Ch. 7
Alcohols and Phenols
BY
MAHWASH HAFEEZ
General Formulas
and
Functional Groups

Both of these families contain a hydroxyl group (OH)
as functional group


Alcohols
Phenols
ALCOHOLS

Bent molecule
Central oxygen atom
 Hydrogen and alkyl group attached (R) to central
“OXYGEN” atom
(An alkyl group is formed by removing one hydrogen
from any alkane)

PHENOLS
Ar – OH
An aryl group attached to a hydroxyl “OH” group.
(An aryl group is formed by removing one hydrogen
from any a benzene ring)

Classification and Nomenclature
of Alcohols

Alcohols can be of three main types depending upon
the number of alkyl groups( carbon atoms) attached
to the main carbon atom to which is the functional
group attached.

Primary (1°) carbon atom

Secondary (2°) carbon atom

Tertiary (3°) carbon atom
Classification and Nomenclature
of Alcohols

Generally
Primary Alcohol


R – CH2 –OH
Secondary Alcohol


R2–CH – OH
Tertiary Alcohol

R3 –C – OH
NOMENCLATURE
(ALCOHOLS & PHENOLS)
STEP 1 Select the longest chain containing the hydroxyl and
replace the –e ending of the corresponding parent with
–ol
STEP 2 Number the carbons of the parent chain beginning at
the end nearer the hydroxyl
STEP 3 Number all substituents according to their position on
the chain, and write the name listing the substituents in
alphabetical order.
STEP 4 If there are more than one substituents on the same
chain then start the numbering from the side to give
minimum sum of the positions of all those substituents.
EXAMPLES
Alkane
Methane
alcohol name
Methanol
Alcohol structure
CH3-OH
(methyl alcohol)
Ethane
Ethanol
CH3-CH2-OH
(ethyl alcohol)
propane
Propanol
CH3-CH2-CH2-OH
(propyl alcohol)
propane
2-propanol
(isopropylalcohol)
butane
Pentane
hexane
heptane
1-Butanol
1-Pentanol
1-Hexanol
1-Heptanol
OH
ǀ
CH3-CH-CH3
CH3-CH2-CH2-CH2-OH
CH3-CH2-CH2-CH2-CH2-OH
CH3-CH2-CH2-CH2-CH2-CH2-OH
CH3-CH2-CH2-CH2-CH2-CH2-CH2-OH
PREPARATION OF ALCOHOLS
1. Hydration of Alkenes:
Alcohols can easily be prepared on industrial
scale by hydration of alkenes.
CH2═CH2 + H2O  CH3 ─ CH2─OH
ethylene
ethyl alcohol
2. Hydrolysis of alkyl Halides:
Alcohols can be prepared by the hydrolysis of
alkyl halides by means of water or an aqueous alkali.
H O
R – X+ NaOH 2
R – OH + NaX
3. Grignard synthesis:
Any carbonyl compound when reacted with
grignard reagent in the presence of water or a dilute acid
gives an alcohol.
O
X
RMgX + H –C – H H2O RCH2OH + Mg
4. Reduction of carbonyl compounds:
OH
Alcohols can be easily prepared by the reduction
of aldehydes or ketones either by hydrogenation in the
presence of metal catalysts such as nickel, palladium or
platinum.
O
R – C - H  RCH2OH
O
R – C – R  R2CHOH
═
═
═

Physical Properties of Alcohols





Alcohols are generally neutral colourless liquids but some
alcohols particularly high molecular weights are solids.
Not as homologous as alkanes
They mostly have high melting and boiling points due to
strong intermolecular attractions.
The -OH groups of alcohols can hydrogen bond with one
another and with other molecules.
Solubility
 The more compact the molecule is,the more soluble it is
 4-5 carbons or less—soluble in water.
Markovnikov’s Rule

The hydroxyl group goes on the carbon with
fewer hydrogens
Sec. 14.6
Chemical Properties of Alcohols

Reactions




Occur on the functional groups
May involve hydrogen atoms as well
Dehydration
Oxidation
Dehydration

During dehydration of alcohols a water molecule
is removed and ethylene is produced. Sulphuric
acid is used as a catalyst.
Oxidation

═

When alcohols are treated with oxygen, different alcohols
yield different products. i.e.
Primary alcohol yields an aldehyde on oxidation.
O
[O]
RCH2OH
R–C–H
Secondary alcohols yields ketone on oxidation.
O
[O]
R2CHOH
R–C–R
Tertiary alcohols generally do not react with oxygen.
═


PREPARATION OF PHENOLS
1. Fusion of sodium benzosulphonate with alkali:
Benzene sulphonic acid fuses with sodium hydroxide
to form sodium salt of benzene sulphonic acid which then
produces phenol.
2. Hydrolysis of Chlorobenzene:
In this process chlorobenzene is hydrolysed with 10%
aqueous sodium hydroxide solution to produce phenol.
heat
3. Oxidation of Cumene:
Air oxidation of cumene results in the formation of
phenol.
cumene
Physical properties of phenols




They are sparingly soluble in water but
solubility increases with increase in the
number of hydroxyl ions.
They are acidic in nature.
Generally have high melting points
They have high boiling points.
Phenols

Used as:
Antiseptic
 Disinfectants
First used was pure phenol—proved to be too toxic


Methyl derivatives

Cresols

Creosote
Phenols

Dihydroxybenzenes

Components of biochemical molecules
Reactions of Phenols
1. Salt formation:
Most phenols can be converted to their salts by
aqueous sodium hydroxide.
2. Ester formation:
Phenols can be allowed to form esters by allowing
them to react with an acid chloride or anhydride in the
presence of an acid or a base.
aq.NaOH
NaCl +H O
2
3. Williamson ether synthesis:
Phenols form alkyl or aryl ethers on treatment
with alkyl halides in the presence of aqueous sodium
hydroxide.
4. Nitration:
Phenol on treatment with conc. nitric acid is
converted into 2,4,6- trinitrobenzene.