318-13 - Organic Lecture Series CH 318 N LECTURE 13...

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Organic Lecture Series 1 CH 318 N LECTURE 13 Textbook Assignment: Chapter 16 Homework (for credit): POW 6 posted Today’s Topics: Aldehydes/Ketones-reactions Notice & Announcements: Organic Lecture Series 2 Aldehydes Aldehydes And And Ketones Ketones
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Organic Lecture Series 3 Dean Dean -Stark Trap Stark Trap Organic Lecture Series 4 Acetals Acetals as Protecting Groups as Protecting Groups • How to bring about a Grignard reaction between these compounds: 5-Hydroxy-5-phenylpentanal (racemic) 4-Bromobutanal Benzaldehyde ?? + H O H O H OH O Br BrMg H O This Grignard cannot be made!!
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Organic Lecture Series 5 • a Grignard reagent prepared from 4-bromobutanal will self-destruct ( decompose decompose ). – first protect the -CHO group as an acetal: – then prepare the Grignard reagent: – hydrolysis (not shown) gives the target molecule H O Br A cyclic acetal + H + H 2 O HO OH + O O O O 1. Mg, ether 2. C 6 H 5 CH O O O O - MgBr + A chiral magnesium alkoxide (produced as a racemic mixture) Acetals Acetals as Protecting Groups as Protecting Groups Organic Lecture Series 6 • Tetrahydropyranyl (THP) protecting group – the THP group is an acetal and, therefore, stable to neutral and basic solutions, and to most oxidizing and reducting agents – it is removed by acid-catalyzed hydrolysis RCH 2 + O OR C H 2 O Dihydropyran A tetrahydropyranyl ether H + THP group Acetals Acetals as Protecting Groups as Protecting Groups
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Organic Lecture Series 7 • Ammonia, 1° aliphatic amines, and 1° aromatic amines react with the C=O group of aldehydes and ketones to give imines imines (Schiff bases) • Water is removed by Dean-Stark trap or chemical dehydration (e.g. molecular sieves) CH 3 H 2 N H + 3 CH=N H 2 O + + Acetaldehyde Aniline An imine (a Schiff base) O An imine (a Schiff base) Ammonia Cyclohexanone + +N H 3 H 2 O O NH H +
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This note was uploaded on 10/10/2010 for the course CH 57689 taught by Professor Goddard during the Spring '10 term at University of Texas at Austin.

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318-13 - Organic Lecture Series CH 318 N LECTURE 13...

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