Class 12 Chemistry – Aldehydes, Ketones and Carboxylic Acids

Part 1 – Introduction, Nomenclature, Structure & Preparation

1. Carbonyl Compounds

Organic compounds containing the carbonyl group (>C=O) are called carbonyl compounds.

Types

Compound	Functional Group	General Formula
Aldehyde	–CHO	R–CHO
Ketone	>C=O	R–CO–R′
Carboxylic Acid	–COOH	R–COOH

Difference between Aldehyde and Ketone

Aldehyde	Ketone
Carbonyl carbon is attached to one H atom	Carbonyl carbon is attached to two carbon atoms
Always present at end of chain	Can occur in middle of chain
More reactive	Less reactive

2. Nomenclature of Aldehydes & Ketones

There are two systems:

Common names
IUPAC names

A. Common Names

Aldehydes

Common names are obtained from the corresponding carboxylic acid.

Acid	Aldehyde
Formic acid	Formaldehyde
Acetic acid	Acetaldehyde
Propionic acid	Propionaldehyde
Butyric acid	Butyraldehyde

Remember: Replace “-ic acid” → “aldehyde”

Ketones

Common names are formed by writing the names of the two alkyl groups attached to the carbonyl carbon.

Examples:

CH₃COCH₃ → Dimethyl ketone (Acetone)

CH₃COC₂H₅ → Methyl ethyl ketone

B. IUPAC Names

Aldehydes

Replace -e of alkane by -al

Examples

Formula	IUPAC Name
HCHO	Methanal
CH₃CHO	Ethanal
CH₃CH₂CHO	Propanal
CH₃CH₂CH₂CHO	Butanal

Ketones

Replace -e by -one

Examples

Formula	IUPAC Name
CH₃COCH₃	Propanone
CH₃COCH₂CH₃	Butan-2-one
CH₃CH₂COCH₂CH₃	Pentan-3-one

Important Naming Rules

✔ Aldehyde carbon is always Carbon-1

✔ In ketones, numbering starts from the end nearest to the carbonyl group.

✔ For cyclic aldehydes use carbaldehyde

Example

Cyclohexane-CHO

→ Cyclohexanecarbaldehyde

✔ Benzaldehyde is an accepted IUPAC name.

Board Important Common ↔ IUPAC Names

Common Name	IUPAC Name
Formaldehyde	Methanal
Acetaldehyde	Ethanal
Acetone	Propanone
Acrolein	Prop-2-enal
Benzaldehyde	Benzaldehyde
Valeraldehyde	Pentanal

Tip: Learn these directly. They are frequently asked in boards.

3. Structure of Carbonyl Group

Hybridisation

Carbonyl carbon is sp² hybridised

Shape → Trigonal planar

Bond angle → 120°

Nature of Carbonyl Bond

Carbonyl bond consists of

One σ bond
One π bond

Polarity

Oxygen is more electronegative than carbon.

Therefore

Oxygen → δ⁻

Carbon → δ⁺

Hence,

Carbon acts as an electrophilic centre
Oxygen acts as a nucleophilic centre

This polarity explains many reactions of aldehydes and ketones.

4. Preparation of Aldehydes & Ketones

1. Oxidation of Alcohols

Primary alcohol

Primary alcohol → Aldehyde

Example

CH₃CH₂OH → CH₃CHO

Secondary alcohol

Secondary alcohol → Ketone

Example

CH₃CHOHCH₃ → CH₃COCH₃

2. Dehydrogenation of Alcohols

Alcohol vapours are passed over Cu or Ag catalyst.

Primary alcohol → Aldehyde

Secondary alcohol → Ketone

3. Ozonolysis of Alkenes

Alkene + O₃

followed by Zn/H₂O

↓

Aldehydes and/or Ketones

4. Hydration of Alkynes

Ethyne gives Ethanal
Other alkynes give Ketones

Preparation of Aldehydes (Special Methods)

Rosenmund Reduction

Acid chloride

↓

H₂ / Pd–BaSO₄

↓

Aldehyde

Remember: Acid chloride → Aldehyde

Stephen Reaction

Nitrile

↓

SnCl₂/HCl

↓

Hydrolysis

↓

Aldehyde

DIBAL-H Reduction

Nitriles and esters on selective reduction with DIBAL-H give aldehydes.

