Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

110 BTHYLBNB FKOM ETHYL ALCOHOL
It will be remembered that the ethylsulphuric acid first formed
is decomposed when hot (130°) by excess of alcohol and in this way
ether is prepared.
CH3.CH2.O.SO3H + HO.CH2.CH3 —> CH3.CH2.O.CH2.CH3
+ H2SO4.
Ethyl ether is also formed as a by-product during the preparation
of ethylene.
Bthylene, the " oil-forming gas ", was prepared already in 1795
from spirits of wine and oil of vitriol by the five Dutch chemists,
Deiman, Troostwyk, Bondt, Louwerenburgh, and Crells.
Technically, ethylene is obtained from alcohol by catalytic removal
of water with alumina heated to 200°-300° (Senderens). The alcohol
vapour is led over the hot material. 1 For the preparative application
of such reactions aluminium phosphate is as suitable as alumina.
Instead of the acid sulphuric ester of the alcohol, as in our example,
the ester of another acid, e.g. benzoic, is often submitted to thermal
decomposition, and so the charring action of the sulphuric acid is
avoided.
Potassium bisulphate and anhydrous boric or oxalic acid are also used
(acrolein from glycerol, pyruvic acid from tartaric acid). Tschugaev's
xanthate method belongs to this class of reactions also.
The chemical characteristics of the defines depend on their double
bond, which can take part in a great variety of additive reactions.
The following substances are added :
1. Halogens, chlorine and bromine with especial ease, yielding
dihalides.
2. Hydrogen Halides to give alkyl halides. For preparative purposes
hydrobromic acid dissolved in glacial acetic acid is generally used,
and since the reaction proceeds slowly, the components are heated in a
sealed tube.
3. Sulphuric Acid (cf. supra) and other acids, e.g. acetic acid (technical
application in the terpene group).
4. Nitric Acid.—In the presence of concentrated sulphuric acid
ethylene yields the nitric ester of nitroethyl alcohol.
CH2:CH2 —^- CH2.CH2 —^- CH2.CH2
NO2 OH NO2 O.NO2'
5. Hypochlorous Acid according to the equation :
CH2:CH2 J 10 ^ CH2—CH2
Cl OH '
1 Directions suitable for laboratory experiments are given by W. Kesting,
Z. angew. Chem., 1925, 38, 362.