1 / 15

Free Radical Chlorination

Free Radical Chlorination. Experimental Evidence Helps to Determine Mechanism. Chlorination does not occur at room temperature in the dark . The most effective wavelength of light is blue that is strongly absorbed by Cl 2 gas.

reece-davis
Download Presentation

Free Radical Chlorination

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Free Radical Chlorination

  2. Experimental Evidence Helps to Determine Mechanism • Chlorination does not occur at room temperature in the dark. • The most effective wavelength of light is blue that is strongly absorbed by Cl2 gas. • The light-initiated reaction has a high quantum yield (many molecules of product are formed from each photon of light).

  3. Free Radical Species are Constantly Generated Throughout the ReactionPropagation

  4. Termination: Reaction of any 2 Radicals

  5. Chlorination of Propane

  6. H’s are not abstracted at the same rate. For secondary: 70%/4H = 17.5 For primary: 30%/6H = 5.0 Therefore… Relative rate of H abstraction for 1o : 2o is 1 : 3.5

  7. Chlorinationof Methylpropane

  8. 3o Radicals are Easiest to Form

  9. Tertiary H’s removed five times more readily than primary H’s in chlorination reactions Relative reactivity of 1o H abstraction: 65% / 9H = 7.2 Relative reactivity of 3o H abstraction: 35% / 1H = 35 Therefore… Relative rate of H abstraction for 1o : 3o 1:5

  10. Stability of Free Radicals

  11. Bromination is Very Selective

  12. RDS in Bromination is highly endothermic

  13. Consider the free radical monochlorination of 2,2,5-trimethylhexane. Draw all of the unique products (ignore stereoisomers; use zig-zag structures please) and predict the ratio or percent composition of the products.The relative reactivity of H abstraction in a chlorination reaction: 1o: 2o: 3o = 1: 3.5: 5

  14. 2.(12) Consider the free radical monochlorination of 1,4-dimethylcyclohexane. The reaction affords three different products (all C8H15Cl). In this reaction, the rates of hydrogen abstraction of primary : secondary : tertiary are 1 : 3.5 : 5. Draw the three products and predict the percent composition (or ratio) of the product mixture. (Disregard cis / trans isomers for this problem.)

More Related