December
1947
INDUSTRIAL and ENGINEERING
CHEMISTRY....
Reports ON THE CHEMICAL WORLD TODAY REDISCOVERING THE BIG RING The frequency of reference to benzene derivatives has impressed on those even distantly connected with chemistry the importance of this six-carbon aromatic ring. An entire field—\ aromatic chemistry—has been built around this one nucleus and its combinations. It is interesting to compare the field of aliphatic chemistry, wherein the discovery of the value of a chain of given length leads to the investigation of its homologs, built up by the addition of units, in this case CH2 groups. Not so with the aromatic nuclei, the unique character of which is credited to the existence of conjugated, or alternating, double bonds in a carbon ring. The four-carbon ring, next possible aromatic homolog below benzene, has not been made, whereas the next higher or eight-membered ring, synthesized only once until recently, has been a curiosity. Today the picture is changed. Cyclo-octatetraene, the ring of eight carbons with four double bonds, has been made by a method with commercial possibilities and is attracting an interest which has lifted it from the laboratory curiosity class. It has been found that cyclo-octatetraene (COT) can be made from acetylene. As a result the preparation of research quantities has led to the demonstration of its nonaromatic character and reactivity, and not only contributed an advance in theoretical and classical knowledge but opened the possibility, for the first time, that industrial organic chemistry may get into the field of eight-membered rings on a large scale. Diene addition products from COT may be valuable in lacquers and related products. Caprylic lactam and suberic acid, two compounds of interest in the preparation of polyamides, can be made from it, and conceivable possibilities in synthetic rubbers and other polymers are thought-provoking. Suggestions have been made for the use of diesters as plasticizers. COT could be expected to form the basis for alkaloid synthesis, of value in the field of drugs. Even in considerable dilution COT absorbs ultraviolet rays; thus it is of interest in light-stabilization of plastics and surface materials as well as in protective cosmetics. This and other characteristics suggest dyestuffs. COT achieved classical status after its synthesis by Willstatter and his observations relative to the classical problem of aromaticity. He reported in 1911 that the eight-carbon ring containing four conjugated double bonds did not exhibit the diminished unsaturation characteristic of benzene and its difference in reaction from simple alkenes, but was aliphatic. Much attention was drawn to this work, and some doubts were expressed that Willstàtter's compound was of the structure claimed. However, his tedious synthesis, starting with pseudopelletierine, a pomegranate alkaloid— which was converted, through a large number of steps, into COT in yields of 3-4 grams per 100 kg. of pomegranate tree bark—
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remained unrepeated for thirty-five years in spite of the controversy. Other preparative attempts failed, and COT was not reported again until Walter Reppe of I. G. Farbenindustrie included its synthesis among the many remarkable accomplishments he and his workers wrought with acetylene. Reppe's synthesis brought a nickel cyanide catalyst suspended in tetrahydrofuran into contact with acetylene in a nitrogen atmosphere at 15-20 atmospheres total pressure and temperature varying from 70 to 150° C , according to FIAT Final Report 967, edited by K. Kammermeyer; a completely translated version of this is available from the Hobart Publishing Company, Washington, D. C. The reaction was markedly speeded by the presence of either powdered calcium carbide or ethylene oxide. Under these conditions the absorption of acetylene became very slow after 50-60 hours. The reaction products consisted of cuprene, benzene, COT, and C10 and C12 hydrocarbons, which accounted for about 90% of the acetylene added. In general the formation of benzene was 10-15% of the amount of COT, while about an equal amount of resinous material and one third or lees that quantity of cuprene were formed. The yields and proportions varied, of course, with conditions. This reaction was carried out in an autoclave. Attempts to develop a continuous process using either a tower with packing wet by the liquid, over which the gas passed, or a flooded catalyst bed through which the
miuiu
gas bubbled, gave reaction, but neither was so satisfactory as the autoclave method. Either the catalyst plugged or very little COT was formed. The reporting of this work out of Germany revived the interest in COT and also provided a check on the earlier claims. As substantiation of Willstàtter's report, Cope and Overberger of M.I.T. have repeated the synthesis, starting with pseudopelletierine prepared by the combination {Continued on page 8 A)
An interpretative monthly digest for chemists, chemical engineers, and executives in the chemical producing and chemical consuming industries 5A
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PRODUCERS
OF
reports
of glutaraldehyde with methylamine hydrochloride and acetone dicarboxylic acid, and proceeding with the original reactions. Ample evidence indicated identity of this product with that from acetylene, and its variation in melting point from that of the original COT was attributed to the fact that the latter was not purified by fractional distillation. In addition, Cope and Bailey prepared 1,5-cyclo-octadiene more simply from the dimer of chloroprene (2-chloro-l,3-butadiene), dibrominated this, and proceeded from that point by the Willstâtter reactions to COT. Work is being continued at M.I.T. Examination of COT by Reppe indicated that his product was the same as that of Willstàtter, and has also produced substantial evidence that the compound is the symmetrical ring 1,3,5,7-cyclo-octatetraene and that it is aliphatic rather than aromatic in nature. However, it was also shown that it can react to yield derivatives of three fundamental structure types:
