Richard Anschutz (1852-1937), Kekule's Forgotten Successor Part II: The Work George 6.Kauffman California State University, Fresno, Fresno, CA 93740 Work
Anschutz's major publications all dealt with organic chemistry (3).In fact, Paul Walden listed him among "the great scientific pioneers of modern organic chemistry" (16, p. 13). Polybasic Acids When Anschutz began his own scientific research, the problem of the isomerism of maleic and fumaric acids was of great concern to organic chemists in general and to those a t Bonn in particular in view of KekulPs work on the unsaturated dicarboxylic acids. Thus, i t was only natural that Anschutz should first turn to this problem. The historv of the develonment of the conceDt . of geometric (cis-rrnm, isomerism and the determination of the structures of maleic and fumaric acids has heen dealt with bv lhde I 17, and need not be repeated here. It suffices to pointout that in 1874 Jacobus Henricus van't Hoff (1852-1911) used his concept of the tetrahedral carbon atom to explain optical isomerism and then annlied it to another t w e of isomerism caused by "the influence of the new hyposesis upon compounds containine douhlv linked carbon atoms" (18). The first example tha; he was the case of malric and fumaric acids. in n,hich he cons~dercdthe two douhlr-honded carhun atoms to involve the linking of two tetrahedral edges. This resulted in the structural formulas accepted today, viz.,
-
H--C-H H-C-H
H-C-COOH
I
only on these compounds but also on many polybasic acids and their derivatives. Realizing that both maleic and fumaric acids give different salts of one and the same metal but that only fumaric acid gives an ester, Anschutz, in 1878, decided to begin his studies with the preparation of maleic acid ester. Because of the limited budget of the institute, he had to prepare malic acid, the necessary starting material from mountain ash berries (4, Vol. 1, pp. 490-491). After preparing maleic and fumaric acids from malic acid, he treated their silver salts with ethyl iodide and in both cases obtained pure ethyl fumarate (22). However. when Anschutz repeated the exprr,menw with methyl iodide, he f w n d that the ester d>taincdon distillation was not nrmpletely methyl fumarate, which led him to the startling conclusion that traces of iodine from alkyl iodides cause isomerization of esters of maleic acid to those of fumaric acid (23). Anschutz's account of this, his first major discovery, in his biography of Kekulb provides us in his own words with a view of conditions in the institute and of his relations with his teacher: On the other hand, I worked at that time with fumarie and maleic acids, a field for which KekulC's experiments in Ghent hadbeenlaying the foundations and for which van? HofTs stereochemical views of the isomerism of racemic acid and meso-tartaricacid had relevance. Sweral timev I had diirursed ~ i t Kekuli. h theprohlrm of the iwmrrism i,f furnaricand mnlew acldi, which had already heencalled to my nrtentiw during my rimemTuthgen with Virr~y.It hndwcurred ~~
~~
~
~
II
HOCK-C-H
Maleie Acid (cis)
Fumarie Acid (ham)
I
I1
Johannes Wislicenus (1835-1902) clearly recognized the value of van't Hoffs new theory and applied it to a number of cases of what we now know to he geometric isomerism, including maleic and fumaric acids (19). On the other hand, many other chemists such as Liebig, KekuK, Erlenmeyer, Richter, Fittig, Claus, Lossen, Hinrichsen, Michael, Beilstein, and Anschutz opposed this view and attempted to solve the structural problems involved in this kind of isomerism without using van't Hoffs new theory. Whiie Anschiitz assigned the ethylenedicarboxylic acid formula I1 (not to be regarded spatially, however) to fumaric acid, he believed maleic acid to possess a dihydroxylactone structure (20): OH
nr In his mistaken attempts to Drove that maleic and fumaric acids are structural isomers ;ather than geometric isomers l21), Anschutz carried out much u s t h l s y n t h ~ t i cwork not Pat? I, dealing with Anschiitr's life, appeared on pag@627 of the July issue.
Richard Anschutr as an old man. Photo counesy of Professor Dr. Gimler Be,-
gerhotf, UniversitM Bonn.
