Ionic liquids as reagents and solvents in conjunction with microwave heating: Rapid synthesis of alkyl halides from alcohols and nitriles from aryl halides

Article abstract of DOI:10.1016/S0040-4020(03)00214-X

We show that using ionic liquids as reagents in conjunction with microwave heating it is possible to prepare primary alkyl halides from the corresponding alcohols rapidly. Using ionic liquids as solvents in conjunction with microwave heating it is possible to prepare aryl nitriles from the corresponding aryl bromides or iodides. The scope and limitations of using microwave-promotion as a tool in these reactions is discussed.

Full text of DOI:10.1016/S0040-4020(03)00214-X

Tetrahedron 59 (2003) 2253–2258
Ionic liquids as reagents and solvents in conjunction
with microwave heating: rapid synthesis of alkyl halides
from alcohols and nitriles from aryl halides
a,*
a
Nicholas E. Leadbeater, Hanna M. Torenius and Heather Tye
b
a
Department of Chemistry, King’s College London, Strand, London WC2R 2LS, United Kingdom
Evotec OAI, 151 Milton Park, Abingdon, Oxfordshire, OX14 4SD, United Kingdom
b
Received 8 November 2002; revised 13 January 2003; accepted 7 February 2003
Abstract—We show that using ionic liquids as reagents in conjunction with microwave heating it is possible to prepare primary alkyl halides
from the corresponding alcohols rapidly. Using ionic liquids as solvents in conjunction with microwave heating it is possible to prepare aryl
nitriles from the corresponding aryl bromides or iodides. The scope and limitations of using microwave-promotion as a tool in these reactions
is discussed. q 2003 Elsevier Science Ltd. All rights reserved.
1
. Introduction
In this paper we present the first findings from our study into
the scope and limitations of microwave-promotion as a tool
for accelerating organic transformations. The potential
speed and ease of product purification offered by the
microwave/ionic liquid methodology would clearly be of
use when preparing compound libraries. In addition, the
process would be amenable to automation. We focus on the
conversion of alcohols to alkyl halides and the conversion of
aryl halides to nitriles. In the former case, the ionic liquid
acts as a reagent and a solvent and in the latter just as a
solvent. There is precedent in the literature for both these
transformations using ionic liquids as reaction media but
performing the reactions at room temperature or using
Microwave-mediated synthesis is a fast growing area of
research interest as evidenced by the increasing numbers of
papers and patents published in the area. This is because it
is often possible to reduce reaction times from many hours
to a few minutes and it is also opening up avenues for new
1
,2
3
chemistry. Microwave-mediated chemistry is often per-
formed in high boiling polar solvents such as 1-methyl-2-
pyrrolidone (NMP), DMSO and DMF. The high dipole
moments of these solvents means that they can be heated
very rapidly using microwave irradiation. Building on an
4
idea first presented by Ley and co-workers, we have
7
,8
recently explored a methodology for heating non-polar
solvents very rapidly and well above their boiling points by
addition of a small quantity of an ionic liquid to the
medium. Ionic liquids made of organic cations and
appropriate anions have attracted much recent attention as
solvents for chemistry because of the fact that they have
conventional heating methods.
5
2. Results and discussion
2.1. Synthesis of alkyl halides from alcohols
6
melting points close or near to room temperature. They
have negligible vapor pressure and are immiscible with a
range of organic solvents meaning that organic products can
be removed and the ionic liquid recycled. As well as being
used as solvents, a recent report has shown that they can be
Ren and Wu have shown that, using 1,3-dialkylimidazolium
halide-based ionic liquids, it is possible to convert alcohols
to alkyl halides in the presence of either an organic or
7
inorganic acid. However, reaction times are very long
7
used as reagents for synthesis. From the perspective of
generally being between 24 and 48 h. The ionic liquid is
acting as a nucleophile as well as a solvent for the reaction.
When investigating the use of ionic liquids as microwave
heating agents, we found that with those comprising of an
alkylimidazolium cation and a halide anion, when heated
above 2008C decomposition occurs to give an alkyl halide
and an alkyl imidazole as shown in Figure 1. The halide ion,
microwave chemistry the key properties of ionic liquids that
can be exploited are their polarity (around that of methanol)
and, with the appropriate material, their stability at high
temperatures.
