215F07-notes-9-26-07 - Chem 215 F07 Notes Dr Masato Koreeda...

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Chem 215 F07 Notes – Dr. Masato Koreeda - Page 1 of 5. Date: September 26, 2007 Chapter 14 Aldehydes and Ketones: Addition Reactions at Electrophilic Carbons I-1. Irreversible nucleophiles ! ! + Mg(OH) 2 (b) R M (Type 2; organometallic reagents) (cont'd) Note : Reactions with epoxides O H PhMgBr O H Ph OH H Ph MgBr Ph S N 2! work-up with aq NH 4 Cl* * NH 4 Cl: weakly acdic; pKa ~9.7; commonly used for the work-up of organometallic reactions; the only exception is the work-up of a carboxylate product (you need to acdity the solution to pH~1-2). Ph MgBr O MgBr C O Ph O C O Ph C O O H H 3 O pH 1-2 + Br pKa 4.2 Not with aq NH 4 Cl! I-2. Reversible nucleophiles Type 3 : Divalent nucleophiles (ROH & RSH); requires an acid catalyst Type 4 : Trivalent nucleophiles (R-NH 2 & RR'NH); w/o activation by an acid + O ketone oxygen atom ROH, H or L.A. OH OR OR OR ROH, H or L.A. H 2 O + H O aldehyde oxygen atom ROH, H or L.A. H OH OR H OR OR ROH, H or L.A. H 2 O hemiketal hemiacetal ketal acetal Tend to be unsatble intermediates! + O ketone oxygen atom RSH, H or L.A. OH SR SR SR RSH, H or L.A. H 2 O + H O aldehyde oxygen atom RSH, H or L.A. H OH SR H SR SR RSH, H or L.A. H 2 O hemithioketal hemithioacetal thioketal thioacetal (a) ROH (alcohols) (b) RSH (thiols or mercaptans) meaning "mercury capturers"
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Chem 215 F07 Notes – Dr. Masato Koreeda - Page 2 of 5. Date: September 26, 2007 Chapter 14: I-2. Reversible nucleophiles (cont’d) + (c) Mechanism
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