Volume 59 Number 9
Se~ternber1982
745
w me that different a d s of the anme metal could indeed beobrnined for both acids hut thnr only the ester of fumaric acid was known. Kekuli. had abandoned the so-mlledgap formula ILtirkmformell for maleic acid, but he was inclined to v& fumarie &id as a poly&ic maleic acid. When I told him that I intended to prepare the ethyl esters of both acids from the silver salts bv use of ethvl iodide. ~.he thought that the malric acid ester would polymeriw more easily than the free arid. ' Hut why don't you try it?" [he said.] Malic acid. which the Marquart factor). furnished in a very pure state but very expensively, served as starting material for the preparation of both aeids; it was made from mountain ash berries [Vogelbeeren]. In a cellar room of the institute, Kekulb had set up several machines for laree scale oroduction that were heated hv steam. The d~stilledwater f i r the in&~ture was also prepared the,;. kext tothe distillation apparatus itwd a large rupprr retort and a large waporaring dish. Kekul6 wnntpd me u, w e t h ~Pqulpment, s which had newr been used since it was bought, to prepare larger amounts of malic acid. He ordered 9M) kilograms [19& lh.] of half-ripe mountain ash berries, which were easy to obtain, since a series of highways in the vicinity of Bonn are planted with walks of mountain ash trees. He had previouslv had constructed an oblone" wooden troueh in which the mountain ash hernes were to he crushed with n millstme hefme aquerzing. A strong piece of woad shoved hy the m~.lstoneallowcd me and Thclrn, the machinist of the institute, t u crush the muuntain ash berries by rolling it back and forth;an activity requiring great exertion. "By preparing the malic acid in this way the institute will save somucb money," Kekulb said to me, "that we can buy afine horizontal press to make up far it." The two of us bought it in Cologne, and then our factory production really hegan. The mountain ash berries came in tight bags, and in the new press they gave the malic aeid juice, whieh yielded crude calcium malate when neutralized with lime. From the solution of the neutral calcium salt in dilute nitric aeid the more or less brown-colored aeid calcium malate crystallized; it was purified with animal charcoal. To obtain the free malic acid the dilute solution of the acid calcium malate is reacted with the calculated amount of oxalic acid, and the filtrate from the calcium oxalata is evaporated to crystallization. Kekul6 was very pleased by this large-scaleoperation, which furnished me with copious amounts of malic acid. From the malic acid I prepared fumaric and maleic acids, and from their silver salts I prepared the two ethyl esters with ethyl iodide. In reality I obtained identical esters: even the one obtained as silver maleate gave potassium fumarate on saponifying with caustic potash solution (22). When I carried out these experiments using methyl iodide, I observed that on distillation the dimethyl ester prepared from silver maleate was not completely converted to the solid fumaric acid dimethyl ester. I then found that small amounts of iodine, as those whieh are easily liberated on working with alkyl iodides, an distillation convert the maleic acid esters into the corresponding fumaric acid esters (23) [4, Vol. 1,pp. 4904911. ~~
~
I n two articles published with Kekul6, Anschutz showed that the "dihydroxyfumaric acid" (Bioxyfumarsaure) (24a) and trihydroxymaleic acid (Trioxymaleinsaure) (24b) obtained hv Tanatar hv oxidizing fumaric acid and maleic acid. respecti"ely, with alkaline potassium permanganate were actually racemic acid ( 4 , Vd. 1, p. 492; 70) and inactive tartaric acid (meso-tartaric acid), respectively (7b).This important work, which Anschutz always considered one of his most important discoveries, formed the starting point for the investigations that he carried out through many years with numerous co-workers on the constitution and nronerties of saturated and unsaturated dicarhoxylic aciis. kccording to Anschutz. i t was not imnossihle "that the cause of the isomerism of fumaric acid and maleic acid is of the same type as that of racemic acid and inactive tartaric acid." However, Anschutz's attempts to isolate optically active antipodes, of course, did not succeed. Also, a further possibility suggested hy Kekul6 and Erlenmeyer (25), viz., that fumaric acid is a polymer of maleic acid, had been disproved by Hiibner and Schreiber, who found the vapor densities of both acids to correspond to the monomeric formula (26). However, Anschiitz showed that the vapor densities of racemic and tartaric acids are also monomolecular and identical although the molecule of solid racemic acid is composed of one molecule each of d - and 1-tartaric acid (20). From this he concluded that one is not entitled to infer' the equality of the molecular
746
Journal of Chemical Education
Augffil KekulC as an old man. Taken hom Sachtleben.R.. and Hermaon. A., "Von der Alchernie 2°C Grossynthese: Grosse Chemiker." Ernst Banenberg Verlag. Munich. 1960. p. 36.
weights of the solid acids from the eoualitv of the vauor densities of maleic and fumaric acids (2?), an: in arelated study he showed that neither the hydrogen atoms of the carhoxyl groups nor those of the hydroxyl groups can bring about the bonding of the two tartaric acid molecules (28). Thus Anschutz concerned himself with a problem that Paul Pfeiffer later worked so successfully on, viz., the determination of the constitution of organic molecular compounds (29). In attempting to learn if Raoult's method could be used to differentiate between atomic (valence) bonding and molecular bonding-the two types of bonding proposed by Kekul6Anschutz used the method to determine the molecular weight of a true molecular compound, naphthalene-picric acid, which was found to be half the expected value (30). Meanwhile, Anschiitz had expanded his work on polybasic acids to the three isomeric acids resulting from the pyrolysis of citric acid, viz., mesaconic, citraconic, and itaconic acids (31). By use of acetyl chloride, an elegant and versatile reagent that he often usedto prepare acid anhydrides (32), he was able to prepare the unknown itaconic acid anhydride (31a) and later aconitic acid anhydride (31d) and by study of their hehavior on heating to explain the formation of citraconic acid anhydride from the distillation of citric acid (31d). Fittig had found that both maleic and fumaric acids are reduced by nascent hydrogen t o succinic acid and hence contain the structure
(32c), and for fumaric acid Ansrhutz accepted the ethylene dicarboxylicacid formula mentioned above (11). However, Le Bel and van't Hoffs purely stereochemical explanation for the constitution (11 maleic and fumaric acids did not appeal to Anschutr. for he believed it unlikelv "that theslieht difference in the spatial position of the COOH groups should cause such a far-reaching difference in properties" (20). Influenced by Bredt's finding that y-ketonic acids can also react as y-hydroxvlactones (33)and the fact that dialkvlmaleic acids exist only;n the tbrm of their anhydrides just i k e carhon d ~ o x ~ d e , Anschutz orooosed for muleic acid the cvclic dihvdroxvlactone formula mentioned above (III), whieh does not contain a carboxyl group a t all: "The isomerism between fumaric acid and maleic acid thus descends from the sphere of geometric isomerism into that of the wholly ordinary structural isomerism!' However, he explicitly emphasized that a stereochemical formulation of both acids was in no way impossible: "Perhaps the stereochemical difference is even the cause of the different structural-chemical arrangement of the two acids."
