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On the reaction of naphthalene anion radical with water
Tetrahedron Letters No.19, PP. 1349-1353, 1965. Printed in Great Britain.
Pergamon Press Ltd.
ON THE REACTION OF NAPHTHALENE ANION RADICAL WITH
WATER
Shelton Bank Esso Research and Engineering Co. Linden, New Jersey and William D. Closson Department of Chemistry Columbia University New York, New York (Received 22 February 1965; in revised form 16 March 1965) We wish
to report the results of experiments that provide insights
into the mechanism
of
both
and the
this
reaction
hydrocarbon aromatic
is
recovered
hydrocarbons
A mechanism
fhe
(I)
reaction
of
related
unchanged are
proposed
formed, by Paul,
aryl
anion
radicals
carbonation
reaction,
and dihydro
derivatives
in
the
absence
of
with half of
excess
water. of the
alkali
the
In original
parent metal.
(1,2,3)
and Weissman (4), to account for these
Lipkin,
observations, involves the sequence of steps shown in equations 1-3. .2rHr+ ~~0 j
~~2.
+ OH-
ArH2' + ArH'.->ArH2-
(1)
+ ArH
ArH2- + H20 dArH3
(2)
+ OH-
(3)
Two attractive alternate mechanisms which can account for the observed products
involve
reaction,
(II)
disproportionations: (eq.
4.
Al-H’ + 2
a radical
dynamically
less
a radical
disproportionation
5); --
and second,
first
anion
favored(5)
HzO--_j
ArH2. ->
ArH2’
(4)
ArH3 + ArH
disproportionation (but
+ OH-
probably
1349
(III)
(5) to
more reactive)
give
the
dianion
thermo(eq.
6,
7,
8).
No. 19
1350
2 ArH- b
ArH= + ArH
(6)
ArH= + Hz0 .-,
ArH2- + OH-
(7)
ArH2- + H20 ->
ArH3 + OH-
(8)
It is known that partial protonation of certain aryl anion radicals wfth stearyl alcohol in the presence of excess alkali metal yields a solution of the dihydro ani0n~(ArH2-)(~),
and that under certain conditions
some aryl anion radicals disproportionate (eq. 6).
to dianion and hydrocarbon. (5a,7)
And it is known that very recently a stable dianion of naphthalene
was prepared using lithium in tetrahydrofuran.(8)
Nevertheless,
it was not
known whether either of these species is of importance in the reaction with water, nor had any test of the proposed mechanism been performed.
We anticipated
that infor,nation concerning the validity of the above mechanisms
could be
provided by a study of the products resulting from reaction with labeled water. 4 solution of sodium naphthalene
prepared from 1.60 g. (12.5 mmole)
of naphthalene and 0.30 g. (13 mmole) of sodium in 40 ml. of tetrahydrofuren was quenched with 2.0 ml. of Hz0 (1 millicurie/ml.).
The products were
isolated by addition of water and extraction with pentane. ments indicated that recovered material accounted naphthalena.
Separate experi-
for 95-98% of the original
Analysis of the reaction products, performed on a radioassaying
gas chromatography
apparatus, indicated 40.7% dihydronaphthalenes,
naphthalen,?, and 0.6% tetralin. in the dihydronaphthalenes
58.1%
_ All of the radioactivity was concentrated
and tetralin.
the naphthslene by recrystallization
This was confirmed by isolating
(mp 80-80.5') and subsequent analysis
of large s.amples. Hence, no low level activity h‘as present in the naphthalene. The analytical method would have detected 0.1% of the activity found for dihydronaplthalene.
No.19
In a separate added
slowly
to
period
of
drive”
apparatus.
experiment
tritiated
a tetrahydrofuran
two hours.
solution
The water
15% dihydronaphthalenes,
the material
presumably
mixture
to
(1 millicurie/ml.)
sodium
(69% yield)
and analyzed
as above
can make the
reasonable
over rate
consisted
and 2% tetralin.
“dimer.
was
naphthalene
in by a “constant
material
naphthalene,
reaction
of
was metered
The recovered
goes
water
a
syringe
of
83%
The remainder
V(9)
Naphthalene
again
was completely
isolated
of
from
devoid
this
of
radioactivity. If water of
results
the
in attachment
anion
or hydride species is
one
radical ion
ruled
out
from
unless
the
indelibly
transfer
derived
of
it,
proton
marks
between
assumption
the
it
by a normal for
products
of
radical
an act
with
bond,
Proton,
protonated
anion
such
reaction
sigma
reduction.
originally
and liaphthalene
both
that
protonation hydrogen
species,or or neutral
are
eventually
atom,
any naphthalene,
converted
to dihydronaphthalenes, Clearly that
the
mechanism
recovered
effect
is
should
expected
would
of of
formed
have
for
Disproportionation thalene
would
The radical
water
must not
naphthalene
considerations. tritiated
II
course
be labeled by reaction
a corresponding
proton such
be valid
lead
to
this
according
to
of
the
activity
abstraction
a labeled
because
radical
of
anion
by strong
tritium
predicts
following
no kinetic
to naphthalene
incorporation
the
radical
since
reactions
scheme
bases.
and isotope (10)
and dihydronaphin
the
recovered
naphthalene. Moreover, is
unlikely
for
must be very excess
of
irreversible.
the
rapid
water
the
is
results
following if
the
added
When small
suggest reasons.
scheme
is
rapidly, quantities
(but
do not
demand)
The equilibrium to account
reactions of
water
for
the
that
depicted results.
7 and 8 must br rapid arc
added
slowly.
mechanism
III
in equation tihcn 311 nnd moreover however,
the
6
No.19
1352
concentration of ArH2- is expected to build up and proton transfer between ArH2- and ,irH=would seem plausible. of tritium into naphthalene.
This, of course, results in incorporation
Indeed these experiments, which provide the
first test of Paul, Lipkin, and Weissman mechanism, reinforce the proposed scheme. In addition to information about the mechanism of the quenching reaction, our analytical scheme provides the detection of tetralin, heretofore unreported. tetralin fcrmatfon.
The data provide insights into the probable path of
The fact that no activity is found in the naphthalene
while the tetralin does have activity rules out a reaction in which the dihydronaphthalene (ArH3) undergoes base-catalyzed disproportionation, in a manner similar to the reaction of 1,3_cyclohexadiene in the presence of strong base.(l')
It is evident that no dihydronaphthalene can be converted
to naphthalene in the tetralin formation process.
A scheme to account for
these facts is given in equations 9-12. ArH3 + ArH7-j
ArH3' + ArH
(9)
ArH3: + H20 ->
ArH4' + Oy-
(10)
ArH4. + ArH:ArHh- + H20 _Ij
ArH&- + ArH
(11)
ArH5 + OH-
(12)
The critical step in this process, electron transfer from the naphthalene anion radical to.dihydronaphthalene, is quite plausible since the reduction potential oE 1,2_dihydronaphthalene is of the same magnitude as that of naphthalene.(12)
A scheme involving disproportionation of the dihydronaphtha-
lene radical anion to give a dinegative species is far less likely in view of the anticipated high energy of this intermediate.
Insofar as the formation
of dihydronaphthalene from naphthalene and the formation of tetralin from
No.19
1353
dihydronaphthalene are related these considerations contribute additional support that mechanism II is unlikely. Acknowledgement - We would like to thank Dr. A. Schriesheim for his encouragement and stimulation.
REFERENCES 1.
N. D. Scott, J. F. Walker, and V. L. Hansley, J. Am. Chem. Sot., 2442 (1936). W. E. Bachmann, J. Org. Chem.,
2, -
1, 347 (1936).
J. F. Walker and N. D. Scott, J. Am. Chem. Sot., 60, 951 (1938). D. E. Paul, D. Lipkin, and S. I. Weissman, ibid., 2,
116 (1956).
(a) G. J. Hoijtink, E. de Boer, P. H. van der Meij, and W. P. Weijland, RfX. trav. chim. , 75, 487 (1956). (b) S. Wawzonek and J. W. Fang, J. Am. Chem. Sot., 68, 2541 (1946), and previous papers. 6.
N. H. Velthorst, Thesis, Free University of Amsterdam, 1963.
7.
N. S. Hush and J. Blackledge, 3. Chem. Phys.,
a.
J. Smid, J. Am. Chem. Sot.,
9.
N. D. Scott and J. F. Walker, U. S. Patent 2,194,450 (1940).
10.
23, 514 (1955). -
87, 655 (1965).
-
L. 0. Assarson, Acta Chem. Stand.,
l2, 1547 (1958).
-
11. J. E. Hofmann, P. A. Argabright, and A. Schriesheim, Tetrahedron Letters, No. 17, 1005 (1964). 12. A. C. Aten, C. BGthker, and G. J. Hoijtink, Trans, Faraday Sot., 55, 324 (1959).
