What substances are called aldehydes and ketones? The use of aldehydes

Compounds having a carbonyl group in their composition refer to aldehydes or ketones. In the aldehydes (RCOH), the carbonyl group is bonded to one hydrocarbon radical and a hydrogen atom. Otherwise, it can be said that these substances contain an aldehyde group (-COH), in which the carbonyl center is bound to a hydrogen atom. In ketones (RCOR '), two hydrocarbon radicals are attached to the carbonyl group. The name of the aldehydes comes from the name of acids into which, as a result of oxidation, they are transformed, for example, formic (formaldehyde), acetic (acetaldehyde), propionic, butyric, valeric aldehydes. According to the international nomenclature aldehydes are called: ethanol, propanal. The names of ketones form from the name of radicals, to which the ending-ketone is added. For example, dimethyl ketone (acetone), methyl ethyl ketone. The name for the international nomenclature of ketones comes from the name of the hydrocarbon with the addition of the ending -one, and the place of attachment of the carbonyl group is indicated by a number, for example: propanone-2, butanone-2. The use of aldehydes and ketones is due to their physical and chemical properties.

Aldehydes are widely distributed in organic chemistry. Many aromas are associated with these substances. Aldehydes have properties that are diverse and depend on the radical that is part of the molecule. The lowest representative - formic aldehyde - gas, the subsequent - liquids, solids are higher. Formaldehyde and acetaldehyde are very soluble in water, the solubility of the remaining homologues decreases with increasing molecular weight. Formic and acetic aldehydes have a sharp odor. The properties and use of aldehydes are due to the presence of a carbonyl group in their molecule.

The two lowest representatives of this homologous series in the section "the use of aldehydes" have the most important value for industry: formaldehyde and acetaldehyde. Formaldehyde is produced on a large scale, approximately 6 million tons per year. It is mainly used in the production of resins. Polycondensation with urea produces urea-formaldehyde resins, which are necessary for the production of fibreboard and particle board, urea-formaldehyde foam, for the production of moisture-resistant cardboard or paper. Another major use of aldehydes is based on the polycondensation reaction of formaldehyde with phenol. The phenol-formaldehyde resin (bakelite) obtained as a result of this process is an unsurpassed material that is in demand in engineering, in the production of abrasive electrical products, in the production of varnishes and adhesives. Formaldehyde produces pharmaceutical preparations (formaldehyde solution, known as formalin, used in medicine), synthetic rubber, explosives and many other organic substances.

Acetaldehyde was once the dominant product, but production volumes declined, currently it is produced less than 1 million tons / year. Previously, the traditional use of acetaldehyde was as a raw material for acetic acid. This use of acetic aldehyde in recent years has declined, because acetic acid is produced more efficiently from methanol (the Monsanto process and the Cativa process). From the point of view of the condensation reaction, acetaldehyde is an important raw material for pyridine, pentaerythritol and crotonaldehyde derivatives. Acetic aldehyde is necessary for the production of plastics (from urea and acetaldehyde, useful resins are obtained).

Other representatives of this homologous series are also in demand on the market. The commercial use of aldehydes is most often to use them as a raw material for the synthesis of oxo alcohols used in the manufacture of detergents. Some higher aldehydes are produced in small amounts (less than 1000 tons / year) and are used as aromatic ingredients in perfumery. These include cinnamon and its derivatives, citral and lily.