2. CARBON
Carbon is a very important chemical element, with a chemical symbol of C. All known
life on Earth is made from it. Carbon has atomic mass 12 and atomic number 6. It is a
non-metal.
Carbon, hydrogen, nitrogen, oxygen, and some other elements like sulphur and
phosphorus together form most life on earth. Carbon forms a very large number of
organic compounds because it can form strong bonds with itself and with other
elements. Because of the amounts of carbon living things have, all organic things are
considered "carbon-based". Also, each carbon atom can form 4 single covalent bonds.
Many carbon atoms linked together with hydrogen atoms form plastic. Also, Carbon is
the only element that can form long chain-shaped molecules. When iron is heated up
with carbon, hard steel is formed.
3. WHY DOES CARBON FORM A LARGE NO. OF
COMPOUNDS ?
A carbon atom completes its octet only by sharing its valence electrons with
other atoms. As a result, a carbon atom forms four covalent bonds by sharing
valence electrons with other atoms. This is known as tetravalency of carbon
("tetra" means four).
The linkage of atoms of the same element into longer chains is known as
Catenation. Catenation occurs most readily in carbon, which forms covalent
bonds with other carbon atoms to form longer chains and structures. This is the
reason for the presence of the vast number of organic compounds in nature.
These are the reasons why carbon forms large number of compounds.
4. ISOMERISM
An isomer is a molecule with the same molecular formula as another
molecule, but with a different chemical structure. That is, isomers
contain the same number of atoms of each element, but have
different arrangements of their atoms. Isomers do not necessarily
share similar properties, unless they also have the same functional
groups. The existence of two(or more) different organic compounds
having the same molecular formula but different structures is called
isomerism. Isomerism is possible only with hydrocarbons having 4 or
more carbon atoms, because only then we can have two or more
different arrangements of carbon atoms.
5. SATURATED AND UNSATURATED
COMPOUNDS
A saturated compound is a chemical compound that has a
chain of carbon atoms linked together by single bonds.
Alkanes are saturated hydrocarbons. An unsaturated
compound is a chemical compound that contains carbon-
carbon double bonds or triple bonds, such as those found in
alkenes or alkynes, respectively. Saturated and unsaturated
compounds need not consist only of a carbon atom chain.
They can form straight chain, branched chain, or ring
arrangements. They can have functional groups, as well.
6. ADDITION REACTION
Unsaturated hydrocarbons add hydrogen in the presence of catalysts
such as palladium or nickel to give saturated hydrocarbons, this
process is known as addition reaction. Catalysts are substances that
cause a reaction to occur or proceed at a different rate without the
reaction itself being affected. This reaction is commonly known used
in the hydrogenation of vegetable oils using a nickel catalyst.
Vegetable oils generally have long unsaturated carbon chains while
animal fats have saturated carbon chains.
7. SUBSTITUTION
REACTION
Saturated hydrocarbons are fairly unreactive and are inert
in the presence of most reagents. However, in the presence
of sunlight, chlorine is added to hydrocarbons in a very fast
reaction. Chlorine can replace hydrogen atoms one by one.
It is called a substitution reaction because one type of
atoms or a group of atoms takes the place of another. A
number of products are usually formed with the higher
homologues of alkanes.
8. ETHANOL
Ethanol is a liquid at room temperature. It is commonly called alcohol and is the active
ingredient of all alcoholic drinks. In addition, because it is a good solvent, it is also used in
medicines such as tincture iodine, cough syrups, and many tonics. Ethanol is also soluble in
water in all proportions. Consumption of small quantities of dilute ethanol causes drunkenness.
Reactions of Ethanol :-
With Sodium :- 2Na + 2𝐶𝐻3 𝐶𝐻2OH -> 2𝐶𝐻3 𝐶𝐻2 𝑂− 𝑁𝑎+ + 𝐻2
Hot Conc.
With Unsaturated Hydrocarbon :-𝐶𝐻3 𝐶𝐻2 𝑂𝐻 𝐶𝐻2 + 𝐻2 𝑂
𝐻2 𝑆𝑂4
The concentrated sulphuric acid can be regarded as a dehydrating agent which removes water
from ethanol.
9. ETHANOIC ACID
Ethanoic acid is commonly called acetic acid and belongs to a group of
acids called carboxylic acids. 5-8% solution of acetic acid in water is called
vinegar and is widely used as a preservative in pickles. The melting point
of pure ethanoic acid is 290K and hence it often freezes during winter in
cold climates. This gives rise to its name glacial acetic acid.
The group of organic compounds called carboxylic acids are obviously
characterised by a special acidity. However, unlike mineral acids like HCl,
which are completely ionised, carboxylic acids are weak acids.
10. ESTERIFICATION
REACTION
Esters are most commonly formed by reaction of an acid and an
alcohol. Ethanoic acid reacts with absolute ethanol in the presence
of an acid catalyst to give an ester –
𝐶𝐻3 𝐶𝑂𝑂𝐻 + 𝐶𝐻3 𝐶𝐻2 𝑂𝐻 𝐶𝐻3COO𝐶𝐻2 𝐶𝐻3
Esters are sweet-smelling substances. These are used in making
perfumes and as flavouring agents.
11. REACTIONS OF ETHANOIC ACID :
1) Esterification Reaction : Esters react in the presence of an acid or a base to give back the
alcohol and carboxylic acid. This reaction is known as saponification because it is used in the
preparation of soap.
𝐶𝐻3 𝐶𝑂𝑂𝐶2 𝐻5 𝐶2 𝐻5 𝑂𝐻 + 𝐶𝐻3COONa
2) Reaction with a base: Like mineral acids, ethanoic acid reacts with a base such as sodium
hydroxide to give a salt (sodium ethanoate or commonly called sodium acetate) and water:
NaOH + CH3COOH → CH3COONa + H2O
• 3) Reaction with carbonates and hydrogencarbonates: Ethanoic acid reacts with carbonates
and hydrogencarbonates to give rise to a salt, carbon dioxide and water. The salt produced is
commonly called sodium acetate.
• 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
• CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
12. SOAPS AND DETERGENTS
A soap is the sodium salt(or potassium salt) of a long chain carboxylic acid(fatty acid)
which has cleansing properties in water. A soap has a large non-ionic hydrocarbon
group and an ionic group, 𝐶𝑂𝑂−
𝑁𝑎+
. Examples of the soaps are : Sodium Stearate,
Sodium Palmitate. Being basic, a soap turns red litmus paper to blue.
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in
dilute solutions.” These substances are usually alkyl benzenesulfonates, a family of
compounds that are similar to soap but are more soluble in hard water, because the
polar sulfonate (of detergents) is less likely than the polar carboxyl (of soap) to bind to
calcium and other ions found in hard water. In most household contexts, the term
detergent by itself refers specifically to laundry detergent or dish detergent, as opposed
to hand soap or other types of cleaning agents. Detergents are commonly available as
powders or concentrated solutions.
