Organometallic Chemistry - PowerPoint PPT Presentation

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Organometallic Chemistry

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Metal = Li, Na, K (alkali metals) Mg (alkaline earth metals) Ti Cr Mn Fe Co Ni Cu Zn ... the more electropositive metals, i.e. alkali and alkaline earth metals. ... – PowerPoint PPT presentation

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Title: Organometallic Chemistry


1
Organometallic Chemistry
2
Organometallic Compounds
  • Compounds that contain a Metal-Carbon bond.
  • Metal Alkyls, e.g. Tetraethyllead - Leaded Gas
  • Alkyl methyl, ethyl, tert-butyl, etc.
  • Metal Li, Na, K (alkali metals)
  • Mg (alkaline earth metals)
  • Ti Cr Mn Fe Co Ni Cu Zn
  • Zr Ru Pd Hg
  • OS Pt

3
Metal Alkyls
  • General formula R-M (R alkyl, M metal)
  • The C-M bond is a covalent bond!
  • However, C--M or R--M bond tend to be
    polarized.
  • This is especially true for organometallic
    compounds conataining the more electropositive
    metals, i.e. alkali and alkaline earth metals.
  • Generally, the alkyl fragment of the
    organometallic compound is very reactive however
    this depends on the metal, changing the metal
    alters the polarization of the R-M bond.
  • Thus different organometallic compounds are used
    in many different types of organic reactions.

4
Useful Metal Alkyls in Organic Synthesis
  • C-M Bond
  • Organomagnesium Mg (C--Mg)
  • Organolithium - Li (C--Li)
  • Organocopper - Cu (C--Cu)

5
Organomagnesium Compounds
Grignard Reagents
  • Methylmagnesium chloride - CH3Mg Cl-
  • Ethylmagnesium bromide - CH3CH2Mg Cl-
  • Draw the structures of
  • Isopropylmagnesium iodide
  • Sec-butylmagnesium chloride
  • Formation of Grignard Reagents
  • CH3-Cl
    CH3Mg Cl

Mg, Et2O
6
Reactivity of Alkyl Halides
  • R-I gt R-Br gt R-Cl
  • Preparation of Grignards from primary, secondary
    tertiary alkyl halides.
  • Grignard formation from aryl halides and allyl
    halides however these may give Wurtz type
    coupling products.
  • I2 maybe used to speed-up the formation Grignard
    reagents from alkyl bromides or chlorides

7
Organolithium Compounds
Alkyl Lithium Compounds
  • Methyllithium CH3Li
  • Ethyllithium - CH3CH2Li
  • Draw the structures of these Alkyl lithium
    compounds
  • n-propyllithium
  • tert-butyllithium
  • Preparation of organolithium reagents
  • CH3-Br CH3Li
    LiBr

2 eq. Li, Et2O
8
Organocopper Compounds
  • Lithium Dialkylcopper (organocuprate ) (R)2Cu-
    Li
  • Cuprates are less reactive than organolithium
  • R acts as a Nucleophile
  • Oxidation state of copper is Cu(I).
  • Nucleophile R will attack various organic
    electrophiles.
  • Organocuprates are used in cross-coupling
    reactions to form higher alkanes.
  • Cross-Coupling Reaction coupling of two
    different alkyls R and R to yield a new alkane
    (R-R). This type of reaction is used to make
    new C-C between alkyl groups.

9
Organocuprates
  • Preparation of organocuprates
  • 2 CH3Li (CH3)2Cu- Li LiI
  • As a reagent for Organic Synthesis
  • (CH3)2Cu- Li CH3CH2CH2I CH3CH2CH2CH3
  • Formation of new C-C bonds
  • The electrophile CH3CH2CH2I (R-X) must be a 1
    alkyl halide for a good product yield.

CuI, Et2O
-RCu, -LiI
10
Organic Synthesis
  • Give a stepwise synthesis for Isobutane.
  • 2,2-dimethylheptane
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