones (which contain the carbonyl group) undergo nucleophilic addition reactions.
Carboxylic group (–COOH):
- The carboxyl group is composed of a carbonyl group (C=O) and a hydroxyl group (–OH) attached to the same carbon.
- Due to resonance, the carboxyl group exists as a hybrid of two structures, making the C–O bonds equivalent.
- The O–H bond is highly polar, so carboxylic acids are acidic in nature and readily donate a proton (H ).
- They form dimers through strong intermolecular hydrogen bonding, giving them higher boiling points.

- Sodium hydrogen sulphite reacts with aldehydes and ketones to form addition compounds, such as bisulfite adducts.
- Phenyl hydrazine reacts with carbonyl compounds (like acetone and benzaldehyde) to form hydrazones.
- Fehling's solution reacts with aldehydes, especially in the presence of a reducing agent.
- Grignard reagents do not react directly with acetone or benzaldehyde, as they are more likely to react with carbonyl compounds to form alcohols upon hydrolysis. Grignard reagents typically do not react with the carbonyl group in the way that sodium bisulfite or hydrazine does.
Therefore, the correct answer is option (D) Grignard reagent.

Step 1: Functional group tests.
2,4-DNP test (A) contains a carbonyl group (aldehyde/ketone).
Tollens/Fehling tests not an aldehyde (A) is a ketone.
Iodoform test with I /NaOH methyl ketone fragment .

Step 2: Unsaturation test.
No decolourisation of Br -water/alkaline KMnO no reactive in the side chain (an aromatic ring does not respond to these).

Step 3: Use formulas to infer the skeleton.
Given molecular formula C H O with a methyl-ketone group suggests (acetophenone, phenyl methyl ketone).

Step 4: Check with oxidation product.
Strong oxidation of an aryl side chain (including aryl methyl ketones) with chromic acid gives benzoic acid, C H O , which matches (B).
(Consistency check: iodoform reaction of (A): )

The Cannizzaro reaction is a redox (disproportionation) reaction that occurs when an aldehyde without an -hydrogen atom (such as formaldehyde, benzaldehyde) is treated with a concentrated alkali.
In this reaction:
- One molecule of the aldehyde is oxidized to a carboxylate ion, and
- Another molecule of the same aldehyde is reduced to a primary alcohol.
General reaction:

Example with formaldehyde:

Thus, the Cannizzaro reaction simultaneously produces an alcohol and a carboxylate salt.

Tollen’s test is used to detect the presence of **aldehydes** in a given sample. The reagent used is **Tollen’s reagent**, which is a solution of silver nitrate (AgNO ) in aqueous ammonia (NH ). Step 1: Reaction with aldehydes.
When an aldehyde is present, it reduces the Tollen’s reagent, resulting in the deposition of **silver mirror** on the inner surface of the test tube. The aldehyde is oxidized to a carboxylic acid in the process: Here, **RCHO** is the aldehyde group, and **RCOOH** is the corresponding carboxylic acid. The silver ions (Ag ) are reduced to metallic silver, which deposits as a mirror.
Step 2: Application.
This test is widely used for the qualitative detection of aldehydes, as ketones do not react with Tollen's reagent. Final Answer:

(i) 3-Hydroxybutanol (3-hydroxybutan-1-ol 1,3-butanediol) from ethanol
(ii) But-2-enal (crotonaldehyde) from ethanol

Fehling's solution is reduced by aldehydes and by formic acid (HCOOH), forming red Cu O.
- HCHO (formaldehyde) and CH CHO (acetaldehyde) are aliphatic aldehydes give positive Fehling test.
- HCOOH is a special case: though it is a carboxylic acid, it is readily oxidized to CO and reduces Fehling's solution.
- CH COOH (acetic acid) is a typical carboxylic acid and is not a reducing agent does not reduce Fehling's solution.

(A) Toluene:
Toluene can be oxidized to benzoic acid using potassium permanganate: (B) Ethane nitrile:
Ethane nitrile (ethyl cyanide) can be hydrolyzed to acetic acid: (C) Ethanamide:
Ethanamide can be hydrolyzed to acetic acid under acidic conditions: (D) RMgX:
Grignard reagents (RMgX) can react with carbon dioxide to form carboxylic acids: v) Benzoic anhydride:
Benzoic anhydride can be hydrolyzed to benzoic acid: Final Answer: (A) Toluene → Benzoic acid with potassium permanganate
(B) Ethane nitrile → Acetic acid with water and acid
(C) Ethanamide → Acetic acid with water and acid
(D) RMgX → Carboxylic acid with CO₂
v) Benzoic anhydride → Benzoic acid with water Correct Answer: Equations for each reaction are shown above.

Step 1: Identify the Type of Compounds
Fehling’s solution is used to identify **reducing sugars** and **aldehydes**. It contains copper((B) ions that are reduced to copper((A) oxide when reacted with reducing agents.
Step 2: Chemical Equation
When Fehling’s solution reacts with an aldehyde group, the copper((B) ions are reduced, and a red precipitate of copper((A) oxide forms: where is the aldehyde, and is the red precipitate. Final Answer: Fehling’s solution identifies reducing sugars and aldehydes. Correct Answer: Reducing sugars and aldehydes.