WINDSOR UNIVERSITY
SCHOOL OF MEDICINE
ALCOHOLS,
ACIDS & ESTERS
TO KNOW WHAT IS RIGHT AND NOT TO DO IT IS THE
WORST COWARDICE.
CONFUCIUS
Ch.15
J.C. Rowe
ALCOHOLS
Physical properties
1.
Melting & boiling points
2.
Solubility & volatility
Reactions of alcohols
1.
Combustion
2.
Reaction with sodium
3.
Dehydration & oxidation /reduction
Preparation of ethanol
Physical properties of alcohol
The properties of an alcohol depend on 2 factors :
 The functional group (-OH)
 The length of the hydrocarbon chain
 Melting & boiling points.
Increase with an increase in the hydrocarbon chain
length of the alcohol.
The boiling point of a substance is the temperature at
which the vapor pressure of the liquid equals the
environmental pressure surrounding the liquid.
The melting point of a substance is the temperature at
which the solid melts to become a liquid.

Physical properties of alcohol Cont’d.
Solubility
More soluble in water than alkanes of a similar
molecular mass because of the hydrogen bonds between
water molecules & alcohol molecules.
 Volatility
Is the ease with which alcohols are converted to vapour.
Alcohols are not as volatile as hydrocarbons with the
similar molecular mass because of the hydrogen bonds
between the alcohol molecules

Ethanol
The most Popular formula of Ethanol is its molecular
formula C2H5OH. It is simply an Ethyl group (CH3CH2-)
attached to Hydroxyl functional group (-OH) to form the
structural formula CH3-CH2-OH
Reactions of alcohols
Combustion.
The products of combustion of ethanol are carbon
dioxide & water.
C2H5OH(l) + 3 O2(g) =Heat=> 2 CO2(g) + 3 H2O(g)
 Reaction with Sodium
Sodium reacts with ethanol at room temp to liberate
hydrogen. The hydrogen atom of the hydroxyl group is
replaced by a sodium atom, forming sodium ethoxide.
2 C2H5OH(l) + Na (s) ==> 2 C2H5ONa (aq) + H2 (g)

Reactions of alcohols Cont’d.
Dehydration of Ethanol
When ethanol is mixed with concentrated sulphuric
acid with the acid in excess and heated to 170 deg C,
ethylene is formed. (One mole of ethanol loses one
mole of water)

C2H5OH (g)+ H2SO4 (l) = => C2H4 (g) + H2O (g)
Reactions of alcohols Cont’d.
Ethanol is oxidised
with acidified Potassium Dichromate, K2Cr2O7, or
with acidified Sodium Dichromate, Na2Cr2O7, or
with acidified potassium permanganate, KMnO4,

The oxidising agent [O] usually used for this reaction is
a mixture of sodium dichromate or potassium dichromate
and sulphuric acid which react together to provide
oxygen atoms .the alcohol acts as a reducing agent.
C2H5OH + 2[O] ==> CH3COOH + H2O

Preparation of ethanol
Preparation
Ethanol is prepared as 95% alcohol (i.e. a 95%
solution of ethanol in water) by distillation of the
solution which results from the fermentation of
sugars.
 Manufacture
There are two major industrial pathways to ethanol.
Ethanol which is intended for industrial use is made
by the first method, while ethanol intended for food
use tends to be made by the second method

A. Preparation of ethanol Cont’d.

Reaction of Ethene with Steam
Most of the ethanol used in industry is
made, not by alcoholic fermentation,
but by an addition reaction between
ethene and steam.
C2H4 + H2O ==> C2H5OH
B. Preparation of ethanol Cont’d.



alcoholic Fermentation
A solution of sucrose, to which yeast is added, is
heated.
An enzyme, invertase, which is present in yeast is
added and this acts as a catalyst to convert the
sucrose into glucose and fructose.
C12H22O11 + H2O + invertase
==> C6H12O6 + C6H12O6
C. Preparation of ethanol Cont’d.
The glucose, C6H12O6, and fructose, C6H12O6,
formed are then converted into ethanol and carbon
dioxide by another enzyme, zymase, which is also
present in yeast.
C6H12O6 + Zymase ==> 2C2H5OH + 2CO2
 The fermentation process takes three days and is
carried out at a temperature between 250C and
300C. The ethanol is then obtained by fractional
distillation.

D. Preparation of ethanol Cont’d.

Absolute Ethanol
Whatever method of preparation is used, the ethanol is
initially obtained in admixture with water. The ethanol is
then extracted from this solution by fractional
distillation.
Although the boiling point of ethanol, 78.3 deg C, is
significantly lower than the boiling point of water, 100
deg C, these material cannot be separated completely
by distillation.
Instead, an azeotropic mixture (i.e. a mixture of 95%
ethanol and 5% water) is obtained, and the boiling
point of the azeotrope is 78.15 deg C.
E. Preparation of ethanol Cont’d.


In a distillation, the most volatile material (i.e. the
material that has the lowest boiling point) is the first
material to distill from the distillation flask, and this
material is the azeotrope of 95% ethanol which has the
lowest boiling point.
If an efficient fractionating column is used, there is
obtained first 95% alcohol, then a small intermediate
fraction of lower concentration, and then water. But no
matter how efficient the fractionating column used, 95%
alcohol cannot be further concentrated by distillation
F. Preparation of ethanol Cont’d.


