EARLY HISTORY of ACETALDEHYDE and FORMALDEHYDE A Chapter i n
the H i s t o r y of Organic C h e m i s f r y
FREDERIC WALKER 3702 McKoon Avenue, Niagara Falls, New York
I
N THE introduction to his "Zeittafeln zur Geschichte der organischen Chemie,"' E. 0. von Lippmann points out that the history of organic chemistry is comparatively little known. Things that happened only a little before the era that we may designate as contemporary chemistry lie in terra incognita and when questions are asked as to how, when, and by whom even important and well-known chemicals were first prepared, very unsatisfactory answers are obtained. Von Lippmann also refers to the fact that our textbooks as a rule da not supply us with this information with the exception of the older edition of Roscoe and Schorlemmer's treatise,%the newer edition of the Meyer-Jacobson textbook, and a few other hooks. Two histories of organic chemistry have been written in the German language, one by Hjelt (1916) and the other by Graebe (1920), but these unfortunately have not been supplied with subject indexes, which makes i t difficult to use them for searching out the history of a particular compound. Von Lippmann's "Zeitfafeln" helps to fill in these deficiencies and is an excellent starting point for investigations in the realm of the history of organic chemistry. Although a great deal has been written on the lives of chemists and the history of theories, little has been written on the history of chemicals. One often wonders just how the various groups of homologous compounds, such as alcohols, aldehydes, esters, etc., came to be discovered and how their inter-relationships were found out. The object of the present paper is to set forth the history of two of the most important members of such a group of compounds. These chemicals are the aldehydes, acetaldehyde and formaldehyde. This history is not only of interest because of the chemistry that it contains hut also because of the interesting sidelights it throws on the personalities of some of the famous chemists who played a part in therstory. ACETALDEHYDE
1. Schee1e.-The fist record in the history of acetaldehyde is probably an observation in Carl Wilhelm Scheele's famous paper on magnesia nigra3 which was published in 1774. It is not surprising that this should -
'
VON LIPPMANN, "Zeittafeln zur Geschichte der organischen Chemie," Julius Springer, Berlin, 1921. "OSCOE AND SCHORLBMMER, "A treatise on chemistry," vol. 3, Macmillan & Co , Ltd., London, 1882. "The collected papers of Carl Wilhem Scheele," translation by DOBBIN,G. Bell & Sons, Ltd., London, 1931, p. 32.
have been the case. Scheele might well be called the first organic chemist. It was not an accident that the discoverer of glycerin, hydrocyanic acid, uric acid, and many other organic compounds, made the first-known observation in the field of aldehyde chemistry. Scheele did not discover the exact nature of acetaldehyde nor did he isolate it in a pure state but, as we shall see, his observations concerning it were not far from the h t h . Men sometimes deprecate the work of early chemists because they think that with an undiscovered domain before them, discoveries were easy, whereas they are difficult today. This, however, is not so. Discoveries are all around us. A clever scientist and accurate observer can still make revolutionary finds with nothing more than a test-tube and common reagents. I n the essay on magnesia nigra, Scheele states that "When a mixture of manganese, spirit of salt or spirit of vitriol, and spirit of wine is digested several days in a well-closed bottle, and thereafter gently distilled, no effervescence arises, but spirit of wine passes over; it has, however, and this is noteworthy, a strong smell of ether of nitre." As is now known, acetaldehyde must have been one of the main products of this reaction. "Ether of nitre" or ethyl nitrate was prepared from alcohol and nitric acid and accordingly contained acetaldehyde as an impurity. That Scheele should have recognized this odor attests to the accuracy of his observations. ., In the treatise, "Experiments'hnd Observations on Ethern4Scheele again returned to the study of the product obtained when manganese dioxide and sulfuric acid were allowed to act on alcohol. In this essay he gives more definite directions for carrying out the experiment. He says that when spirit of wine (1 ounce), manganese (1 ounce), and acid of vitriol ounce), are mixed and warmed gently, the mixture becomes hot of itself and during this action there distils "an ether which has a fine smell" and that when the iire is increased vinegar passes over. Another experiment is then described in which ether of vitriol (diethyl ether) is used in place of spirit of wine. Hiat was also evolved in this experiment and "the ether which is here recovered, except a smaller part, has a finer smell than before." As by-products of the reaction, vinegar and "aerial acid" (carbon dioxide) were obtained.
"The collected papers of Carl Wilhelm Scheele," loc. cit., pp. 229-37.
