2. Catalysis is the process in which the rate of a chemical reaction is either increased
or decreased by means of a chemical substance known as a catalyst
What is a Catalyst?
a. Heterogeneous
b. Homogeneous
Types of Catalytic reactions
3. Catalytic Hydrogenation
Hydrogenation is the chemical reaction that results from the addition of
hydrogen. The process is usually employed to reduce or saturate organic
compounds. The process typically constitutes the addition of pairs of hydrogen
atoms to a molecule. Catalysts are required for the reaction to be usable; non-
catalytic hydrogenation takes place only at very high temperatures. Hydrogen
adds to double and triple bonds in hydrocarbons.
Application in the food industry:
Vanaspathy preparation
(unsaturated fatty acids(oils) are converted into
saturated derivatives)
4. Ziegler-Natta Polymerization
• Karl Ziegler and Giulio Natta
were awarded the Nobel Prize in
Chemistry in 1963 for their
discovery of these titanium-based
catalysts.
• Based on titanium compounds
and organometallic aluminium
compounds, such as undefined
methylaluminoxane or well-
defined triethyl aluminium,
(C2H5)3Al.
• Ziegler-Natta catalyst can be used
to prepare stereoregular polymers
like isotactic, syndiotactic and
atactic.
Ti
R
Cl
Cl
Cl
Cl
Vacant
site
Structure of the active catalyst
species
5. Y
R1 +
R2
Y R2
R1
The Diels-Alder reaction, namely [4+2]- cycloaddition of a diene and a
dienophile as discovered in 1928, is one of the most powerful method for the
regio- and stereo-specific preparation of carbocyclic and heterocyclic ring
systems. Lewis acid increase the rate of the reaction and its regio, endo, and π–
face selectivity by coordination with the dienophile, i.e. with a conjugated
carbonyl or nitrile group.
Diels-Alder Reaction
6. Interaction between the centers of the frontier orbital having the largest orbital
coefficients.
For dienophile with electron-withdrawing or electron releasing substituents,
orbital coefficients are higher at β-carbon.
For the regiochemical relationships can be best understood by considering the
atomic coefficients of the frontier orbitals.
The regiochemistry can be predicted on the basis of the generalisation that the
strongest dienes with electron withdrawing or electron releasing substituents at C-
1 carbon, the orbital coefficients are higher at C-4. So C-4 of diene and β-carbon
of the dienophile interact more strongly leading to ortho like orientation.
8. What is Green Chemistry?
Green chemistry is the use of chemistry for pollution prevention.
• Pollution prevention is “the use of materials, processes, or practices that reduce or
eliminate the creation of pollutants or wastes at the source. It includes practices
that reduce the use of hazardous and nonhazardous materials, energy, water, or
other resources as well as those that protect natural resources through efficient
use.” -U.S. EPA
• The design of chemical products and processes that are more environmentally
benign.
• Encompasses all aspects and types of processes that reduce negative impacts to
human health and the environment.
• Focuses on processes and products that reduce or eliminate the use and
generation of hazardous substances.
• Became a formal focus of the U.S. EPA in 1991 with the formation of their Green
Chemistry Program.
– Promotes research, development and implementation of inventive chemical
technologies that accomplish pollution prevention in both a scientifically-
sound and cost-effective manner.
10. Environmental Chemistry versus
Green Chemistry
• Environmental chemistry is “the study of sources, reactions, transport and fate of chemical
entities in the air, water, and soil environments as well as their effects on human health and
the environment.”
• Focuses on the environmental management of chemicals.
• Concerned not only with the chemical pollutants in the environment but also with the
behavior of natural chemicals in natural systems.
• “When chemical use results in environmental contamination, it is necessary to set standards
for acceptable concentrations in water, air, soil and biota.”
• Has focused on the effects of what man has put into the environment and how to deal with
and remediate contamination sites.
“Dilution is the solution to pollution”
• In contrast, green chemistry focuses on how to change what human activity puts into the
environment in order to eliminate or reduce effects and prevent contamination sites.
“An milligram of prevention is worth a kilogram of cure.”
11. Green chemistry is the design of chemical products and processes
that reduce or eliminate the use and generation of hazardous
substances- Sustainable Science
It encompasses all aspects and types of chemical processes
including synthesis, catalysis, analysis, monitoring, separations, and
reaction conditions that reduce negative impacts on human health and
the environment relative to the current state of the art.
The twelve principles of green chemistry/ engineering proposed by
Anastas and Warner, 1998, Anastas and Zimmerman, 2003,serve as
guidelines for practicing chemists/ engineers in developing and
assessing how green a synthesis, compound, process, design or
technology is .
GREEN CHEMISTRY
