Esters are derivatives of alcohols, in the molecules of which the hydrogen atom of the OH group is replaced by a carboxylic radical. Esters are characterized by metamerism and isomerism of the hydrocarbon chain.
The isomerism of the hydrocarbon chain is due to its branching.
Metamerism is a type of isomerism in which two andmore ethers have a similar molecular formula, but a different structure of molecules, due to different radicals on both sides of the oxygen "bridge". For example, three esters correspond to the molecular formula C4H10O:
- CH3-O-CH (CH3) 2;
- CH3-O-C3H7;
- C2H5-O-C2H5.
These substances are obtained synthetically, including dimethyl ether. The formula of this compound is represented by two methyl radicals, which are linked by an oxygen "bridge".
It should be noted that in nature, esters in the freecondition not found. Dimethyl and methyl ethyl ethers are gases. The next few representatives are liquids, while higher esters are solids. They are very poorly soluble in water, excellent in organic solvents. Medium representatives (dipropyl, propyl ethyl, diethyl) are excellent organic solvents. The physical properties of these organic compounds vary with molecular weight.
Dimethyl ether: preparation
Описываемое вещество хорошо растворяется в воде, ethanol, diethyl and dipropyl ethers. This ester is obtained by the dehydration of methanol and as a by-product of the production of methanol from H2 and CO. Used in refrigeration as a refrigerant.
In the near future, diesel engines will betranslated not to gas, but to dimethyl ether. Such a reconstruction of them will cost much less compared to the transition to natural gas. The leading countries for the production of such engines are the United States, Russia and Japan.
At the beginning of the 21st century, the Russian government adopteddecision on the use of alternative fuels in motor vehicles. Dimethyl ether is used on trucks. This cardinal decision was made due to the fact that emissions of nitrogen compounds from diesel engines installed on trucks exceed the established standards several times. Dimethyl ether is ideally suited for this type of engines, they practically do not need to be reconstructed. Only due to the use of a new alternative type of fuel, the new modernized engine has reached the level of environmental friendliness Euro-3.
Many governments around the world are confident thatThe fuel of the future for diesel engines will be dimethyl ether. Today, this substance is produced mainly by the processing of natural gas. In the first stages of the process, natural gas is reformable, resulting in synthesis gas. After that, it turns into methyl alcohol. Next, methanol is amenable to dehydration, as a result of which dimethyl ether is obtained. There is another method for the synthesis of this ester - direct conversion of synthesis gas to methanol.
Esters compared with diesel fuel have their ownadvantages and, of course, disadvantages. In the structure of the ether molecule there are no "carbon-carbon" bonds. Due to the significant oxygen content, good spraying is ensured when ether is injected into an environment with a temperature above boiling point of the substance itself. These characteristics improve the combustion of fuel. Through the use of this alternative fuel, the engine noise level is reduced, and its reliability is increased.
The main disadvantages of this ether include lower heat value and lower density. All this leads to an increase in fuel consumption. This substance has very poor lubricating properties.
