chemi~tryon /tamp/ edited by.
JAMES 0 SCHRECK Univers~h.of Nomilern Colorado Greeley. CO 80639
C. MARVINLANG Univers~lyof Wisconrm Stevens Point. WI 54481
Organic Chemistry on Postage Stamps James 0. khreck University of Northern Colorado, Greeley, CO 80639 A course in organic chemistry is an important part of the curriculum of &iny students. Fundamental concepts in organic chemistry are the thrust of texthooks written for majors in chemistry, as well as for those whose main interest is in agriculture, biology, health sciences, nursing, or pharmacv. T o maintain student interest, increasing emphasis has been placed on practical applications of organic chemistry to evervdav life. Another way t o heiahten interest is 10 incorporate-the-aspects of organic che&try on postage stamps in teaching organic chemistry ( I ) . This article describes organic chemistry as depicted on postage stamps in terms of some of the course topics routinely discussed. Carbon, from the Latin word meaning "charcoal" and with symbol C (stamp no. l), is found in Group IVA. I t exists in two common allotropic forms. Diamond (no. 2) is colorless when pure. One of the hardest substances known, diamond is used for grinding, machining, and engraving hard metals and other substances. Diamond's hardness is accounted for bv its closelv interlocked, three-dimensional structure. Iliamond has two properties that give i t "fire" and sparkle. Because of a high refractive index, light entering it from the air is bent strongly toward the interior of the diamond. I t also shows great dispersion, which means that the angle of bending of light varies with its wavelength. The second allotropeof carbon, graphite, is a soft, black solid with a semimetallic luster. Graphite has a layered structure in which the carbon atoms in each layer are arranged in a hexagonal ~ n t t e r n(no. 3). This kind of r e ~ e a t i n ehexagonal fieure is &d tesselation. The flat, hexagonal Lssel&on c&easily s l i over ~ another similar laver. This model accounts for the successful use of graphite as a lubricant. Carbon exists in several hybridized states. The sp2-hybridized state, in which carbon is trigonal, is depicted on stamp no. 4. The very large and important branch of chemistry devoted to the study of carbon compounds is organic chemistry. The name "organic" is actually a relic of the past, when chemical compounds produced from once-living matter were called "organic" and all other compounds were called "inorganic". In 1828 Friedrich Wohler found that heating crystals of the inorganic salt ammonium cyanate produced urea. This important discovery was depicted on a German stamp (no. 5). A ball-and-stick model of urea and the equation for the decomposition of ammonium cyanate are shown on the stamp and in the following equation: heat
1
(NH4)+(NCO)- --t NH2 NHI 624
Journal of Chemical Education
Hydrocarbons Hydrocarbons are organic compounds that contain only carbon and hydrogen. The chief sources (2)of hydrocarbons are petroleum, coal, and natural gas (no. 6-8).Natural gas is predominantly methane, which is used as a fuel in many parts of the United States. Kerosene, chiefly a C11-Cn hydrocarbon mixture, finds considerable use as fuel for jet engines. I t is also used in small heating units and lamps (no. 9). Paraffin wax, used in candles (no. lo), is amixture of very high molecular weight saturated hydrocarbons similar enough in structure t o pack together to give a semicrystalline solid. Whale oil (no. 11) is not a hydrocarbon mixture but rather a mixture of unsaturated fatty acids containing 20-24 carbon atoms and ~almitoleicacid. Each of the three previous stamps represen& a characteristic chemical property of hydrocarbons and other organic compounds: combustion. Adamantane (ClnHld .. .. is a tricvclic svstem that contains a three-dimensional array of c y c ~ ~ h e x a nrings e (no. 12), all of which are in the chair conformation. Certain derivatives of adamantane have potential uses as antiviral agents. Natural rubber is a hydrocarbon with the composition (C5H8)",and when i t is decomposed in the absence of oxygen i t yields isoprene. A ball-and-stick model of isoprene is shown on stamp no. 13. Natural rubber occurs as latex (an emulsion of rubber particles in water) that oozes from rubber trees when they are cut (no. 14). Precipitation of the rubber particles yields a gummy mass that is elastic and water-repellent but very sticky. Rubber, of course, is the primary component of tires (no. 15). ~
