Organic 2 Review Problem 299

Organic 2 Review Problem 299 - P REPARATIONS 283 /H HC-OMgI...

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Unformatted text preview: P REPARATIONS 283 /H HC-OMgI + HO H = M eCH 2 OH -f M g(OH)I \N , , E thanol Me This r eaction is of great value for a scending the h omologous series of a lcohols: ROH -* RBr -> R MgBr -> R CH 2 OH Note t hat ethylene o xide reacts with t he G rignard reagent t o g ive a 2 -substituted e thanol: e.g. w ith methyl magnesium iodide: Me-CH 2 CH 2 OMgI -+ M e-CH 2 CH 2 OH (5) K etones similarly give tertiary alcohols. CH 3 CH3 >C:O -f M eMgI 7 CH 3 Acetone CH3 CH 3x / OMd yC/ CH 3 / \VIe / OMgI )C( H OH _, 7 X Me CH3x X )H )C( -t M g(OH)I. X CH3/ Me Tertiary butanol Note.—Grignard reagents readily act as d ehydrating agents by v irtue of Reaction ( i). Since aliphatic tertiary alcohols u sually r eadily lose water, a n excess o f the G rignard reagent m ay t ake t he above reaction o ne s tage further to give a n u nsaturated hydrocarbon. CH 3 , /OH yC/ -H2O = CH 3 / \ Me CH2^ ^C-Me CH37 (6) Esters ( a) a nd acid chlorides ( b) r eadily r eact w ith G rignard reagents t o give k etones, which immediately r eact w ith a s econd e quivalent o f the r eagent as in (5) to give tertiary a lcohols as b efore. , O Kt I MgMc (a) C H 3 C:O ,Me - -- C H 3 C:O + M g(OEt)I Ethyl acetate , Cl (6) CH,C:O Acetyl chloride I MgMc ,Me -> C H 3 C:O 4- M gClI* (7) Nitriles also react w ith Grignard reagents to give ketones, which a rise from t he h ydrolysing action o f the d ilute sulphuric acid o n the i ntermediate addition p roduct. A cid amides behave similarly. CH 3 -C:X+MeMgI -* C H 3 -CiNMgI -> C H 3 -CO-fNH 3 / Me / Me * i.e., e quimolecular quantities o f m agnesium c hloride a nd i odide. ...
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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