By a series of shrewd arguments and experiments Anschiitz endeavored to nrovc that maleic acid has the dihsdroxvlactone structure. For example, he used it to explain the acid-catalyzed isomerization of maleic acid to fumaric acid (21):
a reaction which had been previously interpreted correctly by Wislicenus: H4-COOH
II
H4-H
+w
+
H\
COOH
0 /COOH
I
i %Mam
CI
\A/"
-Ha
I
C
HcI'OOH H
MaIeie Acid
Monoehlorosuecinie Acid
HOOOC-H
n H-6-COOH
Fumarie Acid
In the course of his attempts to prove his dihydroxylactone formula Anschutz carried out valuable research on anils of maleic, fumaric, citraconic, and mesaconic acids (31,34), the isomeric diphenylsuccinic acids (351, the action of phosphom ( V ) chloride on the imides of dibasic acids (361, the semiesterification of unsymmetrical dicarboxylic acids and the semisaoonification of their neutral esters (37). the seoaration and characterization of isomeric acid estersby use of acid anilides (31.37). and reactions of ~henvlsuccinicacid (37.38). Anschutz adhered to h:s dihydro&lackne formula for mdeir acid and its derivatives almost to the end of his career. Onlv . hk in 1928, in his very last publication on this topic ( 2 1 ~ )did favor the open formula for maleic acid and its derivatives, based on his work on acid amides carried out with 0. Scharfenberg, P. Tmmmel, and A. von Volborth. However, he adhered to his dibydroxylactone formula for the alkylmaleic and phenylmaleic acids. Oxalic Acid and Its Derivatives The starting point for Anschutz's investigations on oxnlic arid and its drrivativei (391 was his av~licationto anhydrous oxalic acid of his previously discovered method of re paring dicarboxylic acid anhydrides by heating the acids with acetyl chloride (32). By use of anhydrous oxalic acid he was able to convert b e n d chloride to benzaldehyde and benzotricbloride to benzoyl chloride (39a). He also investigated the action of antimony(V) chloride on oxalic acid (40). Anschutz found anhydrous oxalic acid to be an unusually suitable reagent for splitting off water and thereby effecting condensation. By its use he was able to prepare leucomalachite green, fluorescein, and other compounds (396). When anhvdrous oxalic acid reacts with alcohols. the corresponding fdrmic acid ester is always obtained along with the neutral oxalic acid ester if the reaction mixture is distilled a t atmospheric pressure. However, by distilling under reduced Dressure. a techniaue in which he was a oioneer. Anschiitz was Hble to obtain methyl-, ethyl-, n - propyi-, and &opropyloxalic acid esters (39c, 41a, 4Ib). Also by use of distillation under reduced pressure, he was able to isolate dichlorooxalic acid esters of general formula
P
ROCOC--CL , '0.~
a new class of organic compounds, from the reaction between phosphom(V) chloride on oxalic acid esters (3%). On distillation at atmospheric pressure these dichlorooxalicacid esters decompose to the alkyloxalic acid chlorides. By treating them
:.. .. -1
I.
August Kekule Room in Darrnstadt (collected by Richard Anschutz). Photo courtesy of Professor Dr. Gunter Bergerhoff, Universitit Bonn.
