Chemistry 201 - C
Alkyl Halides
This presentation was created by
Professor Carl H. Snyder
Chemistry Department
University of Miami
Coral Gables, FL 33124
[email protected]
Copyright 2004 by Carl H. Snyder,
University of Miami. All rights
reserved.
Naming Alkyl Halides
Naming Alkyl Halides
Naming Alkyl Halides
Naming Alkyl Halides
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Alkyl Halides From C=C
Additions
Halogenation of Alkanes - Free
Radical Chlorination of CH4
chloromethane
dichloromethane
trichloromethane
tetrachloromethane
By anti addition of X2
By Markovnikov addition of HCl, HBr, or
HI
Chlorination of Methane: A
Free Radical Reaction
Free radical chlorination of methane gives
chloromethane (methyl chloride)
dichloromethane (methylene chloride)
trichloromethane (chloroform)
tetrachloromethane (carbon tetrachloride).
Initiation
The mechanism is initiated by free radicals and
proceeds with the creation and reaction of free
radicals.
Light, as a reaction condition, can be
represented as hν
ν where h represents Planck’s
constant, and ν represents the radiation
frequency.
Propagation
Termination
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Free Radical Halogenation of
Alkanes: Mechanism
Halogenation of Alkanes with
Multiple Classes of Hydrogens
Rate = (1/Eact) x (conc.) x (probability factor)
Radical Stabilities
Relative Rates of Chlorination:
A Function of Radical
Stabilities
The order of stabilities of alkyl free radicals is
the same as the order of stabilities of
carbocations.
Free Radical Bromination
Free radical
bromination is
more selective
than chlorination.
Reason: The
Hammond
Postulate.
Bromination is
more endothermic
T.S. is more like
the free radical
product.
T.S. stability
reflects free
radical stability.
Allylic Bromination With
N-Bromosuccinimide (NBS)
N-Bromosuccinimide (NBS) effects bromination
exclusively in the allylic position.
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NBS Bromination: Free
Radical Mechanism
A Complete Set of Radical
Stabilities
NBS produces a low concentration of Br2
The result is a free radical bromination at the
allylic carbon.
Alcohol to Alkyl Halide: HX
Alcohol to Alkyl Halide: PBr3
The Grignard Reagent
Alcohol to Alkyl Halide: SOCl2
Reaction of an alkyl halide, R-X, with
magnesium, Mg, yields a Grignard reagent,
RMgX.
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Alkyl Halide to Alkane via
Grignard Reagent
R-X + Mg → RMgX
RMgX + H2O → R-H + Mg(OH)X
The H of H2O replaces the MgX of RMgX
Use of D2O yields R-D, a deuteroalkane
CH3CH2MgBr + D2O → CH3CH2D + Mg(OH)X
The Gilman Reagent
C-C Bond Formation Via The
Gilman Reagent
Reaction of RX with Li yields an alkyllithium.
Alkyllithium and CuI produce R2CuLi, the Gilman
reagent.
C-C Bond Formation Via The
Gilman Reagent
Oxidation In Organic
Chemistry
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Oxidation In Organic
Chemistry
Oxidation In Organic
Chemistry
Reduction In Organic
Chemistry
Reduction In Organic
Chemistry
Reduction In Organic
Chemistry
End
Alkyl Halides
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