In general the drug may be defined as the substances used in the prevention, diagnosis, treatment or cure of
disease in man or animals. Drug may be single chemical substance or a combination of two or more different
substances. An ideal drug should satisfy the following requirements
This classification is based on pharmacological effect of the drug. It is useful for doctors because it provides
them the whole range of drugs available for treatment of particular type of health related problem for example,
analgesics have pain killing effect antiseptics kill or stop the growth of micro organisms, tranquilizers
reduces mental stress
Macromolecules of biological origin perform various functions in the body for example proteins which perform the
role of biological catalysts in the body are called enzymes, and those which are crucial to communication
system in the body are called receptors.
Receptors are proteins that are crucial to body’s communication process. Majority of these are
embedded in cell membranes in such a way that their small part possessing active site project
out of the surface of the membrane and open on the outside region of the cell membrane
Hormones are a group of chemicals which are produced in the ductless (endocrine) glands. These enter the
blood stream and travel to different parts of the body activating all the receptors which recognise them for
message transfer
Nerves transfer message through neurotransmitters.
There are small molecules such as acetyl choline, dopamine and serotonin.
These bind to the receptor (target) for a very short time to transfer message to it and depart quickly unchanged
after transfering the message
*The chemicals which are used to reduce the acidity of the stomach are called antacids. Acidity is one of the
common ailments associated with digestion.
*Antacids are nature is basic. Their PH value is in the range of 7.0 to 8.0.
*Omeprazole and lansoprazol are also marketed as antacid. They prevent the formation of acid in the stomach.
Their strucutures are as follows
*Antigens from environment and food create allergic reactions in our body. In this situtation Histamine a chemical
released from certain cells in our body during allergic reaction, are produced.
*Antihistamines are the drugs which diminish or abolish the effects of histamine.
*Synthetic drugs Brompheniramine (Dimetapp), Chlorpheniramine and terphenadine (selane) act as antihistamine.
*The antihistamine do not effect the secretion of acid in stomach because antiallergic and antacid drugs work on
different receptors
*The chemicals which are used to reduce mental tension, relieve anxiety and mental stress are called Tranquilizer.
They act on central nervous system and are hypnotics.
*Tranquilizers are effective in such mental disorder when ordinary hypnotics or sedatives fail. These are called as
psychotherapeutic drugs
*The chemicals which stop the growth or kill the micro organism such as bacteria, virus, fungi, moulds etc are
called antimicrobials.
* Antibiotics, antiseptics and disinfectants are antimicrobial drugs
*The chemicals which stop the growth or kill the micro organism such as bacteria, virus, fungi, moulds etc are
called antimicrobials.
* Antibiotics, antiseptics and disinfectants are antimicrobial drugs
“Chemcial substances which are used to check pregnancy in women are called anti-fertility drugs or
birth control pills or oral contraceptivesâ€.
*It is known that estrogens control the menstrual cycle while progesterone suppresses ovulation.
*Birth control pills essentially contain a mixture of synthetic estrogen and progesteron derivatives.
Both of these compounds are hormones.
Chemicals are added to food for their preservation, enhancing their appeal and adding nutritive values in them
Main catergories of food additives are as follows
*Natural sweeteners e.g. sucrose added to calorie intake and therefore many people prefer to use artificial
sweeteners for example like Saccharine (It is ortho-sulphobenzimide which is insoluble in water but its sodium
or potassium salts are soluble in water It is the first popular artificial sweetening agent used since 1879. It is
about 550 times more sweet as cane sugar
*The chemical which are used to stop undesirable change in food caused by microorganism and save
them from spoiling are called preservatives. It reduces (stop the growth) and rate reactions occuring due
to bacteria in food).
*The chemical substance which reduce the rate of reaction with oxygen in food, thus help in
their preservation are called antioxidants.
*Soaps are sodium or potassium salts of long chain fatty acids e.g steric, oleic and palmitic acids. soap
containg sodium salts are formed by heating fat (i.e. glyceryl ester of fatty acid) with aqueous sodium hydroxide
solution.
The synthetic products , which like soaps remove dust and grease from a surface are called detergents, since
they are not soap but work like a soap so they are also called as soapless soap.