Pergamon Press Ltd.
ON THE REACTION OF NAPHTHALENE ANION RADICAL WITH
WATER
Shelton Bank Esso Research and Engineering Co. Linden, New Jersey and William D. Closson Department of Chemistry Columbia University New York, New York (Received 22 February 1965; in revised form 16 March 1965) We wish
to report the results of experiments that provide insights
into the mechanism
of
both
and the
this
reaction
hydrocarbon aromatic
is
recovered
hydrocarbons
A mechanism
fhe
(I)
reaction
of
related
unchanged are
proposed
formed, by Paul,
aryl
anion
radicals
carbonation
reaction,
and dihydro
derivatives
in
the
absence
of
with half of
excess
water. of the
alkali
the
In original
parent metal.
(1,2,3)
and Weissman (4), to account for these
Lipkin,
observations, involves the sequence of steps shown in equations 1-3. .2rHr+ ~~0 j
~~2.
+ OH-
ArH2' + ArH'.->ArH2-
(1)
+ ArH
ArH2- + H20 dArH3
(2)
+ OH-
(3)
Two attractive alternate mechanisms which can account for the observed products
involve
reaction,
(II)
disproportionations: (eq.
4.
Al-H’ + 2
a radical
dynamically
less
a radical
disproportionation
5); --
and second,
first
anion
favored(5)
HzO--_j
ArH2. ->
ArH2’
(4)
ArH3 + ArH
disproportionation (but
+ OH-
probably
1349
(III)
(5) to
more reactive)
give
the
dianion
thermo(eq.
6,
7,
8).
No. 19
1350
2 ArH- b
ArH= + ArH
(6)
ArH= + Hz0 .-,
ArH2- + OH-
(7)
ArH2- + H20 ->
ArH3 + OH-
(8)
It is known that partial protonation of certain aryl anion radicals wfth stearyl alcohol in the presence of excess alkali metal yields a solution of the dihydro ani0n~(ArH2-)(~),
and that under certain conditions
some aryl anion radicals disproportionate (eq. 6).
to dianion and hydrocarbon. (5a,7)
And it is known that very recently a stable dianion of naphthalene
was prepared using lithium in tetrahydrofuran.(8)
Nevertheless,
it was not
known whether either of these species is of importance in the reaction with water, nor had any test of the proposed mechanism been performed.
We anticipated
that infor,nation concerning the validity of the above mechanisms
could be
provided by a study of the products resulting from reaction with labeled water. 4 solution of sodium naphthalene
prepared from 1.60 g. (12.5 mmole)
of naphthalene and 0.30 g. (13 mmole) of sodium in 40 ml. of tetrahydrofuren was quenched with 2.0 ml. of Hz0 (1 millicurie/ml.).
The products were
isolated by addition of water and extraction with pentane. ments indicated that recovered material accounted naphthalena.
Separate experi-
for 95-98% of the original
Analysis of the reaction products, performed on a radioassaying
gas chromatography
apparatus, indicated 40.7% dihydronaphthalenes,
naphthalen,?, and 0.6% tetralin. in the dihydronaphthalenes
58.1%
_ All of the radioactivity was concentrated
and tetralin.
the naphthslene by recrystallization
This was confirmed by isolating
(mp 80-80.5') and subsequent analysis
of large s.amples. Hence, no low level activity h‘as present in the naphthalene. The analytical method would have detected 0.1% of the activity found for dihydronaplthalene.
No.19
In a separate added
slowly
to
period
of
drive”
apparatus.
experiment
tritiated
a tetrahydrofuran
two hours.
solution
The water
15% dihydronaphthalenes,
the material
presumably
mixture
to
(1 millicurie/ml.)
sodium
(69% yield)
and analyzed
as above
can make the
reasonable
over rate
consisted
and 2% tetralin.
