72 Biological Chemistry. 



what is known as Grignard's reaction, which has been 

 largely employed for the synthesis of alcohols. Many 

 other synthetical methods will be mentioned in the 

 following pages. 



Qrignard's Method. When an alkyl bromide or 

 iodide (see p. 64) is treated with magnesium powder in 

 the presence of pure ether, a derivative of the type 

 MgBrR or MglR is formed (R = alkyl radicle). The 

 derivative from ethyl iodide would thus have the formula 

 MgC 2 H 6 I. Such substances readily react with a variety 

 of other organic compounds. Thus, if treated with an 

 aldehyde of the general formula R/CHO they react in the 

 following manner : 



,0-MgBr 



R'CHO + RMgl = R'CH 



\R 



This addition product is readily decomposed by dilute 

 hydrochloric acid, according to the equation 

 ,0-MgBr 



R'CH + HC1 = R'CH + MgClBr 



\R \R 



The product of reaction obtained in this case is a secondary 

 alcohol. It will be seen that the product obtained con- 

 tains two alkyl groups. The reaction may be illustrated 

 by the following example. It has been already stated 

 that when ethyl alcohol, CH 3 CH 2 OH, is oxidized under 

 certain conditions it yields aldehyde, CH 3 CHO. If, now, 

 the magnesium derivative of isopropyl iodide (which has 



r^TT \ 



the formula ~* ;>CHI) is treated with the aldehyde, and 

 OM 3 X 



the reaction product is then decomposed with hydro- 

 chloric acid, a secondary alcohol will be obtained which 

 can only have the constitution 



