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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.
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