Etard Reaction ⭐

Toluene

↓

CrO₂Cl₂

↓

Benzaldehyde

Gattermann–Koch Reaction ⭐

Benzene

↓

CO + HCl

AlCl₃/CuCl

↓

Benzaldehyde

Side-chain Chlorination

Toluene

↓

Benzal chloride

↓

Hydrolysis

↓

Benzaldehyde

Preparation of Ketones

From Acyl Chlorides

Acid chloride

↓

Dialkyl cadmium

↓

Ketone

From Nitriles

Nitrile

↓

Grignard reagent

↓

Hydrolysis

↓

Ketone

Friedel–Crafts Acylation ⭐

Benzene

↓

Acid chloride + AlCl₃

↓

Aromatic ketone

Very Important Board Reaction

Board Exam Named Reactions (Learn These)

Reaction	Product
Rosenmund Reduction	Aldehyde
Stephen Reaction	Aldehyde
Etard Reaction	Benzaldehyde
Gattermann–Koch	Benzaldehyde
Friedel–Crafts Acylation	Ketone

One-Minute Revision

Carbonyl Group

C=O

↓

Polar

↓

Carbon = Electrophilic

↓

Oxygen = Nucleophilic

Hybridisation

sp²

↓

120°

↓

Planar

Alcohol → Product

Primary alcohol → Aldehyde

Secondary alcohol → Ketone

Most Important Named Reactions

Rosenmund Reduction
Stephen Reaction
Etard Reaction
Gattermann–Koch Reaction
Friedel–Crafts Acylation

Memory

“RSEGF” = Order of important preparation reactions

R → Rosenmund
S → Stephen
E → Etard
G → Gattermann–Koch
F → Friedel–Crafts Acylation

Part 2 – Physical Properties & Chemical Reactions of Aldehydes and Ketones

5. Physical Properties

A. Physical State

Compound	State at Room Temperature
Methanal	Gas
Ethanal	Volatile liquid
Higher aldehydes & ketones	Liquid or solid

B. Boiling Point

Order

Hydrocarbons < Ethers < Aldehydes ≈ Ketones < Alcohols

Reason

Aldehydes and ketones have dipole–dipole attraction.
Alcohols have intermolecular hydrogen bonding, so their boiling points are higher.

Example

n-Butane < Methoxyethane < Propanal < Propan-1-ol

C. Solubility

Lower members (methanal, ethanal, propanone)

✔ Completely miscible with water

Reason:

They form hydrogen bonds with water.

As carbon chain length increases,

➡ Solubility decreases.

D. Odour

Lower aldehydes → Sharp, pungent smell
Higher aldehydes & ketones → Pleasant fragrance

Many are used in perfumes and flavouring agents.

6. Chemical Reactions of Aldehydes & Ketones

Both contain the carbonyl group (>C=O), so many reactions are similar.

The most important reaction is:

Nucleophilic Addition

Why Does Nucleophilic Addition Occur?

Carbonyl carbon carries a partial positive charge (δ⁺).

Hence, nucleophiles attack this carbon.

General Steps

Step 1

Nucleophile attacks carbonyl carbon.

↓

Step 2

Intermediate is formed.

↓

Step 3

Proton (H⁺) adds.

↓

Final Product

Addition product

Remember: Carbon changes from sp² → sp³ hybridisation during the reaction.

Reactivity Order

Aldehydes are more reactive than ketones.

Reason

(i) Steric Effect

Ketones have two alkyl groups, making it difficult for the nucleophile to approach.

Aldehydes have only one alkyl group.

(ii) Electronic Effect

Alkyl groups donate electrons (+I effect), reducing the positive charge on the carbonyl carbon.

Ketones have two electron-donating groups, so they are less reactive.

Overall Order

Formaldehyde > Other Aldehydes > Ketones

Board Tip: This is one of the most frequently asked reasoning questions.

7. Important Nucleophilic Addition Reactions

A. Addition of HCN

Carbonyl compound + HCN

↓

Cyanohydrin

Product

Contains both

–OH
–CN

Use: Cyanohydrins are useful intermediates in organic synthesis.

B. Addition of Sodium Hydrogen Sulphite (NaHSO₃)

Carbonyl compound + NaHSO₃

↓

Bisulphite addition compound

Importance

Used for purification of aldehydes.
Most aldehydes readily form this compound.

