Thefelkinahnmodelforadditionstocarbonylcompoundscanbeu

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Unformatted text preview: on
the
adjacent
carbon.

For
small
nucleophiles,
such
as
LiAlH4,
 the
steric
interaction
is
lower
in
energy
that
this
torsional
strain
and
an
axial
attack
is
favored.

For
bulky
 nucleophiles,
such
as
LiBH(s‐Bu)3,
the
steric
interactions
with
the
1,3
diaxial
hydrogens
is
larger
than
the
 torsional
strain
and
an
equatorial
attack
is
favored.
 
 Problem
#2.)
The
Felkin‐Ahn
model
for
additions
to
carbonyl
compounds
can
be
used
to
 accurately
 determine
 the
 stereochemistry
 of
 the
 product.
 
 Given
 what
 you
 know
 of
 this
 model,
please
explain
the
difference
in
stereoselectivity
seen
below.

 CN 
 
O NC OH When
an
electronegative
heteroatom,
in
this
case
Cl,
is
 Me KCN H 
 on
the
alpha
carbon,
the
electronegative
g...
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This note was uploaded on 01/24/2014 for the course CHEM 436 taught by Professor White during the Spring '08 term at University of Illinois, Urbana Champaign.

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