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CBSE Class 12 · Chemistry

Aldehydes, Ketones and Carboxylic Acids

Official NCERT chapter from Chemistry Part I–II (book code lech1). ExamMaster notes are original teaching at CBSE Class 12 depth.

This lesson follows the official chapter “Aldehydes, Ketones and Carboxylic Acids” in Chemistry Part I–II. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 12
  • Medium level
  • 8 concepts

1Nomenclature and Structure of Carbonyl Group

Carbonyl nomenclature and structure: -CHO is aldehyde, C=O in a chain is ketone as taught; C is trigonal. Ethanal, propanone as cases. A name is a rule-output; the structure is a planar C=O.

Calling every C=O a carboxyl is a miss — that needs OH too.

Figure. Both families share one C=O. An aldehyde keeps a hydrogen on that carbon (R–CHO). A ketone replaces the hydrogen with a second carbon group (R–CO–R′). The H is the naming test, not a decoration.

How it works

  1. Spot H–C=O versus C–(C=O)–CThe split.
  2. Write the taught -al or -one nameThe name.
  3. Keep C trigonalThe shape.

2Preparation of Aldehydes and Ketones

Preparation of aldehydes and ketones: from alcohols (oxidation as taught), from acid chlorides or the lesson’s list. Preparation is a from-what. One school route each is enough.

A carboxylic-acid dump as the only prep is a skip of this heading.

Figure. A primary alcohol oxidises to an aldehyde and, if the oxidant is not stopped, to a carboxylic acid. A secondary alcohol oxidises to a ketone and stays there. That stop is the school distinction, not a longer reagent list.

How it works

  1. Name the starting lookThe from.
  2. Name the taught reagentThe route.
  3. Keep aldehyde ≠ ketone as the product-lookHonest.

3Physical Properties

Physical properties: boiling and mix as taught — carbonyls are polar; they mix better than hydrocarbons of like size as framed. Physical is a look, not a mechanism.

A nucleophilic-add as a physical property is a swap.

Figure. Same two-carbon chain, three functional groups. Ethanal 293 K has only a dipole. Ethanol 351 K adds O–H hydrogen bonds. Ethanoic acid 391 K dimerises through two hydrogen bonds, so it boils highest. The bars are the NCERT boiling points in kelvin.

How it works

  1. Name bp or mix as taughtThe property.
  2. Keep polarity as the whyThe look.
  3. Refuse a mechanism herePhysical.

4Chemical Reactions

Chemical reactions: nucleophilic addition as the school carbonyl-job; oxidation of aldehydes (Tollens/Fehling if named) that ketones sit out as framed. Reaction is who-adds-to-C=O, not a boil.

Treating ketones as equally easy to oxidise as aldehydes is a miss if the lesson split them.

Figure. Nucleophilic addition at C=O is the shared first step. Tollens reagent then asks whether the carbonyl can reduce Ag⁺ to a silver mirror. An aldehyde does. An ordinary ketone does not. The figure is the board test, not a mechanism cartoon.

How it works

  1. Name addition to C=OThe job.
  2. Keep aldehyde-oxidise as the extra test if taughtThe split.
  3. Refuse a physical bp as this headingChemistry.

5Uses of Aldehydes and Ketones

Uses of aldehydes and ketones: formalin, acetone as taught — one honest use each. Use is a column, not a brand-ad and not a how-to.

A scare or a workshop-recipe is the wrong size.

Figure. School uses stay attached to one compound: formalin is 40% methanal used to preserve, propanone is the common solvent, benzaldehyde is the flavour note. A use-list without the compound is not this heading.

How it works

  1. Name the taught compoundThe case.
  2. Attach one school useThe sentence.
  3. Refuse a how-toThis class.

6Nomenclature and Structure of Carboxyl Group

Carboxyl nomenclature and structure: -COOH as taught; a resonance-look if named. Ethanoic acid as the case. Carboxyl is OH on a carbonyl — a different group from aldehyde.

An aldehyde labelled acid because both have C=O is a miss.

Figure. A carboxyl carbon already carries C=O and OH. That extra oxygen is why R–COOH is not just “an aldehyde with an acid name”. The left stack is one carbon; the right pair is the aldehyde contrast with no extra O.

How it works

  1. Spot -COOHThe group.
  2. Write the taught -oic acid nameThe name.
  3. Keep it not an aldehydeTwo groups.

7Methods of Preparation of Carboxylic Acids

Preparation of carboxylic acids: oxidation of aldehydes/alcohols as taught, or from nitriles if listed. Preparation is a from-what. One school route is enough.

A ketone-oxidation as the default acid-route is a miss if the lesson did not allow it.

Figure. The two Class-12 routes that must be drawable without a mechanism: oxidise the primary alcohol (or its aldehyde) all the way to the acid, or hydrolyse a nitrile with acid. Both end at the same RCOOH box.

How it works

  1. Name the starting lookThe from.
  2. Name the taught oxidise or hydrolyseThe route.
  3. Keep the product as -COOHThis heading.

8Uses of Carboxylic Acids

Uses of carboxylic acids: vinegar (ethanoic) as taught — a named use, school-size. Use is a column, not a kitchen-manual.

A how-to pickle as the whole heading is the wrong size.

Figure. Ethanoic acid is vinegar and the acetate industry. Sodium salts of long-chain acids are soaps. Sodium benzoate is the food preservative. The compound is named first; the use hangs on it.

How it works

  1. Name the taught acidThe case.
  2. Attach one school useThe sentence.
  3. Refuse a how-toThis class.
An aldehyde has
  1. H–C=O as taught
  2. Only C–(C=O)–C
  3. -COOH

The H on the carbonyl.

Notes

  • Mapped to the official NCERT chapter “Aldehydes, Ketones and Carboxylic Acids”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Formulas

  • aldehyde: H–C=O
  • ketone: C–(C=O)–C
  • acid: -COOH

Recap

Hold these pegs from the official chapter “Aldehydes, Ketones and Carboxylic Acids”. The wording is ExamMaster’s teaching, not a textbook recap.

Nomenclature and Structure of Carbonyl Group
Carbonyl nomenclature and structure: -CHO is aldehyde, C=O in a chain is ketone as taught; C is trigonal.
Preparation of Aldehydes and Ketones
Preparation of aldehydes and ketones: from alcohols (oxidation as taught), from acid chlorides or the lesson’s list.
Physical Properties
Physical properties: boiling and mix as taught — carbonyls are polar; they mix better than hydrocarbons of like size as framed.
Chemical Reactions
Chemical reactions: nucleophilic addition as the school carbonyl-job; oxidation of aldehydes (Tollens/Fehling if named) that ketones sit out as framed.
Uses of Aldehydes and Ketones
Uses of aldehydes and ketones: formalin, acetone as taught — one honest use each.
Nomenclature and Structure of Carboxyl Group
Carboxyl nomenclature and structure: -COOH as taught; a resonance-look if named.

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