C. Addition of Grignard Reagent (RMgX)

After hydrolysis:

Carbonyl Compound	Product
Formaldehyde	Primary alcohol
Other aldehydes	Secondary alcohol
Ketones	Tertiary alcohol

Very Important Conversion

D. Addition of Alcohol

One molecule of alcohol

↓

Hemiacetal

Contains

–OH
–OR

Two molecules of alcohol

↓

Acetal

Contains

Two –OR groups

Ketones

Ketones react similarly to form ketals.

E. Addition of Ammonia & Its Derivatives

Carbonyl compounds react with ammonia derivatives to form C=N derivatives.

Important Derivatives

Reagent	Product
NH₃	Imine
Hydroxylamine	Oxime
Hydrazine	Hydrazone
Phenylhydrazine	Phenylhydrazone
Semicarbazide	Semicarbazone
2,4-DNP	2,4-DNP derivative

Importance

These crystalline derivatives are used to identify aldehydes and ketones.

8. Reduction Reactions

A. Reduction to Alcohols

Reagents

NaBH₄
LiAlH₄
H₂/Ni

Products

Compound	Product
Aldehyde	Primary alcohol
Ketone	Secondary alcohol

B. Reduction to Hydrocarbon

Clemmensen Reduction

Reagent:

Zn(Hg)/Conc. HCl

Carbonyl group

↓

CH₂ group

Wolff–Kishner Reduction

Reagent:

NH₂NH₂/KOH

Heat

Carbonyl group

↓

CH₂ group

Board Trick

Both convert C=O → CH₂.

9. Oxidation Reactions

A. Aldehydes

Very easily oxidised

↓

Carboxylic acids

Common Oxidising Agents

KMnO₄
K₂Cr₂O₇
HNO₃

B. Ketones

Resist oxidation.

Strong oxidising agents break the carbon chain to form smaller carboxylic acids.

10. Tests to Distinguish Aldehydes & Ketones

Tollens’ Test

Reagent

Ammoniacal AgNO₃

Observation

Silver mirror forms.

Result

✔ Aldehydes → Positive

✘ Ketones → Negative

Fehling’s Test

Reagent

Fehling’s solution A + B

Observation

Brick-red precipitate (Cu₂O)

Result

✔ Aliphatic aldehydes → Positive

✘ Ketones → Negative

✘ Aromatic aldehydes (e.g., benzaldehyde) → Negative

2,4-DNP Test

Positive for both aldehydes and ketones.

Observation:

Yellow/orange precipitate.

Cannot distinguish between aldehydes and ketones.

11. Reactions Due to α-Hydrogen

What is α-Hydrogen?

Hydrogen attached to the α-carbon (carbon next to the carbonyl carbon).

Aldol Condensation

Condition

Dilute NaOH or KOH

Requirement

At least one α-hydrogen must be present.

Product

β-Hydroxy aldehyde (Aldol)

β-Hydroxy ketone (Ketol)

On heating,

↓

Water is removed

↓

α,β-unsaturated carbonyl compound

Cross Aldol Condensation

Occurs between two different aldehydes and/or ketones.

If both have α-hydrogen, a mixture of products is obtained.

12. Cannizzaro Reaction

Condition

Concentrated NaOH or KOH

Requirement

Aldehyde must NOT have α-hydrogen.

Reaction

One molecule is oxidised to a carboxylate salt.

Another molecule is reduced to an alcohol.

Example

Methanal

↓

Methanol + Sodium formate

Remember: Ketones do not undergo Cannizzaro reaction.

13. Electrophilic Substitution in Aromatic Aldehydes & Ketones

The –CHO and –COR groups:

Deactivate the benzene ring.
Direct incoming electrophiles to the meta position.

Board Exam Summary

Reactions to Remember

Reaction	Product
HCN	Cyanohydrin
NaHSO₃	Bisulphite compound
Alcohol	Hemiacetal / Acetal
NH₂OH	Oxime
NH₂NH₂	Hydrazone
Semicarbazide	Semicarbazone
RMgX	Alcohol
NaBH₄ / LiAlH₄	Alcohol
Zn(Hg)/HCl	Hydrocarbon
NH₂NH₂/KOH	Hydrocarbon

Important Tests

Test	Aldehyde	Ketone
Tollens’	✅ Positive	❌ Negative
Fehling’s	✅ Positive (aliphatic)	❌ Negative
2,4-DNP	✅ Positive	✅ Positive