with sodium alcoholate Anschutz obtained tetraalkyloxalic acid esters or half orthooxalic acid esters, R.OM).C-0-R, '0.~
the first representatives of the half ortho esters of a dibasic acid (39c). Higher Aromatic Hydrocarbons and the Function of Aluminum Chloride Anschutz's work on higher aromatic hydrocarbons began with his collaboration with a student of Carl Graebe's, Gustav Schultz (12). who spent the years 18761877 at Bonn as Kekul8's Privatassistent. When Schultz left for Strasbourg, Anschtitz continued work in this area. He summarized the results of his experiments on the oxidation of phenanthroquinone (9) in his so-called law of pyrocondensation: "Pyrocondensations of phenyl-phenyl derivatives to phenyleneohenvlene . . derivatives onlv take d a c e so that the atoms or atom groups holding together the phenyl residues assume the diortho oosition to the hondine. position of the vhenvl resi.. . dues" ( i 2 ~ 1 )These . inveutirations formed the basis for Anschutz's vreviouslv mentioned Ilahil~lotrr)nsschr~ft. In thecourse ofbis studies of the maleic acid-fumaric acid isomerism, Anschutz, over a period of four gears, investicated the preparation and physicaiproperties of bromoethanei and hromoethylenes (42d). He proved that all the hitherto described methods for preparing tetraphenylethane, e.g., reduction of benzhvdrol with zinc and hydrochloric acid, distillation of beniophenone with zinc dust, reduction of beuzpinacone and 8-benzpinacol with hydriodic acid, yield the same hvdrocarbon. which is identical with the tetraphenylethane formed b; the reduction of tetraphenylethylene with sodium and alcohol (39b. . .42b).. He thus nroved that the reaction of asyrn-tetrabromoethane with benzene and aluminum chloride is accompanied by a rearrangement. Volume 59
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Anschutz then carried out a series of Friedel-Crafts reactions (43) of brominated ethanes and ethylene8 with benzene and aluminum chloride (44-49). The most important and surprising of these was the reaction of benzene and aluminum chloride on acetylene tetrahromide (1,1,2,2-tetrabromoethane) (44), which yielded, along with hromobenzene and asym-diphenylethane, anthracene, H I
a reaction which confirmed the formula proposed for anthracene by Graebe and Liehermann (49). Also, by the action of benzene and aluminum chloride on ethylidene chloride and ethylidene bromide, Anschutz obtained the hitherto unknown sym-dimethyldihydroanthracene(45a, 47). In these reactions, Anschutz used carbon disulfide for the first time as a solvent and obtained almost quantitative conversions. He also studied the shifting of alkyl side chains on the ring in these reactions (42f,46a, 47). The Action of Phosphorus Chlorides on Phenol, Phenolcarboxylic Acids, and Phenolsulfonic Acids Anschutz's research on this tonic. . . which beean in 1885 and continued for more than four dlwdl%(50-561,waisn extenhion uf his itiveiti~ationc g f the action of antimunv(\') chloride on anhydrous oialic acid (40). Starting with'the initially purely practical question of synthesizing pure salicyl chloride, he broadened his studies to include the action of both phosphorus(II1) and phosphorus(V) chlorides on other hydroxy compounds, especially the isomeric hydroxybenzoic and hydroxvhenzenesulfonic acids ( 5 0 ~50c. . 51a. 52. 5 8 ~ ) In . so doini, he confirmed the anahngy between ~henolc&,oxy~ic and phenolsuliunic acids postulawd in 1867 by KekulE r50c,
without deciding between the two, although favoring formula VIII in his later works. Once again his son Ludwig proved him wrone when in 1924 he showed the structural formula IX to be correct (57a). While salicvl chloride was not obtained bv the action of PC1on salicylic acid, the action of PC15 on salicylic acids in wbici the second ortho nosition to the ohenolic hvdroxvl " monn - . was occupied by a sibstituent yieided quite-easily the corresponding free phenolcarboxylic acid chlorides (506). The chemical character of the ortho substituent had no special influence on this reaction. and Anschutz and his students prepared a great number of methyl-, chloro-, bromo-, iodo-, and nitrosalicylic acid chlorides (53). Also, a-bydroxy-0-naphthoic acid, in which the ortho substituent is a carbon atom of a twin ring, is easily converted into the free hydroxynaphthoyl chloride. On the other hand, all salicylic acids in which the position ortho to the phenolic hydroxyl group is not substituted as well as salicylic acid itself yield the phosphorus hydroxychloride derivatives of the acid chloride. From this Anschutz concluded that in the reaction between PC15 and salicylic acid the ortho substituents protect the phenolic hydroxyl group from further attack by the phoapho-m hydroxichloride that is formed. The true nature of these reactions was later clarified by his son Ludwig (57b). The analogy which Anschutz found between the phenolcarboxylic acids and the phenolsulfonic acids extended to the behavior toward PC15 of o-phenolsulfonic acids which contain a second ortho substituent along with the phenolic hydroxyl group. Together with Curten, Anschutz showed, in the examnle of D-cresol-6-nitro-2-sulfonic acid and of D-cresoldisulfonic acid, that even in these cases the free phenolsnlfonic acid chlorides are obtained without the PCIq actine" on the hydroxyl group "pinched" (eingeklemmt) between two ortho substituents (56).
Salicylides. Dithiosalicylides, and Sulfonylides This aspect of Anschutz's work (58-65) began with his 6.1 --,.l clarification of the reaction between phosphorus oxychloride In equimolar ratios, salicvlic acid was found to react with PCIBtohield a compou~dof f o r m u l a ~ ~ ~ ~ 0 ~and ~ ~with 1 ( 5 1 )and salicylic acid, which had been investigated earlier by Gerhardt, Kraut, and Hugo Schiff without any noteworthy PC15 to vield a comoonnd of formula C~HAOXPCL . ~. .(52). For result. By carrying out the reaction in toluene or xylene, Anboth of these prod;cts cyclic and open formulas were posschutz was able to isolate in a pure state the first two polymers sible: of the nonexistent salicylic acid lactone-tetrasalicylide
IV
v
and
and polysalicylide
rwCO1 .