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Benzene Benzene was f i s t isolated from a whale oil byproduct by Michael Faraday in 1825. However, Friedrich August KekuE(1829-1896), a German chemist (3a), proposed a satisfactory structure for benzene. In 1856 he obtained a professorship a t Heidelberg, where he pursued his ideas of valence. In 1858, the same year he took up a professorship a t Gent in Belgium, he presented his ideas of structural formulas: the idea of connecting atoms by little dashes. In 1861 Kekul6 published the first volume of a textbook of organic chemistry in which he was the first t o define organic chemistry as merely the chemistry of carbon compounds; no mention was made of living organisms, and this definition gave another blow to vitalism. Kekul6 is best known for his structure of benzene. In 1865Kekul6 proposed astructure with alternate douhle
and single bonds (no. 16). Whether or not KekulB's "vision" came out of a dream is the subject of discussion ( 4 ) ,and, as great an achievement as coming up with the structure for benzene was, the structure is not satisfactory. With the aid of quantum theory, modern chemists realize that benzene is
a resonance hybrid of two structures (no. 17). In 1867, Kekul6 moved on t o the University of Bonn, where he spent the remainder of his life. On the centenary of this discovery the Belgian government issued a commemorative stamp (no. 18). Volume 66
Number 8
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Other Organlc Compounds
Although hydrocarbons are widely used as fuels, they are also used as sources of other compounds. Of particular importance are the compounds that result when one or more 626
Journal of Chemical Education
hydrogens of ahydrocarbonare replaced by another atom or, particularly, by groups of atoms, that is, a functional group. One such functional group has been depicted on two stamps. A Czechoslovakian stamp (no. 19) shows a -COOH group
IdentMcatlon and Description of Stamps
smn Stamp No.
issuing Countly
Year of issue Catal~gNumber
Finland Israel unned Nations Mexico
*many Great Britain Great Britain Great Britain USA USA USA Czectaslwakh Malaysia Malaysia Malaysia German Democratic Republic HaUt~Volla Belgium CzechDslwakla Russia Germany France France Iran Sweden Great Brllaln Japan Great Brllain Russia Cuba France Gab04 Hungary Great Brltaln Great Brbln Russia Great Britain France Belgium German hmooratic Republic Germany Russia Malaysia China (People's R6wblic) Japan Sweden Sweden USA German DemDcranc Republic ivory c.3asl Brazil Romania Argentina Canada Russia German Democratic Republic Qatar
a n d a Russian s t a m p (no. 20) depicts t h e group, -CH2COOH. The hydroxyl group is characteristic of a class of compounds called alcohols. The word alcohol appears in German on a stamp (no. 21). Oreanic chemists often represent a class of com~oundsbv formula. An example is RMgX, the c rig nard ria aeent. which amears on a 1971French stamp (no. 22). This & m i also codtains the portrait of Victor ~ r & a r d (Yb). Grienard (1871-1935) embarked upon a course of experiments-in which he was attempting to add a methyl group to a molecule. The problem was to find the right catalyst. Magnesium seemed to offer hope, but results were irregular and
unreliable. Comhinations of zinc with oreanic com~ounds had been prepared previously by using diethyl ethe; as the solvent. and Grienard wondered whether he could not do the same &th magnesium. The trick worked, and this device proved extremelv versatile. and a whole series of com~ounds now known as ~ i i g n a r dreagents is a useful synthetic intermediate for organic chemists. In 1901 Grimard presented the work as hi;; doctor's thesis, and in 19i2 he shared the Nobel Prize in chemistry with Paul Sabatier. A French chemist, ~ a b a t i e r(1854-1941) approached organic chemistry entirely through the failure of an experiSabatier (no. 23) knew ment he had conducted in 1897 (3~). that nickel formed a volatile c&&ound, nickel cahonyl, through combination with carbon monoxide. He decided to see whether ethylene, which is similar to CO, might behave similarlv to CO with nickel. However. the experiment failed. and no volatile nickel ethylene compound was formed. ~ u t Sabatier saved the gases that did form for later analysis and to his surprise found that ethane was present. Apparently the nickel had acted as a catalyst, bringing about the addition of hydrogen to ethylene to form ethane. These results intrigued Sabatier, and he spent the rest of his career studying catalytic hydrogenations. This work proved very fruitful; nickel replaced the expensive P t and Pd catalysts that were routinelv used. The use of metal catalvsts eventuallv - proved . to be an important step in organic synthesis and, in particular. in industrial chemistrv. Nickel catalvsis has made oossible the formation of edible fats such-as margarines and shortenings from inedible plant oils. Fischer Prolection
