Commercial ethers

Absolute diethyl ether. The chief impurities in commercial ether (sp. gr. 0- 720) are water, ethyl alcohol, and, in samples which have been exposed to the air and light for some time, ethyl peroxide. The presence of peroxides may be detected either by the liberation of iodine (brown colouration or blue colouration with starch solution) when a small sample is shaken with an equal volume of 2 per cent, potassium iodide solution and a few drops of dilute hydrochloric acid, or by carrying out the perchromio acid test of inorganic analysis with potassium dichromate solution acidified with dilute sulphuric acid. The peroxides may be removed by shaking with a concentrated solution of a ferrous salt, say, 6-10 g. of ferrous salt (s 10-20 ml. of the prepared concentrated solution) to 1 litre of ether. The concentrated solution of ferrous salt is prepared either from 60 g. of crystallised ferrous sulphate, 6 ml. of concentrated sulphuric acid and 110 ml. of water or from 100 g. of crystallised ferrous chloride, 42 ml. of concentrated hydiochloric acid and 85 ml. of water. Peroxides may also be removed by shaking with an aqueous solution of sodium sulphite (for the removal with stannous chloride, see Section VI,12). 

Table 4. Price and Availability of Some Commercial Ethers ...

Commercial Ether is made from methylated spirit and contains alcohol, water, and other impurities, and for many... 

The ice-cold fluoboric acid solution is added rather rapidly, with stirring, to the finished tetrazo solution, the temperature being kept below io°. A thick paste of 4,4 -biphenylene-bis-diazonium borofluoride forms. The mixture is stirred at io° for twenty to thirty minutes. It is then collected on a 19-cm. Buchner funnel, and washed consecutively with about 200 cc. of cold water, 200 cc. of cold commercial methyl alcohol, and 200 cc. of commercial ether the cake is sucked as dry as possible between washings. It is then dried in a vacuum desiccator over concentrated sulfuric acid (sp. gr. 1.84). The yield of the dry solid is 393 400 g. (68-69 Per cent of the theoretical amount). The product decomposes at 135-1370. 

The chief impurities in commercial ether are alcohol and water, with traces of aldehyde, methyl alcohol, acetone, due to it being made from methylated spirit. It may be purified as above. The presence of alcohol may be proved by shaking with a spirit soluble dye, e.g., aniline violet. If alcohol is present a blue solution is obtained. Water is detected by the cloudiness formed on mixing with carbon disulphide. 

Purification of commercial ether. Divide the contents of a Winchester bottle of ether into approximately two equal volumes and shake each in a large separatory funnel with 10-20 ml of the above iron(n) sulphate solution diluted with 100 ml of water. Remove the aqueous solution and combine the two ether portions in a clean dry Winchester bottle and add 100-200 g of anhydrous calcium chloride. Allow this mixture to stand for 24 hours with occasional shaking the water and ethanol are largely removed during this period. Filter the ether through a large fluted filter paper into another clean dry Winchester... 

The preparation of the Grignard reagent involves extraordinary cleanliness and care. In particular, all substances and apparatus used must be free from moisture. Absolute ether must be used. For its preparation commercial ether is first shaken with calcium chloride to remove part of the water and alcohol. The ether is then filtered into a flask containing metallic sodium and allowed to stand overnight. The next day the ether is distilled from the excess sodium into a flask protected from moist air by a calcium chloride tube. For details see pages 156-157. 

Pure ether for Grignard reagent. In the preparation of Grignard reagent and other work in the organic laboratory pure dry ether is required. The impurities in commercial ether are water and ethanol. Though ether and water are regarded as immiscible... 

Shake 200 grammes of commercial ether in a separating funnel with half its volume of water the latter is allowed to run off, and the operation repeated a second time with a fresh quantity of water, by which the alcohol is removed. The ether is dried by standing over calcium chloride, not too little, two hours. It is then filtered through a folded filter, and can now be used for the above reaction. 

Ethers have the general formula R—O — R where R and R stand for alkyl groups (Table 12.6), which may be the same or different. Methyl-t iary-butyl ether (MTBE) was once an important commercial ether because of its use in oxygenated and reformulated gasolines. 

Typical commercial ethers are methyl, ethyl, hydroxyethyl, hydroxypropyl, carboxy-methyl, aminoethyl, and benzyl. 

The most important commercial ether is diethyl ether. It is prepared from ethanol and sulfuric acid. 

Diethyl ether is the most important commercial ether. It can be prepared by the following reaction ... 

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