Download Chemicals in Everyday Life

General Outline
We will be looking at:
► Food Chemicals
► Detergents
These Include
Food Coloring
Flavorings and
Sweeteners
Flour Improvers and
Bleaches
Antioxidants
Preservatives and
nutritional
supplements
Sucrose
► Natural
Sweetener
► Adds to calories
Natural vs. Artificial
Disadvantages of natural sweeteners:
► Adds to calories (hence unsuitable for
people on a diet)
► Increases blood sugar levels (hence
unsuitable for diabetics)
Natural vs. Artificial
Advantages of Artificial Sugars:
► Does not add to calories
► Not metabolized in the body
► Inert, harmless
Saccharine
► Also
known as orthosulphobenzimide
► Excreted in urine
► Inert in body
Aspartame
Methyl ester of aspartic
acid-phenylalanine
dipeptide
Aspartame
As it is unstable at high
temperatures, it is
unsuitable for cooking.
Hence it is used in cold
drinks and foods.
Alitame
► More
stable than
aspartame
► As it is 2000 times
sweeter than sucrose
control of sweetness
difficult
Sucralose
► Tri-chloro
derivative of sucrose
► Same taste and appearance as sucrose
► Stable at cooking temperature
► Does not add to calories
Preservatives include:
Table salt (NaCl)
Sugar
Preservatives include:
Sodium Benzoate
And……
Salts of sorbic acid and propanoic acid
Sodium Benzoate
► Metabolized
in the
body
► Used in limited
quantities
Types of detergents
► Soaps
► Synthetic
detergents
Saponification
The general equation for saponification is
as follows:
Fat + Alkali
Soap + Glycerol
Saponification
Fatty acids used are:
► Stearic acid
► Oleic acid
► Palmitic acid
The soap is precipitated with NaCl (Why?)
Varieties of soap
Bath Soap
► Better
quality fat used
► Excess alkali removed
► Perfumes and colors
added
Varieties of soap
Floating soap
Air bubbles beaten in
before hardening
Varieties of soap
Transparent soap
► Soap
dissolved in
ethanol
► Excess solvent
evaporated off
Varieties of soap
Medicated Soaps:
Medicinal substances
added
Varieties of soap
Shaving soap:
► Glycerol
added to
prevent drying
► Rosin added which
forms sodium rosinate
which lathers well
Varieties of soap
Laundry soap:
Fillers like sodium
rosinate, sodium
silicate and sodium
carbonate added
Varieties of soap
Soap chips:
Melted sheet of soap run
into a cool chamber
and soap scraped off
in small broken pieces
Varieties of soap
Soap or scouring
powder:
It consists of soap,
abrasives like
powdered pumice or
finely divided sand and
builders like sodium
carbonate and trisodium phosphate.
Disadvantages of Soap
Soaps cannot work in hard water. This is
because hard water contains calcium and
magnesium ions. These react with soaps to
form insoluble Ca and Mg soaps when soaps
are dissolved in hard water.
The reaction is as follows:
2C17H35COONa + CaCl2
2NaCl +
(C17H35COO)2M
M = Ca or Mg
Disadvantages of Soap
These separate out as scum and are useless
for washing. These make washing harder as
they form a gummy mass which adheres to
cloth, preventing cleaning action of soap
Other Disadvantages of Hard
Water
► Hair
washed in hard water looks dull
► Dye does not absorb evenly on cloth
washed with hard water
Advantages of Synthetic Detergents
over soaps
► Have
all the properties of soaps
► Can be used in both hard and soft water to
give foam
► Gives foam even in ice-cold water
Types of Synthetic Detergents
►Anionic
Detergents
►Cationic Detergents
►Non-ionic Detergents
Anionic Detergents
Sodium salts of sulphonated long chain
alcohols or hydrocarbons.
Alkyl hydrogensulphates made by treating
long chain alcohols with conc. H2SO4 and
then neutralized with NaOH
H SO
CH3(CH2)10CH2OH
2 4
CH3(CH2)10CH2OSO3H(Lauryl hydrogensulphate)
NaOH (aq)
CH3(CH2)10CH2OSO3-Na+(Sodium
lauryl
sulphate)
Anionic Detergents
Anionic Detergents are
mainly used in
household cleaning
agents
Cationic Detergents
► These
are quaternary ammonium salts of
amines with acetates, chlorides or bromides
as anions.
► It is called cationic as the cationic part
posses long hydrocarbon chains and positive
charge on nitrogen atom.
E.g..: Cetyl tri-methyl ammonium bromide
Cationic Detergents
Cationic detergents have
germicidal properties
and are expensive.
These are usually used
in hair conditioners.
Non-Ionic Detergents
These detergents do not contain any ion in
their constitution.
CH3(CH2)16COOH + HO(CH2CH2O)nCH2CH2OH
-H O
2
CH3(CH2)16COO(CH2CH2O)nCH2CH2OH
Non-Ionic Detergents
These detergents use the
same cleaning
mechanism as soaps.
Disadvantage of Synthetic
Detergents
If the detergent molecule is highly branched,
it is difficult to degrade by bacteria, leading
to accumulation in the environment, i.e.
they are non-biodegradable.