This is useful to post graduate students. It gives detail explanation about Transition State Theory and Lindemann Theory- derivation, application, limitation

1. 1
Dr. Y. S. THAKARE
M.Sc. (CHE) Ph D, NET, SET
Assistant Professor in Chemistry,
Shri Shivaji Science College, Amravati
Email: yogitathakare_2007@rediffmail.com
CHEMICAL DYNAMICS
Transition State Theory and Lindemann Theory

2. Transition state theory (TST)
Activated complex theory (ACT)
Absolute reaction rate Theory (ARRT)
Henry Eyring
1901 - 1981
 E  activation energy
Eyring, Polany and Evas in 1935

3. Henry Eyring, M. Polyani & M G Evans

5. Transition State Theory
This theory is given by Eyring, Polany and Evas in 1935. According to this theory
not only collision between reacting molecule forms a product but there is the
existence of transition state (T.S.) or activated complex (A.C.) which decompose to
give the product.
Consider the bimolecular reaction
In collision theory fast approaching A2 and B2 slow down due to gradual repulsion
between their electron cloud. In this process K.E. of two molecules is converted in to
P.E.
As molecule come closer there is interpenetration of their electron cloud which allow
the rearrangement of valence electron.
The partial bonds between the atoms A and B is formed with weakening the bond
between A2 and B2. This leads to the formation of an A.C. or T.S.

6. Assumption of transition state theory
i) As reacting molecule approach to each other bond distance
changes these changes are accompanied by the energy changes
ii) The reactant molecules changes into activated complex or
transition state
iii) The activated complexes are formed by bonding of reactant
molecule with necessary rearrangement of valence bond and
energy of the reactant is unimolecular the reactant molecules
may produced activated complex by rearrangement of atom and
redistribution of energy
iv)The activated complex remain in equilibrium with reactants
and its potential energy is maximum finally the activated
complex decompose into product
v)The activation energy of reactant is the additional energy
which the reacting molecule must acquired to form the activated
complex

7. The two molecules A2 and B2 must receive an additional energy called as the
activation energy which converted the molecule in to activated complex (A.C.).
The activated complex is a special molecule in which one vibrational degree of
freedom is converted in to translational degree of freedom along the reaction co-
ordinate.
It must be remembered that the A.C. is not nearly intermediate in the process of the
breaking and making of the chemical bond. It is unstable because it is situated at
maximum P.E. barrier separating a product from reactant. There are two types of
reaction depending on P.E. of product.
P.E. of product may be less than that of reactant.
P.E. of product may be more than that of reactant

8. “Reaction Coordinate” Diagram
(for a one-step atom transfer)
Not a realistic trajectory, but rather
a sequence of three species
Starting
Materials Products
Transition “State”
G
each with H and S, i.e. Free Energy (G)

9.  KE can be converted into PE and vice versa
When the child is at points (a) and
(c) they have only PE; at point (b)
only KE. Total energy is conserved
(PE + KE = constant).
When fully
compressed or
extended only
PE; at natural
length only KE.
Total energy is
conserved.
The potential energy that resides in chemical
bonds is called chemical energy

10. DERIVATION OF EYRING EQUATION
OR
THERMODYNAMIC FORMULATION OF ACTIVATED
COMPLEX THEORY
Which determine or measure the probability that of the activated complex molecule passes over
the energy barrier will keep on going and not to return back.

12. Evaluation of standard entropy of activation and standard entropy of
activation

14. H H2
H2 H
HHH
H H H
Henry
Eyring
(1935)
Dissociation followed
by association requires
high activation energy.
SLOW
Make-as-you-break
“displacement” is much easier.
FAST
Application of transition state to reaction between atoms and
molecules

16. THEORIES OF UNIMOLECULAR REACTION
OR
LINDEMANN THEORY
Lindemann (1922)

19. Limitation of Lindemann-Christiansen Theory and its explanation

20. Thank you for your attention!