Named Reactions to Memorise

Aldol Condensation
Cross Aldol Condensation
Cannizzaro Reaction
Clemmensen Reduction
Wolff–Kishner Reduction

Memory Trick

“THF-ACW” for common board tests and reactions:

T → Tollens’ test
H → HCN addition (Cyanohydrin)
F → Fehling’s test
A → Aldol condensation
C → Cannizzaro reaction
W → Wolff–Kishner reduction

Part 3 – Carboxylic Acids: Nomenclature, Structure, Preparation & Physical Properties

14. Carboxylic Acids

Organic compounds containing the functional group:

–COOH (Carboxyl Group)

are called carboxylic acids.

General Formula

R–COOH

where:

R = alkyl group → aliphatic acid
R = aryl group → aromatic acid

Examples:

CH₃COOH → Ethanoic acid

C₆H₅COOH → Benzoic acid

15. Structure of Carboxyl Group

The carboxyl group contains:

Carbonyl group (>C=O)
Hydroxyl group (–OH)

Structure:

     O
     ||
R — C — OH

Important Points

Carboxyl carbon is sp² hybridised.
Bond angle is approximately 120°.
The carbon atom is less electrophilic than aldehydes and ketones because of resonance.

16. Nomenclature of Carboxylic Acids

A. Common Names

Many carboxylic acids have common names based on their natural sources.

Examples:

Formula	Common Name	Source
HCOOH	Formic acid	Ants
CH₃COOH	Acetic acid	Vinegar
CH₃CH₂COOH	Propionic acid	Milk products
CH₃CH₂CH₂COOH	Butyric acid	Butter

B. IUPAC Names

Rules:

Rule 1:

Replace -e of alkane with:

-oic acid

Example:

CH₃CH₂COOH

Propane → Propanoic acid

Rule 2:

The carboxyl carbon is always numbered as Carbon-1.

Example:

CH₃CH₂CH₂COOH

Butanoic acid

Rule 3:

For compounds with two –COOH groups:

Use:

dioic acid
trioic acid

Examples:

HOOC–COOH

→ Ethanedioic acid

HOOC–CH₂–COOH

→ Propanedioic acid

Important Common & IUPAC Names

Common Name	IUPAC Name
Formic acid	Methanoic acid
Acetic acid	Ethanoic acid
Propionic acid	Propanoic acid
Butyric acid	Butanoic acid
Oxalic acid	Ethanedioic acid
Malonic acid	Propanedioic acid
Benzoic acid	Benzenecarboxylic acid

17. Preparation of Carboxylic Acids

1. From Primary Alcohols

Primary alcohols are oxidised to carboxylic acids.

Reagents:

KMnO₄
K₂Cr₂O₇
CrO₃

General reaction:

R–CH₂OH

↓

R–COOH

2. From Aldehydes

Aldehydes are easily oxidised.

R–CHO

↓

R–COOH

Oxidising agents:

KMnO₄
K₂Cr₂O₇
Tollens’ reagent

3. From Alkyl Benzenes

Alkyl benzene undergoes vigorous oxidation.

Example:

Toluene

↓

Benzoic acid

Reagents:

KMnO₄
Chromic acid

Important:

The entire side chain is converted into –COOH.

4. From Nitriles and Amides

Nitrile Hydrolysis

R–CN

↓

R–COOH

Conditions:

Acidic medium (H⁺)
or
Basic medium (OH⁻)

5. From Grignard Reagent

Grignard reagent reacts with carbon dioxide.

Reaction:

RMgX + CO₂

↓

Magnesium carboxylate

↓

Hydrolysis

↓

Carboxylic acid

Importance

This method increases the carbon chain by one carbon atom.

Example:

Ethyl magnesium bromide

↓

Propanoic acid

6. From Acid Chlorides and Anhydrides

Acid chloride hydrolysis

RCOCl + H₂O

↓

RCOOH + HCl

Acid anhydride hydrolysis

(RCO)₂O + H₂O

↓

2RCOOH

7. From Esters

Acidic Hydrolysis

Ester + Water

↓

Carboxylic acid + Alcohol

Basic Hydrolysis (Saponification)

Ester + NaOH

↓

Carboxylate salt

↓

Acidification

↓

Carboxylic acid

18. Physical Properties of Carboxylic Acids

A. Physical State

Type	State
Lower acids (up to C₉)	Colourless liquids
Higher acids	Wax-like solids

B. Boiling Point

Carboxylic acids have:

Higher boiling points than alcohols, aldehydes and ketones

Reason:

They form strong intermolecular hydrogen bonding.

Two acid molecules combine to form a:

Dimer

RCOOH ........ HOOC R

This increases molecular association.

C. Solubility in Water

Lower acids:

✔ Soluble in water

Reason:

Hydrogen bonding with water.

Higher acids:

✘ Less soluble

Reason:

Large hydrophobic alkyl group.

D. Solubility in Organic Solvents

Carboxylic acids dissolve in:

Benzene
Ether
Alcohol
Chloroform

Benzoic acid is almost insoluble in cold water.

Quick Revision Table

Topic	Key Point
Functional group	–COOH
General formula	RCOOH
Carbon hybridisation	sp²
Shape	Planar
IUPAC suffix	oic acid
Carbonyl carbon number	Always 1
Strong H-bonding	Highest boiling point
Grignard reagent + CO₂	Carboxylic acid
Nitrile hydrolysis	Carboxylic acid

Must Remember for Boards

Preparation Methods:

Alcohol → Oxidation → Acid

Aldehyde → Oxidation → Acid

Nitrile → Hydrolysis → Acid

Grignard + CO₂ → Acid

Ester → Hydrolysis → Acid

Part 4 – Acidity, Chemical Reactions, Uses & Complete Revision Sheet

19. Chemical Reactions of Carboxylic Acids

Carboxylic acids mainly show reactions involving:

Cleavage of O–H bond
Cleavage of C–OH bond
Reactions involving –COOH group
Substitution reactions in hydrocarbon part

20. Acidity of Carboxylic Acids

Carboxylic acids are acidic because they release H⁺ ions.

General reaction:

RCOOH ⇌ RCOO⁻ + H⁺

The conjugate base formed is:

Carboxylate ion (RCOO⁻)

It is stabilised by resonance.

Why are carboxylic acids more acidic than alcohols?

Carboxylate ion:

Negative charge is distributed over two oxygen atoms.
It is highly stable.

Alkoxide ion (from alcohol):

Negative charge is mainly on one oxygen atom.
Less stable.

Therefore:

Carboxylic acid > Alcohol in acidity

Acid Strength and pKa

Relation:

pKa = –log Ka

Lower pKa → stronger acid
Higher pKa → weaker acid

Example:

Trifluoroacetic acid is stronger than acetic acid because its pKa is lower.

21. Effect of Substituents on Acidity

Substituents affect the stability of carboxylate ion.

A. Electron Withdrawing Groups (EWG)

Examples:

–NO₂
–Cl
–F
–CN
–CF₃

Effect:

Increase acidity

Reason:

They stabilise the negative charge on carboxylate ion.

B. Electron Donating Groups (EDG)

Examples:

–CH₃
–OCH₃

Effect:

Decrease acidity

Reason:

They destabilise the carboxylate ion.

Acidity Order of Halogen Acids

FCH₂COOH > ClCH₂COOH > BrCH₂COOH > ICH₂COOH

Reason:

Fluorine has maximum electron withdrawing effect.

Important Order

CF₃COOH > CCl₃COOH > CHCl₂COOH > CH₃COOH

22. Reactions Involving Cleavage of O–H Bond

A. Reaction with Metals

Carboxylic acids react with active metals.

Example:

2RCOOH + 2Na

↓

2RCOONa + H₂

Hydrogen gas is released.

B. Reaction with Bases

RCOOH + NaOH

↓

RCOONa + H₂O

(Product: Sodium carboxylate)

C. Reaction with Sodium Bicarbonate

Carboxylic acids react with NaHCO₃ to produce CO₂.

Reaction:

RCOOH + NaHCO₃

↓

RCOONa + CO₂ + H₂O

Importance:

Used to identify carboxylic acid group.

Observation:

Brisk effervescence due to CO₂ gas

23. Reactions Involving Cleavage of C–OH Bond

A. Formation of Anhydrides

Two molecules of carboxylic acid combine on heating.

