Alcohol and ethers

By
Dr KHALED ALGARIRI
CAMS- QASSIM UNIVERSITY
November 2020

INTRODUCTION
An alcohol is an organic compound in which an -OH group is bonded to a
saturated carbon atom. A saturated carbon atom is a carbon atom that is
bonded to four other atoms.
The -OH group, the functional group that is characteristic of an alcohol, is
called a hydroxyl group. A hydroxyl group is the -OH functional group.

Nomenclature for Alcohols
IUPAC rules for naming alcohols that contain a single hydroxyl group
follow.
Rule 1: Name the longest carbon chain to which the hydroxyl group is attached. The
chain name is obtained by dropping the final -e from the alkane name and adding the
suffix -ol.
Rule 2: Number the chain starting at the end nearest the hydroxyl group, and use the
appropriate number to indicate the position of the -OH group. (In numbering of the
longest carbon chain, the hydroxyl group has priority over double and triple bonds, as
well as over alkyl, cycloalkyl, and halogen substituents.)
Rule 3: Name and locate any other substituents present.
Rule 4: In alcohols where the -OH group is attached to a carbon atom in a ring, the
hydroxyl group is assumed to be on carbon 1.

Alcohols with More Than One Hydroxyl
Group
Polyhydroxy alcohols—alcohols that possess more than one hydroxyl group—can be
named with only a slight modification of the preceding IUPAC rules. An alcohol in
which two hydroxyl groups are present is named as a diol, one containing three
hydroxyl groups is named as a triol, and so on. In these names for diols, triols, and so
forth, the final -e of the parent alkane name is retained for pronunciation reasons.

Important Common Alcohols
1- Methyl Alcohol (Methanol)
 Methyl alcohol, with one carbon atom and one!OH group, is the simplest alcohol.
This colorless liquid is a good fuel for internal combustion engines. Methyl alcohol
also has excellent solvent properties, and it is the solvent of choice for paints and
varnishes.
 Drinking methyl alcohol is very dangerous. Within the human body, methyl alcoholis
oxidized by the liver enzyme alcohol dehydrogenase to the toxic metabolites
formaldehyde and formic acid.
 Formaldehyde can cause blindness (temporary or permanent). Formic acid causes
acidosis . Ingesting as little as (30 mL) of methyl alcohol can cause optic nerve
damage.

2- Ethyl Alcohol (Ethanol)
 Ethyl alcohol, the two-carbon monohydroxy alcohol, is the alcohol present in alcoholic
beverages and is commonly referred to simply as alcohol or drinking alcohol. Like
methyl alcohol, ethyl alcohol is oxidized in the human body by the liver enzyme alcohol
dehydrogenase.
 Acetaldehyde, the first oxidation product, is largely responsible for the symptoms of
hangover. The odors of both acetaldehyde and acetic acid are detected on the breath
of someone who has consumed a large amount of alcohol. Ethyl alcohol oxidation
products are less toxic than those of methyl alcohol.
 Long-term excessive use of ethyl alcohol may cause undesirable
effects such as cirrhosis of the liver, loss of memory, and strong
physiological addiction. Links have also been established
between certain birth defects and the ingestion of ethyl alcohol
by women during pregnancy (fetal alcohol syndrome).

3- Isopropyl Alcohol (2-Propanol)
 Isopropyl alcohol is one of two three-carbon monohydroxy alcohols; the
other is propyl alcohol.
 Isopropyl alcohol’s rapid evaporation rate creates a dramatic cooling
effect when it is applied to the skin, hence its use for alcohol rubs to
combat high body temperature. It also finds use in cosmetics formulations
such as after-shave lotion and hand lotions.
 Isopropyl alcohol has a bitter taste. Its toxicity is twice that of ethyl
alcohol, but it causes few fatalities because it often induces vomiting and
thus doesn’t stay down long enough to be fatal. In the body it is oxidized
to acetone.
 Large amounts (about 150 mL) of ingested isopropyl alcohol can be fatal;
death occurs from paralysis of the central nervous system.

4- Ethylene Glycol (1,2-Ethanediol) and Propylene Glycol (1,2-
Propanediol)
Ethylene glycol and propylene glycol are the two simplest alcohols
possessing two –OH groups. Besides being diols, they are also classified as
glycols. A glycol is a diol in which the two -OH groups are on adjacent
carbon atoms.
Both of these glycols are colorless, odorless, high-boiling liquids that are
completely miscible with water.
Their major uses are as the main
ingredient in antifreeze and airplane
“de-icers and as a starting material for
the manufacture of polyester fibres.

 Ethylene glycol is extremely toxic when ingested. In the body, liver enzymes oxidize
it to oxalic acid.Oxalic acid, as a calcium salt, crystallizes in the kidneys, which leads
to renal problems.
 Propylene glycol is essentially nontoxic and has been used as a solvent for drugs.
Like ethylene glycol, it is oxidized by liver enzymes; however, pyruvic
acid, its oxidation product, is a compound normally found in the human body, being
an intermediate in carbohydrate metabolism

5- Glycerol (1,2,3-Propanetriol)
Glycerol is a clear, thick liquid that has the consistency of honey. Its molecular structure
involves three -OH groups on three different carbon atoms.
Glycerol is normally present in the human body because it is a product of fat metabolism.
It is present, in combined form, in all animal fats and vegetable oils

Physical Properties of Alcohols
Alcohol molecules have both polar and nonpolar character. The hydroxyl groups
present are polar, and the alkyl (R) group present is nonpolar
1. Alcohols have higher boiling points than
alkanes of similar molecular mass.
2. Alcohols have much higher solubility in
water than alkanes of similar molecular mass.