“dimer.
was
naphthalene
in by a “constant
material
naphthalene,
reaction
of
was metered
The recovered
goes
water
a
syringe
of
83%
The remainder
V(9)
Naphthalene
again
was completely
isolated
of
from
devoid
this
of
radioactivity. If water of
results
the
in attachment
anion
or hydride species is
one
radical ion
ruled
out
from
unless
the
indelibly
transfer
derived
of
it,
proton
marks
between
assumption
the
it
by a normal for
products
of
radical
an act
with
bond,
Proton,
protonated
anion
such
reaction
sigma
reduction.
originally
and liaphthalene
both
that
protonation hydrogen
species,or or neutral
are
eventually
atom,
any naphthalene,
converted
to dihydronaphthalenes, Clearly that
the
mechanism
recovered
effect
is
should
expected
would
of of
formed
have
for
Disproportionation thalene
would
The radical
water
must not
naphthalene
considerations. tritiated
II
course
be labeled by reaction
a corresponding
proton such
be valid
lead
to
this
according
to
of
the
activity
abstraction
a labeled
because
radical
of
anion
by strong
tritium
predicts
following
no kinetic
to naphthalene
incorporation
the
radical
since
reactions
scheme
bases.
and isotope (10)
and dihydronaphin
the
recovered
naphthalene. Moreover, is
unlikely
for
must be very excess
of
irreversible.
the
rapid
water
the
is
results
following if
the
added
When small
suggest reasons.
scheme
is
rapidly, quantities
(but
do not
demand)
The equilibrium to account
reactions of
water
for
the
that
depicted results.
7 and 8 must br rapid arc
added
slowly.
mechanism
III
in equation tihcn 311 nnd moreover however,
the
6
No.19
1352
concentration of ArH2- is expected to build up and proton transfer between ArH2- and ,irH=would seem plausible. of tritium into naphthalene.
This, of course, results in incorporation
Indeed these experiments, which provide the
first test of Paul, Lipkin, and Weissman mechanism, reinforce the proposed scheme. In addition to information about the mechanism of the quenching reaction, our analytical scheme provides the detection of tetralin, heretofore unreported. tetralin fcrmatfon.
The data provide insights into the probable path of
The fact that no activity is found in the naphthalene
while the tetralin does have activity rules out a reaction in which the dihydronaphthalene (ArH3) undergoes base-catalyzed disproportionation, in a manner similar to the reaction of 1,3_cyclohexadiene in the presence of strong base.(l')
It is evident that no dihydronaphthalene can be converted
to naphthalene in the tetralin formation process.
A scheme to account for
these facts is given in equations 9-12. ArH3 + ArH7-j
ArH3' + ArH
(9)
ArH3: + H20 ->
ArH4' + Oy-
(10)
ArH4. + ArH:ArHh- + H20 _Ij
ArH&- + ArH
(11)
ArH5 + OH-
(12)
The critical step in this process, electron transfer from the naphthalene anion radical to.dihydronaphthalene, is quite plausible since the reduction potential oE 1,2_dihydronaphthalene is of the same magnitude as that of naphthalene.(12)
A scheme involving disproportionation of the dihydronaphtha-
lene radical anion to give a dinegative species is far less likely in view of the anticipated high energy of this intermediate.
Insofar as the formation
of dihydronaphthalene from naphthalene and the formation of tetralin from
No.19
1353
dihydronaphthalene are related these considerations contribute additional support that mechanism II is unlikely. Acknowledgement - We would like to thank Dr. A. Schriesheim for his encouragement and stimulation.
REFERENCES 1.
N. D. Scott, J. F. Walker, and V. L. Hansley, J. Am. Chem. Sot., 2442 (1936). W. E. Bachmann, J. Org. Chem.,
2, -
1, 347 (1936).
J. F. Walker and N. D. Scott, J. Am. Chem. Sot., 60, 951 (1938). D. E. Paul, D. Lipkin, and S. I. Weissman, ibid., 2,
116 (1956).
(a) G. J. Hoijtink, E. de Boer, P. H. van der Meij, and W. P. Weijland, RfX. trav. chim. , 75, 487 (1956). (b) S. Wawzonek and J. W. Fang, J. Am. Chem. Sot., 68, 2541 (1946), and previous papers. 6.
N. H. Velthorst, Thesis, Free University of Amsterdam, 1963.
7.
N. S. Hush and J. Blackledge, 3. Chem. Phys.,
a.
J. Smid, J. Am. Chem. Sot.,
9.
N. D. Scott and J. F. Walker, U. S. Patent 2,194,450 (1940).
10.
23, 514 (1955). -
87, 655 (1965).
-
L. 0. Assarson, Acta Chem. Stand.,
l2, 1547 (1958).
-
11. J. E. Hofmann, P. A. Argabright, and A. Schriesheim, Tetrahedron Letters, No. 17, 1005 (1964). 12. A. C. Aten, C. BGthker, and G. J. Hoijtink, Trans, Faraday Sot., 55, 324 (1959).