Kinetic and thermodynamic control

Kinetic and thermodynamic control - More resonance...

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Kinetic and thermodynamic control 1,2 vs. 1,4 addition of hydrognen halides to conjugated dienes, 1,2 products is formed more often at low temps which is more unstable than 1,4 product due to the internal vs. external double bonds in order for the less stable product to form: 1. less stable product forms more rapidly 2. products must not come to equilibrium under reaction conditions Kinetically controlled when products do not come to equilibrium possible to give product distribution at equilibrium Thermodynamically controlled when products do come to equilibrium imposible to give products distribution other than wats at equilibrium in halide addition - rate limiting step is when the first double bond is broken - the product determinie step is when the halide can either bond to cation or the double bond is moved - product occurs because chloride is closer to positively charged carbon for 1,2 product Resonance Resonacne hybrid molecules can be resonancestablized= more stble
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Unformatted text preview: More resonance structures more stable the molecule Resonance structures show delocalization of electrons Most stable resonance structure most important Resonance importance 1. identical structures are equally important 2. structures that have complete octets are most important 3. structures with postive charge on less electronegative and negative on more electronegative are more important 4. if orbital overlap symbolized by a resonance structre is impossible cant happen COT vs. BENZENE Benzene has resonance because carbon 2p orbital’s can overlap COT does not because there is no overlap between 2p orbital’s Empirical resonance energy energy difference of 141 kJ 1/mol of benzene Criteria for Aromaticity 1. contain one or more rings that have cyclic arrangments of p orbital’s 2. every atom of aromatic ring has a p orbital 3. rings are planer 4. must contain 4n+2 pie electrons...
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This note was uploaded on 04/26/2011 for the course CHEM 221 taught by Professor Sffe during the Spring '11 term at Dickinson.

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Kinetic and thermodynamic control - More resonance...

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