VI
VII
With no convincing proof for the PC13 product, Anschutz favored cyclic structure IV and therefore called it salicylophosphorous acid monochloride. It was not until 1924 that his son Ludwig showed that the open structure V was correct ( 5 7 ~ )On . the other hand, since the PC15 product behaved more like a derivative of POCl3 than one of PC15 and since mand p-hydroxybenzoic acids yielded similar products with PC15, in which a cyclic structure would be impossible, Anschutz nronosed the m e n structure VII for this nroduct. For tbe three isomeiic phenolcarboxylic acids; further reaction of the compounds C7H4O3PCI3with PC15 causes replacement of one of the oxygen atoms by two chlorine atoms, resultine in the com~oundsC7HaO?PCls. . . - -. for which Anschktz proposed the two possible structural formulas:
VIII
748
IX
Journal of Chemical Education
. .
Tetrasalicylide, unlike the insoluble polysalicylide, separates from chloroform on cooline in the form of a crvstalline compound with two molecules of chluroform otcryatsllizarion (113 of its weirhtj. The rhlumfurm liheratrd on heating this compound isparticularly pure and stable and was therefore recommended as an anaesthetic by Anschutz Gab, 59d). I t is still used today and designated "Anschutz" chloroform. This important practical discovery began with Anschutz's work on diglycolic acid and thiodiglycolic acid anhydrides (59,63) and glycolide (58e). Many years later, in 1919, Anschutz, on distilling acetylsalicylic acid (aspirin) under reduced pressure, observed the formation of two isomeric disalicylides (58h). One, which he designated 8-salicylide, had been prepared previously by Einhorn and Pfeiffer bv another method (66). Anschutz designated the second an; main product as a-disaiicylide, and he found that, mixed with a lesser amount of the /%isomer, it could also be obtained by distilling under reduced pressure an entire series of other salicylic acid derivatives (acetylsalicylic acid anhydride, salol, O-salicylsalicylic acid chloride,
0-acetyl-0-salicylsalicylicacid, tetrasalicylide,polysalicylide, and nure a- and R-disalicvlides) (58i. 65.69). BY distilling acet;lrhiosalicyliL:acid under reduced pressure ~ h c h i ~and tz Khodius (61) obtained the dithiosalicvlide rorresponding to
Hy the action of POC1:g on phenol- and naphtholsulfonic acids or their alkali metalsalts Ansrhiitrohtaint:d thec.vclicdouble esters of these acids corresponding to the a-salicykdes, which he designated sulfonylides (50b, 58g, 62).
Ionic ester and consequent lactone formation accompanied by separation of sodium chloride Anschutz obtained substituted P-hydroxycoumarin a-carboxylic acid esters, from which 0-hydroxycoumarin could he obtained by treatment with aqueous sodium hydroxide. T o stress the far-reaching similarity of 8-coumarin to tetronic acid, in which the methylene group is replaced by a phenylene gruup, Anschutz proposed to call it benruretronic acid: H&
'"-i"
qOH)=CH
'0-co
Tetronie Acid
ao-b
Benzotetronie Acid
Anschutz also devised new syntheses for coumarin and Dihydroxflartaric Acid and Tartrazine (67-70) tetronic acid, and he synthesized pure dimethyltetronic acid, Dihydroxytartaric acid has long played an important role and in his last published experimental paper (75) he synthein the history of the constitution of benzene, but after KekulB sized a ring homologue of tetronic acid-y,y-dimethylhad shown in 1884thatcarboxytartronicacid HOOCC(0H)0-methylcyclohomotetronicacid: .(COOH)* is dihydroxytartaric acid, he did not continue his work on this compound. By repeated treatment of its sodium salt with alcohol and hydrochloric acid and distillation under ".., reduced pressure, Anschutz and Parlato, in 1892, obtained, (2%-&o-h not the expected dihydroxytartaric acid ester, but dihydroxyMiscellaneous Experimental Work snccinic acid ester (68a). In a similar manner thev ohtained Among Anschutz's most important smaller works are his hydroxymalonic acid ester from mesoxalic acid (6i(b). Distilinvestigations of pipitzahoinic acid, derived from the root of lation at atmosnheric oressure of dihvdroxvsuccinic acid ester Trixis pipitzahuac (his only work on a natural product) (76), and of hydroxymalonicarid e3ter yields o d i c acid ester (690J. a new preparative reaction for isocyanic acid esters, which From dihvdroxvs~a.c~nir acid and ohenvlhvdrazine Anschutz a comolete exolanation of the nrocesses takina.place . and paniy obtained "three ~ r ~ ~ t a l l ~ ~ r ~ different ~ h i c a l l involved ~ in the Hofmann mustiird uil reaction (77), the formation and osazones with different meltine as the first case of an ..noints . ronstitution of mesitonic and nhorunic acids (78). the addition osxzone isomerism, an isomeric phenomenon which recalls of hydrucyanic ac~dtn hemaiacetuphenone (371, mesitylenethat of the three srereuisomcrir hcnzildioximes" (6YbJ.The lactonr and isudehvdroaretic acid (791.the halfway reduction amber-yellow osazones are easily converted into a red pyrazof aromatic polyniiro compounds by tin(11) chloGde in alcoolone: holic HCI solution (80). the preparation of aromatic selenic acids (81 I, the thermal cleaviged aryl esters of l'umaric and cinnamir acids to diarvlethvlenes (82). the action of nitric arid on mym-diphenyleth&e &d asym-diphenylethylene (83), and the constitution of the tert-bntvl- and tert-amylphenols Thii reaction gave Anschutz the idea that tartrazine (modem, (84). Acid Yellow 23 or FDC Yellow No. 5, the most widely used We have already seen how Anschutz made effective use of yellow food dye) might not have the osazone formula provacuum distillation in the isolation and purification of nnposed in 1884 by J. H. Ziegler, its discoverer, stable liquid substances a t a time when this elegant technique had not yet become commonplace (58h, i, j; 65; 67a; 85). In fact, Anschutz and another of Kekulgs students, Wilhelm Dittmar, independently of each other, were the first chemists to distill under reduced pressure, and Anschutz wrote a book but rather the phenylhydrazonopyrazolonestructure: on the subject (86). He also devised various items of laboratory apparatus, e.g., a fractionating system for the distillation of easily solidified substances and the short thermometer that still bears his name (7,12,87). ~
Anschutz showed that the analysis and conversion reactions of tartrazine are incompntihle with the osarone strurture hut eompatihle with the pyrarolone structure, which isaccepted Tetronic and Benzotetronic Acids ( 71-75) Anschutz's discovery of free phenolcarboxylic acid chlorides by the action of PCls on ortho-substituted salicylic acids naturally suggested their application to nuclear synthetic reactions. Thus reaction of these chlorides with benzene and aluminum chloride furnished a series of substituted o-hydroxyhenzophenones (42g). Anschutz and his students thoroughly investigated the reaction of phenolcarboxylic acid chlorides with the sodium salts of malonic ester, cyanoacetic ester, and acetoacetic ester (71a, b) and found that the phenolic hydroxyl group had not completely lost its reactivity by the second ortho-substitution. By reaction with sodium ma-
Biography, History of Chemistry, and Literary Works When KekulB died in the summer of 1896,Emil Fischer, on behalf of the Deutsche Chemische Gesellschaft, asked Anschiitz to write a detailed obituary. Anschiitz was the ideal person for this task, for of all KekulB's students and w-workers not only had he spent the most time with (21 years) and been the closest in personal and professional contact with KekulB, but also he had a strong interest in the history of chemistry. Although he worked on KeknlB's biography . . during ~ all his tenure at Bonn, he really only made any progress on %during semester vacations, and he completed the work only after his retirement. Thirty-three years after KekulB's death, the two-volume book appeared on the centennial of his birth (4). Far more than a definitive biography and appreciation of KekulB, the hook details the origin and development of valence theory, the theory of the tetravalence of the carbon atom, and the benzene theory, and i t discusses the work of all of KekulB's students and co-workers as well as of all later authorities who contributed to the development of his theories. Volume 59
Number 9 September 1982
749
Two of Anschiitz's most important contrihutions to the of chemistry-his discoveries of the fate of Archibald Scott C o u ~ e (1831-1892) r ( 8 8 )and of a lona foreotten article by ~oseph'l.usrhn~idt ,1821 18951 ( 8 9 ) -o&inated from his rrsearch on t h r Kekul6 biuaraohv. Coui)er's most i m ~ o r t a n t puhlication, the eompleteG forgotten i n d neglected "On a New Chemical Theorv" ( 9 0 ) . in which he Drooosed the tetrwalence u t carbon and the self-linking o f u i l r i m atcms sim u l r a n e u ~ ~ s lwith y and indeoendentlv 01' Kekul6 (911,was translated in& German and edited by ~nschiitzfor "Ostwald's Klassiker der exakten Wissenschaften" (92).Anschutz's first acquaintance with Couper occurred in 1885 when he was beginning his own research on the action of PC15 on salicylic acid (50a). In the English version (93b) of Couper's paper "Researches on Salicylic Acid" (93a),Anschutz found the first structural formulas in the modern sense of the word: "In fact, I know of no publication from that time, which attempted to display the mutual bonding of single carbon atoms!'Anschutz made an intensive effort to locate information about the unknown C o u ~ e rand . with the assistance of Alexander Crum Brown of ~ d i n d u r ~ University h he succeeded in this so-called " C o u ~ e rQuest." the details of which have a ~ ~ e a r eindJ. CHEM. E&C. ( 2 0 ) .In 1908 Anschiitz resurrected the tragic tale of Cou~er'slife and work from oblivion in a hioeraohical article that'appeared in both English ( l a ) and ~ e r k averi sions ( I b ) .Immediately after World War I, when the German authorities censured Anschutz for his friendliness toward British occuoation trooDs attendina his lectures in Bonn. he replied, here may be anothe; Couper among th&" (88a). Anichutz's attention to Loschmidt's hrurhure