Estudiante

An alcohol is an organic compound that contains a hydroxyl group, ··OH, €0‘“‘
lently bonded to an alkyl group. Thus, a methyl group, Cl-l3·~ , bonded to H hY‘
droxyl group gives the alcohol CH3Ol-I called methyl alcohol. This is the con1m0¤
name. lts IUPAC nameis methanol. The ~OH group, which is present in all alco-
hols, is called the jimctional group. We shall later describea wide varietyof 60m'
pounds with different functional groups.
To give the IUPAC name of an alcohol, simply replace the final —e of the parent
alkane with the letters —0l. Thus, CH3OH is methanol, and CHBCHZOH is €ih¤¤"l·
There are two isomers of propanol, one with the ··OH group positioned on the
first carbon, l-propanol, and the other with the *0H group on the number 2 caf-
bon, 2-propanol. The2~pr0panol isomer is lilgely to be more recognizable by its .
common name. isopropyl alcohol. ln 70% solutions it is used as rubbing al€0h"l·
Structures of these isomers are i

There are four butyl alcohols, They are formed when an ·-OH group bonds to one
of the four butyl groups (see Table 19.5).
All alcohols can be placed into one of three classes known as the primary (l°),
secondary (2°), andtertiary (3°) alcohols. These classes are based on the number
of carbon atoms attached to the carbon atom that bears the hydroxyl group. An al»
cohol with the structure

is classified as a primary alcohol because the —OH group is attached to a primary
carbon atom, that is, a carbon attached to only one alkyl or aryl group (and two hy-
drogen atoms). The following alcohol structure

issecondary because the —OH group is attached to a secondary carbon, that is,
one that is bonded to two other alkyl or aryl groups and one hydrogen atom. Finally,
if the hydroxyl group is attached to 21 carbon bonded to three alkyl or aryl groups,
the alcohol is tertiary.

Figure 19.15 shows that each of the four butyl alcohols can be classified as a
primary, secondary, or tertiary alcohol.Differences in reactivities of the alcohols
are related to the primary, secondary, or tertiary structure at the site of the WOH
group.
Methanol, CH3OH (methyl alcohol), the simplest alcohol, is a liquid that boils
at 34°C and is quite toxic. Ingestion of as little as 30 ml. (1 oz) can cause permanent
blindness or death. Biochemists use the abbreviation LD50 to indicate the dosage-
in grams perkilogram of body weight—that would be lethal to 50% of a population
of test animals. Toxicities of some alcohols are listed in Table 19.8.
Methanol is sometimes called wood alcohol because it can be made by heating
wood in the absence of air until the wood breaks down. The vapor produced during
the reaction contains methanol—along with other substances—which is collected

as it forms. Thisprocess is called destructive distillation (Figure 19.16). Cornrner-
cial methanol production involves a reaction of carbon monoxide with hydrogen.

The catalyzed reaction is carried out at high temperature and pressure.
Approximately 5 billion kg of methanol is produced annually in the United
States. It is used as a solvent, as a fuel, E and as a starting material for the produc-
tion of fueladditives, adhesives, tibers, and plastics.
Ethanol, CHBCHZOH, with a boiling point of 78°C, is the second member of
the homologous series of alcohols. It is perhaps better known by its other names;
ethyl alcohol and grain alcohol. For beverage use, the alcohol is produced by the
fermentation of grain. Like methanol, and other alcohols with a low molar mass.
` ethanol is toxicw One pint(aboute500emL)rof pure ethanokrapidly ingested, will kill"
most people. See the box on ethyl alcohol for more details.
In addition to its use as a beverage, about 250,000 kg (a half million lb) of
ethanol is produced synthetically in the United States each year. lt is used as a fuel.
as a solvent, and as a starting material for many other chemical products. Most
ethanol produced industrially is...