1ST YEAR M PHARMACY

1. Oxidation

2. Oxidation
• Oxidation is any chemical reaction that involves the
moving of electrons. Specifically, it means the substance
that gives away electrons is oxidized. Normally, this is a
reaction between oxygen and a substance such as iron.
• When iron reacts with oxygen it forms a chemical
called rust because it has been oxidized (the iron has
lost some electrons) and the oxygen has
been reduced (the oxygen has gained some electrons).
• Formula of rusting is:
4Fe + 3O2 → 2Fe2O3
xH2O→Fe2O3.x H2O

3. • Oxidation is the opposite of reduction. A reduction-
reaction always comes together with an oxidation-
reaction. Oxidation and reduction together are
called redox (reduction and oxidation). Oxygen does not
have to be present in a reaction for it to be a redox-
reaction.
• Oxidation is the loss of electrons.
• In terms of oxygen transfer, oxidation may be defined as
the chemical process in which a substance gains oxygen
or loses electrons and hydrogen.
• When one of the reactants is oxygen, then oxidation is
the gain of oxygen. Reduction is a loss of oxygen. For
example:
• Fe2O3 + 3CO → 2Fe + 3CO2

4. Oxidizing agent
• It could be a chemical that releases oxygen atoms. For
example, potassium chlorate has a chemical formula of
KClO3. When it oxidizes a reducing agent, such
as powdered aluminum metal, it loses its oxygen to the
aluminum and becomes potassium chloride, KCl.
• Another definition is a chemical that
accepts electrons from a reducing agent. For example,
potassium permanganate has an oxidation state of +7.
In acid solution, it gains 5 electrons (e-), becoming
a manganese compound with an oxidation state of +2.
Most oxidizing agents of the second (electron-accepting)
definition have oxygen, but not all. For
example, fluorine (F2), the most powerful oxidizing agent,
does not have any oxygen in it.

5. TYPES OF OXIDATIVE
REACTIONS
In the organic chemical industry, oxidation constitutes one of the
most powerful tools used in the synthesis of chemical compounds. The
oxidation processes are many and varied and are manifested in a
variety of net effects. The principal types of oxidative reactions may be
set forth as follows:
• 1. Dehydrogenation is illustrated in the transformation of a primary
alcohol to an aldehyde:
C2H5OH + ½ O2  CH3CHO + H2O
Or a secondary alcohol to a ketone:
CH3CHOH.CH3 + ½ O2  CH3COCH3 + H2O
• 2. An atom of oxygen may be introduced into a molecule, as is
illustrated by the oxidation of an aldehyde to an acid:
CH3CHO + ½ O2  CH3COOH
Or of a hydrocarbon to an alcohol:
(C6H5)3CH + 1/2O2 (C6H5)3COH

6. • Oxidation or Dehydrogenation of Alcohols to Aldehydes and
Ketones
Primary alcohols can be converted to aldehydes and secondary
alcohols to ketones
• Oxidation of Phenols and Aromatic Amines to Quinones
Ortho and para diols are easily oxidized to ortho- and para-
quinones, respectively.

7. • 3. A combination of dehydrogenation and introduction of
oxygen may occur, as in the preparation of aldehyde from
hydrocarbons:
CH4+O2  CH2O + H2O
Or the preparation of benzoic acid from benzyl alcohol
C6H5CH2CH.OH + O2  C6H5COOH + H2O
4. Dehydrogenation may also be accompanied by molecular
condensation, as is the case when two molecules of benzene
from diphenyl or two molecules of toluene from stilbene or
when methyl, anthraquinone is converted to anthracene
yellow
C2C6H5 + ½ O2 C6H5 - C6H5 + H2O  2C6H5.CH3 + O2
C6H5.CH = CH.C6H5 + 2H2O
5. Dehydrogenation, oxygen introduction and destruction of
carbon linkages may all occur in the same process of oxidation,
e.g. in the oxidation of naphthalene to phthalic anhydride:
C10H8+4.5O2  C8H4O3 + 2H2O + 2CO2

8. liquid-phase oxidation
• Liquid phase oxidation processes are one of main pathways to
convert petroleum-based hydrocarbon raw materials into important
commodity chemicals used in the fine chemical industry.
• Liquid-phase oxidation is discussed in terms of the free radical chain
mechanism proposed by Bolland and his co-workers. This scheme
was devised for certain oxidations in which hydroperoxide is the
major product.
• It is shown, however, that this mechanism is applicable in its
essentials to other oxidations in which the hydroperoxide is not the
main product.
• In such cases the products are to be explained in terms of the
further reactions of the hydroperoxide formed, or the wastage by
other reactions of the radicals involved in the chain, or shortening of
of the chain length as may be produced by catalysts.
As examples, the oxidation of paraffins, of olefins and of
acetaldehyde are discussed.

10. Non Metallic Oxidizing Agent
1. Hydrogen peroxide
Hydrogen peroxide acts as both a reducing agent and oxidizing
agent depending upon the nature of the reacting species. In
which case does peroxide act as a reducing agent in acid
medium

11. Ozonolysis
• When compounds containing double bonds are treated with ozone,
usually at low temperatures, they are converted to compounds
called ozonides (16) that can be isolated but, because some of them
are explosive, are more often decomposed with zinc and acetic acid,
or catalytic hydrogenation to give 2 equivalents of aldehyde, or 2
equivalents of ketone, or 1 equivalent of each, depending on the
groups attached to the alkene
• The decomposition of 16 has also been carried out with
triethylamine and with reducing agents, among them trimethyl
phosphite,thiourea, and dimethyl sulfide However, ozonides can also
be oxidized with oxygen, peroxyacids, or H2O2 to give ketones
and/or carboxylic acids or reduced with LiAlH4
• Ozonolysis is therefore an important synthetic reaction.