of 1801 entitlrd 'Chrmische Studien" wasdrawn hy a note i n KekulB's fiunuus p:tprr 01' 1865. "Sur la cunstiturion des substanres ar~~mutiaues" (9.2).in which the henzene ring is oostulated. After a lbng search, Anschutz finally located a copy of this extremely rare publication from the Vienna antiquary Franz Deuticke. Recognizing its value for the history of chemistry, he devoted two articles to it (95) and reprinted and edited it for "Ostwald's Klassiker" (96). This overlooked classic auticipated Kekul6 hv four years in assigning . .a six-atom cvclic str"cture to benzene, and it contains many features of great interest, e.g., an explanation of the isomerism between henzyl alcohol, CfiHsCHzOH, and cresol, CH3C6H40H, and the representation of cyanuric acid by a ring structure of three carbon atoms alternately linked with three nitrogen atoms by single and double bonds. Among Anschutz's other historical contrihutions are his biographical articles on Ludwig Claisen ( 8 ) (his last published paper), Carl Glaser (97),Wilhelm Korner (98),Hans Landolt ( 9 9 ) ,and Eherhard Rimbach (100).On June 9,1903, he presented a lecture on liis mentor Kekulb's life and work at the dedication of the Kekd6 monument at the Chemical Institute of the Universitiit Bonn, which was erected upon his initiative (101 ). After his return to his home city of Darmstadt in the summer of 1925. Anschutz.. toeether with Ernst Berl. collected all of his numerous letters, notes, photographs, and other mementos of Kekul6 to he preserved in a Kekul6 Room at Anschutz's alma mater, the Darmstadt Technische Hochschule. Anschutz's lecture at the dedication of the AueustKekul6-Zimmer held on June 25.1927, was his last academic lecture Anschutz's endeavors in textbook writing, like many of his other activities, were initiated by Kekul6, who asked him to write the sections on homologues of henzoic acid and primary aromatic hydroxy alcohols and hydroxy aldehydes and to collaborate with him on the sections on primary aromatic alcohols and aromatic aldehvdes for the third volume (Lieferung) of his famous textbook "Lehrbuch der organischin Chemie" (102),which appeared "unter Mitwirkung von Dr. R. Anschutz in Bonn und Dr. G. Schultz in Strasshurg." In 1891, when Victor von Richter, the author of widely used history
750
Journal of Chemical Education
textbooks on inorganic and organic chemistry, died, his puhlisher in Bonn turned to the younger Dozenten at the universitv t o continue these hiehlv .. , successful hooks. Heinrich ~ l i n & rundertouk rrviie the inorganic hook and Ansrhutz the orzanic h w k . Thr first w l u m ~to , he revised In Ansrhutz was thk 7th edition, which appeared in 1894, anduin1935, at the age of eighty-three, Anschutz published the second volume of the 12th edition (13).During his more than forty years work on this project, this text became known throughout the world as the "Richter-Anschutz Lehrhuch" and "little Beilstein." As the most widely circulated and recognized textbook of organic chemistry, it served as an indispensable advisor for several generations not only of students hut also of academic and industrial chemists (16, p. 30). Literature Cited (16) Walden, P.."Gesehiehtederor~snischen Chemieseit 1880:JuliusSpringer. Berlin, 1941.
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1hde.A.J., J. C H E M . E D U C . , ~ ~ , (1959). ~~O v d t Hdf,J. H., Archiuss n&rlondaiaedar seisnees eractas d nafurdles,9.445 11874): far an English translationsee Richardson. 0. M. itraonl. and ed.l."Foundatims of Stereoehemi~try.Memoirj by Pasteur, van't Hoff, Lo Bel, and Wislieenus."American Book Co., New York. N.Y., 1901,pp. 37-46. Wislieenus. J., Abhandl. kaniei. idchs. Gesall. Wissensch. Lcipzip. Math-Phyz. Klasss, 14,1i1887); Ber,20.1W8(1887):21,S8L118881. Anech0tz,R.,Ann.,239,161 (18871. Anrehiltz, R.. (81 Bsr, 21,518 (1888):ihl Ann.. 254, 168 11889);lcl Ann.. 461, 155 11928). Anseh0tz.R.. Bet. 11.1644 l18781. A D S C ~ O ~ ZR.; ; BDI: 12: 2280 i1879i. Tanatar,S.,Ber., 11, ( 8 ) 2293, ih) I383 11878). Erlenmeyer, E., Be?., 3,339 11870):19.1936 (18861. Hilbner,H..and Sehreiber,G.,Z.fir Chem.,7,7L2 11871). Ansch8ta.R.Bsr. 18, 1397 (18851. Anseh0tz,R.,Ann.,247.111 (1888). Pfeiffe~P., "Olganlsche MoleWverhindungen.l'2ndEd.. Ferdinand Enke. Stultgart. ,a""
Anschntz.R., Ann., 253,34311889):Be,.. 22,980 (1889). la) Ansehiltz, R,and Petri,W.,Ber, 13,1539,154111880):lb) AnschOtz,R.,Rer,14, 2784 11881):b)Ber,38,690 11905):Id) Ansch0tz. R.,snd Bertram,W.. Ber.37, 3967 (1904):(el Ansch0tz. R.. and Routher,F., Ann., 254.129 (1889); 10Ansch0tz. R., Ann.,353,139(19071, Amhilh.R..ial Be?, 10.325,1881(1877):(b)Ann..226,1118M):(el Fittig.R..Anh, 188.42 (18771. Bredt,J.,Ann.,256,314118891. Ansch0C. R.. Ann.. 259,137 118901. Ansch0tr,R.,andBendh.P.,Ann.,259,61(1890). R.. Be,., Anreh0h.R.. and Beauis,C..Ann..263.1FA 11891):295.n (1897);AnschOtz. 28.59 11895);Ann., 295.27 11897):Ansch0tz. R., and Guenther,A,, Ann.. 295.43 (1897):Ansehilb, R, and Meyerfeld, J.. Ann., 295.56 11897):Anschntz. R., and Schroeter,G.,Ann.,295,67 11897).
