Page 280 - Theory and Problems of BEGINNING CHEMISTRY
P. 280
CHAP. 18] ORGANIC CHEMISTRY 269
Table 18-4 Formulas for Functional Groups
Characteristic
Type Functional Group Example
Alcohol OH R OH or ROH
Ether O R O R′ or ROR
Aldehyde C O R C O or RCHO
H H
Ketone C R C R′ or RCOR
O O
Acid C OH R C OH or RCO 2 H
O O
Ester C O R C OR′ or RCO 2 R
O O
Amine NH , NH, N R NH , RNHR′, RR′R′′N
2
2
Amide C N R C N R′ or RCONRR
O O R′′
The radicals labeled R or R may be the same as or different from the radicals labeled R in the same
compounds.
functional group they contain. The most important classes of such compounds include (1) alcohols, (2) ethers,
(3) aldehydes, (4) ketones, (5) acids, (6) amines, (7) esters, and (8) amides. The general formulas for these
classes are given in Table 18-4, where the symbol for a radical, R, is written for the hydrocarbon part(s) of the
molecule.
Molecules of some compounds contain more than one functional group, and there may be even more than
one kind of functional group in each molecule. The purpose of this discussion is merely to describe some of
the possible compounds. Therefore, the methods of preparation of the various classes of compounds will not be
given here for every class, nor will more than a few of their properties be described.
18.7. ALCOHOLS
Compounds containing the functional group —OH are called alcohols. The —OH group is covalently
bonded to a carbon atom in an alcohol molecule, and the molecules do not ionize in water solution to give OH −
ions. On the contrary, they react with metallic sodium to liberate hydrogen in a reaction analogous to that of
sodium with water.
2 HOH + 2Na −→ H 2 + 2 NaOH
2ROH + 2Na −→ H 2 + 2 NaOR
The simplest alcohol is methanol, CH 3 OH, also called methyl alcohol in a less systematic system of naming.
Methanol is also known as wood alcohol. Ethanol, CH 3 CH 2 OH, also known as ethyl alcohol or grain alcohol, is
the active constituent of intoxicating beverages. Other alcohols of importance are included in Table 18-5. Note
that the systematic names of alcohols characteristically end in -ol.