Another general formula for organic compounds is the Fischer projection as shown for an amino acid (no. 24). Interestingly, a Fischer projection is shown for the less common D-amino acid. It was the German chemist, Emil Fischer (1825-1919), who introduced the letters D- and L- to describe the stereoehemistrv of suears (3d). Fischer. a student of Kekul6, devoted his ~ r o f e s s ~ o n ~tol iextraordinarily f~ fruitful researches in various branches of organic chemistrv. In 1875 he worked on organic derivatives of hydrazine add showed how they could be used to separate and identifv sugars. He placed stereochemistry on akound footing when he showed during the 1880's that the different arrangement of six carbons i n a suear could be reconciled usine ~ d a r i z e d light. He eventually'showed that there were two'series of sugars, mirror images of each other, which he called the Dseries and the L- series. At the same time he worked with purines elucidating their structure in detail. This was an important contribution as these compo~ndswere eventuallv found to be an internal part of nucieic acids, key molecule^ of living systems. In 1902 Fischer received the Nobel Prize for chemistry for his research in sugars and purines (no. 25). Hy now,however, he had hewn todelve into proteinchemistrv. A t the time it was known-that proteins were composed of amido acids, but Fischer demonstrated the sequence of amino acids within the protein molecule. In 1907 he succeeded in svnthesizine a of 18 amino acids. Furthermore, he iearned &at enzvmes react with his svnthetic protein exactlv as thev did witk natural protein. ~ h u s he , iaid the pound w o k for Sanger's efforts in protein chemistry. Even with all his accomplishments, Fischer's life came to a tragic end. During WWI he organized Germany's food and chemical production but was embittered by the war during which he lost two of his three sons. Despondent over his personal and national tragedies, and because he was suffering from cancer, he committed suicide. Structural Formulas
A number of soecific chemical formulas amear on stamps. These include &clopentane (no. 26). ethyl'&ohol (no. f7), phenol (no. 28), and aniline (no. 29). Stamp no. 27 shows a Volume 66 Number 8 August 1989
627
reactor and distillation column for making ethyl alcohol (presumably through the hydration of ethylene). On stamp no. 28, the likeness of Joseph Lister is shown along with the structure of phenol. Lister, a London surgeon, was the first touse phenol (carbolicacid),in 1867,toprevent infections in wounds. Some structures of organic compounds known primarily for their use as medicinals have been depicted on stamps. The cinchona plant is pictured on stamp no. 30. From the bark of this tree the alkaloid, quinine, can he isolated. Quinine (no. 31) is a naturally occurring antimalarial that has beenused since the 1600's. It was first isolated by the French chemists Pierre Joseph Pelletier and Joseph Caventou in 1820 and synthesized by Robert Woodward and William Doerine in 1944 (5). . . Two other recent antimalarial drum are also shown on stamp no. 30, chloroquint and primaquine, derivativesof quinoline. Many quinolines have been studied for their antimalarial propertica. Penicillin (nos. 32 and 331 represents a mour, of antihiotic compounds obtained from ~ e n k l l i u m mild o; by a synthetic process. These compounds have excellent antibacterial activity. Stamp no. 34 depicts a variety of compounds used as medicinals. Although they are difficult to see (see figure), the background of this stamp shows the formulas of 16 drugs; some are incomplete, either hidden by the illustration, or cropped by the edge. They are all drugs used in Africa and other tropical regions for the treatment of common tropical diseases. Dimensional representations of organic molecules have also appeared. Examples include a ball-and-stick model of ascorbic acid (no. 35), adamantane (no. 12), a space-filling model of isoprene (no. 13). the hond-line notation for a pyran derivative (no. 36), and a conformational formula fora steroid (no. 37). The 1969 Nobel Prize was awarded to Derek Barton for his studies on conformations of steroids. This stamp depicts the basic structure of all steroids-three cyclohexane rings and one cyclopentane ring fused together. Many steroids find application in the pharmaceutical industry, and the stamp shows pictures of several products.
