Download Properties of Alcohol

Properties of Alcohol
Introduction

Alcohol is any compound in which a hydroxyl
functional group (-OH) is bound to a carbon
atom.

There are three classes (types) of alcohols:
 primary
 secondary
 and
tertiary
Introduction, cont.
Primary Alcohol:

In a primary (1°) alcohol, the carbon which
carries the -OH group is only attached to one
alkyl group.
General formula: RCH2OH
Introduction, cont.
Primary Alcohol:
Methanol
Ethanol
Introduction, cont.
Secondary Alcohol:

In a secondary (2°) alcohol, the carbon
with the -OH group attached is joined
directly to two alkyl groups.
General formula: R2CHOH
Introduction, cont.
Tertiary Alcohol:

In a tertiary (3°) alcohol, the carbon atom
holding the -OH group is attached directly to
three alkyl groups.
General formula: R3COH
Physical Properties of Alcohol

Molecular state:
straight chain alcohols with up to 12 carbon atoms are
liquids.

Solubility:
 alcohols
with a small organic part as methanol or
ethanol are much like water, thus miscible with water.

Alcohols with a larger molecular weight are more like
alkane and less like water.
 Alcohols
with more than two -OH groups are more water
soluble than similar alcohols with only one -OH group.
Physical Properties of Alcohol

In general each -OH group can solubilize four to five
carbon atoms.
For

example: Glycerol
Boiling point:
 the
boiling point of an alcohol is always much higher than
that of the alkane with the same number of carbon atoms.
 alcohols
with two or more –OH groups have higher
boiling point.
Physical Properties of Alcohol
Methanol, Ethanol and Glycerol:
Color
colorless
Odor
they have faint odor (alcoholic odor) except glycerol
which is odorless.
Solubility
completely miscible with water.
Flammability
flammable with blue, non smoky flame.
State
liquid except glycerol which is viscous liquid.
Acid-base
properties
neutral
Chemical Properties of Alcohol
Oxidation:

The oxidising agent used is a solution of
potassium dichromate (K2Cr2O7) acidified with
sulphuric acid (H2SO4).

If oxidation occurs, the orange solution
containing the dichromate ions is reduced to a
green solution containing chromium ions.
Chemical Properties of Alcohol
Oxidation of Primary Alcohol:

Primary alcohol is first oxidised to an aldehyde
which is then oxidised further to the carboxylic
acid.
Chemical Properties of Alcohol
Oxidation of Secondary Alcohol:

Secondary alcohol can be oxidised into a
ketone.
Oxidation of Tertiary Alcohol:

No reaction.
Chemical Properties of Alcohol
Oxidation Tests:

Tests for methanol and ethanol:

In test tube mix 1 part of alcohol, 1 drop of
k2Cr2O7, what is the color?

Then add 4 drops of conc. H2SO4.
Chemical Properties of Alcohol
Esterification:

The reaction between alcohol and carboxylic
acid to make ester.

Esters usually have pleasant, fruit like odors
H2SO4
Chemical Properties of Alcohol
Esterification Tests:

Test for methanol:
Mix in a test tube 1 part of methanol, about 0.2 g of
salicylic acid, 3 drops of conc. H2SO4 then warm for 5
min.
In a beaker prepare Na2Co3 solution. Add the content of
the test tube into the beaker.
O
OH
OH
H2SO4
CH3OH +
methanol
Salicylic acid
???
methyl salicylate
+H2O
Chemical Properties of Alcohol
Esterification Tests:

Test for ethanol:
Mix in a test tube 1 part of ethanol, about 1 ml of dil.
acetic acid, 3 drops of conc. H2SO4 then warm for 5
min.
In a beaker prepare Na2Co3 solution. Add the content of
the test tube into the beaker.
H2SO4
Chemical Properties of Alcohol
Iodoform Reaction:
iodoform test forms a characteristic for alcohols like ethanol,
2-propanol.
alcohols may be oxidized to form α-methyl carbonyl 
compounds.
Test for methanol: 
Mix in a test tube about 1 part of methanol, 4 parts of dil.
NaOH solution, and 1 ml of iodine solution then warm.
-ve

Chemical Properties of Alcohol
Iodoform Reaction:
Test for ethanol: 
Mix in a test tube about 1 part of ethanol, 4
parts of dil. NaOH solution, and 1 ml of iodine
solution then warm.
Chemical Properties of Alcohol
Special Test for Glycerol:

Test for glycerol with a solution of borax:
Mix in a test tube about 1 part of borax solution, 1 drop of
phenolphthalein solution then shaking. What is the
color?
Add 1 part of glycerol and shaking.
+
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