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Before going further in this discussion, it should be and the immortal Lavoisier. Since Fourcroy was a emphasized that in Scheele's day the term ether did not member of the committee of public safety a t the time have the specialized meaning that it has today in or- Lavoisier was killed, many historians have felt that he ganic chemistry. "By the term ether," says Scheele, could have saved the life of this famous chemist had he "there is understood in chemistry a very volatile, pene- wished to do so. Rumors of the time have added trating, colorless, aromatic-smelling oil, soluble in credence to this belief. However, since there is some water." Pure acetaldehyde would meet with the re- evidence against this accusation, I am sure that a short quirements of this definition better than diethyl ether. excursus in the interest of a scientist's honor will be In the treatise on ether, the preparation of sulfuric pardoned. ether, acetaldehyde, ethyl acetate ("acetic ether"), Fourcroy was made a member of the revolutionary and ethyl benzoate, are described. convention in the autumn of 1793 when the reign of Scheele's conclusions concerning the reaction of man- terror was a t its height. France was then under the ganese dioxide, alcohol, and sulfuric acid are of especial absolute rule of Robespierre. In those days it was alinterest. Since, as he states, it is already known that most equally dangerous for a member of the convention manganese "possesses a strong gffinity for the inflam- to remain silent or to take an active part in its business. mable principle when any acid acts upon it," i t is evi- In his history of chemistry, Thomson5statesthat "Fourdent that "when this metallic calx, spirit of wine, and croy never opened his mouth in the convention until acid of salt or vitriol come together" . . . . "the man- after the death of Robespierre." It was during this ganese attracts a part of the phlogiston from the spirit period that Lavoisier was murdered on the guillotine. of wine." . . . . "The heat which becomes so evident in Later Fourcroy had more influenceand was able to save the action . . . . is that which in consequence of its the life of Darcet (Rouelle's son-in-law) among others. separation from phlogiston has become free, and con- Darcet did not know until long after who it was that sequently the fine oil of the spirit of wine, ether sepa- had saved him. Finally Fourcroy's own life was rates from the water." . . . . "The small quantity of vine- threatened and he lost his influence. Cuvier amply gar and of aerial acid . . . . arises from the total destruc- , acquitted this scientist of any guilt as far as Lavoisier tion of a small portion of the ether." If we translate was concerned. In his "Eloge de Fourcroy," he says these conclusions from the language of the phlogiston that the charge was urged against him by those who theory into more modem terms, we find that he has were envious of his elevation. "If in the rigorous resaid that alcohol on oxidation yields an "ether" (i. e., searches which we have made," says Cuvier, "we had a volatile, aromatic-smelling, water-soluble oil) which found the smallest proof of an atrocity so horrible, no on further action of oxidizing agents yields acetic acid human power could have induced us to sully our mouths and water. with his praise." We must now return to the subject The fact that Scheele showed that sulfuric ether was of our history. oxidized to an ether having "a finer smell" shows that In the year 1800, one, citizen Dahit, recommended he does not consider that the "ether which has a fine an improved method for the preparation of sulfuric smell" (acetaldehyde) and sulfuric ether are exactly ether. This consisted in the addition of the black oxide the same thing but the distinction is not altogether of manganese to the mixture of sulfuric acid and alcoclear. hol used in making ether by the usual method. Dabit Some chemical historians consider the phlogiston believed that ether was produced by the removal of a theory which Scheele espoused as a great impediment part of the hydrogen in alcohol followed by its oxidato the progress of chemistry and even remark that i t tion to water. Hence he believed that the manganese prevented Scheele from making many discoveries. dioxide which he used in his ether preparation served This does not seem to be the case. The phlogiston to facilitate the reaction since it supplied oxygen more theory was a useful tool for Scheele and it did not keep readily than sulfuric acid. In order to test out Dabit's him from making discoveries. Theories always impede hypothesis, Fourcroy and Vauquelin checked his exsmall minds hut to larger minds they are of value. If periments and published their results in an article there had been nothing to take the place of the phlogis- entitled, "Sur I'6lher prdNr4 d la manidre du Ciloyeu ton theory before Lavoisier, the progress of chemistry Dabit."s the product of their preparation, they ohwould have been hindered a great deal. It enabled tained "a liquid whose odor had some analogy with scientists to correlate those processes which we now call that of nitric ether and whose taste was bitter and very oxidation and reduction if nothing else, and the above disagreeable." This material was found to be cominstance testifies to its utility. pletely soluble in water, which showed i t to be different 2. Fourcroy and Vauque1in.-The recognition of from sulfuric ether. Their product, .however, could acetaldehyde as a chemical individual quite different not have been pure acetaldehyde, for they state that in its properties from sulfuric ether was the result of a its density was greater than that of alcohol and that research carried out by Fourcroy and Vauquelin. more heat was needed to vaporize it than was needed This was at the end of the French revolution in the days ' TnoMsoN, "The history of chemistry." Colburn & Bentlup, when the coup dretat of Napoleon Bonaparte had just London. 1831, vol. 2, pp. 169-70. made him the first consul of the land. 6 Founcno~ AND VAUQUELIN, "Sur l'&therprepare B la manisre The name of Fourcroy brings to mind the revolutiou du Citoyen Dabit," Annabs de ckimic, 35, 318 (1800).
by ordinary ether. I t was probably contaminated with alcohol and its trimer, paraldehyde. