1) Transition state theory (TST) explains reaction rates by assuming a special type of equilibrium between reactants and unstable transition state complexes that have partially formed bonds between reactants and products. 2) TST can be used to calculate activation parameters like enthalpy, entropy and Gibbs energy of activation based on experimentally determined rate constants. 3) According to TST, a reaction will occur if the concentration of the transition state complex is high enough and if the complex breaks apart to form products rather than reverting back to reactants.

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2. Presentation
TOPIC:
Conventional Transition State Theory
Asked by Sir AR Memon
Given by Rahat Inayat Ali (14CH23)
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3. Introduction
• In 1930 while studying on Quantam Mechanics the
two scientists namely EYRING and POLANYI gave this
theory.
• Transition state theory (TST) explains the reaction
rates of elementary chemical reactions.
• The theory assumes a special type of chemical
equilibrium (quasi-equilibrium)
between reactants and activated transition
state complexes.
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4. •TST is used primarily to understand qualitatively how
chemical reactions take place.
• it has been successful in calculating the
standard enthalpy of activation (Δ‡Hɵ), the
standard entropy of activation (Δ‡Sɵ), and the
standard Gibbs energy of activation (Δ‡Gɵ) for a
particular reaction if its rate constant has been
experimentally determined.
• TST is also referred to as "activated-complex theory,"
"absolute-rate theory," and "theory of absolute reaction
rates.
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5. Continue..
• Before the development of TST, the Arrhenius rate law
was widely used to determine energies for the
reaction barrier.
• An intermediate stage lies between thereactants and
the products is
transition state.
• The transitional species with partial bonds is
activated complex.
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6. Few REACTION PROFILEs are given
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7. 2NOCl→2NO + Cl2 ∆H =+ve
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8. THERMODYNAMICS
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9. Characteristics of an Activated
Complex
• Very unstable
• It has a short half-life
• Its potential energy is greater than reactantsor products
• In an activated complex, the bonds in thereactant
molecules are in the process of breaking while the new
bonds in the productmolecules are starting to form.
• The activated complex and the reactants are inchemical
equilibrium
• It decomposes to form products or reactants.
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10. Is a transition state stable?
•All chemical reactions must go through the transition
state to form a product from a substrate molecule. It has
more free energy in comparison to the substrate or
product; thus, it is the least stable state.
•What is the transition state of an enzyme?
•The enzyme's ability to make the reaction faster depends
on the fact that it stabilizes the transition state.
The transition state's energy or, in terms of a reaction,
the activation energy is the minimum energy that is
needed to break certain bonds of the reactants so as to
turn them into products.
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11. TST postulates three major factors that
determine whether or not a reaction will occur.
These factors are:
• The concentration of the activated complex.
• The rate at which the activated complex breaks apart.
• The mechanism by which the activated complex
breaks apart; it can either be converted into products,
or it can "revert" back to reactants.
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12. Difference Between Collision
Theory and CTST
•Collision theory is only for reaction involving gaseous
reactants .....while transition state theory can be
applied to reactions taking place in solution as well as
in the gas phase.
• In the collision theory reaction occurs when two
molecules collide, but only if the collision is
sufficiently vigorous
•transition state theory is used to explain in detail what
happens when reactant molecules come together in a
collision . 1226/04/2017

13. APPLICATION
• Application of TST is important in terms of deriving an
extended form of rate equation,
which can be used to understand even mpst
complicated or complex reactions in qualitative way
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