Reagents with Carbon-Metal Bonds

1
Chapter 15

• Reagents with Carbon-Metal Bonds
• Organometalic Synthesis of Alcohols

2
Section and Problem Assignments

• SKIP Section 15.6 and 15.9
• In-Text Problems 15.2 - 15.7 15.10 - 15.13
• End of Chapter Problems 1 - 3

3
Sect. 15.1 structure and properties of
organometallic compounds

• Organometallic compounds are prepared by the
  reaction of halides with metals such as sodium,
  lithium and magnesium.
• These reactions involve reduction!!

4
Organolithium compounds
d-
d
d
d-
5
Formation of Organolithium Reagents
Examples
ether
2

butyllithium


phenyllithium
6
Organomagnesium compounds Grignard Reagents
d-
d-
d
d-
d
7
Victor Grignard
Nobel Prize 1912
Source Michigan State University, Department of
Chemistry http//www.chemistry.msu.edu/Portraits/P
ortraitsHH_collection.shtml
8
SOLVENTS THAT ARE FREQUENTLY USED
..
diethyl ether
..
Ethers work especially well since they can make
complexes with Grignard reagents and solvate
them.
THF tetrahydrofuran
..
..
pentane
..
benzene
..
..
..
..
..
1,4-dioxane
..
..
9
Properties of organometallic compounds

• polar covalent bond
• partial negative charge on carbon
• carbon is basic!
• dont memorize Table 15-1!

10
BASES AND NUCLEOPHILES
All of these reagents react as nucleophiles or
bases
-

Which are bonded, to various degrees, to the
accompanying metal.
11
Sect. 15.2 Reaction of Organometallic compounds
with water and acid

• Organolithium and organomagnesium compounds give
  alkanes when reacted with water and acid

12
REACTIONS OF ORGANOLITHIUM COMPOUNDS
strong base
good nucleophile
43 ionic
57 covalent
ether
or
strong bases react with acids (even water and
alcohols)
CH3- H
strong base
acid
13
The reaction with H2O also means that you must
rigorously exclude water ( and water vapor air
) from your reactions.
14
REMOVING A HALOGEN
The reaction with water is a way of reducing an
alkyl halide ( converting C-X to C-H ).
ether
H2O
Li
15
MAKING DEUTERIUM COMPOUNDS
ether
Li
Li
ether
D2O
Li
phenyllithium
This reaction of an alkyllithium compound with
water is generally not useful unless you use
D2O, which is a way of placing a deuterium atom
in your compound.
16
Sect. 15.3 Reaction of Organometallic Reagents
with epoxides
d-
Grignard reagent
a terminal alcohol
17
Organolithium
d-
d
d
d-
Notice which carbon
got the nucleophile.
18
Sect. 15.4 Synthesis of Alcohols using Grignard
reagents
ketone
tertiary alcohol
19
THE CARBONYL GROUP
electrophiles attack here
nucleophilic at oxygen
H or E
_
electrophilic at carbon
Nu
nucleophiles attack here
20
REACTIONS WITH THE CARBONYL (CO) GROUP
..
d-
Since oxygen is more electronegative than
carbon, the carbonyl group is electron-deficient
at carbon, that is an electrophile.

d
..
-
MgBr


-

BrMg
new C-C bond
The organometallic compound (R-MgBr) behaves as a
nucleophile with an unshared pair on the carbon.
NUCLEOPHILIC ADDITION TO CARBONYL
21
SYNTHESIS OF ALCOHOLS
Reaction of RMgBr with aldehydes and ketones
yields alcohols
formaldehyde
primary alcohol
RMgX
other aldehydes
secondary alcohol
RMgX
RMgX
ketones
tertiary alcohol
The type of alcohol depends on whether you use
formaledhyde, another aldehyde, or a ketone.
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SYNTHESIS PROBLEM
from
23
Sect. 15.5 Synthesis of Alkanes the Wurtz
reaction

2 R-X 2 Na R-R 2 NaX
24
Skip Section 15.6
25
Sect. 15.7 Preparation of lithium dialkyl
cuprates
26
ALKYLATION WITH R2CuLi
0o C
R-X R2CuLi
R-R R-Cu LiX
ether
X Cl, Br, I
EXAMPLES
(CH3)2CuLi CH3(CH2)4-I
CH3-(CH2)4-CH3

Corey-House Reaction
27
MORE LITHIUM DIALKYLCUPRATE COUPLING

CHBr3
28
Reaction of cuprates with acid
chlorides
Cuprates react with acid chlorides to give
ketones
29
Sect. 15.8 Formation of organometallic reagents
from alkynes
These reagents add to carbonyl groups!! Good
stuff!!
30
Sect. 15.9 Organoboron Compounds revisited

• Been there, done that!! See Chapter 14.