Topic 3 Synthesis, Addition, and Addition- Elimination Reactions of - PowerPoint PPT Presentation

Chem 2312 Solomons and Fryhle: Chapter Sections Lecture 19, October 6, 2003 12.8A, 12.10, 16.11, 12.9 Topic 3 Synthesis, Addition, and Addition- Elimination Reactions of Aldehydes and Ketones New Molecule of the Week Part - V 1

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O + CH 3 -M gX H O + LiAlH 4 CH 3 or NaBH 4 3

O - CH 3 -MgI O CH 3 OH CH 3 O CH 3 CH 3 CH 3 O + CH 3 -MgX CH 3 O + Ph-MgX H 3 C CH 3 HOW????? O + 2 x CH 3 -MgX O CH 3 4

R-CH 2 -OH 1 o R-CH 2 -CH 2 -OH 1 o OH HOW????? ‘ R' H 2 o R 5

OH << Three different R R' R" groups R OH << Two same R R' R groups R HOW????? H 2 O O N + R-MgX R C N R' R R' R 6 -- negative charge makes this species not electrophilic

O Mg-X Note>>>>> others disconnects would not yield 4 carbon units 7

O OH Mg-X + or Li Cl LAH O S O Mg or Or NaBH 4 Li HOW????? Br OH 1. Ts-Cl 2. KBr 8

Problems>>>> How would you prepare From O OH 1. O OH Br 2.. 2 x CH3MgX From + OH Mg-Br Want>>> HOW????? + O RCO 3 H 9 O

INSTEAD Ph-MgX O O excess O O OH O H + O O OH 1. Ph-MgX excess OH NO No O O-MgX 1. H 2 O/H + No!!!! O HOW????? O OH 10

R 3 O R 1 HO O R 4 R 2 Br Zn O R 1 R 2 O NOTE: R-Zn-Halide is not reactive enough to react with esters>> only keto and aldehyde groups 11

Elimination!!!!!!! R X Can be viewed as a source of CH 3 :- 12

Bu 13

O 14

O .. Cl O + CuLi 2 CuI HOW????? Br Li Li 15

O Prepare From>>>> O 1. TsCl LAH O First Way Br OH 2. KBr Mg PCC O O OH Br Mg Second Way O Br O Zn O Zn Br O O O H + O O OH O H 2 /Pt DIBAL O 16 O O

Email: arthur.ragauskas@chemistry.gatech.edu Next Exam: October 17 17