2
X , acts as a nucleophile in attacking the cation with the
subsequent elimination of alkyl-X. This decomposition at
elevated temperatures is not totally unexpected. Vacuum
Keywords: ionic liquids; alkyl halides; nitriles.
*
Corresponding author. Tel: þ44-20-7848-1147; fax: þ44-20-7848-2810;
e-mail: nicholas.leadbeater@kcl.ac.uk
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00214-X

2254
N. E. Leadbeater et al. / Tetrahedron 59 (2003) 2253–2258
Table 2. Conversion of alcohols to alkyl halides using ionic liquids
a
Entry
Alcohol
IL
Time
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
1
1
1
1
1
2
3
1
2
3
1
2
3
1
2
3
2
1
2
3
1
2
3
30 s
77
95
75
73
98
52
73
89
54
1-Heptanol
3 min
10 min
30 s
3 min
10 min
30 s
3 min
3 min
3 min
3 min
10 min
3 min
30 s
3 min
10 min
1 min
3 min
10 min
Figure 1. Decomposition of ionic liquids on microwave heating.
pyrolysis of 1-methyl-3-alkyl-imidazolium halides in the
range 300–6008C leads to a similar decomposition, again
forming the corresponding methyl halide and alkylimida-
1-Decanol
10-Undecen-1-ol
9
zole. We wanted to exploit and control this reactivity in the
rapid microwave-promoted conversion of alcohols to alkyl
halides.
b
53
c
b
1,8-Octanediol
86
b
2
3
4
5
50
d
2-Propyn-1-ol
Geraniol
Dec
Dec
Our first objective was to develop a set of working
conditions for the microwave mediated process. Focusing
on 1-octanol, we screened a range of reaction conditions,
varying the microwave irradiation time, the ionic liquid (IL)
and acid used and also investigated the effects of adding a
d
b
47
b
16
30
b
46 (72)
e
1
1
1
7
8
9
b
68
b
Benzyl alcohol
17
1
0
toluene co-solvent. CAUTION!! The results are shown in
Table 1. The ionic liquids chosen for use in our experiments
were 1–3. The temperature of the reaction mixture was
carefully controlled. A microwave power of 100 W was
used, this heating the ionic liquids to 2008C in a matter of
a few seconds (#15 s). The reactions performed using a
co-solvent (2 mL of toluene) took a little longer to heat up
but still reached 2008C within a matter of 30–40 s. We then
held this temperature for the allotted time.
Reactions were run using 1 mmol alcohol, 1 mmol ionic liquid and 1 mmol
acid. Reactions were run using a power of 100 W, a temperature threshold
of 2008C and a pressure threshold of 200 psi. Times shown represent hold
times at the target temperature of 2008C.
a
Isolated yield.
With co-solvent (2 mL toluene).
b
c
0
.5 mmol alcohol used.
Dec¼decomposition observed.
min.
d
e
3
the optimum times being 30 s, 3 min and 10 min, respec-
tively. An important point to note however is that the control
of the reaction time when using 1 is very important. At 30 s
a yield of 1-iodooctane of 81% is obtained, but if the
reaction is left for a further 30 s then product decomposition
is observed. For the reactions involving 1–3 the best
product yields were obtained in the absence of co-solvent.
The use of 2 mL of toluene as a co-solvent decreased the
yield of product formed.
The results show that p-toluene sulfonic acid is superior to
sulfuric acid in the reactions involving the iodo- bromo- and
chloro-ionic liquids. This concurs with the observations of
7
Rex and Wu for the reactions of iodo- and chloro-ionic
liquids in the conversion of alcohols to alkyl halides at room
temperature but differs for bromo-ionic liquids where they
found mineral acids were better than organic acids. As
expected, reaction times using our microwave method are
greatly reduced over those for the room temperature
reactions but follow the same trend i.e. reaction times
increase in going from iodo to bromo to chloro substitutions,
Having found suitable conditions for the reaction we
proceeded to screen a range of different alcohols the results
being shown in Table 2. As with octanol, it is possible to
prepare alkyl halides in good yield from other simple
primary alcohols (entries 1–9). It is also possible to di-
halogenate 1,8-octanediol (entries 10–12) but we find that
this is best achieved with 1–3 using the co-solvent method.
