Chemical Kinetics deals with the speed of a reaction and its mechanism, the stepwise changes in which
reactants undergo in there conversion of product
Order of reaction
The representation of rate of reaction in terms of the concentration of the reactants is
called the rate law
State in which partial dissociation and partial formation of bonds takes place is
known as transition state
Chemical reaction involve the making and breaking of chemical bonds. Since different type of
bonds have different bond strengths
These reactions take place in single step without formation of any intermediate
Reaction which proceed in more than one steps. or having some mechanism. Complex reaction
takes places in a sequence of a number of elementary reactions
The number of molecules that react in an elementary step is the molecularity of the elementary reaction. Molecularity
is defined only for the elementary reactions which is equal to no of molecules which make transition state or
activated complex because of collisions in proper orientation and with sufficient energy
The minimum amount of energy required by reactant molecules to participate in a reaction is called activation
Factors affecting rate of chemical reaction
The slowest step of the mechanism known as rate determining step of the
reaction
all reactions are initiated with bond dissociation. There are two types of bond dissociation
A reagent generates three type of attacking species. Which are nucleophile, electrophile and
radical
The tendency to give e– pair to an electron deficient carbon atom is defined as nucleophilicity
The best leaving groups are those that become the most stable ion after they leave, because leaving group
generally leave as a negative ion, so those leaving group are good, which stabilise negative charge most effectively
and weak base do this best, so weaker bases are always good leaving groups. A good leaving group
always stabilize the transition state and lowers its free energy of activation and there by increases the rate of the
reaction.
Types of solvents
Type of reactions
Unimolecular nucleophilic substitution reaction
Bimolecular nucleophilic substitution reaction
Characteristic reaction of acid and it’s derivatives (acid halide, anhydride, amid and ester).
Nucleophilic acyl substitution usually takes place by an addition-elimination mechanism.The incoming
nucleophile adds to the carbonyl to form a tetrasubstituted intermediate with a tetrahedral carbon
Bimolecular nucleophilic substitution in aromatic compound
Like an alkene, benzene has clouds of pi electrons above and below its sigma bond framework. Although
benzene’s pi electrons are in a stable aromatic system still they are available to attack a strong electrophile to
give a carbocation. This resonance-stabilized carbocation is called a sigma complex because the electrophile
is joined to the benzene ring by a new sigma bond
Characteristic reaction of alkanes are free radical substitution reaction, these reactions are generally chain
reactions which are completed in three steps
There are three type of addition reaction
(a) Electrophilic Addition (b) Nucleophilic Addition (c) Free Radical Addition
It is a characteristic reaction of carbonyl compounds
Free Radical Addition of HBr : Kharasch Effect or Peroxide Effect
Elimination reaction In an elimination reaction two atoms or groups (YZ) are removed from the substrate and generally resulting
E2 is the characteristic reaction of alkyl halide.
The over all reaction mechanism can be visualised with as followed
Unimolecular elimination by conjugate base reaction
