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Aldehydes, Ketones and Carboxylic Acids

Carbonyl Group – Nomenclature and Structure

Nomenclature

In the IUPAC system, aliphatic carboxylic acids are named as follows:

  • By replacing the ending ‘− e’ in the name of the corresponding alkane with ‘− oic acid’

  • Carboxylic carbon is numbered one.

  • If more than one carboxyl groups are present, then the ending ‘− e’ of the alkane is retained.

  • The number of carboxyl groups is indicated by adding prefix, di, tri, etc. to the term ‘oic’.

The given table lists the common and IUPAC names and structures of some carboxylic acids.

Names and Structures of Some Carboxylic Acids

Structure

Common name

IUPAC name

HCOOH

Formic acid

Methanoic acid

CH3COOH

Acetic acid

Ethanoic acid

CH3CH2COOH

Propionic acid

Propanoic acid

CH3CH2CH2COOH

Butyric acid

Butanoic acid

(CH3)2CHCOOH

Isobutyric acid

2-Methylpropanoic acid

HOOC-COOH

Oxalic acid

Ethanedioic acid

HOOC −CH2-COOH

Malonic acid

Propanedioic acid

HOOC -(CH2)2-COOH

Succinic acid

Butanedioic acid

HOOC -(CH2)3-COOH

Glutaric acid

Pentanedioic acid

HOOC -(CH2)4-COOH

Adipic acid

Hexanedioic acid

HOOC -CH2-CH(COOH)-CH2-COOH

Propane-1, 2, 3-

tricarboxylic acid

Benzoic acid

Benzenecarboxylic acid

(Benzoic acid)

Phenylacetic acid

2-Phenylethanoic acid

Phthalic acid

Benzene-1, 2-dicarboxylic

acid

Structure of Carboxyl Group

  • Carboxyl carbon is less electrophilic than carbonyl carbon because of resonance.

  • Bonds to the carboxyl carbon lie in one plane and are separated by about 120°.

Methods of Preparation of Carboxylic Acid

  • From primary alcohols

  • From aldehydes

Oxidising agents − HNO3, KMnO4, K2Cr2O7 and mild oxidising agents as well like Tollen’s reagent and Fehling’s reagent.

  • From alkyl benzenes

  • 1° and 2° alkyl benzene are oxidised in this manner.

  • Tertiary group is not affected.

  • From nitriles and amides

  • From Grignard reagents

  • From acyl halides

  • From acid anhydrides

  • From esters

  • Ester Carboxylic acid + Alcohol

Example:

  •  

Examples:

Nomenclature

Common Names of Aldehydes

  • Often called by their common names instead of IUPAC names

  • Derived from the common names of the carboxylic acids by replacing the ending ‘−ic’ of the acid with aldehyde

  • Location of the substituent in the carbon chain is indicated by the Greek letters α, β, γ, δ, etc.

  • Example:

Common Names of Ketones

  • Derived by naming two alkyl or aryl groups bonded to the carbonyl group

  • Locations of substituents are indicated by the Greek Letters, α, α′, β, β′, and so on 

  • The simplest dimethyl ketone is called acetone.

  • Alkyl phenyl ketones are usually named by adding the acyl group as prefix to phenone.

IUPAC Names

  • For open-chain aliphatic aldehydes and ketones, IUPAC names are derived from the names of the corresponding alkanes by replacing the ending ‘−e’ with ‘−al’ and ‘−one’ respectively.

  • In the case of aldehydes, the longest chain is numbered starting from the carbon of the aldehydic group.

  • In the case of ketones, the numbering begins from the end nearer to the carbonyl gro…

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