310-11 - CH 310 N T Th 2-3:30 LECTURE 11 Textbook...

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CH 310 N T Th 2-3:30 LECTURE 11 Textbook Assignment: Chapter 16 Continue Homework (for credit): POW 5 posted Today’s Topics: Aldehydes & Ketones (cont’d) Notice & Announcements: Organic Lecture Series 2 Aldehydes Aldehydes And And Ketones Ketones
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Organic Lecture Series R C OH O R C OR' O R C H O R C R' R C O H Carboxylic Acids & Esters Ketones Aldehydes Alcohols R C H H Hydrocarbon (lowest oxidation) Oxidation Reduction Organic Lecture Series 4 Oxidation of Aldehydes Oxidation of Aldehydes • Aldehydes are oxidized to carboxylic acids by a variety of oxidizing agents, including *H 2 CrO 4 • They are also oxidized by Ag(I) – in one method, a solution of the aldehyde in aqueous ethanol or THF is shaken with a slurry of silver oxide CHO H 2 CrO 4 COOH Hexanal Hexanoic acid Vanillic acid Vanillin + + CH HO 3 O O O 3 O COH Ag 2 O THF, H 2 O NaOH HCl H 2 O * See 10.8 for Jones reagent & PCC: pyridine + •ClCrO 3 -
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Organic Lecture Series 5 Oxidation of Aldehydes Oxidation of Aldehydes Aldehydes are oxidized by O 2 in a radical chain reaction – liquid aldehydes are so sensitive to air that they must be stored under N 2 Benzoic acid Benzaldehyde + CH OO COH 2 O 2 2 Organic Lecture Series 6 – ketones are not normally oxidized by chromic acid (H 2 CrO 4 ) – they are oxidized by powerful oxidants at high temperature and high concentrations of acid or base Hexanedioic acid (Adipic acid) Cyclohexanone (keto form) Cyclohexanone (enol form) HNO 3 O HO OH O O One of the starting materials for Nylon 6,6 “Oxidation Oxidation ” of Ketones of Ketones
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Organic Lecture Series 7 Reduction Reduction aldehydes can be reduced to 1° alcohols ketones can be reduced to 2° alcohols the C=O group of an aldehyde or ketone can be reduced to a -CH 2 - group Aldehydes Can Be Reduced to Ketones Can Be Reduced to OO OH RCH RCH 2 OH RCH 3 RCR' RCHR' RCH 2 R' Organic Lecture Series 8 Metal Hydride Reduction Metal Hydride Reduction The most common laboratory reagents for the reduction of aldehydes and ketones are NaBH 4 and LiAlH 4 – both reagents are sources of hydride ion, H: - a very powerful nucleophile Al H H H H Li + B H H H H Na + H Lithium Aluminum Hydride LAH Sodium Borohydride NaBH 4 Hydride
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Organic Lecture Series 9 – reductions with NaBH 4 are most commonly carried out in aqueous methanol, in pure methanol, or in ethanol – one mole of NaBH 4
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310-11 - CH 310 N T Th 2-3:30 LECTURE 11 Textbook...

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