Ethyl-sulphuric acid

Diethyl ether may be prepared from ethyl alcohol by the sulphuric acid process. A mixture of alcohol and sulphuric acid in equimolecular proportions is heated to about 140° and alcohol is run in at the rate at which the ether produced distils from the reaction mixture. Ethyl hydrogen sulphate (or ethyl sulphuric acid) is first formed and this yields ether either by reacting directly with a molecule of alcohol or by the formation and alcoholysis of diethyl sulphate (I) ... 

Dony-Henault observed that alcohol is oxidized in sulphuric-acid solution already at an anode potential of 1.3 volts, as measured in connection with the hydrogen electrode. The oxidation of acetaldehyde, on the contrary, requires a potential of 1.66 volts to convert the aldehyde into acetic acid. Hence, the alcohol can be oxidized only to aldehyde between 1.3 and 1.66 volts. The experiment proved that, when a platinized platinum electrode is employed, only acetaldehyde is formed, and this quantitatively. The aldehyde yield decreases at a higher potential, the acid content of the electrolytes increases, and, at the same time, ethyl-sulphuric acid can be detected, as already shown by Itenard. Dony-Henault ascribes the formation of tliis acid to the discharge of the SCVions. According to Elbs, a purely chemical action of the sulphuric acid (which becomes concentrated at the anode) on the alcohol is the more probable. 

When ethyl sulphuric acid is boiled with water it acts as do esters in general. The reaction of its formation is reversed and alcohol and sulphuric acid are reformed. 

Ethyl sulphuric acid Alcohol Sulphuric acid... 

Now in the first stage of the preparation of ether, ethyl sulphuric acid is formed. When this is heated to 140° and fresh alcohol is added the reaction is analogous to that between ethyl sulphuric acid and water, ether is formed and sulphuric acid is regenerated. 

This sulphuric acid then unites with more alcohol forming ethyl sulphuric acid which again reacts with alcohol and yields ether and sulphuric acid. Thus the sulphuric acid remains in the reaction mixture either as ethyl sulphuric acid or as free sulphuric acid. It acts as a carrier of the ethyl radical or it is perhaps better to say as a dehydrating agent removing the water which is the other product of the first step in the reaction. We have said that the reaction goes on indefinitely. 

This is not strictly true because the water formed, though partly removed by distillation, gradually dilutes the acid until it is too weak to react with the alcohol, i.e, until the reversible reaction occurs and the ethyl sulphuric acid, as fast as it is formed, is decomposed again into alcohol and sulphuric acid. Also the heat of the reaction gradually uses up the acid owing to its reduction by means of the alcohol. 

If, however, double molecular proportions of sulphuric acid are used and, at 160°, additional sulphuric acid and alcohol are added, the first reaction above is the same then, with the excess sulphuric acid, the ethyl sulphuric acid yields ethylene and sulphuric acid is regenerated, as follows ... 

This benzene ethyl sulphonic acid is analogous to ethyl sulphuric acid, HOSO2OC2H5, and as the latter with excess of alcohol yields ethyl ether and reforms sulphuric acid so benzene ethyl sulphonic acid with excess alcohol yields ethyl ether and reforms the benzene sulphonic acid. 

A compound, acid ethyl sulphate, commonly called ethyl sulphuric acid, is formed. This substance subsequently decomposes thus —... 

Ethylene is absorbed slowly by concentrated sulphuric acid, and ethyl sulphuric acid is formed —... 

It will be remembered that at about 170° ethyl sulphuric acid undergoes decomposition into ethylene and sulphuric acid. 

If alcohol is heated to 160°-180° with concentrated sulphuric acid, the ethyl sulphuric acid first formed is decomposed and ethylene is produced. It will be remembered that the unsaturated hydrocarbons of the ethylene series can be prepared in a similar way from other alcohols. 

Ether is usually prepared by the action of concentrated sulphuric acid on alcohol. For this reason it is sometimes called sulphuric ether.Alcohol reacts with sulphuric acid when gently heated and forms ethyl sulphuric acid, which is the acid ethyl ester of sulphuric acid —... 

The sulphuric acid regenerated serves to convert more alcohol into ether. The process is thus a so-called continuous one. As only a part of the water formed distills over with the ether, the acid, which becomes more and more diluted as the reaction proceeds, finally ceases to react with the alcohol and the production of ether stops. Other reactions take place which tend to interfere with the process at the temperature used a part of the alcohol is oxidized and the sulphuric acid is reduced to sulphur dioxide. Notwithstanding these facts, sulphuric acid will convert about sixteen times its weight of alcohol into ether before the process becomes inefficient. If a small amount of aluminium sulphate (about 5 per cent) is added to the ethyl sulphuric acid the conversion into ether takes place at about 120° without the formation of by-products. 

Ethyl Hydrogen Sulphate, C2H5.HSO4, is an oily liquid, resembling sulphuric acid, which can not be distilled without decomposition. It is usually called ethyl sulphuric acid as it... 

Ethyl sulphuric acid is both an acid and an ester. When heated with water it is hydrolyzed —... 

The rate at which an alcohol reacts with an acid to form an ester, is markedly increased when the reaction takes place in the presence of a catalytic agent. Sulphuric acid and hydrogen chloride are frequently employed for this purpose the former is usually used in the preparation of ethyl acetate. The catalytic effect of sulphuric acid is probably due to the fact that it unites with the alcohol to form ethyl sulphuric acid, which, in turn, reacts with acetic acid to form ethyl acetate. Sulphuric acid is regenerated and serves to convert more of the alcohol and acid into the ester. The equation for the reaction is as follows —... 

Ethylene reacts with sulphuric acid to form ethyl sulphuric acid which on subsequent treatment with ethanol results into the formation of ether. 

Mercaptans — Sulpho compounds — Sodium isethionate — Methyl-sulphuric acid—Potassium-trichlorrmethyl sulphate — Potassium-trichlor-methyl sulphonate — Ethyl-sulphuric acid—Potassium-isoamyl sulphate—Potassium xanthate—Dimethyl-dithiocarbamic acid.47 49... 

Ethyl-sulphuric Acid.—Ethyl-sulphuric acid gave, according to Renard, on being subjected to electrolysis, at the negative pole hydrogen, and at the positive pole acetic acid, some formic acid, aldehyde, and sulphuric acid. In concentrated solution a greater proportion of acetic acid was formed. The potassium salt on electrolysis breaks up, according to Hittorf, into K - and - OSO,.OC,H,. 

Ethyl sulphuric acid is an ester (see below) of ethanol and the alcohol can be recovered when the ester is hydrolysed (see below) by dilution with water and the mixture is distilled. 

A modern theory assumes that ethyl sulphuric acid forms an ethyl ion, which adds to alcohol to form ether ... 

C2H5OH -h H2SO4 — C2H50-S02-0H + H2O ethyl sulphuric acid (ethyl hydrogensulphate)... 

The surface of hair has both acidic and basic groups (i.e. amphoteric in nature). For unaltered human hair, the maximum add combining capacity is approximately 0.75 mmol per g hydrochloric, phosphoric or ethyl sulphuric acid. This corresponds to the number of dibasic amino acid residues, i.e. arginine, lysine or histidine. The maximum alkali combining capacity for unaltered hair is 0.44 mmol per g of potassium hydroxide, which corresponds to the number of acidic residues, i.e. aspartic and glutamic side-chains. The isoelectric point (i.e.p.) of hair keratin (i.e. the pH at which there is an equal number of positive, -NH+ and negative, -COO groups) is pH 6.0. However, for unaltered hair, the i.e.p. is at pH 3.67. 

---