Reactioncanoccurwith

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Unformatted text preview: by
 oxymercuration‐demercuration,
and
(c)
hydration
by
hydroboration‐oxidation.

 Alcohols
as
Acids
 Alcohols
have
acidities
similar
to
water.

Sterically
hindered
alcohols
such
as
tert‐butyl
 alcohol
are
less
acidic
(have
higher
pKa
values).

Why?:
The
conjugate
base
is
not
well
 solvated
and
so
is
not
as
stable.
 Alcohols
are
stronger
acids
than
terminal
alkynes
and
primary
or
secondary
amines.
 An
alkoxide
can
be
prepared
by
the
reaction
of
an
alcohol
with
sodium
or
potassium
 metal.
 Conversion
of
Alcohols
into
Alkyl
Halides
 Hydroxyl
groups
are
poor
leaving
groups,
and
as
such,
are
often
converted
to
a
group
 that
can
depart
as
a
weak
base;
hydroxyl
groups
are
converted
to
good
leaving
groups.
 Three
general
methods
exist
for
conversion
of
alcohols
to
alkyl
halides,
depending
on
 the
classification
of
the
alcohol
and
the
halogen
desired.

Reaction
can
occur
with
 hydrogen
halides,
phosphorus
tribromide,
or
thionyl
chloride.
 Alkyl
Halides
from
the
Reaction
of
Alcohols
 with
Hydrogen
Halides
 The
order
of
reactivity
is
as
follows:
HI

>

HBr

>

HCl
>
HF.

Type
of
alcohol
3o
>
2o
>
1o
<
 methyl.
 Mechanism
of
the
Reaction
of
Alcohols
with
HX:

SN1
mechanism
for
3o,
2o,
allylic
and
 benzylic
alcohols.

These
reactions
are
prone
to
carbocation
rearrangements.
 In
Step
1
the
hydroxyl
is
converted
to
a
good
leaving
group
by
protonation
to
form
the
 corresponding
oxonium
ion.
 In
Step
2
the
leaving
group
departs
as
a
water
molecule,
leaving
behind
a
carbocation
 In
Step
3
the
halide,
a
relatively...
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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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