Table 1. Screening of conditions for the reaction of 1-octanol
a
b
Yield (%) without co-solvent
b,c
Yield (%) with co-solvent
Entry
IL
Time
Acid
1
2
3
4
5
6
7
8
9
1
1
1
1
2
2
2
2
3
3
3
30 s
1 min
30 s
1 min
30 s
3 min
30 s
1 min
3 min
3 min
10 min
PTSA
PTSA
81
53
3
56
38
55
15
42
32
59
40
0
H
H
2
SO
SO
4
2
4
38
68
95
73
42
32
49
42
PTSA
PTSA
H
H
2
SO
SO
4
2
4
PTSA
SO
PTSA
1
1
0
0
H
2
4
8
35
Reactions were run using 1 mmol alcohol, 1 mmol ionic liquid and 1 mmol acid. Reactions were run using a power of 100 W, a temperature threshold of 2008C
and a pressure threshold of 200 psi. Times shown represent hold times at the target temperature of 2008C.
a
PTSA¼p-toluene sufonic acid, H
2
SO4¼95% sulfuric acid.
b
c
Isolated yield.
Co-solvent is 2 mL toluene.

N. E. Leadbeater et al. / Tetrahedron 59 (2003) 2253–2258
2255
We believe that the co-solvent method is better because the
organic product is more soluble in the organic solvent than
in the ionic liquid and that once formed it moves to the
organic layer and is protected from decomposition which
can occur in the higher-temperature, acidic ionic liquid
environment. When attempting to use propargyl alcohol as a
substrate in conjunction with 2, significant decomposition
occurred (entry 13). We attribute this to the thermal
instability of the halide product. It is possible to use allylic
and benzylic substrates although yields of product are lower
than in the case of simple primary alcohols. Again we find
that the co-solvent method offers the best route to these
products, for the same reasons. With geraniol (entries
Table 3. Screening of conditions for the Rosenmund-von Braun reaction
a
Entry
IL
Substrate
Time
Product yield (%)
1
2
3
4
5
6
7
2
2
2
2
2
2
4
4-Iodotoluene
4-Iodotoluene
4-Iodotoluene
4-Bromotoluene
4-Bromotoluene
4-Bromotoluene
4-Iodotoluene
1 min
3 min
5 min
3 min
6 min
10 min
3 min
17
75
37
23
41
63
0
Reactions were run using 1 mmol 4-iodotoluene, 2 mmol CuCN and
.5 mL ionic liquid. Reactions were run using a power of 100 W, a
0
temperature threshold of 2008C and a pressure threshold of 200 psi. Times
shown represent hold times at the target temperature of 2008C.
Isolated yield.
a
1
4–16), not unexpectedly geranyl iodide cannot be isolated
but the bromide and chloride can both be obtained. With
benzyl alcohol (entries 17–19), it is possible to obtain the
iodide in moderate yield, the bromide in good yield but only
a low yield of the chloride.
screened a range of reaction conditions, varying the
microwave irradiation time and the IL used. The results
are shown in Table 3. We chose as ILs, 2 and 4. These differ
in the anion and were chosen because they were most easily
manipulated at room temperature, the PF salts of 1 or 2
6
being on the solid/liquid inerface at room temperature.
Our results with primary alcohols compliment those
obtained from the room temperature studies. For simple
aliphatic primary alcohols, our product yields are com-
parable if not better than those obtained at room temperature
although our reaction times are much shorter (30 s–3 min
instead of 5–48 h). Our work with geraniol and benzyl
alcohol represents the first reported attempt to use allylic or
benzylic substrates in the reaction. Our attempts to use
secondary and tertiary alcohols as substrates however have
not met with success; rapid decomposition occuring. This
clearly is a disadvantage of the microwave-methodology
since both secondary and tertiary alcohols can be converted
to the corresponding halides at room temperature albeit
with long reaction times. It could be that when using our
microwave methodology, the product is formed rapidly but
then decomposes, explaining the observation that a mixture
of unreacted starting material and decomposition is all that
is observed at the end of the reaction.
