Thisreactionoccursatlowertemperaturethanthecompetingde

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Unformatted text preview: 
good
nucleophile,
reacts
with
the
carbocation.
 Primary
and
methyl
alcohols
undergo
substitution
by
an
SN2
mechanism.
 Primary
and
secondary
chlorides
can
only
be
made
with
the
assistance
of
a
Lewis
acid
 such
as
zinc
chloride.
 In
Class
Problem:
 Outline
a
reasonable
mechanism
for
the
following
reaction:
 Alkyl
Halides
from
the
Reaction
of
Alcohols
with
 PBr3
and
SOCl2
 These
reagents
only
react
with
1o
and
2o
alcohols
by
means
of
an
SN2
mechanism.

In
 each
case
the
reagent
converts
the
hydroxyl
to
an
excellent
leaving
group.

No
 rearrangements
are
seen.
 Reaction
of
phosphorous
tribromide
to
give
alkyl
bromides:
 Reaction
of
thionyl
chloride
to
give
alkyl
chlorides:
 Mechanism:
 Often
an
amine
is
added
to
react
with
HCl
formed
in
the
reaction.
 The
hydroxyl
group
of
an
alcohol
can
be
converted
to
a
good
leaving
group
by
conversion
 to
a
sulfonate
ester.
 Tosylates,
Mesylates,
and
Triflates:
 Leaving
Group
Derivatives
of
Alcohols
 Sulfonyl
chlorides
are
used
to
convert
alcohols
to
sulfonate
esters.

Base
is
added
to
react
 with
the
HCl
generated.
 A
sulfonate
ion
(a
weak
base)
is
an
excellent
leaving
group.
 If
the
alcohol
hydroxyl
group
is
at
a
stereogenic
center
then
the
overall
reaction
with
the
 nucleophile
proceeds
with
inversion
of
configuration.

The
reaction
to
form
a
sulfonate
 ester
proceeds
with
retention
of
configuration.
 Triflate
anion
is
such
a
good
leaving
group
that
even
vinyl
triflates
can
undergo
SN1
 reaction.
 In
Class
Problem:
 Draw
the
configurations
of
the
products
when
(R)‐1‐phe...
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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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