Chapter:12

What are Aldehyde Ketone and Carboxylic Acids ?

Nomenclature Of Aldehydes

Aldehydes are named by replacing the final ‘-e’ of the name of the corresponding alkane with ‘-al’.

Examples

NOMENCLATURE OF ALDEHYDES

Preparation of Aldehyde s

By dry distillation of calcium salts of fatty acids

By reduction Reactions

  • Rosenmund Reduction
  • Stephen Reduction

From alkenes

From alkynes

Physical Properties Of Aldehydes

  • Lower aldehydes are soluble in water while higher aldehydes are soluble in organic solvents.
  • Lower members have unpleasant odour whereas higher members possess fruity smell.
  • Lower members except HCHO (is a gas) are colourless and volatile liquids whereas higher members are solid.
  • Boiling points increases with increase in molecular weights.

Chemical Properties Of Aldehydes

Aldehydes contains carbonyl group attached to an alkyl group online hand and to a hydrogen atom on the other.
Thus, the reactions are classified into the following groups :

  • Reactions due to alkyl group.
  • Reactions due to carbonyl group.
  • Reactions due to the hydrogen atom.
  • Replacement of carbonyl oxygen atom with other groups.
  • Special reactions.
CHEMICAL PROPERTIES OF ALDEHYDES

Uses Of Aldehyde

  • In chemical industry aldehydes and ketones are used as solvents, starting materials and reagents for the synthesis of other products.
  • Formaldehyde is well known as formalin (40%) solution used to preserve biological specimens and to prepare Bakelite (a phenol-formaldehyde resin), urea-formaldehyde glues and other polymeric products.
  • Acetaldehyde is used primarily as a starting material in the manufacture of acetic acid, ethyl acetate, vinyl acetate, polymers and drugs.
  • Benzaldehyde is used perfumery and in dye industries.
  • Acetone and ethyl methyl ketone are common industrial solvents.

Nomenclature Of Ketones

Ketones are named by replacing the final ‘-e’ of the name of the corresponding alkane with ‘-one’.

The parent chain is then numbered in the way that gives the carbonyl carbon atom the lowest possible number, and this number is used to indicate is position.

NOMENCLATURE OF KETONES

Preparation Of Ketones

Ketones constitute a class of compounds characterised by the presence of a carbonyl group, > C = O united to two alkyl group. Ketones are of two types one is simple ketones in which alkyl groups are same and the other is mixed ketones in which both the alkyl groups are different. Ketones are isomeric with aldehydes and form a homologous series having general formula CnH2nO.

General Methods of Preparations

  • By direct oxidation of secondary alcohols
  • From Acid chlorides
  • By heating calcium salt of fatty acids  

Physical Properties Of Ketones

  • Lower ketones are colourless liquids while higher ketones are colourless solids.
  • Density of ketones are less than that of water.
  • Ketones are polar compounds.
  • Lower ketones are soluble in water, higher ketones are soluble in alcohol and ether.

Chemical Properties Of Ketones

  • Structurally ketones are similar to aldehydes, hence, the characteristics are mostly similar to aldehydes.
  • Reaction with primary amines.
  • Oxidation of Ketones.
  • Reduction of Ketones.

Uses Of Ketones

  • As a solvent in the manufacture of cordite, artificial silk.
  • As an ingredient of nail polishes.
  • As a raw material for making chloroform, tear gas.
  • For making cellulose acetate rayon.

Nomenclature Of Carboxylic Acids

  • Organic compounds which contain the carboxyl functional group are called as carboxylic acids.
  • The name carboxyl is derived from carbonyl (C = O) and hydroxyl (OH) because in the carboxyl group these two groups are directly bonded to each other.
NOMENCLATURE OF CARBOXYLIC ACIDS
  • Carboxyl group are further classified as monocarboxylic acid, dicarboxlic acid, tricarboxylic acid.
  • The long chain monocarboxylic acids are commonly known as fatty acid.

Carboxylic Acids Introduction

Carboxylic acids are characterised by the presence of the functional group and —COOH or O —C—OH or CO2H, it has been given this name because it is constituted of two groups :

(a) Carbonyl group O —C—
(b) Hydroxyl group —OH—

Classification of C arboxylic Acid

Aliphatic Carboxylic Acids

Monocarboxylic acids (Fatty acids)
Monocarboxylic acids (Fatty acids)

  • Saturated
  • Unsaturated

Di-carboxylic acids
Mixed carboxylic acids

Aromatic Carboxylic Acids
In these; carboxylic group is attached directly to the nucleus.

General Methods Of Preparation Of Carboxylic Acids

Oxidation of primary alcohols with acidified KMnO4 or K2Cr2O7.
  • Oxidation of methyl ketones.
  • By carbonation of Grignard Reagents.
  • By oxidation of aldehydes
  • From Alkyl cyanides.

Physical Properties Of Carboxylic Acids

  • Lower members are colourless liquids, while other members are waxy solids.
  • Solubility in water decreases as we go higher up in the series. All acids are soluble in ether and alcohols.
  • They are weak electrolytes hence, acidic character decreases as we go higher.
  • Boiling points are in irregular gradation.

Chemical Properties Of C arboxylic Acids

  • Reaction of Alkyl group
  • Reaction of Carboxylic group
  • Reaction due to Decomposition of the Molecule.

Uses Of Carboxylic Acids

  • Carboxylic acids are used in some food items. Vinegar is dilute ethanoic acid. This is used in preparations for pickles, salads, sauces, etc.
  • Carboxylic acids are used in the manufacture of soaps. Sodium salts of fatty acids are used in soap and detergent industries.
  • Carboxylic acids find use in medicines. Ethanoic acid is used in aspirin.
  • Carboxylic acids are used as industrial solvents.
  • Carboxylic acids are used in preparing perfumes and artificial essences used in food manufacturing.
  • Carboxylic acids (e.g. butanoic acid) are produced in the sweat glands. Dogs can track humans by detecting the characteristic blend of these acids in the sweat.