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Patented July 11, 1950
‘i 7
2,514,387
ES PATENT 1'
2,514,387
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PREPARATION-0F LI-DICYANO ETHYLENE
;:BY ‘THE PYROLYSIS OF 1,1,3,3-TETRA
CYANO PROPANE
“ Harry Gilbert, Cuyahoga Falls, Ohio, asslgnor to
vThe B. F. Goodrich Company, New York, N.,Y., .
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a corporation of New York
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‘No Drawing. Application March 4. 1949,
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Serial No. 79,712
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(01. 260-4658)
11 Claims.
This invention relates to a method for the
preparation of 1,1-dicyano ethylene. which meth
therefore desirable that reduced pressures "or
higher temperatures, preferably both, be “em
ployed, whereupon the thermal decomposition of
the 1,1,3,3 -tetraoyano‘propane proceeds quite
od involves the thermal decomposition of 1,13,3
tetracyano propane.
In copending applications of 'Alan E. Ardis,
rapidly. In this connection it has beenpfound
that pressures‘ of approximately 2;to,;50 mm. of
mercury are preferably used while temperatures
of from 150° C. to;250° C. are especially preferred.
Serial Nos. 785,520,'?led November 7, 1947 now
Patent Number 2,476,270, and 63,434, ?led Decem
ber 3, ‘1948 now ,Patent Number 2,502,412, two
,novel'methods'i'or the preparation of ,1,1-dicyano
'jethylene'j‘are disclosed. Tha?rst. method in
_:'volves, the pyrolysis of l-acetoxy-Ll-dicyano
The thermal decomposition reaction maybe
carried out in any one of a number-of di?ferent
manners.
For. examplerone preferred-method
ethane to give 1,1-‘dicyano, ethylene and acetic
consists simply in heating the 1,1,3,3-tetracy_ano
acid, and the second method involves the pyrolysis
_', of compoundsof the general formula
propane, a white solid, in a distillation apparatus
whereupon vapors of 1,1-‘dicyano ethylene) are
formed, and collecting and condensing itheji/re
suiting vapors in a suitable receiver, preferably
provided with external cooling means. _ Alterna
Qwh'ereinX and "Y are selected from the class con-,
sisting of ,-_—'CN and‘—CONHz groups to give 1,1
dicyanoethylene' and butadiene.
_‘
' '
'
I have now discovered that 1,1-dicyano'ethyl
‘tively, however, the reaction may be, carried out
by passing the 1,l,3,3-'tetracyano propane through
20 a heated metal or glass pyrolysis tube and con
densing the eiiluent vapors or by other methods
- of thermal decomposition. When the thermal de
composition is accomplished in the above manner
the product which collects in thereceiver is a mix
1,1,3,3-,~._ .25 ture of 1,1-dicyano ethylene, malononitrile, and in
ene may also be readily prepared in excellent
,yields by the thermal decompositionof
tetracyan'o propane. In addition to l,l-dicyan_o
ethylene, some malononitrile is alsov formed, the
'_ pyrolysis’ ‘reaction proceeding substantially as fol
lows:
_.
'
some instances; small quantities of 1,1,3,3-tetr-a
cyano propane. The l,l-dicyano ethylene is then
separated from the mixture ‘by utilizing any. of
several methods of separation. For example; one
.
p30 method of separating the 1,1,-dicyano' ethylene
consists in utilizing the tendencyof monomeric
I,1-dicyano ethyleneto polymerize on standing
or on heating, and allowing “it to polymerize,.;or
-' even adding'water to hasten the'polymerization.
i
reactionprovides a valuable‘ and economi-ii 35 An alcohol such as ethyl, propyl or butylalcohol.
or the like, is then added to the mixture to dis
solve the malononitrile and any 1,1,3B-tetra
cal method for the preparation of 1,1-dicyano
ethylene since the starting material, 1,l,3,3-tetra
’ cyano propane which might be present and'the
cyano propane, is easily prepared by the reaction
of malon'onitrile and .formaldehyde in aqueous
~solution.
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The precise ‘conditions under which the'thermal
I.‘ decomposition, reaction is carried out are‘not
strictly critical provided, of course, that the heat
insoluble polymer is removed by ?ltering.’ vThe
.
polymerized 1,1-dicyano ethylene ' can then be
depolymerizedi by pyrolysis, preferably at term
' peratures of 170° C. to 250° C., to obtain very pure
monomeric‘ 1,1-dicyano ethy1en'e,- a process dis‘
closed ‘in a cope'nding application, Serial -_No.