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H-C
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1,2,4,5-Dimetliylene2,5-cyclohexadiene
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Extensive thermochemical studies arc in progress at the National Bureau of Standards under Rossini, Prosen, and Johnson, who have recently reported measurements of heats of formation and combustion and have concluded COT to be less stable than styrene. Controversy over the spatial arrangement of the atoms within COT is not yet settled to the satisfaction of all investigators. Two forms, a "tub" and a "crown," are now being supported. It has even been suggested that two forms may exist. Work relative to this question has been reported from England and Norway, as well as from this country. (Continued on page 10 A)
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Reppe h a s reported reactions effected through each of t h e three forms. Suberic acid is m a d e from reactions of compound I. I t s catalytic t r e a t m e n t with water gas gives cyclo-octyl carbinol, which can be oxidized to t h e eight-carbon, straight-chain dicarboxylic acid. Easy hydrogénation of I yields cyclo-octene which can be oxidized t o suberic acid, or t h e ring can be converted, b y t h e use of perbenzoic acid, t o t h e oxide, reduced with hydrogen t o cyclo-octanol, then oxidized t o t h e acid. On t r e a t m e n t with sulfuric acid, t h e oxide is aromatized t o yield phenylacetaldehyde quantitatively. T h e latter compound can also be prepared b y t h e t r e a t m e n t of C O T with mercuric sulfate and water, t h e reaction presumably proceeding through form I I . T h e diene synthesis, or addition reaction with compounds such as maleic anhydride or quinone, a p p a r e n t l y proceeds through stage I I . Examples of reactions in which form I I I is an intermediate are t h e oxidations with hypochlorous acid or chromic oxide t o yield terephthalic aldehyde or acid, respectively.
are d e t e r m i n e d
When the Plans Are Drawn That's w h y it's SO important to
F r o m cyclo-octene a n d glacial acetic acid can be made cyclooctyl acetate, convertible stepwise t o t h e corresponding octanol, ketone, oxime, and caprylic lactam. T r e a t m e n t of I with sodium or lithium followed b y carbon dioxide effects t h e addition of two carboxyl groups across one of t h e pairs of conjugated double bonds. Alcohol t r e a t m e n t yields t h e diestcr. A number of other reactions a n d supporting evidence for these conclusions are described in t h e F I A T report. Another center of extensive research on C O T is t h e Polytechnic I n s t i t u t e of Brooklyn where M a r k , Bergmann, Fankuchen, Klotz, a n d Overberger a r e studying preparation, dimerization and polymerization, structure, a n d higher homclogs. T h e investigation in G e r m a n y which began in 1940 a n d was stopped in 1944 was still in t h e research stage, a n d Kammermcyer states t h a t little p a t e n t protection exists in this country on t h e work. Large-scale developments m a y grow from t h e improvement of t h e synthesis described here, which lies in a comparatively new field, into a more economic process. Work on C O T is now proceeding in a number of industrial laboratories b u t few, if a n y , are willing to talk about their investigations a t t h e present time. Benzene remains unique in its aromaticity, b u t its quadruply u n s a t u r a t e d eight-carbon cousin is promising real achievement in its own right. R.L.K.
choose as your design a n d e n g i n e e r i n g counsel a f i r m of b r o a d e x p e r i e n c e and proven ability. F r o m d r a w i n g b o a r d , t h r o u g h cons t r u c t i o n , to test o p e r a t i o n of t h e completed plant, P r i t c h a r d engineers b r i n g to bear u p o n y o u r p r o b l e m s a thorough familiarity with latest t r e n d s and s o u n d i n g e n u i t y in a p p l y ing new t e c h n i q u e s . A l s o t h e y k n o w and c o n s i d e r in t h e l i g h t of y o u r req u i r e m e n t s e v e r y c o m m e r c i a l l y sign i f i c a n t m e t h o d from past and p r e s e n t p r a c t i c e t h a t will a s s u r e m a x i m u m p r o d u c t i o n and p r o f i t from y o u r investment
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Crystalline sodium chloride is a common contributor to every meal, b u t the salt crystals produced a t the Oppau-Ludwigshafen plant of I. G. Farbenindustric during the war were intended for bigger things than increasing the palatability factor of your morning eggs. In fact the 30-cm.-diameter crystals produced by Herr Ingénieur Korber undoubtedly would obliterate the eggs, bacon, breakfast plate, and perhaps the table as well. The crystals were grown for use in infrared spectrometer optical systems by suspending a cylindrical seed crystal in a sodium chloride melt held a t a temperature around 870° C. The seed was held in a water-cooled chuck which rotated once every 2 hours and rose 1 mm. per hour. The diameter of the crystal was limited to about 30 cm. by the size of the melting crucible, but the length was determined only by the volume of the melt and the stroke of chuck. {Continued on page 12 A)
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The finished crystal was dropped onto a conical pile of quartz sand in an annealing furnace. The sand prevents the incorporation of impurities into the plastic lower portion, which might cause differential cooling contraction. The an nealing furnace is held at 600° C. for 8 to 10 days and then cooled at about 0.5° C. per hour. Other salts, notably potassium chloride and sodium bro mide, were also processed in the same equipment but seemed to offer no advantages over inexpensive rock salt for the opti cal units desired. M.L.K.