Classification of Alcohols
Alcohols are classified as primary (1°), secondary (2°), or tertiary (3°) depending
on the number of carbon atoms bonded to the carbon atom that bears the hydroxyl
group.
A primary alcohol is an alcohol in which the hydroxyl-bearing carbon atom is bonded to
only one other carbon atom.
A secondary alcohol is an alcohol in which the hydroxyl-bearing carbon atom is bonded to
two other carbon atoms.
A tertiary alcohol is an alcohol in which the hydroxyl-bearing carbon atom is bonded to
three other carbon atoms. Chemical reactions of alcohols often depend on alcohol class
(1°, 2°, or 3°).

Chemical Reactions of Alcohols
1- Oxidation
Primary and secondary alcohols, the two types of oxidizable alcohols, yield
different products upon oxidation. A 1° alcohol produces an aldehyde that
is often then further oxidized to a carboxylic acid, and a 2° alcohol
produces a ketone.

2-Dehydration reaction is a chemical reaction in which the components of water
(H and OH) are removed from a single reactant or from two reactants (H from one and OH
from the other). In intramolecular dehydration, both water components are removed from
the same molecule.

Dehydration of an alcohol can result in the production of more than one alkenen
product. This happens when there is more than one neighboring carbon atom
from which hydrogen loss can occur. Dehydration of 2-butanol produces two
alkenes.

Halogenation
Alcohols undergo halogenation reactions in which a halogen atom is
substituted for the hydroxyl group, producing an alkyl halide.
Combustion
Alcohols are also flammable; as with hydrocarbons, the combustion products
are carbon dioxide and water.

ETHERS
An ether is an organic compound in which an oxygen atom is bonded to two
carbon atoms by single bonds. In an ether, the carbon atoms that are
attached to the oxygen atom can be part of alkyl, cycloalkyl, or aryl groups.

Nomenclature for Ethers
Common names for ethers are formed by naming the two hydrocarbon groups
attached to the oxygen atom and adding the word ether. The hydrocarbon
groups are listed in alphabetical order. When both hydrocarbon groups are the
same, the prefix di- is placed before the name of the hydrocarbon group.

In the IUPAC nomenclature system, ethers are named as substituted
hydrocarbons. The smaller hydrocarbon attachment and the oxygen atom are
called an alkoxy group, and this group is considered a substituent on the
larger hydrocarbon group. An alkoxy group is an -OR group, an alkyl (or aryl)
group attached to an oxygen atom. Simple alkoxy groups include the
following:

The steps in naming an ether using the IUPAC system are
1. Select the longest carbon chain and use its name as the base name.
2. Change the -yl ending of the other hydrocarbon group to -oxy to obtain
the alkoxy group name; methyl becomes methoxy, ethyl becomes ethoxy, etc.
3. Place the alkoxy name, with a locator number, in front of the base chain
name.

Physical and Chemical Properties of Ethers
1- The boiling points of ethers are
similar to those of alkanes of
comparable molecular mass and are
much lower than those of alcohols
of comparable molecular mass.
2-Ethers, in general, are more soluble in water than are alkanes of similar
molecular mass because ether molecules are able to form hydrogen bonds
with water.

Two chemical properties of ethers are especially important.
1. Ethers are flammable. Special care must be exercised in laboratories where
ethers are used. Diethyl ether, whose boiling point of 35°C is only a few degrees
above room temperature, is a particular flash-fire hazard.
2. Ethers react slowly with oxygen from the air to form unstable hydroperoxides
and Peroxides.

Reactions of Ethers
 Ethers resemble hydrocarbons in their resistance to chemical
reaction. For example, they do not react with oxidizing agents, such
as potassium dichromate.
 Likewise, they do not react with reducing agents such as H2 in the
presence of a metal catalyst.

THIOLS COMPOUNDS
Thiols, the sulfur analogs of alcohols, contain -SH functional groups instead of
-OH functional groups. The thiol functional group is called a sulfhydryl group.
A sulfhydryl group is the -SH functional group. A thiol is an organic compound
in which a sulfhydryl group is bonded to a saturated carbon atom. An older
term used for thiols is mercaptans.

Nomenclature for Thiols
1-Thiols are named in the same way as
alcohols in the IUPAC system, except that
the –ol becomes -thiol. The prefix thio-
indicates the substitution of a sulfur
atom for an oxygen atom in a compound.
2-As in the case of diols and triols, the -e at the end of the alkane name is
also retained for thiols
3-Common names for thiols are based on use of the
term mercaptan, the older name for thiols. The name
of the alkyl group present (as a separate word)
precedes the word mercaptan.

Properties of Thiols
1-Two important properties of thiols are low boiling points (because of
lack of hydrogen bonding) and a strong, disagreeable odor.
2-Thiols are easily oxidized but yield different products than their alcohol
analogs.
Thiols form disulfides. Each of two thiol groups loses a hydrogen atom, thus
linking the two sulfur atoms together via a disulfide group, -S-S- .
Reversal of this reaction, a reduction process, is also readily accomplished.
Breaking of the disulfide bond regenerates two thiol molecules.

Garlic and Onions and Thiols compounds
1-Garlic and onions, which botanically belong to the same plant genus, are
vegetables known for the bad breath—and perspiration odors—associated
with their consumption. These effects are caused by organic sulfur-containing
compounds. The total sulfur content of garlic and onions amounts to about
one percent of their dry weight.
2- Garlic has been shown to function as an antibacterial, antiviral, antifungal,
antiprotozal, and antiparasitic agent. In the area of heart and circulatory
problems, garlic contains vasodilative compounds that improve blood fluidity
and reduce platelet aggregation.

A major contributor to the typical smell of the human armpit is a
compound that contains both an alcohol and a thiol functional group.

Alcohol and ethers

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