3066
H. Simuste et al. / Journal of Organometallic Chemistry 690 (2005) 3061–3066
precipitate and deprives the supernatant solution of ac-
tive species. In this context diethyl ether proves to be the
most effective donor affording Grignard reagents with a
very small content of the base.
Acknowledgment
This work was supported by Dow Corning Corpora-
tion (Midland, USA).
From the data in Table 4 the activation parameters
¼
¼
were estimated: DH = 49.9 3.8 kJ molꢁ1, and DS =
ꢁ129 10 J molꢁ1 Kꢁ1. The difference between the val-
References
¼
ues of DH for chloro- and bromobenzene is not only
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statistically significant but also expected, based on the
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