310-8 - CH 310 N T Th 2-3:30 LECTURE 8 Textbook Assignment...

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CH 310 N T Th 2-3:30 LECTURE 8 Textbook Assignment: Chapter 15 Begin Homework (for credit): POW 4 posted Today’s Topics: Aldehydes & Ketones Notice & Announcements: Exam I: Grading in Progress
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Organic Lecture Series 2 Aldehydes Aldehydes And And Ketones Ketones
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Organic Lecture Series 3 One of the most common reaction themes of a carbonyl group is addition of a nucleophile to form a tetrahedral carbonyl addition compound (intermediate). Tetrahedral carbonyl addition compound + C R R O C Nu O - R R Nu - Reaction Themes Reaction Themes
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Organic Lecture Series 4 A second common theme is reaction with a proton or other Lewis acid to form a resonance- stabilized cation-- protonation protonation increases the electron deficiency of the carbonyl carbon and makes it more reactive toward nucleophiles B - CO R R H-Nu H-B R R H - R R H C Nu O-H R R R R H H-B + fast + + + + slow Tetrahedral carbonyl addition compound + + + Reaction Themes Reaction Themes
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Organic Lecture Series 5 – often the tetrahedral product of addition to a carbonyl is a new chiral center – if none of the starting materials is chiral and the reaction takes place in an achiral environment, then enantiomers will be formed as a racemic mixture Nu - CO R R' O R O R + H 3 O + OH R R + A racemic mixture A new chiral centeris created Approach from the bottom face the top face
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Organic Lecture Series 6 Addition of C Addition of C Nucleophiles Nucleophiles Addition of carbon nucleophiles is one of the most important types of nucleophilic additions to a C=O group – a new carbon carbon - - carbon bond carbon bond is formed in the process – Focus on addition of these carbon nucleophiles: RMgX RLi - C RC C - N A Grignard re ag e nt An organolithium An alkyne anion Cyanide ion
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Organic Lecture Series 7 Grignard Reagents • Given the difference in electronegativity between carbon and magnesium (2.5 - 1.3), the C-Mg bond is polar covalent, with C δ - and Mg δ + – in its reactions, a Grignard reagent behaves as a carbanion Carbanion: Carbanion: an anion in which carbon has an unshared pair of electrons and bears a negative charge – a carbanion is a good nucleophile and adds to the carbonyl group of aldehydes and ketones
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Organic Lecture Series 8 –addition of a Grignard reagent to formaldehyde followed by H 3 O + gives a 1° alcohol CH 3 2 -MgBr O H-C-H O - [MgBr] + 3 2 -CH 2 HCl H 2 O OH 3 2 2 Mg 2+ ether 1-Propanol (a 1° alcohol) Formaldehyde + + A magnesium alkoxide Grignard Reagents
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This note was uploaded on 10/31/2009 for the course CH 310n taught by Professor Iverson during the Spring '08 term at University of Texas.

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310-8 - CH 310 N T Th 2-3:30 LECTURE 8 Textbook Assignment...

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