Page 13 - A TEXTBOOK OF ORGANIC CHEMISTRY

THEORY OF TYPES T
These obtained a firmer basis through Gerhardt's Theory of
Types, which received support more especially from the dis-
covery of ethylamine and other ammonia bases (Wurtz, 1849,
and Hofmann, 1849, 1850), the proper interpretation of the
formulae of the ethers (Williamson, 1850), and the discovery
of the acid anhydrides (Gerhardt, 1851). All compounds,
inorganic as well as organic, were in this way compared with
simpler inorganic substances taken as " Types", of which
Gerhardt named four, viz.:

0,
The first two of these really belong to the same type. Thus
the following formulae were arrived at;
3 S Cl 0,,o]
Cl
Potassium chloride Ethyl chloride Acetyl chloride
lo lo lo o )o

Potassium hydroxide Nitric acid Alcohol Acetic acid
lo N9,Jo 94Jo q,,9Jo
No,
C,IL,O
Potassium oxide Nitie anhydride C,H, Acetic anhydride
Ether
il ew N C,H,O}
H N
H
H
H
Eth amine Acetamide
l
&c. &e. Organic compounds could thus, like inorganic, be
referred to inorganic types by assuming in them the presence
of Radicals (e.g. ethyl, OH,; acetyl, C,H,O, &c.), i.e. of groups
of atoms which play a part analogous to that of an atom of
an element, and which can be transferred by double decom-
position from one compound to another. Thus ethyl chloride,
C,H,Cl; alcohol, C,H,O; ethylamine, C,H,N; ether, CH,O;
&e., were represented as containing the same radical G,H,
ethyl, and the close relationship existing between these com-
pounds now found expression in the type formula.
Sulphuric acid, H,SO,, was derived from the double water
type, thus:
Jo (69)%,
H,'
H,