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TABLE 12.5 Methanol
H
Selected organic functional groups
H C OH
Name of General General
Functional Group Formula Structure
H
Organic halide RCl R Cl (methyl alcohol)

Alcohol ROH R O H Ethanol
H H
Ether ROR´ R O R´
H C C OH
Aldehyde RCHO R C H H H
O (ethyl alcohol)

Ketone RCOR´ R C R´ 1-propanol
O H H H
Organic acid RCOOH R C O H H C C C OH
O H H H
(n-propyl alcohol)
Ester RCOOR´ R R C C O O R´

O O 2-propanol
H OH H
Amine RNH 2 R N H
H C C C H
H
H H H
(isopropyl alcohol)
ALCOHOLS
FIGURE 12.14 Four different alcohols. The IUPAC name is
An alcohol is an organic compound formed by replacing one given above each structural formula, and the common name is
or more hydrogens on an alkane with a hydroxyl functional given below.
group (–OH). The hydroxyl group should not be confused with
–
the hydroxide ion, OH . The hydroxyl group is attached to an are produced by the yeast fermentation reaction, but some are
organic compound and does not form ions in solution as the made from ethanol derived from petroleum refining.
hydroxide ion does. It remains attached to a hydrocarbon group Alcohols with six or fewer carbon atoms per molecule
(R), giving the compound its set of properties that are associ- are soluble in both alkanes and water. A solution of etha-
ated with alcohols. nol and gasoline is called gasohol (Figure 12.15). Alcoholic
The name of the hydrocarbon group (Table 12.4) deter- beverages are a solution of ethanol and water. The proof of
mines the name of the alcohol. If the hydrocarbon group in such a beverage is double the ethanol concentration by vol-
ROH is methyl, for example, the alcohol is called methyl alcohol. ume. Therefore, a solution of 40 percent ethanol by volume
Using the IUPAC naming rules, the name of an alcohol has the in water is 80 proof, and wine that is 12 percent alcohol by
suffix -ol. Thus, the name of methyl alcohol is methanol. volume is 24 proof. Distillation alone will produce a 190 proof
All alcohols have the hydroxyl functional group, and all are concentration, but other techniques are necessary to obtain
chemically similar (Figure 12.14). Alcohols are toxic to humans, 200 proof absolute alcohol. Denatured alcohol is ethanol with
except that ethanol can be consumed in limited quantities. Con- acetone, formaldehyde, and other chemicals in solution that
sumption of other alcohols such as isopropyl alcohol, or “rubbing are difficult to separate by distillation. Since these denatur-
alcohol,” can result in serious gastric distress. Consumption of ants make consump tion impossible, denatured alcohol is sold
methanol can result in blindness and death. Ethanol, C 2 H 5 OH, without the consumption tax.
is produced by the action of yeast or by a chemical reaction of Methanol, ethanol, and isopropyl alcohol all have one
ethylene derived from petroleum refining. Yeast acts on sugars hydroxyl group per molecule. An alcohol with two hydroxyl
to produce ethanol and CO 2 . When beer, wine, and other such groups per molecule is called a glycol. Ethylene glycol is per-
beverages are the desired products, the CO 2 escapes during fer- haps the best-known glycol since it is used as an antifreeze.
mentation, and the alcohol remains in solution. In baking, the An alcohol with three hydroxyl groups per molecule is called
same reaction utilizes the CO 2 to make the dough rise, and the glycerol (or glycerin). Glycerol is a by-product in the making
alcohol is evaporated during baking. Most alcoholic beverages of soap. It is added to toothpastes, lotions, and some candies

308 CHAPTER 12 Organic Chemistry 12-10