General OrganicChemistry
1. Introduction:
Organic reaction involve the breaking and making of covalent bonds. The breaking and making of
covalent bonds usually occurs in several descrete steps before transformation into product. The detailed
sequential description ofall stepsofthe transformation into products is called the mechanism ofa
reaction.
Complete informationregarding all the steps is seldomobtained. However, a good dealof data can be
gatheredfromthe following
(a) study ofkinetics ofthe reactions
(b) isolation ofintermediate, if isolable.
(c) studyofreactions in the presence ofothersimilar substrate.
(d) study ofthe isotopically labelled atomin the reactants.
(e) trapping of free radicals
(f) crossover experiments
(g) stereochemicalaspects etc.
Reactionmechanismcontaining following tools
Intermediate
Reactant sovle nt OR
temperature/light
pressure Transition state # Product
(i) Reactant:
Reactant are classified into substrate and reagent
(A)
substrate species at which reagent attack.
(B)
Reagent attacking species (more reactive species)
Case-I: If reaction occursbetween organic and inorganic species, organic species act as substrate and
inor- ganic species act as reagent.
Organic species Inorganic species Product
substrate reagent
Case-II: If reaction takes place between organic species then higher charge species act as reagent, other
species act as substrate.
Organic species Organic species Product
less charge excess charge
substrate reagent
, 2 General Organic Chemistry
Example:
H3C CH2 CH2 + KOH H3C CH2 CH2 OH + KBr
Br
reagent product
substrate (inorganic)
(organic)
O O
OH O
C H3O+
H C C H + HC
C
CH CH CH CH3
HC C
3 2 2 3 3
H2 H2C CH
2
CH2
(substrate) (reagent)
1.2. Electrophiles :
(Electron loving species) electrophiles are electrons-deficient species and tend to attack the substrate at a
site of high electron density. They may be neutral species as examplified by Lewis acid (such as BF3,
AlCl3, ZnCl2), carbene and carbocations.
H O
+ OH
Proton as H H
hydroxide ion water
electrophiles
as nucleophile
Classification of electrophiles:
(a) Species having positive charge
Example : H , R , Cl , NO , NO 2, C H6 5N , CH
2
C3 O etc.
(b)Neutralspecies having vacant p-orbitals
Example : BF3, BCl3, BBr3, carbene,
etc. (c)Specieshaving vacant d-orbital
Example : FeCl3, ZnCl2, FeCl2 etc.
(d)Species having low lying -antibonding molecular
orbital. Example : Br2, Cl2, I2 etc.
-bonding molecule:
O
O
Example : SO3, , R C N , , etc.
CO2,
(f) Element in their atomic state :
Example : O, S etc.
3. Nucleophiles:
(Nucleus-loving species) Nucleophiles are electron donar species. Nucleophilic reagents tend to attack the
electron deficient species (electrophiles).
Classification of Nucleophiles:
(a) Negative chargespecies:
OH , OR , SH , SR , R , Cl , Br , I etc
(b) Organometallic reagent:
RMgX, RLi, RCuLi, RCd, R Zn etc
2 2 2
(c) Lone pair containing species:
1. Introduction:
Organic reaction involve the breaking and making of covalent bonds. The breaking and making of
covalent bonds usually occurs in several descrete steps before transformation into product. The detailed
sequential description ofall stepsofthe transformation into products is called the mechanism ofa
reaction.
Complete informationregarding all the steps is seldomobtained. However, a good dealof data can be
gatheredfromthe following
(a) study ofkinetics ofthe reactions
(b) isolation ofintermediate, if isolable.
(c) studyofreactions in the presence ofothersimilar substrate.
(d) study ofthe isotopically labelled atomin the reactants.
(e) trapping of free radicals
(f) crossover experiments
(g) stereochemicalaspects etc.
Reactionmechanismcontaining following tools
Intermediate
Reactant sovle nt OR
temperature/light
pressure Transition state # Product
(i) Reactant:
Reactant are classified into substrate and reagent
(A)
substrate species at which reagent attack.
(B)
Reagent attacking species (more reactive species)
Case-I: If reaction occursbetween organic and inorganic species, organic species act as substrate and
inor- ganic species act as reagent.
Organic species Inorganic species Product
substrate reagent
Case-II: If reaction takes place between organic species then higher charge species act as reagent, other
species act as substrate.
Organic species Organic species Product
less charge excess charge
substrate reagent
, 2 General Organic Chemistry
Example:
H3C CH2 CH2 + KOH H3C CH2 CH2 OH + KBr
Br
reagent product
substrate (inorganic)
(organic)
O O
OH O
C H3O+
H C C H + HC
C
CH CH CH CH3
HC C
3 2 2 3 3
H2 H2C CH
2
CH2
(substrate) (reagent)
1.2. Electrophiles :
(Electron loving species) electrophiles are electrons-deficient species and tend to attack the substrate at a
site of high electron density. They may be neutral species as examplified by Lewis acid (such as BF3,
AlCl3, ZnCl2), carbene and carbocations.
H O
+ OH
Proton as H H
hydroxide ion water
electrophiles
as nucleophile
Classification of electrophiles:
(a) Species having positive charge
Example : H , R , Cl , NO , NO 2, C H6 5N , CH
2
C3 O etc.
(b)Neutralspecies having vacant p-orbitals
Example : BF3, BCl3, BBr3, carbene,
etc. (c)Specieshaving vacant d-orbital
Example : FeCl3, ZnCl2, FeCl2 etc.
(d)Species having low lying -antibonding molecular
orbital. Example : Br2, Cl2, I2 etc.
-bonding molecule:
O
O
Example : SO3, , R C N , , etc.
CO2,
(f) Element in their atomic state :
Example : O, S etc.
3. Nucleophiles:
(Nucleus-loving species) Nucleophiles are electron donar species. Nucleophilic reagents tend to attack the
electron deficient species (electrophiles).
Classification of Nucleophiles:
(a) Negative chargespecies:
OH , OR , SH , SR , R , Cl , Br , I etc
(b) Organometallic reagent:
RMgX, RLi, RCuLi, RCd, R Zn etc
2 2 2
(c) Lone pair containing species:
