Aug. 15, 1967 ' P. 0. 'zAvlTsAN'os 3,336,359 ' I 'DICYANOACETYLENE’SYNTHESIS Filed Dec. 18, 1964 ‘ 14 35v \24 26 INVENTOR, PETER D. ZAVITSANOS BY/Mw; W/fwfm AGENT 3,336,359 United States Patent 0 ” cIce Patented Aug. 15,- 1967 1 2 3,336,359 in more detail hereinafter) lies in the ?eld of inductor DICYANOACETYLENE SYNTHESIS 20 (here represented as edgewise wound copper strip, Peter D. Zavitsanos, Norristown, Pa., assignor to General sectioned at a plane through its central axis) which is the Electric Company, a corporation of New York output coil of a radio frequency furnace or induction heater Filed Dec. 18, 1964, Ser. No. 419,427 22 of the kind used for many years in outgassing radio 3 Claims. (Cl. 260—465.8) tubes during manufacture. A source of nitrogen 24 (rep resented as a conventional compressed gas cylinder) is represented connected through a conventional diaphragm ABSTRACT OF THE DISCLOSURE reducing valve 26 to a U-tube 28, whose lower part is Dicyanoacetylene is formed by direct combination of 10 immersed in a beaker 30 which is partly ?lled with a solu gaseous nitrogen with carbon heated to 2376 to about 3,000 tion 32 of carbon dioxide in acetone. In actual practice, degrees K., uncombined nitrogen and reaction products beaker 30 will be surounded by some thermal insulation ?owing away to a cooler region where products may be such as glass wool or simple cotton batting; or a Dewar separated by condensation. ?ask may replace the beaker 30. The function of the ?rst 15. U-tube 28 is simply to refrigerate incoming nitrogen to insure the removal of most of the water or hydrocarbon This invention pertains to the art of organic chemistry vapor present in the commercial gas. It is particularly de and speci?cally to a way of preparing dicyanoacetylene, sirable to minimize the hydrogen concentration in the ap C4N2. paratus because hydrogen will readily enter into combina Dicyanoacetylene was ?rst prepared by C. Maureau in 20 tion with the reactive materials present, producing un 1909, as reported in Bull. Soc. Chim. (V), p. 846. His desired side products. The nitrogen thus puri?ed passes process involved several steps. First, he replaced the hy through a tube 34 to a port 36 at the top of tube 12, ?ow drogen in each carboxyl group of acetylene dicarboxylic ing downward past sample 18 to an exit 38 at the bottom acid with a methyl group derived from methyl alcohol. of tube 12. Exit 38 is connected to a ground glass joint 40 By treatment with ammonium hydroxide each methyl 25 which leads to a stopcock 42 of a U-tube 44 whose lower group and an adjacent oxygen were replaced by an amino part is immersed in a solution 46 of carbon dioxide in group. The hydrogens-of the amino group and the sur acetone, contained in a beaker (or Dewar ?ask) 48. The viving oxygen of the original carboxyl were then con exit from the U-tube runs through a stopcock 50. The densed out over phosphorus pentoxide, ‘leaving a triple product of the synthesis, as will be explained further in detail, appears as condensate 52 at the bottom of the U bonded nitrogen and carbon in place of the original car tube 44. boxyl group. Although this compound has been known In the preferred operation of the apparatus described, for over ?fty years, the tedious nature of the canonical regulator 26 is so adjusted as to produce a ?ow of puri process ‘for producing it has apparently discouraged de ?ed nitrogen at a linear velocity of about 15 centimeters tailed exploration of its properties, although Benes, Peska, 35 per second past sample 18, which may conveniently be and Wichterle have reported (page 562 of Chemistry and a cylinder of graphite about % inch in diameter and 1/2 Industry for Mar. 24, 1962.) that dicyanoacetylene forms inch high. The radio frequency furnace 22 is adjusted to a solid black polymer when brought into contact with heat the sample 18 to a temperature of about 3,000 de oxygen. The high energy of formation (which may readily grees Kelvin. The condensate 52 appears at the bottom of be understood by consideration of the three triple bonds in 40 U-tube 44. In my original demonstration of this process, the molecule) leads to the directly useful property that I analyzed this product in the mass spectrometer (which dicyanoacetylene when burned with oxygen produces ?ame -was connected to the U-tube 44 through stopcock 50). temperatures of the order of 5500 degrees centigrade. Typical results obtained were as follows: This last property in a material which is liquid at room temperature and at atmospheric pressure is enough to 45 Compound: Relative intensity justify interest in its production ‘(although the structure cm, _ __ __ 100 