: ing'of the‘1,1,3,3-tetracyano propane be su‘?icient
"
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'- 1
- 5
‘to cause ‘the'evolution of vapors.‘ The tetra 45 79.713, ?led Mar. 4, 1949.
"A second and the preferred method consists
icyanoi propane is‘! itself thermally unstable and
simply in fractionating the mixture from there
does not exist in the gaseous formii Vapors con
ceiver in an efficient column, and ‘preferably at
taining the desired 1,1edicyano iethylene are
evolved when l,l,3,3‘-tetracyano propane is heated “reduced pressures. "l,l-'-dicyano ‘ethylene 'distills
at 47° C. at 2 mm. and malononitrile 'atf90°'C2.at
under atmospheric pressure, towa temperature
just above its melting point, thatis, just above
2mm‘.
A third
. useful
.
i method of separation
>
involves
I
137° C., and accordingly these conditions are op
treating the reaction mixture with a conjugated
erative. However,- the reaction proceeds very
slowly at atmospheric pressures when tempera
.d-iole?n such as '"butadiener' or :cyclopentadiene
tures belowabout 150° C-uare utilized and it is 55 which‘ reacts- with the > 1,1-dicyano - ethylene, to
2,514,887
3
temperature of 150° C. 44.7 parts (93%) or sub
stantially pure monomeric 1,1-dicyano ethylene
form a solid substituted cyclohexane which can
be separated from the malononitrile and impuri
ties and pyrolyzed again at temperatures in ex
cess of 400° C. to give monomeric 1,1-dicyano
(M. P. 8° C.) are obtained.
Example III
60 parts of 1,1,3,3-tetracyano propane are
ethylene and the conjugated diolefln.
When using either of the latter two methods,
it is desirable that the 1,1-dicyano ethylene be
stabilized against polymerization from the time
that it is formed. This may beaccomplished
pyrolyzed at a pressure of 2 mm. and a tempera
ture of 180° C. through a plug of phosphorus
pentoxide into a receiver maintained at a tem
by using a suitable LI-dicyanqethylene stabilizer * X perature of 770" C. until all the material is
pyrolyzed. The mixture in the receiver is then
fractionated ‘into a ?ask containing phosphorus
(that is, a polymerization inhibitor) which‘ may
be mixed with the l,l,3,3-tetracyano propane
prior to pyrolysis or placed in the receiver for
the pyrolysis product. Such a stabilizer is also
pentoxide whereupon 20 parts of monomeric 1,1
dicyano ethylene (M. P. 8° C.) are obtained.
vii'mample IV
preferably present in the receiver used to col- - Li
lect the 1,1-dicyano ethylene when it is separated
by distillation and when it is" desired to obtain,
the monomer by pyrolysis of the polymer or the
conjugated diole?n product. suitablestabilizers
include phosphorus pentoxide and phosphorus
.12 ‘parts of 1,l,3,3-tetracyano propane are '
heated at a temperature of 180° C. and a pressure
- of 2 mm. in a distillation ?ask and the vapors
conducted into a receiver maintained at -70° C.
1.9 parts of monomeric LL-dicyano ethylene and
vpentasul?de, which are preferred, as well as cer
7.7 parts of polymeric 1,1-dicyano ethylene are
obtained. 1 part of malononitrile is also ob
tained. The polymer thus obtained is converted
to substantially pure monomer by depolymeriza
tion at temperatures of 170° -C. to 250° C.
Example V
10 parts of 1,1,,3,3-tetracyano propane are
tain phenolic materials such as vpicric acid, trini
trobenzene and pyrogallol,' or the stabilization
may be accomplished simply by passing a cur
rent of sulfur dioxide through the pyrolysis sys
tem, the oxides of sulfur in general being excellent
stabilizers for the monomer. The stabilizer may
be present in any desired amount but in gen
eral as little as 0.5 to 3% based on, the amount
heated at a temperature of 200° C. and a pressure
of monomer is suiiicient to prevent polymeriza 30 of 50 mm. in, a distillation ?ask connected to a
tion for extended periods of time.