Reagent:

P₂O₅
Concentrated H₂SO₄

Reaction:

2RCOOH

↓

(RCO)₂O + H₂O

B. Esterification

Carboxylic acid + Alcohol

in presence of conc. H₂SO₄

↓

Ester + Water

General reaction:

RCOOH + R′OH

⇌

RCOOR′ + H₂O

Mechanism of Esterification

Step 1:

Protonation of carbonyl oxygen.

↓

Step 2:

Alcohol attacks carbonyl carbon.

↓

Step 3:

Water molecule leaves.

↓

Step 4:

Ester is formed.

This is a nucleophilic acyl substitution reaction.

C. Reaction with PCl₅, PCl₃ and SOCl₂

The –OH group of carboxylic acid is replaced by chlorine.

General reaction:

RCOOH + SOCl₂

↓

RCOCl + SO₂ + HCl

Product:

Acid chloride

Why is SOCl₂ preferred?

Because products:

SO₂
HCl

are gases and escape easily.

This makes purification easier.

D. Reaction with Ammonia

Carboxylic acid + NH₃

↓

Ammonium carboxylate

On heating:

↓

Amide

Example:

CH₃COOH + NH₃

↓

CH₃COONH₄

↓

CH₃CONH₂

24. Reactions Involving –COOH Group

A. Reduction ⭐

Carboxylic acids are reduced to primary alcohols.

Reagent:

LiAlH₄
Diborane (BH₃)

Reaction:

RCOOH

↓

RCH₂OH

Important:

NaBH₄ does not reduce carboxylic acids.

B. Decarboxylation

Removal of CO₂ from carboxylic acid salts.

Reagent:

Soda lime

(NaOH + CaO)

Reaction:

RCOONa

↓

RH + Na₂CO₃

Kolbe Electrolysis

Electrolysis of sodium salts of carboxylic acids produces hydrocarbons.

Product contains:

Double number of carbon atoms

Example:

CH₃COONa

↓

C₂H₆

25. Reactions in Hydrocarbon Part

Hell–Volhard–Zelinsky (HVZ) Reaction

Carboxylic acids having α-hydrogen undergo halogenation.

Reagents:

Cl₂ or Br₂

in presence of red phosphorus

Product:

α-halo carboxylic acid

Example:

CH₃COOH

↓

BrCH₂COOH

26. Aromatic Carboxylic Acids

Benzoic acid undergoes electrophilic substitution.

The –COOH group:

✔ Deactivates benzene ring

✔ Directs substitution to meta position

Reason:

Strong electron withdrawing nature.

27. Uses of Carboxylic Acids

Compound	Use
Methanoic acid	Rubber, textile, leather industries
Ethanoic acid	Vinegar and solvent
Hexanedioic acid	Nylon-6,6 manufacture
Benzoic acid esters	Perfumes
Sodium benzoate	Food preservative
Higher fatty acids	Soaps and detergents

COMPLETE CHAPTER QUICK REVISION

Functional Groups

Compound	Group
Aldehyde	–CHO
Ketone	>C=O
Carboxylic Acid	–COOH

Important Preparations

Aldehydes

Alcohol oxidation → Aldehyde

Acid chloride + H₂/Pd-BaSO₄ → Aldehyde

Nitrile + DIBAL-H → Aldehyde

Toluene + CrO₂Cl₂ → Benzaldehyde

Ketones

Secondary alcohol oxidation → Ketone

Acid chloride + Dialkyl cadmium → Ketone

Friedel-Crafts acylation → Ketone

Carboxylic Acids

Alcohol oxidation → Acid

Aldehyde oxidation → Acid

Nitrile hydrolysis → Acid

Grignard + CO₂ → Acid

Ester hydrolysis → Acid

Most Important Named Reactions

Reaction	Key Conversion
Rosenmund	Acid chloride → Aldehyde
Stephen	Nitrile → Aldehyde
Etard	Toluene → Benzaldehyde
Gattermann-Koch	Benzene → Benzaldehyde
Friedel-Crafts Acylation	Benzene → Ketone
Aldol Condensation	Carbonyl compound with α-H
Cannizzaro	Aldehyde without α-H
Clemmensen	C=O → CH₂
Wolff-Kishner	C=O → CH₂
HVZ Reaction	α-Halogenation of acids

Most Asked Tests

Test	Detects
Tollens’ Test	Aldehydes
Fehling’s Test	Aliphatic aldehydes
2,4-DNP Test	Aldehydes & Ketones
NaHCO₃ Test	Carboxylic acids