ETHERS, in chemistry, those compounds which may be regarded as derived from water by the replacement of each of the hydrogen atoms by a basic or alcoholic radical. The ether is "simple" if the basic radicals that are so substituted are alike, and it is "mixed" if they are unlike. The formation of a simple ether may be conveniently illustrated by the case of common, or "diethyl" ether, (C21:1020.
This may be prepared in various ways, but the sulphuric-acid method will serve best to illus trate the nature of the compound. When alcohol, C2112.0H, is heated to 285° F. with sulphuric acid, HSO., one of the hydrogen atoms of the acid, is replaced by the alcohol radical ethyl GH., according to the equation Cs1-14.0H HS0.= (GHO HSO. H2O, the compound (GHOHSO4 being known as hydro genethyl-sulphate, or usulphovinic add.° When the hydrogen-ethyl-sulphate comes in contact with another molecule of the alcohol, it under goes a second transformation, by which another ethyl radical is taken up, and a molecule of sul phuric acid again set free, as indicated by the equation (GHOHSO. Gli•.OH= (GH.)20 + }LSO.. It will be seen that although a mole cule of sulphuric acid is used up in the first part of the process, it is regenerated in the second part, so that on the whole there has been no change in the quantity of acid present. The water produced in the first stage, and the ether, (GIL) 20, produced in the second stage, pass off in the state of vapor, and the apparatus is ready for the admission of a new supply of alcohol. The process by which an ether is formed, as here illustrated, is called etherifica tion; and the etherification is said to be °con tinuous° if it can go on, as in this case, by merely passing a stream of the alcohol into one end of the apparatus, and withdrawing the vapor of ether and water at the other end Methyl ether, for example, can be formed by the action of sulphunc acid upon methyl alcohol in a manner precisely analogous to that explained above. The equations in this case are CH,.OH H2O -I- (CH,) HSO.;
(CHO HSO4 CH2OH == }LSO. ( CHO sO ; where CH,.OH is methyl alcohol, (CH.)20 is methyl ether, and (CHOHSO. is hydrogen methyl-sulphate.
As an illustration of a mixed ether, the case of methyl-ethyl ether may be cited. If ethyl alcohol be heated with iodine in the presence of phosphorus, a substance known as ethyl iodine is formed. Thus: 5C2R..OH + 51 + P = 5GH..I + }LP°. + H2O. On the right of this equa tion, H,PO4, is phosphoric acid, and C,H,.I is ethyl iodide, which is a liquid boiling at 152° F., readily separable from the phosphoric acid by distillation. Now if ethyl iodide be mixed with potassium ethylate (obtained by dissolving metallic potassium in absolute ethyl alcohol), the following reaction occurs, and ethyl ether is formed: C,H,.I C2H..OK = KI (C2H.)30. But if the ethyl iodide is mixed with potassium methylote, CHs.OK, which is obtained by dissolv ing metallic potassium in absolute methyl alco hol, then the ether that is formed contains the radical methyl, CHs, and also the radical ethyl C211., and hence is a mixed ether; GILT + CsTis.O.CHs. The mixed ether, Cslis.O.CH.s, is known as methyl-ethyl ether. The reactions that have here been given at some length are typical of similar ones that hold true very generally of the alco hols and ethers. In all the more familiar cases the iodide of a given alcohol radical can be prepared by treating the corresponding alcohol with iodine and phosphorus; and a potassium can be formed by dissolving metal lic potassium in the corresponding (anhydrous) alcohol. Then if we wish to prepare a proposed mixed ether, we have only to treat the iodide of one of its radicals with the potassium compound of the other one, as indicated above. The com moner ethers, both simple and mixed, strongly resemble one another in their general properties. Thus they will not mix with water, nor combine with ammonia nor other alkalies, nor with me tallic sodium, nor with dilute acids. The resem blance is also close in other respects. For °compound ethers° see ESTERS.