Chapter 8 Notes

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Unformatted text preview: vnikov
Syn
Hydration
 The
reaction
leads
to
syn
and
anti‐Markovnikov
addition
of
water
to
alkenes
 Hydroboration:
Synthesis
of
Alkylboranes:
The
elements
of
hydrogen
and
boron
are
added
 across
the
double
bond.

In
practice,
a
borane
complex
with
the
solvent
tetrahydrofuran
 (THF)
is
often
used.
 Mechanism
of
Hydroboration:

Boron
hydride
adds
successively
to
three
molecules
of
 alkene.
 Boron
becomes
attached
to
the
least
substituted
carbon
of
the
double
bond.

The
bulky
 boron
group
can
approach
the
least
sterically
hindered
carbon
more
easily.

This
 orientation
also
allows
a
δ+
charge
in
the
transition
state
to
reside
at
the
most
 substituted
carbon.

This
orientation
leads
to
anti‐Markovnikov
product.

The
boron
and
 hydride
add
with
syn
stereochemistry.
 Oxidation
and
Hydrolysis
of
Alkylboranes:
Oxidation
and
hydrolysis
to
the
alcohol
 takes
place
with
retention
of
stereochemistry
at
the
carbon
bonded
to
boron.
 Hydroboration
of
methylcyclopentene
gives
the
anti‐Markovnikov
product
with
syn
 addition
of
the
elements
of
water.
 Summary
of
Alkene
Hydration
Methods:
 (1)
Acid‐catalyzed
hydrolysis:
Markovnikov
addition
 (2)
Oxymercuration:
Markovnikov
addition

 (3)
Hydroboration‐Oxidation:...
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This note was uploaded on 06/19/2009 for the course CHEM 2311 taught by Professor Tyson during the Fall '07 term at Georgia Institute of Technology.

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