We found that the optimum reaction time for iodo-
substituted substrates is 3 min, leading to a 75% yield of
product, representing a significant improvement over the
isolated yields obtained using similar substrates by heating
using conventional methods (44%). For bromo-substituted
substrates a reaction time of 10 min was required, this
giving a lower yield than in the case of the iodo analogue. Of
particular interest is that only the reactions using the halide-
based ionic liquid worked. Other halide-based ionic liquids
could be used but did not lead to any improvement in
product yields. We have not been able to offer a rationale for
why the reaction using 4 was unsuccessful, but it is rather
surprising. At the temperatures used in these experiments,
2
.2. Synthesis of aryl nitriles from aryl halides
the PF would be expected to be more robust and our
6
The Rosenmund-von Braun reaction (reaction between aryl
halides and copper cyanide to give aryl nitriles) has been
expectation was that this would be a better reaction medium.
It could be that the halide anion in 2 is non-innocent in the
reaction, or offers the optimum ionic environment for
facilitating the reaction. The work-up procedure is very
important. In order to remove all the product from 2 at the
end of the reaction it is necessary to wash the ionic liquid
repeatedly (up to six times) with a hexane: ethyl acetate
mixture. This highlights one of the problems that can be
encountered when using ionic liquids as solvents, namely
product extraction. Although by GC/MS analysis, quanti-
tative yields may be reported, actual isolated yields are often
significantly lower. We screened a range of organic solvents
for their potential for product removal and found that a 4:1
hexane: ethyl acetate mixture was best. This mixture
allowed satisfactory extraction of the product without
solublising the ionic liquid and contaminating the product.
The reactions were run using an excess of CuCN because
the addition of cyanide to aryl halides in the reaction is
known to be reversible so a high concentration of cyanide is
key to driving the reaction towards completion.
1
1
known for over 80 years (Fig. 2). The reaction is usually
carried out at high temperatures (150–2508C) using
solvents such as nitrobenzene, however recently there has
8
been a report of the use of ionic liquids as solvents. When
using 1,3-dialkylimidazolium halide-based ionic liquids it is
possible to obtain moderate isolated yields of product when
performing the reaction using aryl iodides, 2 or 3 equiv. of
CuCN and heating at around 90–1308C for 24 h. We were
keen to investigate the possibility of decreasing the reaction
time and increasing the substrate scope using microwave
promotion.
Our starting point was to develop a set of working
conditions for the microwave mediated process. We
Having found suitable conditions for the reaction we
proceeded to screen a range of different aryl halides the
Figure 2. The Rosenmund-von Braun reaction.

2256
N. E. Leadbeater et al. / Tetrahedron 59 (2003) 2253–2258
Table 4. Conversion of aryl halides to nitriles
Teflon-coated magnetic stir bar in the vessel. In the
reactions presented here, a target temperature was set
together with a maximum microwave power. This maxi-
mum power was then used to heat the reaction mixture to the
target temperature and once there, the microwave power
was varied to hold the mixture at this temperature. This is
defined as the ‘hold time’. A maxiumum pressure of 200 psi
is set, this being a safety precaution since the tubes hold, at
a maximum, a pressure of 250 psi. At the end of a reaction,
the tube and contents were cooled rapidly using a stream of
compressed air. All chemicals used in the reactions were
a
Entry
Alcohol
Reaction time (min)
Yield (%)
1
2
3
4
5
6
7
7
8
4-Iodotoluene
3
75
63
0
4-Bromotoluene
4-Chlorotoluene
4-Iodoanisole
4-Bromoanisole
4-Bromoacetophenone
4-Iodonitrobenzene
4-Bromonitrobenzene
10
10
3
10
10
3
65
40
64
b
55
10
10
16
19
0
4,4 Dibromobiphenyl
1
31
reagent grade and used as purchased. H and P NMR
spectra were recorded at 250 MHz and 293 K.
Reactions were run using 1 mmol aryl halide, 2 mmol CuCN and 0.5 mL
ionic liquid. Reactions were run using a power of 100 W, a temperature
threshold of 2008C and a pressure threshold of 200 psi. Times shown
represent hold times at the target temperature of 2008C.
4
.1.1. Preparation of 1-n-propyl-3-methylimidazolium
a
Isolated yield.
Reaction run at 1508C.