>
i
receiver containing para-isopropyl toluene (para—
In addition to the methods disclosed herein
above, still another useful method for collecting
cymene).
The vapors formed are introduced
into the receiver below the surface of the para
and separating the 1,1-dicyano ethylene exists.
iscpropyl toluene. The monomeric 1,1-dicyano
This method comprises directing the pyrolysis 35 ethylene
and the maloncnitrile formed are solu
vapors ‘into a receiver containing a liquid hydro
ble in the para-isopropyl toluene while the small
carbon such as toluene, isopropyl toluene (p
amount of 1,1,3,3-tetracyano propane which is
cymene) and the like. 1,1-dicyano ethylene and
formed by the reversibility of the thermal decom
malononitrile are soluble in such hydrocarbons
while any 1,1,3,3-tetracyano propane present is 40 position reaction is insoluble and is removed by
?ltering. The ?ltrate is fractionated and 2 parts
insoluble and can ‘be removed simply by ?ltering.
of monomeric 1,1_-dicyano ethylene .(M. P. 'Z°—8°
Upon fractionation of the ?ltrate, ‘monomeric
C.) are obtained.
17,1-dicyano ethylene is obtained in a very pure
Example VI
form. Alternatively, the 1,1-dicyano ethylene
can be recovered from the liquid mixture by cool
ing; to a temperature below about »i~.20° C. where
(5
upon the monomer crystallizes and can be re
moved by ?ltering.
' '
10 parts of l,1',3,_3-tetracy_.ano, propane are
heated to a temperature of 170° C. and at a, pres
sure of 2 mm. in a distillation ?ask connected
to a receiver. A current of sulfur dioxide is con
‘
The following speci?c examples are. intended
tinuously passed through the entire apparatus
to illustrate the preparation of 1,1-dicyano 50 to inhibit the polymerization of the 1,1-dicyano
ethylene ‘by, the method of this invention, .but
ethylene. The contents of the receiver are frac
are not intended to be construed as limiting the
tionated in a 12 inch column packed with glass
scope thereof, for there are, of course, numerous
helices and 4 parts of substantially pure mono
possible variations and modi?cations. In the
meric 1,1-dicyano ethylene (M. P. 6°-8° C.) are
examples all parts are by weight.
obtained. 3% parts of malononitrile are also
obtained.
Example I
Example ‘VII
190 parts (1.32 moles) of l,l,3,3-tetracyano
propane are placed in a distilling ?ask which is
connected to a receiver. The receiver is cooled
to -5' C. and is lined with phosphorus pentoxide
10 parts of 1,1,3,3!tetracyano propane main
tained in a pyrolysis ?ask are heated to a tem
perature of 200° C. at 1 mm. pressure and the re
sulting vapors condensed in a receiver cooled to
‘to inhibit the polymerization. of the 1,1-dicyano
ethylene. The LLSB-tetracyano propane is then
0° C. ‘Polymeric Ll-dioyano ethylene is, recov
ered from the mixture
the receiver by adding
ethyl alcohol to the mixture and filtering off the
heated to a temperature of 180° C‘. and at a pres
sure of 2 mm. until all the starting material is
thermally decomposed. ‘The contents of the re
ceiver are then fractionated’ through a 12 inch
insoluble polymer. The polymer thus obtained
gives the following analysis:
column packed with glass helices. 82.5 parts
680%) of monomeric Ll-dicyano ethylene (Np2o
1.442, M; P. 8° C., B. P. 47° (1/2 mm.) are ob
tained. '70 parts of malononitrile are also, ob
tained.
-'
Example If
70
‘
-
Calculated
Found
C, 51.55%
H, 2.58%
C, 60.03%
H, 2.99%.‘
N.e,5.e0%,
N, 36.58%
7
'90' parts (.65 mole) of 1,1,3,3-tetracyano pro
pane are pyrolyzed as in Example I, utilizing a 75
When the above examples are repeated utiliz
2,514,887
5
ing atmospheric pressures and/or temperatures
monomeric 1,1-dicyano ethylene from the result
in excess of 250° C., 1,1-dicyano ethylene is again
obtained in good yield although the yields are
ing condensate.
not as high as those obtained when the preferred
tetracyano propane at a temperature in excess of
150° C., at a reduced pressure, andin the pres—
‘
7. The method which comprises heating 1,13,3
conditions are utilized.
