The document discusses various reactive intermediates in chemical reactions: 1. Intermediates are chemical species that are neither the starting reactants nor the final products but appear as transient intermediates in step-wise reactions. 2. Common types of reactive intermediates discussed include carbocations, carbanions, free radicals, carbenes, nitrenes, and arenynes. 3. Specific details are provided about the electronic structure and reactivity of each intermediate.

1. By:
Neha Jain
Ms. Neha Jain
(M.Sc., M.Phil, Research Scholar)
Laboratory of Endocrinology,
Department of Biosciences,
Barkatullah University,
Bhopal-462026, M.P., India

2. 1. If a reaction occurs in more than one step, it must involve species
that are neither the reactant nor the final product.
2. These are called reaction intermediates or simply “intermediates”
3. Each step has its own free energy of activation.
4. Reactive intermediates are usually short lived and are very
seldom isolated.
5. The complete diagram for the reaction shows the free energy
changes associated with an intermediate.
2

3. For example, consider this hypothetical stepwise reaction:
A+B →C+D
The reaction includes these elementary steps:
A + B → X*
X* → C + D
The chemical species X* is an intermediate.

4.  CARBOCATION
 CARBANION
 FREE RADICLE
 CARBENE
 NITRENE
 ARENE/BENZYNE

5. 5

6. 6

8. •This is the species with central carbon atom with two bonds and two
electrons.
•These are uncharged species and 6 valence electrons.
•These electrons are may be paired or unpaired.
•These are very short lived species.
•The smallest and simplest species of this class is methylene, this is
non isolable species.
When the electrons are paired the Carbene has singlet state and in
case of unpaired electrons the Carbene has triplet state.
These are extremely reactive species and can be
As these species are short lived and very reactive hence it is difficult
to detect.

16. 1. Nitrene is electro-neutral monovalent electron
species.
2. This has similar properties as that of carbene.
Hence Nitrene is called as nitrogen analogue of
carbene.
3. There are six electrons present on nitrogen in
Nitrene.
4. Carbenes are less stable than Nitrene.
5. Generation of Nitrene is possible in both triplet
and singlet state but mostly the ground state for
Nitrene is triplet.

20. 1. It is non isolable very reactive species with the hexagonal planar rind
structure with 6 pi delocalizing and 2 additional pi electrons.
2. The addition two pi electrons do not affect the aromatic character of ring as
it does not interfere with the Huckel number.
3. This is a six membered ring containing C-C triple bond this triple bond
gives high reactivity to the species.

25. A Kulkarni and Kalyani. D. Asgaonkar Study of
Various Reaction Intermediates Juilee., P 325 -351,
Vol. 3 (1) Jan – Mar 2012 www.ijrpbsonline.com
Sachin Kumar Ghosh, General organic chemistry, A
modern approach, fundamentals of organic
reaction mechanism, new Alipore college New
central book agency, May 1994, 384-403.
www.wikipedia.com

26. Thanks !!!