Organic Chemistry

Reaction with the metal converts the alkyl halide into a compound that will react with

electrophiles instead of nucleophiles. Thus, organolithium and organomagnesium

compounds react as if they were carbanions.

Alkyl halides, vinyl halides, and aryl halides can all be used to form organolithium

and organomagnesium compounds. Alkyl bromides are the alkyl halides most often

used to form organometallic compounds because they react more readily than alkyl

chlorides and are less expensive than alkyl iodides.

The nucleophilic carbon of an organometallic compound reacts with an electrophile.

For example, in the following reactions, the organolithium reagent and the Grignard

reagent each react with an epoxide.

Notice that when an organometallic compound reacts with ethylene oxide, a primary

alcohol containing two more carbons than the organometallic compound is formed.

PROBLEM 28

What alcohols would be formed from the reaction of ethylene oxide with the following

Grignard reagents?

a. b. c.

PROBLEM 29

How could the following compounds be prepared, using cyclohexene oxide as a starting

material?

Organomagnesium and organolithium compounds are such strong bases that they

will react immediately with any acid that is present in the reaction mixture—even with

very weak acids such as water and alcohols. When this happens, the organometallic

compound is converted into an alkane. If is used instead of a deuterated

compound will be obtained.

D 2 O H 2 O,

CH 2 CH 3

a. b. c.

CH 3

Br

CH 3 CH 2 CH 2 MgBr CH 2 MgBr MgCl

ethylmagnesium bromide

phenyllithium

CH 3 CH 2 MgBr

Li reacts as if it were

reacts as if it were CH 3 CH 2 MgBr

−Li+

− +

+

H+

CH 3 CH 2 H 2 C CH 3 CH 2 CH 2 CH 2 O− CH 3 CH 2 CH 2 CH 2 OH

+ Mg^2 + + Br−

CH 2

O

MgBr

H+

CH 3 CH 3 CH CHCH 3

O

Li + CH 3 CHCHCH 3

O−

CH 3 + Li+

CH 3 CHCHCH 3

OH

CH 3

468 CHAPTER 12 Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds

3-D Molecules:

Phenyllithium;

Ethylmagnesium bromide

Francis August Victor Grignard

(1871–1935)was born in France, the

son of a sailmaker. He received a

Ph.D. from the University of Lyons in

1901. His synthesis of the first
      Grignard reagent was announced in


1902. During the next five years,
      some 200 papers were published
      about Grignard reagents. He was
      a professor of chemistry at the
      University of Nancy and later at
      the University of Lyons. He shared
      the Nobel Prize in chemistry in 1912
      with Paul Sabatier (p. 173). During
      World War I, Grignard was drafted
      into the French army, where he
      developed a method to detect war
      gases.

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