The Chemistry of Powder and Explosives - Sciencemadness Dot Org

224 NITRIC ESTERS
which yields glycol by hydrolysis, but bromine is expensive.
Ethylene also combines readily with chlorine, but, even if care
is exercised always to have the ethylene present in excess, substitution
occurs, and tri- and tetrachloroethane are formed along
with the ethylene dichloride, and these do not yield glycol by
hydrolysis. Ethylene is now produced in large quantities during
the cracking of petroleum. Its comportment with chlorine water
has been found to be much more satisfactory for purposes of
synthesis than its comportment with chlorine gas. Chlorine water
contains an equilibrium mixture of hydrogen chloride and hypochlorous
acid.
Cl2 + H2O ±? HC1 + H0C1
Ethylene cJds hypochlorous acid more readily than it adds either
moist chlorine or hydrogen chloride. Bubbled into chlorine water,
it is converted completely into ethylene chlorohydrin, and by the
hydrolysis of this substance glycol is obtained. Ethylene chlorohydrin
is important also because of its reaction with ammonia
whereby mono-, di-, and triethanolamine are formed, substances
which are used in the arts and are not without interest for the
explosives chemist. Ethylene may be oxidized catalytically in the
gas phase to ethylene oxide which reacts with water to form
glycol and with glycol to form diglycol which also is of interest
to the dynamite maker.
CH2-OH
CH2 \^ / ^-"^ CH2-OH
Dlglycoi
Glycol is a colorless liquid (bluer than water in thick layers),
syrupy, sweet tasting, less viscous than glycerin, specific gravity
1.1270 at 0°, 1.12015 at 10°, and 1.11320 at 2O 0 . 41 It shows a
tendency to supercool but freezes at temperatures between —13°
and -25°, and melts again at —11.5°. It boils at 197.2° at
atmospheric pressure. It is very hygroscopic, miscible in all pro-
41 C. A. Taylor and W. H. Rinkenbach, Ind. Eny. Chem., 18, 676 (1926).