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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 , ,
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
CH 3 /
\VIe / OMgI
)C( H OH
_, 7 X Me CH3x
-t M g(OH)I.
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
CH 3 /
\ Me CH2^
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
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 * 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.
- Fall '06
- Organic chemistry