12
b
iodide, 1. To a toluene solution (30 mL) of 1-methyl-
imidazole (5.1 g, 5.0 mL, 62.1 mmol) was added 1-iodo-
propane (10.8 g, 7.20 mL, 63.9 mmol) whilst stirring
vigorously. The mixture was then heated for 3 h during
which time the ionic liquid product 1 separated as a phase
under the toluene solution. After allowing the reaction
mixture to cool, the toluene was decanted off the ionic liquid
and the orange viscous liquid product washed with ethyl
results being shown in Table 4. We found that as well as
being able to use aryl iodide substrates it was also possible
to use aryl bromides and obtain moderate to good yields of
product. This opens up the substrate scope of the reaction.
In the conventional heating experiments, only bromo-
napthalenes have been activated. In the cases of the aryl
iodides we are able to obtain higher isolated product yields
than when the reaction is run using conventional heating and
we also have the advantage of significantly reduced reaction
times. The fact that chloro substrates cannot be activated is
not surprising.
1
acetate (4£20 mL) and dried under vacuum. (97% yield). H
1
NMR (CDCl
, ppm): H 9.80 (s, 1H, NCHN), 7.57 (d, 1H,
3
J¼1.4 Hz, NCHv), 7.54 (d, 1H, J¼1.4 Hz, NCHv), 4.22
(t, J¼7.1 Hz, 2H, CH CH CH ), 3.94 (s, 3H, N-CH ), 1.87
(m, 2H, CH CH CH ).
), 0.89 (t, 3H, J¼7.3 Hz, CH
2
2
3
3
2
2
3
3
4.1.2. Preparation of 1-i-propyl-3-methylimidazolium
bromide, 2. An analogous route to that for 1 was employed
3. Conclusions
but using 2-bromopropane in the place of 1-iodopropane.
1
The yellow viscous product was isolated in 81% yield. H
We have shown here that is is possible to greatly accerate
the rate of reactions performed in ionic liquids as solvents
by using microwave promotion. In the case of the synthesis
of alkyl halides from alcohols, we find that reaction times
can be reduced from 24–48 h down to 3 min. The reaction
works well for primary alcohols but fails when using
secondary or tertiary alcohols as substrates. In the case of
the synthesis of aryl nitriles from the corresponding halides,
we find that reaction times can again be reduced from 24 h
down to 3 min. The reaction works for a range of aryl iodide
and bromide substrates.
NMR (CDCl
J¼1.8 Hz, NCHv), 7.55 (d, 1H, J¼1.8 Hz, NCHv), 4.67
(sep, J¼6.7 Hz, 1H, CH(CH ), 3.94 (s, 3H, N-CH ), 1.43
, ppm): d 10.14 (s, 1H, NCHN), 7.60 (d, 1H,
3
)
3
2
3
5
,12
(d, 6H, J¼6.7 Hz, CH(CH
) ).
3 2
4.1.3. Preparation of 1-n-butyl-3-methylimidazolium
1
3
chloride, 3. To a 1-chlorobutane solution (32 mL) of
1-methylimidazole (5.1 g, 5.0 mL, 62.1 mmol) was added
and then the mixture heated at reflux for 24 h during which
time the ionic liquid product 3 separated as a phase under
the chlorobutane solution. After allowing the reaction
mixture to cool, the chlorobutane was decanted off the
ionic liquid and the colourless viscous product washed with
ethyl acetate (4£20 mL) and dried under vacuum (73%
yield). H NMR (CDCl , ppm): H NMR (CDCl , ppm): d
3 3
4. Experimental
1
1
4
.1. General experimental
1
0.14 (s, 1H, NCHN), 7.79 (d, 1H, J¼1.8 Hz, NCHv),
Microwave experiments were conducted using a CEM
Discovere Synthesis Unit (CEM Corp., Matthews, NC).
The machine consists of a continuous focused microwave
power delivery system with operator selectable power
output from 0 to 300 W. Reactions were performed in glass
vessels (capacity 10 mL) sealed with a septum. The pressure
is controlled by a load cell connected to the vessel via a
7.63 (d, 1H, J¼1.8 Hz, NCHv), 4.37 (t, 2H, J¼7.2 Hz,
CH
CH
CH
CH
CH
2
CH
2
CH
CH
), 4.16 (s, 3H, N–CH
), 1.40 (m, 2H, CH
CH CH CH ).
), 1.92 (m, 2H,
CH CH ) 0.98 (t,
2
2
2
2
3
3
3
CH
2
2
2
3
J¼7.2 Hz, 3H, CH
2
2
2
3
4.1.4. Preparation of 1-n-butyl-3-methylimidazolium
1
4
hexafluorophosphate, 4.
