ON Tus APPLICATIONS OF GRIGNARD’S REACTION. 293 
than when ether is used. Further, in those cases where the reagent is 
formed with difficulty by the ordinary method, the higher temperature at 
which the Tschelinzeff reagent is formed would appear to be an advantage. 
The author of this report has tried the Tschelinzeff method, with little 
success, however. In spite of what is claimed for it, the method, so far 
at least, has a theoretical interest only : it does not appear to have been 
applied at all, except in the very few cases mentioned by Tschelinzefl 
himself. 
(6) Acceleration of the formation of the reagent.—Tissier and Gri- 
gnard! found that, whilst alkyl bromides or iodides in ethereal solution as 
a rule readily interact with magnesium, the action with aryl halides is 
accelerated by heating or by the addition of a trace of iodine. A drop 
of methyl iodide? serves the same purpose ; this may be used, for example, 
in the preparation of magnesium a-naphthyl bromide. Iodine and methyl 
iodide are the catalysers generally used. Monochlorides may not interact 
with magnesium and ether alone, but do so when a trace of iodine is 
added.’ Aluminium chloride and hydriodic acid‘ may also be used as 
catalysers. An interpretation for the use of iodine in the formation of 
magnesium organic compounds from chlorides is advanced by Wohl,’ 
namely, 
2RCl+ Mel, = 2RI + MgCl, 
2KI + 2Me = 2RMgI 
2RMelT + 2RCl=2RMgOCl1 + 2RI 
In cases where interaction with the halide could not be effected by 
the usual methods, special devices have been employed. Thus, Ehrlich 
and Sachs © found that an ethereal solution of p-bromodimethylaniline is 
not acted on by magnesium even when the mixture is heated for several 
days in the presence of a little iodine. The interaction, however, was 
brought about as follows : The magnesium is covered with absolute ether 
and ethyl bromide added ; the action soon becomes vigorous, as usual, 
and is then moderated by cooling the flask in ice-cold water ; the super- 
natant liquid is poured off quickly from the magnesium and an ethereal 
solution of »-bromodimethylaniline is then added. By this treatment the 
magnesium had been rendered more active, and the magnesium compound 
desired was readily obtained by gentle warming. The fact, however, 
that the yield was far from quantitative, and that the product was 
necessarily mixed with a little magnesium ethyl bromide, occasioned 
y. Baeyer’ to try other methods to make the magnesium active. This 
result is attained when the magnesium is coated with a thin layer of its 
iodide. Magnesium filings were heated in a round-bottomed flask over a 
free flame with constant shaking and half the weight of iodine gradually 
added. The temperature must not be so high as to cause the mass 
to melt. With 10 grams of magnesium this operation requires from 15 to 
30 minutes. The product obtained must be protected carefully from 
moisture. This ‘ activirtes’ magnesium was used by Baeyer himself 
for the preparation of the magnesium compounds of the iodoanilines and 
iododimethylanilines, and good results were also obtained by Gomberg 
and Cone* with diphenylbromomethane when other methods failed. 
1 Compt. rend., 1901, 182, 1182. 2 Klages, Ber., 1904, 37, 1449, 
3 Compare Hesse, ibid., 1906, 39, 1146. 
4 Zelinsky, J. Russ. Phys. Chem. Soc., 1908, 35, 399. 
5 Ber,, 1906, 39, 1952. 6 Tbid., 1903, 86, 4296, 
7 Tbid., 1905, 38, 2759. 8 Thid., 1906, 39, 1467. 
