![A concerted but non-pericyclic reaction, E2 elimination
A concerted and a pericyclic reaction, [3,3] sigmatropic
rearrangement also known as Claisen rearrangement.](https://image.slidesharecdn.com/module1-230122193727-e23df0d1/85/MODULE-1-pptx-8-320.jpg)
MODULE 1.pptx
- 1. PERICYCLIC REACTIONS MODULE 1: Introduction - Activation of chemical reactions S. SANKARARAMAN DEPARTMENT OF CHEMISTRY IIT MADRAS CHENNAI 600036, INDIA sanka@iitm.ac.in
- 2. Course objectives: To develop expertise in the areas of pericyclic reactions To understand the fundamental concepts as well as applications in these two areas. Learning outcome: Able to understand and appreciate fundamental concepts. Become familiar with reaction mechanisms this area. Able to apply the knowledge in practical applications such as synthesis of organic compounds.
- 3. What is activation of a chemical reaction? In every chemical reaction the reactants must be activated in order to cross over a barrier to reach the product state. The reactant molecules that are usually at room temperature may not possess sufficient potential energy to cross over the reaction barrier. Therefore energy must be supplied to the reactant molecules to make them more reactive. The collision between molecules become effective. Energy can be supplied through heat (Thermal) or through irradiation using photons (Photochemical).
- 4. Activation of chemical reactions – a comparison Thermal activation Photochemical activation Supply of heat Irradiation of light Supply photon energy Reaction of electronic ground state (GS). Excited vibrational states of the GS may be involved. Reaction of electronically excited state (ES). Non selective activation of all the molecules present in the flask Selective activation of only one type of molecule in the flask Reaction usually from ground singlet state Reaction can be from electronically excited singlet or triplet states
- 7. Concerted reactions (can be either thermal or photochemical) Reactions involving only a transition state and no intermediates There are two types: (a) Without involvement of cyclic transition state (E2 elimination and SN2 substitution reactions) (b) Through cyclic transition state - pericyclic reactions (Diels-Alder reaction, Clasien rearrangment)
- 8. A concerted but non-pericyclic reaction, E2 elimination A concerted and a pericyclic reaction, [3,3] sigmatropic rearrangement also known as Claisen rearrangement.
- 9. Why study pericyclic reactions? Pericyclic reactions are rich in mechanistic and stereochemical details. In order to understand the mechanistic details it is necessary to study pericyclic reactions. Pericyclic reactions are usually highly stereoselective. In order to make use of the high stereoselectivities of pericyclic reactions in organic synthesis it is necessary to understand them.
- 10. Resources for Pericyclic Reactions
- 11. THANK YOU