Laboratory Methods of Inorganic Chemistry, 2nd English Ed. 1928

212 ESTERS.

pure, unsymmetrical diethyl sulphite boils sharply at 214°-215°

(760 mm.). Yield, 12 to 18 grams of a colorless oil, quite similar

to the symmetrical ester. It is immiscible with water, but is slowly

saponified by it. Alkalies in alcoholic solution cause saponifica-

tion to take place more quickly.

C 2 H 5 SO 2 .OC 2 H 5 + H 2 O = C2H.SO2.OH + C 2 H 5 OH.

Allow four drops of the ester to stand a few minutes with an

equal amount of alcoholic potassium hydroxide solution. The

mixture becomes warm and a solid separates. On acidifying

with sulphuric acid and boiling, no sulphur dioxide is evolved.

This behavior distinguishes the unsymmetrical from the sym-

metrical ester.

157. Triethyl Phosphate, PO(OC 2 H 5 ) 3.

Add 14 g. of freshly-cut sodium to 150 c.c. of absolute alcohol,

and after the reaction moderates, heat the mixture on the water-

bath with a return condenser until all the metal has dissolved.

Cool the sodium ethylate solution with ice and salt, then add,

drop by drop, 31 g. of phosphorus oxychloride (No. 46); each drop

reacts energetically and much heat is evolved. After some time,

drain the solution on a Biichner funnel from the precipitated

sodium chloride and rinse the residue with a little anhydrous ether.

The sodium chloride is so finely divided, however, that it cannot

be removed completely. Distil the alcohol and ether from the

filtrate, placing the bulb of the flask on the water-bath and wrap-

ping the upper part and neck with a towel. Pour the residual

liquid through a smaller filter — it still comes through somewhat

cloudy — and distil it from a fractionating flask with a side-arm

condenser (Fig. 7, p. 6). Collect the first runnings up to 110

p

and the main portion above 110°; some sodium chloride is left

in the flask. Fractionate the distillate which comes over above

110° twice more from the same distilling flask, after cleaning it; a

pure product is readily obtained which boils sharply at 217°—218°.

Yield, 20 to 25 g. Triethyl phosphate is a colorless oil having a

typical etherial odor. It is miscible with water and is saponified

by it to diethyl phosphoric acid.