Lecture 3 - R, R, R = long chain alkyl groups Can be...

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1 Reading for Friday ± Finish Chapter 15 Dr. Benson’s office hours for today (Wednesday) are cancelled Mon. 6:00-7:30 pm MAL 3092 Tues. 2:30-4:00 PM MAL 2007 Wed. 5:00-6:30 PM MAL 2001 Thurs. 9:30-10:50 AM MAL 1003 Sat. 11:00 AM-1:00 PM MAL 2007 CHEM 626 PLUS Sessions Chapter 15 Radical Reactions Chlorination vs. Bromination (15.6) Chlorination is faster than bromination Chlorination is less selective than bromination In fact, bromination often leads to a single product. Chlorination of Propane: First Propagation Step is Exothermic less stable 1º radical more stable 2º radical
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2 Bromination of Propane: First Propagation Step is Endothermic less stable 1º radical more stable 2º radical Allylic Bromination (15.10) Allylic carbon: adjacent to a double bond Allylic bromination is highly selective Autoxidation at allylic carbons (15.11) Autoxidation: reaction with O 2 Products are hydroperoxides (ROOH) Recall from Chapters 10 and 12: Triacyl glycerols (triglycerides)
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Unformatted text preview: R, R, R = long chain alkyl groups Can be saturated or unsaturated Double bonds almost always cis (Z) cis-Fatty acids are kinked, which prevents tight packing of triglycerides containing them. This is why triglycerides with lots of unsaturated fatty acids tend to be oils. Autoxidation of Unsaturated Lipids (15.11 and 15.12) Unsaturated chains susceptible to autoxidation at allylic carbons This leads to spoiling of foods containing triacyl glycerols, and contributes to biological ageing. 3 (Aut)oxidation of Unsaturated Lipids (Fig. 15.8) o A lipid o A natural phenolic anti-oxidant (Radical chain terminator) o Obtained from vegetable oils, nuts and seeds (including whole grains) Vitamin E Synthetic Phenolic Anti-Oxidants B utylated H ydroxy T oluene (BHT) B utylated H ydroxy A nisole ( BHA) t ert-B utyl H ydro q uinone (TBHQ)...
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Lecture 3 - R, R, R = long chain alkyl groups Can be...

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