(Et 2 O) (THF)
ii) Most organolithium compounds slowly attack ethers by bringing about an
elimination reaction.R :δ− Liδ+ + HCH 2 CH 2 OCH 2 CH 3 RH++H 2 CCH 2 Li+ −OCH 2 CH (^3)
iii) Ether solutions of organolithium reagents are not usually stored but are used
immediately after preparation.
iv) Organolithium compounds are much more stable in hydrocarbon solvents.
2) Examples of organolithium compounds prepared in ether
− 10 oC
CHButy 3 CHl brom 2 CH 2 CHide 2 Br +2Li Et 2 O CH (^3) ButylithiumCH 2 CH 2 CH 2 Li + LiBr
80-90%
R X +2Li Et 2 O R Li + LiX
(or Ar−X)(or ArLi)
3) The order of reactivity of halides is RI > RBr > RCl (Alkyl and aryl fluorides are
seldom used in the preparation of organolithium compounds).
12.6B GRIGNARD REAGENTS
- Organomagnesium halides were discovered by the French chemist Victor
Grignard in 1900.
- Grignard received the Nobel Prize in 1912 and organomagnesium halides are
now called Grignard reagents. - Grignard reagents have great use in organic synthesis.
- Grignard reagents are usually prepared by the reaction of an organohalide and
magnesium metal (turnings) in an ether solvent.