Ch 8Aldehydes, Ketones and Carboxylic Acids — Class 12 Chemistry, concept-first.

By the end of this chapter, you should be able to:

Aldehydes and ketones are both carbonyl compounds — every molecule in either family carries a carbon-oxygen double bond, , as its characteristic functional group.

Aldehydes and ketones are the simplest and most important carbonyl compounds, and each one can be named in two ways: an older common name and a systematic IUPAC name.

The carbonyl carbon atom is -hybridised. It uses its three orbitals to form three sigma () bonds — two to the substituents (R groups or hydrogen) and one to the oxygen atom.

Having seen how the carbonyl group is put together electronically in 8.1, the natural next question is how a chemist actually installs a into a molecule. The methods split into two kinds:

The most direct way to reach a carbonyl compound is to oxidise the corresponding alcohol. A primary alcohol, oxidised carefully, stops at the aldehyde; a secondary alcohol, oxidised under the same kin…

An acyl (acid) chloride can be hydrogenated directly to the corresponding aldehyde using hydrogen gas over a palladium catalyst that has been partially deactivated by depositing it on barium sulphate.…

An acyl chloride reacts with a dialkylcadmium reagent to give a ketone. The dialkylcadmium itself is made first, by reacting a Grignard reagent with cadmium chloride.

Among the carbonyl compounds, methanal (formaldehyde) is a gas at ordinary room temperature, while ethanal (acetaldehyde) is a liquid so volatile that it boils just above room temperature.

Aldehydes and ketones both carry the carbonyl group, , as their functional group, and this shared group is why the two classes undergo largely parallel chemistry.

Aldehydes and ketones are not just laboratory curiosities — they are everyday industrial workhorses. Across the chemical industry they are put to work in three broad roles:

Compounds that carry a group are called carboxylic acids. This group is really two familiar groups fused together — a carbonyl () and a hydroxyl () sharing the same carbon — and that fusion is exactly…

Because carboxylic acids were among the very first organic compounds ever isolated, many of them are still known chiefly by their traditional, non-systematic names.

The carboxyl carbon is planar: the three groups attached to it — the alkyl/aryl group, the doubly-bonded oxygen, and the oxygen — all lie in a single plane, arranged around the carbon at bond angles o…

Carboxylic acids can be built up from several different starting functional groups — alcohols, aldehydes, aromatic side chains, nitriles, amides, esters, Grignard reagents, and acyl derivatives.

Aliphatic carboxylic acids with up to nine carbon atoms are colourless liquids at room temperature and carry a sharp, unpleasant (pungent/sour) smell — acetic acid, for instance, is the sour-smelling…

Carboxylic acids owe their rich chemistry to three separate reactive sites in the group: the acidic bond, the bond (which behaves somewhat like the C–OH of an alcohol), and the carboxyl carbon itself,…

The hydrogen is acidic. Like alcohols, carboxylic acids liberate hydrogen gas with reactive (electropositive) metals, and like phenols they form salts with alkalis.

In these reactions the entire of the carboxyl group is replaced by another group while the carbonyl carbon is retained — this is exactly analogous to reactions at the bond of an alcohol.

These reactions affect the carboxyl group as a whole, rather than just one bond within it.

Once a carboxyl group is present, it also influences how the rest of the hydrocarbon skeleton — the alkyl chain in an aliphatic acid, or the ring in an aromatic acid — reacts further.

Carboxylic acids are not just a functional group to name and prepare — several of them are everyday industrial chemicals.

- Carbonyl group () is the functional core: aldehydes have it at chain end (), ketones within chain (). - Nomenclature: suffix -al for aldehydes, -one for ketones; carboxylic acids use -oic acid ().

These are the final answers printed at the end of the NCERT chapter. The book gives answers for some intext questions only — every question below links to our complete worked solution.

Higher-order thinking / exemplar-style practice problems.

Sample papers and previous-year board questions for this subject.