over the spilled area, long strands adhered to both the rag and the table, and their resemblance to silk fibers led Chardonnet to reason that he had a possible starting point for his silk substitute. Six years later, he had produced a synthetic fiber that was comparable to silk. At the Paris Exposition of 1891"Chardonnet silk" was a sensation. It was called rayon because it was so shiny that it seemed to give forth rays of light. The nitrocellulose used was not fully nitrated so it was not explosive. However, rayon was at first dangerously flammable. Later it was shown how the nitro groups could be removed from the rayon after fiber formation to make the material much less flammable. In 1914 Chardonnet was awarded the Perkin Medal for his development of rayon. Polymer chemistry and chemists have been depicted on stamps. Leo Baekland (1863-1944) studied the reaction products of phenol and formaldehyde, which culminated in his discovery (3n in 1907 of phenol-formaldehyde polymers, originally called Bakelite. Bakelite was the first of the thermosetting plastics. It was Bakelite that sparked the modern development of plastics. In 1924 Baekland (no. 39) served as president of the American Chemical Society. Phthalic anhydride, a plasticizer, is shown on stamp no. 40. Stamp no. 41 depicts poly(ethylene terephthalate) polymer ohtained from terephtbalic acid and ethylene glycol.
Another polymer, supposedly obtained from isophthalic acid and phenophthalein, is shown on no. 42 and the structure of the polymer follows. This structure is an artistic model as no known polymer exists having this structure.
Polymers ( 6 )
The first synthetic fiber was rayon. In 1865, the French silk industry was being threatened by an epidemic that was killing silkworms. Pasteur located the source of the disease after afour-year investigation, but it was his assistant, Louis Chardonnet (1839-1924) who realized that the uncertainties in natural silk production would make an artificial suhstitute a highly desirable commercial item (3e). One day, while working in a darkroom developing photographic plates, Chardonnet (no. 38) accidentally spilled a bottle of nitrncellulose. He did not attempt to clean up the spilled material until his work with the plates was completed, and by this time it had become quite sticky. When a cloth was wiped
Stamp no. 43 shows six test tuhes picturing various events in the natural rubber cycle. Included in the third test tube is a portion of a polyisoprene polymeric chain. This stamp commemorates the 50th anniversay of the Rubber Research Institute in Malaysia.
A series of stamps (no. U 8 ) depicts the chemical fiber industry and has been issued printed se-tenant in continuous design. This series of stamps depicts a synthetic fiber feeder (no. 4 4 , drawing out threads (no. 45), weaving (no. 46), dyeing and printing (no. 47), and finished synthetic products (no. 48). Anatural polymer, a segment of apeptide, is illustrated on a Japanese stamp (no. 49). The colored balls clearly indicate the elemental makeup of the molecular segment shown below and on the stamp. 628
Journal of Chemical Education
um, phosphorus, sodium, and calcium. He was the first to experiment with the addition of chemical fertilizers in place of manure. Unfortunately he was of the opinion that plants eenerallv obtained their nitroeen from the atmosnhere. FherefGe, Liehig did not add iitrogen compounds 'to his chemical fertilizers. and thev did not succeed in ~romotine fertility. ~ventu&, though; this mistake was redified.
