2. Victor GrignardVictor Grignard
Grignard ReagentsGrignard Reagents
Grignard, Victor , 1871–1935, French chemist. He shared the
1912 Nobel Prize in Chemistry1912 Nobel Prize in Chemistry for his work in organic synthesis
based on his discovery (1900) of the Grignard Reagent. He taught
at the Univ. of Nancy (1909–19) and at the Univ. of Lyons (from
1919 until the end of his career).
3. R X + Mg R MgX
dry ether
Mg
Br
MgBr
H
I
H
MgI
Cl
MgCl
N
Cl
N
MgCl
The alkyl halides are more reactive than aryl and vinyl halides.
The reactivity of alkyl halide is RI > RBr > RCl whereas
organomagnesium fluoride are not known yet.
Solvents:
diethyl ether (b.p. 34.60
C),
diethylene glycol,
diglyme (b.p. 1600
C),
tetrahydrofuran (b.p. 660
C)
Grignard ReagentsGrignard Reagents
Halide does not contain the following functional groups –
Functional group with active hydrogen –COOH, -C≡CH, -OH, -NH2, -SH, etc
The functional group - -CO-, -CN, -NO2, -SO-, Epoxide, etc.
4.
5. Grignard Reagents - StructureGrignard Reagents - Structure
The Grignard reagent was existing in dimeric form (stabilization of Grignard
reagent) which is in equilibrium with dialkyl magnesium compound and
magnesium dihalide.
R MgX2 R2Mg + MgX2 R Mg
X
Mg R
X
The X-ray diffraction studies - R Mg
X
Mg R
X
OEt2
OEt2
OEt2
OEt2
6. Organometallic NomenclatureOrganometallic Nomenclature
C C
H
H MgBr
H
vinylmagnesium bromide
H3CH2CH2CH2C-Li
Butyllithium
(H3C)2Cu- Li+
Dimethylcopper lithium
H3C MgBr
methylmagnesium bromide
CH MgBr
H3C
H3C
H2C Mg
Br
MgBr
phenylmagnesium bromide
isopropylmagnesium bromide
benzylmagnesium bromide
C Mg
BrH2C
CH3
CH3
H
(R)-sec-butylmagnesium bromide
Organometallic compounds were normally named as substituted metals. e.g. alkyl
metal or alkyl metal halide.
7. • The difference in electronegativity between carbon and magnesium (lithium), the C-MgThe difference in electronegativity between carbon and magnesium (lithium), the C-Mg
(C-Li) bond is polar covalent, with C(C-Li) bond is polar covalent, with Cδδ--
and Mgand Mgδδ++
((LiLiδδ++
))
– Grignard and organolithium reagents behave like carbanions/nucleophile
• CarbanionCarbanion: an anion in which carbon has an unshared pair of electrons and bears a: an anion in which carbon has an unshared pair of electrons and bears a
negative charge.negative charge.
Grignard and Organolithium Reagents – ReactivityGrignard and Organolithium Reagents – Reactivity
• The carbon-lithium bond in CH3Li has about 40% ionic character, and the carbon-
magnesium bond in CH3MgCl has about 35% ionic character. Therefore organolothium
are more reactive than Girgnard reagent.
8. phenylmagnesium bromide
MgBr
Br
Mg/dry ether
H + MgBr(OH)
H2O
ROH
H + MgBr(OR)
O2
OOMgBr OOH
HCl
OH
D2
O
D + MgBr(OD)
RCOOH
H + MgBr(OOCR)
Reactivity of Grignard reagent
with active hydrogen
Grignard Reagents – ReactivityGrignard Reagents – Reactivity
9. phenylLithium
Li
H
Li/dry ether
H + LiOH
H2O
ROH
H + LiOR
O2
OOLi OOH
HCl
OH
D2
O
D + LiOD
RCOOH
H + RCOOLi
Reactivity of organolithium
reagent with active hydrogen
RNH2
H + RNHLi
Organolithium Reagents – ReactivityOrganolithium Reagents – Reactivity
10. formaldehydeformaldehyde to give primary alcoholsto give primary alcohols
aldehydesaldehydes to give secondary alcoholsto give secondary alcohols
ketonesketones to give tertiary alcoholsto give tertiary alcohols
estersesters to give tertiary alcoholsto give tertiary alcohols
COCO22 to give acidsto give acids
epoxides to give primary alcoholsto give primary alcohols
cyanidecyanide to ketone or acidto ketone or acid
Grignard reagents react productively with:Grignard reagents react productively with:
