1 / 18

Oxidative Rancidity

Oxidative Rancidity. A mechanistic look at this reaction. Go to Slide Show mode and click to begin. H. CH=CH-CH-CH=CH. Reactive pentadiene unit in fatty acid chain. Reactive allylic bond. H. CH=CH-CH-CH=CH. Reactive pentadiene unit in fatty acid chain. Heat, light, metal ions

brenden-landry
Download Presentation

Oxidative Rancidity

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. Oxidative Rancidity A mechanistic look at this reaction Go to Slide Show mode and click to begin

  2. H CH=CH-CH-CH=CH Reactive pentadiene unit in fatty acid chain

  3. Reactive allylic bond H CH=CH-CH-CH=CH Reactive pentadiene unit in fatty acid chain

  4. Heat, light, metal ions cause bond cleavage H CH=CH-CH-CH=CH

  5. H CH=CH-CH-CH=CH Bond begins to break

  6. H. . CH=CH-CH-CH=CH Bond is completely broken, forming a pentadienyl free radical

  7. Resonance forms for the pentadienyl radical . CH=CH-CH-CH=CH . CH-CH=CH-CH=CH . CH=CH-CH=CH-CH The resonance hybrid will look more like one of the lower two structures because of the stability of conjugated double bonds

  8. O-O . CH-CH=CH-CH=CH Reaction with atmospheric oxygen

  9. O-O . CH-CH=CH-CH=CH Reaction with atmospheric oxygen

  10. O-O . CH-CH=CH-CH=CH Reaction with atmospheric oxygen

  11. O-O CH-CH=CH-CH=CH Bond begins to form

  12. . O-O CH-CH=CH-CH=CH Unstable hydroperoxyl radical

  13. HR . O-O CH-CH=CH-CH=CH Hydroperoxyl radical reacts with a molecule of the original lipid, removing a reactive allylic hydrogen (this is a propagation step)

  14. .R Returns to propagation O-O-H CH-CH=CH-CH=CH

  15. O-O-H CH-CH=CH-CH=CH Hydroperoxide (unstable, will decompose to form odor compounds)

  16. O-O-H CH-CH=CH-CH=CH Bonds begin to break

  17. Return to propagation . . O-H O . CH CH=CH-CH=CH . Bonds are broken, electrons pair up to form a carbon-oxygen double bond

  18. O CH These aldehydes are the source of the rancid smell in lipid oxidation.

More Related