TEXTILE CINDERELLAS
J I M : Yes, sir, this is the life! And I left everything under control at the office except just one problem — those heat exchangers for the new plant!
When chemists decide that a thing has to be beautified, almost anything can happen. We were startled some years ago when such a commonplace material as glass was spun into fibers and then woven as a soft, silken textile material with remarkable fire-resistant properties. Now you can have draperies and curtains of this noncombustible material in al most any color, thanks to new dyeing techniques. We never heard of anyone dyeing glass either, but the effect is achieved b y applying a thin gelatin type of protein film to the yarn during manufacture. This film is 1 to 2 % by weight of the finished yarn. As a result the coating will absorb the fast soluble vat dyes as well as the more brilliant acid, chrome, and direct colors. There are many other striking results of research shaping up in this ancient business of clothing people and beautifying their homes. The consumer usually does not learn of them, however, until the final result is in the shop window. I t took 20 years of unremitting work and study to apply the art of photography to textiles so t h a t it could be used for printing to replace the century-old screen and roller tech niques. There is nothing new about printing photos on silk or cotton immersed in a photosensitized emulsion, but the Photone method, as it is called, goes far beyond that. I t introduces various colors in subtle shadings to fabrics in place of just flat dyeings. Ammonia vapor is used to bring out the latent image. The emulsion is an unrevealed trade secret; in essence, the chemistry of the operation is somewhat similar to t h a t used in the Ozalid process. New fibers are not discovered every day; still there have been several outstanding contributions in this field since the close of the war. Like nylon and Vinyon, they are noncellulosic and processed from chemicals such as Terylene, a synthetic fiber of yet undisclosed composition derived essen tially from terephthalic acid and ethylene glycol. Strength and heat resistance are the outstanding characteristics, but like nylon, it does not dye too easily. The work of Robert B. Woodward in synthesizing such giant molecular proteins as the polypeptide polymers may open a door to an entirely new class of synthetic silks and woolens. Nonwoven fabrics represent man's third effort on this planet to provide himself with textiles. I t could conceivably take the place of weaving machinery much as the latter succeeded the hand weaver's frame, but we (Continued on page H A) gjflfP tW··
BILL: If that's your only worry, relax and enjoy your self. Whitlock can handle that job for you and do it right. J I M : So I hear, but they're way off in Hartford, Con necticut. I can hardly expect them to send a man to study our job. BILL: That's right — // their man had to come from Hartford! But don't forget that Whitlock has forty or fifty direct sales offices and representatives all over the country, working on jobs like yours. J I M : But some of my jobs are pretty complex, prob ably too difficult for most field engineers — what then? BILL: Very simple — the field engineer's recommenda tions are all mailed to Hartford and reviewed by their Thermal and Production Engineering Divisions imme diately. If necessary, a specialist from Hartford comes out to look the job over, J I M : Bill you're the guy who knows all the answers! That equipment has had me worried. I hadn't realized there was a local Whitlock man who could drop in to talk things over. Now, a phone call should settle m y problem.
There's an experienced Whitlock representa tive near you. Ask his advice on your heat transfer problems and follow his recom mendations.
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prefer to believe that, for the time being, nonwoven textiles will have their own specific uses. Among them are filters, tapes, ribbons, covering for insulation, and containers. Nonwoven fabrics are fibers which have been bonded t o gether,'either through their own adhesive properties such as possessed by Vinyon and cellulose acetate, or with prepared adhesives for nonadhesive fibers such as cotton, wool, and rayon. Heat and pressure are used to lock the fibers in place. Some bonded fabrics introduce dyeing problems, and for these only the pigment-on-fiber coloring method is practical. Resins are being utilized on an ever-broadening scale to improve the utility and enhance the beauty of textiles. They are the "invisibles" which hold wool shrinkage to less than 3 % instead of 30 to 4 0 % by preventing fiber slippage. Resin is also used to impart a built-in crispness and newness to fabrics which withstand repeated launderings by bonding fiber t o fiber and imparting semirigidity to the whole fabric without loss in softness. Resin particles as small as 0.1 micron in diameter are flashed onto the fibers at 250° F. and make them adhere permanently. Visible or invisible, these are all new advances which have endowed us with fibers and fabrics of remarkable usefulness, durability, and appearance. T h e finery of the little lady with the glass slippers would not have turned back to rags by midnight if modern science, instead of that unimaginative old wench with the wand, had come to her aid. H.S.
