Ethers. Characteristic

Ethers are organic substances in which molecules contain hydrocarbon radicals connected by an oxygen atom. It can be written as follows: R'-O-R ", where R" and R 'are the same or different radicals.

Ethers are considered as derivatives of alcohols. These compounds have compound names. In this case, the name of the radicals is used (by increasing the molecular weight) and, in fact, the word "ether" (dimethyl ester CH3OCH3, methyl ethyl ether C2H5OCH3 and so on).

Symmetrical compounds R-O-R are obtained by intermolecular alcohol dehydration. In one molecule, the O-H bond is broken, and in the other, the C-O bond. The reaction can be considered as the nucleophilic substitution of the HO group (in one molecule) by the RO group (from another molecule).

Unbalanced R-O-R 'compounds are formed by the interaction of a halocarbohydrate and an alcoholate.

Ethers (in contrast to isomeric alcohols) have lower melting and boiling points. With water, the compounds hardly mix. This is due to the fact that ethers do not form hydrogen bonds due to the absence of O-H polar bonds in their molecules.

The compounds are inactive. They have a lower reactivity than alcohols.

Ethers are often used as solvents because of their ability to dissolve many organic substances.

The most important compounds include heterocyclic acid-containing substances: dioxane and epoxide (ethylene oxide).

The former is a good solvent. Dioxane is able to mix with both hydrocarbons and water. Due to these qualities this connection is also called "organic water". Dioxane is toxic, but its halogen-containing dibenzo derivatives are the most dangerous.

Cellulose ethers are products of the replacement of a hydrogen atom in the hydroxyl groups of a cellulose macromolecule by alkyl or acidic residues. Synthesis is carried out with the aim of imparting new properties to the substance, in particular, thermoplasticity and solubility. When substituted with acidic residues, complex compounds are formed, when substituted with alkyl radicals, simple compounds.

The former are obtained in the process of acylation and esterification - in the interaction of cellulose with inorganic and organic acids, their acid chlorides and anhydrides. The greatest practical importance is attached to xatogenates. These compounds are obtained by reaction with inorganic acids and are used in the manufacture of cellophane and viscose fibers. Cellulose nitrates are also of industrial importance. They are used in the production of varnishes, films, smokeless powder.

Of the compounds obtained by reaction with organic acids, cellulose acetate is widely used in the industry. They are used in the production of synthetic fibers, plastics and films.

There are also mixed cellulose ethers. They contain various acyl and alkyl substituents.

The properties of all cellulose ethers depend on the nature of the radical. The value has a degree of substitution and polymerization.

Low-substituted simple compounds dissolve in aqueous alkaline solutions and water. This allows them to be used as thickeners and stabilizers in emulsions in the oil, paper, textile, food, pharmaceutical and other industries. Highly substituted esters (complex and simple) are compatible with plasticizers. They are used in the manufacture of plastics and the production of varnishes.

Crown ethers are polyesters containing several oxygen atoms in the cycle. Formally, they are considered as products of cycloligomerization of ethylene oxide. A unique property of these compounds is the ability to form complexes with salts of different alkali metals. These complexes are formed due to electrostatic interaction.