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Fermentation In addition to the equation showing the conversion of ammonium cyanate to urea on stamp no. 5, an equation deoictine the fermentation of a suear to ethvl alcohol has appearei (no. 50). Eduard ~uchne;'(186&19i7), a German chemist (3q),became interested in the orohlem of fermentation through his brother Hans, a ba&riologist. This was both the oldest and newest of biochemical problems. Fermenting of fruit juice to form wine and leavening of dough to make hread are recorded in the Hihle. Toward the latter pan of the 19th centurv. chemists finallv hand; on " had their ~-~~~~ ~~~~-~~~~ - - ~ samples of the a c t i h chemical substances bringing about these changes in organic materials. There was, however, the question as to the role life played in fermentation. Buchner wondered whether it mieht not he ex~erimentallvdemonstrated that alcoholic fermentation was inseparable from life, or at least to present evidence in favor of that view. To do this it was his intention to grind up yeast cells with sand until not one of them was left alive and to show, if he could, that the production of alcohol from sugar would stop. In 1896 he ohtained his cell-free yeast juice and filtered it. He preserved it against bacterial contamination by adding it to a concentrated sugar solution (a high concentration of suear is a oreservative aeainst bacteria). Before lone. he observed thatbubbles of ca;bon dioxide were forming. The completelv dead veast iuice was raoidlv fermentine the suear exactlv e& the intact cells would havehone. lntracellular fermentation and life were therefore not inseparable, and Buchner had demonstrated the reverse of what he intended. The chemical orocesses within cells were carried on by no "vital force" hut by enzymes, as they were soon to he called, contained in the yeast but not the yeast cells themselves. In 1907 Buchner was awarded the Nohel Prize in chemistry for this work (no. 51). Buchner's discovery was closely associated with the work of Arthur Harden, an English hiochemist, and Hans von Euler-Chelpin, a German hiochemist who shared the 1929 Nohel Prize in chemistry for their investigations of the mechanism of suear fermentation and the role of enzvmes in this process. ~ i the & use of molecular models, the sigar-toalcohol reaction has been depicted on a stamp (no. 50). ~~~~
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Lleblg Condenser A funnel routinely used by the organic chemist bears Buchner's name. Similarly, a "Liebig condenser" (no. 52) hears the name of the German chemist (3h), Justus von Liebig (1803-1873). Liebig (no. 53) went to the university at Bonn hut was arrested for nolitical activitv on the side of liberalism and had to leave ~ o n nHe . fled Paris, where in 1822 he ohtained in absentia the doctor's demee. In 1824 he completed his investigation of a series of compounds called fulminates. At the same time Wohler was studvine . -cvanates. . When both papers were published, Gay-Lussac, who was editor, noticed that the formulas of the two sets of compounds were the same. This was the heginning of the realization of the concept of isomerization. R+=N: alkyl cyanate
Agt
'&&=c!
silver fulminate
Liebig also worked in agricultural chemistry. He maintained that the chief factor in the lossof soil fertilitv was the consumption by the plant of compounds containing potassi-
Molecular CurIosRles Some oreanic molecules are interestine simolv of . . bbvirtue their shape. Two such moleculesjoin ranks with a rather odd collection of molecules that are studied more for the intellectual challenge than for any other intrinsically chemical property. Althoueh there is no wav to Drove it (7Lscientists think space c o i d he filled with-soccerane (a1k.a. foothallane or buckminsterfullerene). Soccerane (no. 54) is a dotriacontahedrane, C,y,H,y,, with90 carbon-ckbon bonds and 32 faces (12 pentagons 20 hexagons). Each pentagon is surrounded by five hexagons, and each hexagon is bordered by three pentagons and three hexagons. The special thing about soccerane is that it is a simple and utterly stable democracy of carbon atoms, each indistinguishable in every way from the other 59 atoms in the molecule. No atom is pulled more strenuously than any other. Radio astronomers knew that the gas surrounding certain carbon-rich stars contained large, undefmed carbon molecules but had no idea what shape the molecules might take. Attempts to recreate the interstellar environment in the laboratory produced soccerane. Students of organic chemistry might be interested to know that soccerane has an IUPAC name (8). In 1961, a novel proposal for synthesis of a knotted ring was introduced (9).The approach was based upon the properties of the well-known Mobius strip (no. 55). A Mobius strip usually is visualized as a ribbon that has been joined into a continuous loop containing a half-twist. That halftwist imparts a unique property to the strip, namely, a single, continuous edge. In one study, methods for preparation of ladder-shaped molecular "strips" have been developed (10). The edges of the molecular ladders are composed of long chains of carbon and oxygen atoms (polyether chains), while the rungs of the ladders are simple carhon-carbon double bonds.