The separation of a mixture by fractional distillation
occurs because the vapour has a different
composition from the liquid from which it distils (i.e.
the vapour is richer in the more volatile component).
We cannot separate 95% alcohol into its
components by distillation, because here the vapour
has exactly the same composition as the liquid;
towards distillation, then, 95% alcohol behaves
exactly like a pure compound.
G. Preparation of ethanol Cont’d




A liquid mixture that has the peculiar property of
giving a vapour of the same composition is called an
azeotrope (i.e. a constant-boiling mixture).
Since it contains two components 95% alcohol is a
binary azeotrope.
Most azeotropes, like 95% alcohol, have boiling points
lower than those of their components, and are known as
minimum-boiling mixtures.
Azeotropes having boiling points higher than those of
their components are known as maximum-boiling
mixtures.
CARBOXYLIC ACIDS
Acidic reactions of ethanoic acid
1.
Reaction with metals
2.
Reactions with bases
3.
Reactions with carbonates & hydrogen
carbonates
Non-acidic reactions of ethanoic acid
1.
Combustion
2.
Esterification
Naming Carboxylic Acids



1. COMMON NAME (PREFIX + IC + ACID) {PROPIONIC
ACID}
2. SYSTEMATIC NAME (DROP (E) & ADD (OIC) & ADD
ACID) {HEXANOIC ACID}(C=O CARBON IS #1)
3. COMPLEX COMPOUNDS (ALKANE + CARBOXYLIC
ACID) {CYCLOHEXANECARBOXYLIC ACID}
Derivatives of Carboxylic Acid
Acidic reaction of ethanoic acid


Ethanoic acid is a weak monobasic acid that undergoes a
neutralization reaction with bases or alkali to form
ethanoate salt and water.
This is as expressed by the reaction of ethanoic acid with
sodium hydroxide to form sodium ethanoate and water.
2CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O(l)

It also attack strongly electropositive metals like magnesium
and calcium to liberate hydrogen.
2CH3COOH(aq) + Mg(s) → (CH3COO)2Mg(aq) + H2(g)

Ethanoic Acid and Sodium Carbonate to produce the
ethanoate salt (sodium ethanoate), carbon dioxide &
water.
2 CH3COOH + Na2CO3  2 CH3COONa + H2O + CO2

Ethanoic Acid reacts with metals to produce hydrogen
gas & salt.
2 CH3COOH +2 Na  2 CH3COONa + H2
Non-acidic reactions of ethanoic acid
Combustion: Ethanoic acid will burn in oxygen to form
water and carbon dioxide
CH3COOH (aq)+ 2O2(g)  2CO2 (g) +2H2O (g)

Esterification : Ethanoic acid will react with alcohols in
the presence of concentrated sulfuric acid, to form esters.
ethanol + ethanoic acid  ethyl ethanoate + water.
C2H5OH(aq) + CH3CO2H(aq) CH3CO2C2H5(aq)+ H2O(l)

ESTERS
Reactions of esters
1.
Hydrolysis
2.
Alkaline hydrolysis of an ester
Saponification
Making esters from carboxylic acids
and alcohols

The esterification reaction is both slow and
reversible. The equation for the reaction between
an acid RCOOH and an alcohol R'OH (where R and
R' can be the same or different) is:

So, for example, if you were making ethyl
ethanoate from ethanoic acid and ethanol, the
equation would be:
Reactions of esters



Carboxylic esters hydrolyse to the parent
carboxylic acid and an alcohol.
Reagents : aqueous acid (e.g. H2SO4) / heat, or
aqueous NaOH / heat (known as "saponification").
it is the C-O bond between the acyl group and the
oxygen that is cleaved
Hydrolysis using dilute alkali

Here are examples of 2 reactions:
Saponification




Saponification is the process of making soap from
excess alkaline hydrolysis of natural esters.
Soap molecules consist of a hydrophobic end & a
hydrophilic head
Soapy detergents (made from the hydrolysis of
natural esters)do not clean very efficiently in hard
water (water containing calcium & magnesium ions).
The precipitate formed is called SCUM.
Soapless detergents are made from hydrocarbon
products
Reactions of saponification
General reaction of saponification
Natural Sources of Organic Acids






Lactic Acid – milk
Tartaric acid (2,3-dihydroxybutanedioic acid) – grapes
Butanoic acid – rancid smell of butter
Fats & Oils
Citrus acid – Citrus Fruits
Ascorbic Acid – Vitamin C
Soap and Saponification



Natural soaps are sodium or potassium salts of fatty
acids, originally made by boiling lard or other animal
fat together with lye or potash (potassium hydroxide).
Hydrolysis of the fats and oils occurs, yielding glycerol
and crude soap.
In the industrial manufacture of soap, tallow (fat from
animals such as cattle and sheep) or vegetable fat is
heated with sodium hydroxide.
Once the saponification reaction is complete, sodium
chloride is added to precipitate the soap. The water
layer is drawn off the top of the mixture and the
glycerol is recovered using vacuum distillation.

The crude soap obtained from the saponification
reaction contains sodium chloride, sodium hydroxide,
and glycerol. These impurities are removed by
boiling the crude soap curds in water and reprecipitating the soap with salt. After the
purification process is repeated several times, the
soap may be used as an inexpensive industrial
cleanser. Sand or pumice may be added to produce
a scouring soap. Other treatments may result in
laundry, cosmetic, liquid, and other soaps.
Cross-section through a micelle


When cleaning with
soaps the fat-soluble
end of the soap
(hydrocarbon tail) will
first attack the oil film
surrounding the dirt
particle.
the dirt particle
becomes totally
surrounded & a
micelle is formed.
Norman Vincent Peale
How much one actually achieves depends largely on: (1)
desire, (2) faith, (3) persistent effort and (4) ability. But if
you are lacking in the first three factors, your ability will
not balance out the lack. So concentrate on the first three
and the results will amaze you.