Organic compounds containing the carbonyl functional group C =O, are called carbonyl compounds. In a carbonyl group, a carbon atom is bonded to oxygen with a double bond. In ketones, the carbonyl group is bonded to two carbon atoms, and so it happens within a chain. A ketone might be represented by the general formula,
The homologous series of ketones have the general formula, CnH2nO. The ketonic group exists in camphor and menthone.
Naming of Ketones
The typical names of ketones are obtained by individually writing the names of the alkyl groups connected to the carbonyl carbon. The word ketone is then added as a separate word. The names of the alkyl groups are written alphabetically.
When the two alkyl groups are the same, the prefix di – is included prior to the name of the alkyl group. The positions of other groups are indicated by Greek letters, the α- carbon atom being the one adjacent to the carbonyl group. If the two alkyl groups in a ketone are the same, the ketone is said to be symmetrical, if unlike, unsymmetrical.
The IUPAC names of ketones are originated from the names of alkanes having the exact same number of carbon atoms. The letter e in the name of an alkane is replaced with the suffix -one. The positions of the carbonyl group and of other groups on the chain are indicated by numbers. Numbering is begun with that end which is nearby to the carbonyl group. Aromatic ketones are not given IUPAC names.
Physical Properties of Ketones
Normally the boiling point of ketones increases with an increase in molecular weight. The boiling point depends upon the strength of the intermolecular forces.
Vander Waals dispersion forces:
As the molecules get longer and the number of electrons increases, the attraction in between them also increases. So, the boiling point increases with the increase in the number of carbon atoms.
Vander Waals dipole-dipole attraction:
Because of the presence of carbon-oxygen double bond ketones are polar in nature. There will be an attraction in between permanent dipoles as well as the molecules which are near to it. This is the reason for ketones having boiling point higher than comparably sized hydrocarbons.
Ketones are soluble in water however their solubility decreases with an increase in the length of the chain. Ketones cannot form hydrogen bonds with themselves, but they can have hydrogen bonds with water molecules and this forms the basis for the good solubility of ketones in water. This is also because of dispersion forces and dipole-dipole interactions. Ketones have many applications in various industries. They are extensively used in the production of polymers, blending of perfumes, and also as flavouring representatives.
Nucleophilic Addition Reactions of Ketones
As a result of the unsymmetrical electronic configuration about the carbonyl group, the nucleophilic reagent can start the initial attack on the carbon. It appears that whether the initial attack is to be by a nucleophilic reagent or by an electrophilic reagent relies on a particular reaction and upon the conditions under which that reaction is carried out. Therefore, the majority of the reactions of the carbonyl group will be thought-about to be nucleophilic addition reactions.
In these reactions of ketones, the negative part of the reagent combines with the electrophilic carbon of the carbonyl group, whereas the positive part, which is normally hydrogen goes to the oxygen. The nucleophilic addition reactions of the carbonyl groups are catalyzed by bases or acids.
Remember in mind that whether the addition is base-catalyzed or acid-catalyzed, the adduct is the same. A base catalyst increases the nucleophilic character of the reagent, while an acid-catalyst promotes the nucleophilic attack by increasing the positive character (electrophilic character) of the carbonyl carbon atom.
Oxidation of Ketones
Ketones do not undergo oxidation easily since they need breaking of the strong carbon-carbon bond. They provide no reaction with mild oxidizing agents. They are just oxidized by strong oxidizing agents such as K2Cr2O7/ H2SO4, KMnO4/ H2SO4, and conc. HNO3.
In the oxidation of ketones, just the carbon atoms adjacent to the carbonyl group are attacked. The carbon atom joined to the smaller number of hydrogen atoms is preferentially oxidized. In the case of symmetrical ketones, only one carbon atom adjacent to the carbonyl group is oxidized and a mixture of 2 carboxylic acids is constantly obtained.
However, in the case of unsymmetrical ketones, the carbon atom signed up with to the smaller sized number of hydrogen atoms is preferentially oxidized and the carbonyl group stays with the smaller alkyl group.
Uses of Ketones
- Ketones are typically utilized as solvents and as catalysts in the chemical industry. These are products frequently used in fragrances and paints in order to stabilize the ingredients to avoid deterioration in time. The major ketones in this category include acetophenone, Butanone, and acetone.
- Ketones are utilized for carpet adhesive solvents in the adhesives manufacture industry, in the electroplating market as cold-cleaning solvents and vapor degreasing solvents, as lab chemicals, paint manufacture, Rubber Manufacture, Printing, and Pesticide and Insecticides.
- Glucose is the primary source of fuel for the body. But when carbs are low, ketogenesis becomes the main fuel procedure for the majority of cells. These are the cases where ketones function as a natural byproduct of animal metabolism.