strongly suggests that it will serve also as a useful inter mediate in a number of syntheses). C2N2CGNZ ________________________________ __ 1.93 Brie?y, I have found a process for forming dicyano Since cyanogen is a gas at room temperature, while di acetylene and obtaining a useful yield of it by direct com 50 cyanoacetylene is a liquid, simply raising the temperature bination of nitrogen and carbon. This is done by bringing of the condensate 52 will cause the cyanogen content to the nitrogen gas in contact with the carbon when the latter be reduced by evaporation. is heated to a very high temperature. The production rate of dicyanoacetylene has been found Thus an important object of my invention is the pro to vary with temperature as follows: duction of dicyanoacetylene by direct combination of its 55 constituent elements. Other objects of my invention are to Temperature of sample Product rate in produce dicyanoacetylene rapidly, by a process involving in ‘degrees K.: milligrams/hour cm.2 only a few steps, and from very inexpensive and readily 2673 ._.. ___ 1.5 available starting materials. 2773 _.._ 5.0 For the better explanation and understanding of my 60 2873 a 10 invention, I have provided a ?gure of drawings in which: 2973 _ 30 The ?gure represents a train of apparatus suitable for The area involved in the ‘rate is the nominal super?cial producing dicyanoacetylene in accordance with my inven area of spectroscopically pure graphite. So-called pyro tion. lytic graphite shows a somewhat lower yield than the ?g The reaction chamber actually employed in the first 65 ures given above, probably because it is less porous and demonstration of my invention was a fused silica tube two has less effective surface. inches in diameter, here represented by designation 12. While I have not established rigorously the theoretical At its top it is surmounted by a totally re?ecting prism basis underlying my invention (since this would presum 14 at which there is aimed an optical pyrometer 16, the ably be a task requiring the services of several men for total arrangement permitting the optical pyrometer to view some years), I have come to several tentative beliefs which I here offer rather as suggestions which I personal~ the brightness of sample 18. Sample 18 (to be discussed 1y accept than as unquali?ed statements of fact. The direct 3,386,359 3 4 synthesis of dicyanoacetylene should, according to the perature from at least 2673 to about 3000 degrees presently accepted structural formula Kelvin; (2) Passing a stream of gas consisting essentially of NEC—CEC—CEN nitrogen substantially free of hydrogen over the said O1 surface of carbon at a linear speed of at least 15 be highly endothermic and thus occur appreciably only centimeters per second, thereby producing in the said at high temperatures. On the other hand, a six-atom stream reaction products of the said nitrogen and the molecule with three triple bonds can hardly be expected said carbon; to be stable at very high temperatures. I believe that my (3) Cooling the said stream of nitrogen and reaction invention is operative because the nitrogen ?ows fast products to condense out dicyanoacetylene. enough past the hot carbon so that a molecule of the 10 2. The method of making dicyanoacetylene which product, once formed at or near the solid carbon, has comprises the steps of a fair probability of being swept off in the much cooler (1) Bringing gaseous nitrogen in contact with heated gas stream. Thus one would expect a static or very slow carbon at a temperature from at least 2673 to about ly ?owing nitrogen stream to produce very little or none 3000 degrees Kelvin to form reaction products; of the desired product. Any deleterious results of increas (2) Removing the said reaction products and unreact ing the speed of gas ?ow will be small for speeds con ed nitrogen rapidly to an environment cooler than siderably greater than my preferred speed. Since the the said heated carbon; function of gas speed is primarily to remove the products (3) Separating dicyanoacetylene from the said unre from the hot zone, an increase in the temperature em 20 acted nitrogen. ployed may require somewhat greater speed in order to 3. The method of making dicyanoacetylene which take account of the fact that the high temperature zone comprises the steps of around the hot carbon will extend a little farther away (1) Bringing gaseous nitrogen in contact with heat from the carbon, and consequently the products must ed carbon to a temperature from at least 2673 to move a little farther from the carbon to achieve a given 25 about 3000 degrees Kelvin to form reaction prod degree of stability.