AnachW R.. and Montfort.W . F.,Ann.284.1 11895);AnrehcXzR.. . and Drugmen, J., Be,., M. 2649 11897):Anschiltz. R.. BPI, 30, 2652 11897):Ann.. 354, 117
907):lhl Anachiltz, R.. and Mo O > A , """
(81) AnschQtr, R., KsUcn, J., and Riepenk~3ger,K., Ber., 52,1860 (1919): AnschBtz, R., and Teutenherg, F.. BPI. 57.1018 (19241. (82) Anschutz, R.,Bor, 18. 1915 (1885): AnsehOtr, R., and Wirtz, Q.,E e l , 18, 1947 i. lR P. ,,. , ..
(83) Anschutz, R., and R0mig.E.. Be?,, 18,935 (1885):Ann.,233.327 (1366): Ansehiltz, R.,and Hilhert. A.. B s r , 54.1854 (1921): 57,1697 (1924). (84) Ansch0tz. R..andRauff,G..Ann.,327,201(1903). (85) Anschutz, R., and Evans, N. P.,Ann., 253.95 11889). (85) Ansehutz, R.. "Die Dwtillation unter vermindertem Dmek im Laborsforium." Behrendt, Bonn. 1881; 2nd d.(with H. Reittell, F. Cohen, Bonn,1895. (87) Anrchiitz. R.,J . prokL. Chem., 121 116,291 (1927).
(88) Benfey. O.T., (a) "Arehibald h t t Couper" in Fsrhr,E. lEdito4,"GreatChemidP," . 36.319 lntemienee Publishers, Now York, 1 3 6 1 . 703-715: ~~ (h) J. C ~ MEouC., 15:9, and f 8 1 k u i n g r ) m p ~ l d m p8ll.n $3 Rohm. W .I, hmn . I M I I I I ll,.?hn# (11 " m 1:rllirpie.l'. ('. Ed.ror,."Urt#onary of r entlfc H ~ g r s p h )" ( ' h a r k S;, l.ner'.Sm. NPXY r r l N ) , 1973, \ ' d R III.
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.,.~,,
(90) Coupez,A S. la) Compf. rend, 46.1157 (1850): (h)Phil.Mog., 141 16, lW(1858): h d . and reprinted by L. Dohhi" in ,'On s New Chemical Theory and Researches on WiqlicAeid."AlemhieClubRcpRntz No. 21.E &S.Livkgstone.Mmburgh. 1953, "n*. 9-72 .. ..
(91) Kekul6, A., Ann., 106. 129 (1858): for sn Engl. trand. sea Benfqi, 0. T. (Editor), "Classier in theTheoryof Chemical Comhination,"Do"e~o Publinrtiona, New Y0.k. N.Y., 1963, p p 109-131. (92) Anschiltz, R. (Editor), "Uber eine ncue ehcmische Theorie yon Archibald Scott Couper." Oatvallds Klssikor der erakten Wisenaehaften Nr. 183, Wilhalm en^ gelman", Loipeig. 1911. (93) Couper. A. S., (sl Compt. rand., 46,1107 (1856): (h) Edinburgh New Philomphicol Journol, INS.] 8, 213 (1858): trans!, and reprinted by L. Dobbin in "On a New Chemical Theory and Researches on Salicylic Acid." Alembic Club Reprints NO. 21,E.&S.Livingstone,Edinhuqh.1953,pp. 3 M 5 . (94) Koku1O.A.. la) Rull. Soc. Chim.Frane~,3.98(1865): (h)Ann., 131.129 (1866). (95) Ansch0h,R.,Ber,45,53911912):Z.ongew. Chm~,27.323(19141. (96) AnschOU, R. (EdilorI,"Chemische Studien: Konstitutionsformeln der organkchen Chemie in graphischer Darstellung van Joseph h a h m i d t , " Ostwald's Klassiker der erakten Wissenschsften Nr. 194, Wilhelm Engelmsnn, Leipzig, 1913. (97) AnachWz, R., and MWer, C.,Z ongew. C h m . , 40,273 (1927). (98) Anschutz. R., Be,, 59A, 75 (1926); 60.208 11927). 199) Anseh0tr. R.. "Hans Landolt." Bonnor Zeitung, Mar. 22,1910. 11WI Anachutz,R.,Ber.,67A.73(1934). (101) Anwhlttz,R.,Rec,36,4816 (1903): trannl. into Engl. by E. FarhrinFsrber. E. (Editor), '"Great Chemists," Intemience Publishers. Nev York, N.Y., 1961, pp. 697-702. (102) KekuY,A.,"LehrbuchderarganischehenChemie:'Vol.3,FerdinandEnke.Stuttgsrt. 1882.
Volume 59
Number 9
September 1982
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