30 mmol) in water (10 mL) was cooled to 08C and to this
was added slowly HPF (4.5 mL of a 60% solution in water,
A solution of 3 (5.24 g,
1
4-gauge needle, which penetrates just below the septum
surface. The temperature of the contents of the vessel was
monitored using a calibrated infrared temperature control
mounted under the reaction vessel. All experiments were
performed using a stirring option whereby the contents of
the vessel are stirred by means of a rotating magnetic plate
located below the floor of the microwave cavity and a
6
30.5 mmol). The mixture was allowed to warm to room
temperature and stirred for 16 h. After separation, the
viscous liquid product was washed with water until the
washings were neutral to universal indicator and then dried
1
under vacuum. 4 was obtained in 61% yield. H NMR

N. E. Leadbeater et al. / Tetrahedron 59 (2003) 2253–2258
2257
(
CDCl , ppm): d 9.08 (s, 1H, NCHN), 7.74 (d, 1H, J¼
Fellowship (N. E. L.) and King’s College London for a PhD
studentship (H. M. T.). EvotecOAI are thanked for a CASE
award (H. M. T.). Financial support from King’s College
London is acknowledged.
3
1
2
1
.7 Hz, NCHv), 7.67 (d, 1H, J¼1.7 Hz, NCHv), 4.15 (t,
H, J¼7.2 Hz, CH CH CH CH ), 3.84 (s, 3H, N–CH ),
.79 (m, 2H, CH CH CH CH ), 1.25 (m, 2H, CH CH CH
2
2
2
2
3
3
2
2
2
3
2
2
3
1
CH ) 0.90 (t, 3H, J¼7.3 Hz, CH CH CH CH ). P NMR
3
2
2
2
3
(
CDCl , ppm): 2142.9.
3
4
.2. General procedure for the synthesis of alkyl halides
References
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1
. For reviews on the area see: (a) Lindstr o¨ m, P.; Tierney, J.;
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1
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products were characterised by comparison of H NMR data
1
5
with that in the literature: 1-bromoheptane, 1-iodohep-
17
2
1
6
18
18
tane, 1-chloroheptane, 1-bromodecane, 1-iododecane,
20
1
9
1-chlorodecane, 1-bromo-10-undecene, 1-iodo-10-
2
undecene, 1-chloro-10-undecene, 1,8-dibromooctane,
1
22
23
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1
7
17
7
1
1
,8-diiodooctane, 1,8-dichlorooctane, 1-bromooctane,
25
2
4
26
-chlorooctane,
1-iodooctane,
geranyl bromide,
2
7
28
29
geranyl chloride, benzyl iodide, benzyl bromide,
3
benzyl chloride, 1-bromo-2-propyne.
0
31
10. Organic reagents and co-solvents are heated well above their
boiling point so all necessary precautions should be taken
when performing such experiments. Vessels designed to
withhold elevated pressures must be used. The microwave
apparatus used here incorporates a protective metal cage
around the microwave vessel in case of explosion. After
completion of an experiment, the vessel must be allowed to
cool to a temperature below the boiling point of the solvent
before removal from the microwave cavity and opening to the
atmosphere.
4
.3. General procedure for the synthesis of nitriles from
aryl halides using ionic liquids and microwave
promotion
Ionic liquid 2 (0.5 mL) was placed into a 10 mL glass
microwave tube and to this was added aryl halidel (1 mmol)
and CuCN (2 mmol). After sealing the tube, the mixture was
irradiated in the microwave reactor. Reactions were run
using a maximum microwave power of 100 W, a tempera-
ture threshold of 2008C and a pressure threshold of 200 psi.
Once the temperature threshold was reached, the reaction
mixture was held there for the requisite time. After the
reaction mixture was cooled, the product was extracted from
the ionic liquid by washing the ionic liquid repeatedly with
aliquots of 1:4 hexane/ethyl acetate (2 mL each time).
Combination of the organic washings and removal of the
solvent by rotary evaporation gave product. Reaction
1
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products were characterised by comparison of H NMR
3
2
data with that in the literature: 4-methoxybenzonitrile,
3
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3
34
4
phenone biphenyl-4,4 -dicarbonitrile.
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0
3
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36
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