1,1-dicyano ethylene prepared by the method
ence of phosphorus pentoxide whereupon vapors
are evolved, condensing the e?iuent vapors, and
of this invention is very valuable for the prepara
tion of polymers and copolymers suitable as syn
separating monomeric 1,1-dicyano ethylene from
thetic rubbers, synthetic resins and plastics.
the resulting condensate.
Furthermore, the polymers of 1,1-dicyano ethyl-l 10 8. The method which comprises heating 1,l,3,3
ene are extremely useful in the preparation of
spinning solutions from which can be spun ?bers
and ?laments possessing many valuable proper
tetracyano propane at a temperature in excess
of 150° C., at a pressure below 100 mm., and in
ties including great tensile strength and resist
vapors are evolved, condensing the effluent vapors,
the presence of phosphorus pentoxide whereupon
ance to abrasion and chemical action.
15 and separating monomeric 1,1-dicyano ethylene
This application is a continuation-in-part of
from the resulting condensate.
and a replacement for my application, Serial No.
9. The method which comprises heating 1,1,33
775,149, ?led September 19, 1947, now abandoned.
tetracyano propane at a temperature in excess of
Numerous variations and modifications in the
150° 0., at a reduced pressure whereupon vapors
above procedure will be apparent to those skilled 20 are evolved, collecting said vapors in a receiver‘
in the art and are included within the scope of
containing para-isopropyltoluene, and separat
the invention as de?ned in the appended claims.
ing 1,1-dicyano ethylene from the resulting mix
I claim:
'
ture.
1. The method which comprises heating 1,1,33
‘
10. The method which comprises heating
1,1,3,3-tetracyano propane at a temperature in
tetracyano propane at a temperature and pres
sure such that vapors are evolved, condensing the
excess of 150° 0., at a reduced pressure, and in
the presence of sulfur dioxide whereupon vapors
are evolved, condensing the eiiluent vapors‘, and
eilluent vapors, and separating 1,1-dicyano ethyl~
ene from ,the resulting condensate.
2. The method which comprises heating 1,1,13,3
separating monomeric 1,1-dicyano ethylene from
tetracyan’o propane at a temperature in excess of 30 the resulting condensate.
150° C. whereupon vapors are evolved, condens
11. The method which comprises heating
ing the ef?uent vapors, and separating 1,1-di
1,1,3,3-tetracyano propane at a temperature and
cyano ethylene from the resulting condensate.
pressure such that decomposition occurs to form
3. The method which comprises heating 1,1,3,3
vapors of 1,1-dicyano ethylene and malononitrile
tetracyano propane at a temperature of 150° to 35 and separating the 1,.1-dicyano ethylene from the
250° C. whereupon vapors are evolved, condensing
malononitrile.
the eilluent vapors, and separating 1,1-dicyano
HARRY GILBERT.
ethylene from the resulting condensate.
4. The method which comprises heating 1,1,3,3~
REFERENCES CITED
tetraoyano propane at a temperature in excess 40 The following references are of record in the
of 150° C. and at a reduced pressure whereupon
?le of this patent:
vapors are evolved, condensing the e?luent vapors,
UNITED STATES PATENTS
and separating 1,1-dicyano ethylene from the re
Number
Name
Date
sulting condensate.
5. The method which comprises heating 1,1,3,3~
45
tetracyano propane at a temperature in excess of
150° C. and at a pressure below 100 mm. where
upon vapors are evolved, condensing the e?luent
2,467,378
2,476,270
Gilbert __________ __ Apr. 19, 1949.
Ardis ____________ __ July 19, 1949
OTHER REFERENCES
vapors and separating 1,1-dicyano ethylene from.
the resulting condensate.
6. The method which comprises heating 1,1,3,3
Ostling: Chem. Abstracts, vol. 15, p. 2829
(1921).
Diels et al.: Ber. Deut. Chem., vol. 55, pp.
tetracyano. propane at a temperature in excess
3445-3446 (1922).
of 150° C. and in the presence of phosphorus
pentoxide whereupon vapors are evolved, con
Conn et al,: Ber. Deut. Chem., vol. 56, 2076
2080 (1923).
densing the
e?iuent vapors,
and separating '
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