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Organic Chemical Industry Perhaps the most common chemically related stamp issued by a given country is that depicting some aspect of its organicchemical industry. The pewoleurn chemical industry has been very popular as shown by the earlier examples (nos. 6 8 ) amone others. These include a facilitv for the senaration of aro&atics (no. 56). The importance bf henzene ih the modem oil and chemical industries of Areentina is shown on stamp no. 57. This unusual representaiion of henzene is inaccurate in that it over emphasizes the six CH groups. A Canadian stamp (no. 58) recognizes a very important industry in that country, viz., that of the paper-making process in operation (11). A Russian stamp (no. 59) depicts a spherical reactor and plastics factory. A butadiene plant is shown on an East German stamp (no. 60). Butadiene is copolymerized with styrene to give an elastomer, SBR rubber. Several stamps were issued in 1975 by Qatar to honor its various industries: a fertilizer plant (no. 61) and a natural gas plant (no. 62). One or more of these industries is characteristic of the organic industry in many other countries. In conclusion, there are a variety of postage stamps that depict concepts of interest to organic chemists and students Volume 66
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August 1989
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in organic chemistry courses. Organic chemistry has been illustrated in terms of structural polymen, reactions, and the organic chemical industry. Acknowledgment The author thanks William B. Williamson of the Educational Materials Service for the stamp pho+-ography in many of the articles in this mini-series. Literature Clted 1. (a1 Sehreek, J.; Lao& C. M. J. Chom.Educ. 1985,62,1Ml. (b) Chsnisr, P. J. "Organic Chemicalson 8tampa':Abstradof Papera, 186thNationalMeting ofthe American Chemical Soeiety, Wslhington. DC, August 1983, paper HlST 19. (el Chsnia, P. J. "Orgsnie Chemicals on Stamps': Chemical Institute of Canada, 67th Conference,
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Journal of Chemical Education
joint aith the ~ ~~ d t ~~oftchemist., . r ~ ~ ~i t r r a ~l . c &me ~ a d1984. ~ . 2. Wittmff, H.;Reuben.B. G.Industrial Orgonit Chemicok inPenpoeliw; Wicy: New York, 1980. 3. lisimov. I. ~aimou'a~ i o g m p h i e ~a ~ m y d o p e d i aorseirneo a d ~ e r h n o ~ o bmd y , d; Doubleday:GudenCity,NY,1983:(elp679,lh)p993,(elp~6,ldlp833,lelp743, tfl P 931. ( 9 ) ~ 9 0 3(h) , P 532. 4. ChemEng.New8 1985,INovembn41,~,1385, ID-her 91,% 1985, I D e a m h r 16). 3: 1985, ID^^^^^^ 23). 3: 1986, I J ~ W61, 29: 1186, I J ~ ~ U W201, W, 1986. (February 101.47: 1386, lFehruary241.3: 1986, (March 10). 3: 1986, (April 211,3. R.;Da.ing, W. J Am, Cham, see, 1944,66,%9, 5, woo 6. ~oymour,R 8.; carraher. C. E.. J I . P O I ~ ~ W C h m ~ i s t v ~: c k k c rNsaYork, 1981. I. Chem. Eng. News 1985, (December 23),20: Dkeouer 198% (February). 8( Chem. EM. Now8 1988, I A w s t 29). 8. Castella. J.; Senatosa, F. J. Chon. E d u . 1986,W. 630. 9. hiseh,H.L.;Wasseman,E.J.Am.ChomSac.lW1,83,3789. 10. Walba, D. M.; R i c h d s , R M.; Haltingto'~nger,R C. J. Am. Chem. Sm. 1982,101,3219. 11. Grstlon. R. Philolelio Chim.Phya. L)87,9,54: 1981;9.1W.