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I t is a fascinating thing to watch a new instrut develop and equally fascinating to see the design of an old one modified ; tofindout the "whys" of development or modification, which usually include dissatisfaction with the status quo, and then to see the designer dissatisfied with his ideas and to watch the improvements he makes on the work of his own devising. Such a situation we find well exemplified in the development of a new type polarograph by James H. Schulman, H. Bruce Battey, and Demetrius Jealtis at M.I.T., and the addition of further refinements b y Schulman and his colleagues a t the Naval Research Laboratory. This piece of equipment, described earlier this year in the Review of Scientific Instruments, has been subjected to numerous improvements since then, and is now just being advertised on the commercial market as the Polaro-Analyzer. I t was in listening to the story of the original design and current modifications that this report came into being. **#H.T*i L«?ÉI
men
The whys of the idea behind this modification of existing methods of making polarograms lay in dissatisfaction with speed of operation, with limitations placed on rapidity of voltage changes, with false apparent half-wave potentials, with the presence of personal factors in the estimation of diffusion currents, and with lack of sensitivity. The Heyrovsky type, recording galvanometer deflections photographically,- and another type involving use of a recording potentiometer and producing an inked chart, have as a common characteristic current measuring systems which are highly damped. The simplest definition of a polarograph seems to be "an instrument which applies a constantly {Continued on page 16 A) 14 A
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i&ec reports increasing potential across a solution and at the same time measures the intensity of current through the solution." Because in a highly damped system only average current values are measured and only slow rates of voltage change are possible without falsification of half-wave potentials, Schulman and his co-workers determined to design an instrument of their own, which would eliminate the undesirable factors and add some new elements of design. To get to the end of our story first, there emerged a piece of equipment using negligible damping, in which the voltage change rate had no appreciable effect on the value of the half-wave potential, and which eliminated the personal factor in measuring currents. With the original model the recorder was a separate piece of equipment, external to the cabinet that housed the polarizing unit and the amplifier. The cabinet of the improved instru ment has a built-in recorder. The original voltage range went up to 4 volts; since in no application of polarography up to now has anyone gone beyond 3 volts, the spread in the new design was reduced to that as a maximum figure. Six polarizing ranges—0-1, 0-2, 0-3, 1-2, 1-3, and 2-3 volts— are made available by means of a single control, and three other special ranges are added by throwing an auxiliary switch. Five hundred microamperes was the first figure used as the upper limit of the amplifier range. This corresponds to relatively high concentrations of impurities—in the order of 0.05 molar. Since, in general, polarography is not used for determining impurities in this concentration, or if it is done, the solution can be diluted to bring it into a range of smaller diffusion currents, the amplifier maximum has been reduced to 200 microamperes, with a new lower limit of 0.5 microampere added for increased sensitivity. Operation of the Polaro-Analyzer is simple enough. With the working voltage at 3 volts on the polarizing unit voltmeter, the voltage range is selected, the amplifier is warmed up, cur rent range is chosen, and zero adjustments are made. In the original design the operator had to have split-second reflexes— the recorder chart was started, and then, just when the pointer crossed one of the time markings, the motor switch had to be closed. They soon did away with that. Now the operator manually rolls the chart to a point where the pen coincides with a time marking on the chart; when he starts the actual run the chart automatically begins to roll, and when the run ends the chart drive stops. As regards the personal factor, the damped operation gives a wavy or oscillating line, particularly a t the top of the wave. In addition to a smaller net current recorded by this method, there is also the human element in choosing an average value for the current. In the new instrument the current value is clear-cut, the polarogram being the envelope of all the current peaks. The originators of the Polaro-Analyzer believe that the manufacturers of other commercial instruments, in realiz ing the disadvantages present in the "damped" machines and trying to control these disadvantages by increasing the damp ing still further, have only compounded the evils associated with damped operation. Schulman considers the instrument an excellent piece of apparatus for both research and rapid routine work. In ac curacy it compares favorably with the best of the other meth ods, while in speed an analysis takes a maximum of 5 minutes as compared to 10 to 30 minutes in other designs. W-H-S. 16 A
