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Grignards Reagents

grignard and alcohols

GRIGNARD'S REAGENTS. When an alkyl kaloid, such as methyl iodide, CH31, is added to dry magnesium powder suspended in an ether such as ordinary ethyl ether (C21-10,0, a very reactive compound, known as a grignard reagent (after V. Grignard, who discovered them in 1900 under the direction of Professor Barbier) is formed. In the case just discussed, it appears to have the structural formula at tributed to it by Baeyer, viz.

C2H5 \ / 0 / \ C,H, with tetravalent oxygen. The Grignard re agents are invaluable in organic synthesis on ac count of the number and variety of constructive reactions into which they enter. For example, they enable us to form tertiary alcohols from petones as follows: Again, .we can form tertiary alcohols from acid chlorides.

CH&CO.C1+2CHs.Mg.I.O.(C2116)2=(C21-16)20+ ( CH6).C.O.MgI+ MgIC1.

A closely similar reaction takes place with or ganic esters. Secondary alcohols can be made from aldehydes and Grignard reagents: e.g.

CHLCHO+GIL.Mg.I.0.(C2116) \ I+(C6116)60. Cals / CHs \ C211s/ CHs \ GH./ Fatty acids may be prepared from Grignard reagents and carbon dioxide.

C,61166-1-1.Mg.I.0.(C2116) 2+ Cal 014-1 C0.0MgI+ (C111420 2C2611.6-1-2.00.0MgI+FIS SO4 = 2CnHvH-1 . CO . OH + SO.

Hydrocarbons may be built up by Grignard reactions.

R.Mg.Br.0.( C1116)6+ BrR'= (C4H6)20.

Bromo-derivatives may be transformed into corresponding iodo-compounds.

RBr S. ) RI Mg Aromatic Grignard compounds exist, and react much like their aliphatic Among the organic Grignard reactions is that by which benzaldehyde is prepared from ethyl orthof ormate.

C.H..Mg.Br.O. (C2116)2+CH (0C21-16) (C6116)20+ Mg. Br.O.C61-16+ GH.0 H ( 0 Cali),