Rδ− MgXδ+ + H R H + R + Mg2+ + X −
Grignard reagent
(stronger base)
Alcohol
(stronger acid)
Alkane
(weaker acid)
Alkoxide ion
(weaker base)
OR O −
2) Grignard reagents and organolithium compounds abstract protons that are much
less acidic than those of water and alcohols ⇒ a useful way to prepare
alkynylmagnesium halides and alkynyllithium.
R C C H R C C MgX
δ− δ+ δ− δ+
R' MgX R'
Grignard reagent
(stronger base)
+
Terminal alkyne
(stronger acid)
Alkynylmagnesium halide
(weaker base)
+ H
Alkane
(weaker acid)
R C C H R C C Li
δ− δ+ δ− δ+
R' Li R'
Alkyllithium
(stronger base)
+
Terminal alkyne
(stronger acid)
Alkynyllithium
(weaker base)
+ H
Alkane
(weaker acid)
- Grignard reagents and organolithium compounds are powerful nucleophiles.
12.7B REACTIONS OF GRIGNARD REAGENTS
WITH OXIRANES (EPOXIDES)
- Grignard reagents carry out nucleophilic attack at a saturated carbon when they
react with oxiranes ⇒ a convenient way to synthesize 1° alcohols.
H 2 C CH 2
O δ−
+ O − H O
δ+ δ+ δ+ +
MgX CH 2 CH 2 Mg2+X− CH 2 CH 2 H
Oxirane A primary alcohol
δ−
R R R
Specific Examples
H 2 C CH 2
O
+ OMgBrH O
+
C 6 H 5 MgBr Et 2 O C 6 H 5 CH 2 CH 2 C 6 H 5 CH 2 CH 2 H