Detergents are mainly sodium salts of either sulphuric or sulphonic acids with long chain hydrocarbons. Their
general formula is as follows
Although the action of soap and detergents is similar but there are following differences between
them
*Rocket propellants consists of rocket engines powered by propellants. These are used both in space vehicles
as well as in offensive weapons such as missiles. The propellants are chemical substances which on ignition
provide thrust for the rocket to move forward. These substances are called rocket propellants
The composition of crude petroleum varies with place of occurrence but essentially it is a mixture of
alkanes, cycloalkanes, aromatic hydrocarbons, S, N and oxygen compounds and natural gas, etc
(a) Cracking : It is a process in which high boiling fractions consisting of higher hydrocarbons are
heated strongly to decompose them into lower hydrocarbons with low boiling points.
The process of cracking involves the breaking of C–C and C–H bonds resulting in the formation of
smaller molecules of various types
*Any such chemical substance which beautifies the human body by cleansing, altering or promoting the appearance.
* According to their uses, different cosmetic items are classified into different categories.
1. A dye is a coloured substance that can be applied in solution or dispersion to a substrate, giving it a
coloured appearance.
2. Every coloured substance is not a dye
Generally in most of the bonds between two different elements, the bonding electrons are attracted
more strongly towards one of the two nuclei. An unequally shared pair of bonding electrons is called a
polar covalent bond
Due to difference in electronegativity polarity developes between two adjacent atoms in the
molecule. The degree of polarity of a bond is called dipolemomentc
Due to difference in electronegativity polarity developes between two adjacent atoms in the
molecule. The degree of polarity of a bond is called dipolemoment
Attractions between molecules are particularly important in solids and liquids. In these
Dipole-dipole interactions result from the approach of two polar molecules.
The hydrogen bond is an electrostatic attractive force between covalently bonded hydrogen atom of one molecule
and an electronegative atom (such as F, O, N) of another molecule.
Vander Waals forces or London dispersion force can be observed in nonpolar molecules such
as carbon tetrachloride.
A small temporary dipole moment is induced when one molecule approaches another molecule in
which the electrons are slightly displaced from a symmetrical arrangement.
The boiling point (bp) of a compound is the temperature at which the compound’s vapor pressure
equals the atmospheric pressure. In order for a compound to vaporize, the force that hold the
molecules close to each other in the liquid must overcome. This means that the boiling point of a
compound depends on the strength of the attractive forces between the individual molecules.
Alcohols have much higher boiling points than alkanes or ethers of comparable molecular weight because, in
addition to van der Waals forces and the dipole–dipole interactions of the carbon–oxygen bond alcohols can
form hydrogen bonds
Dipole–dipole interactions, are stronger than van der Waals forces but not as strong as ionic or covalent bonds.
Ethers generally have higher boiling points than alkanes of comparable molecular weight because both van der
Waals forces and dipole–dipole interactions must be overcome for an ether to boil
The boiling points for any homologous series of compounds increase as their molecular weights increase
because of the increase in van der Waals forces. So the boiling points of a homlogous series of ethers,
alkyl halides, alcohols, and amines increase with increasing molecular weight.
The molecules of an alkane are held together by these induced dipole-induced dipole interactions known as
van der Waals forces or London forces. In order for an alkane to boil, these van der Waals forces must be
overcome.
Intermolecular forces are of primary importance in explaining the solubilities of substances. Dissolution of a solid
in a liquid is, in many respect, like the melting of a solid. The orderly crystal structure of the solid is destroyed,
and result in the formation of the more disorderly arrangement of the molecules (or ions) in solution. In the
process of dissolving, too, the molecules or ions must be separated from each other, and energy must be
supplied for both changes. The energy required to overcome lattice energies and intermolecular or interionic
attractions comes from the formation of new attractive forces between solute and solvent
The temperature at which the thermal energy of the particles is great enough to overcome the
intracrystalline forces that hold them in position is known as melting point
The organic compounds derived from natural sources or prepared in the laboratory are seldom pure. They are
usually contaminated with other substances
Chemical separation of organic compounds
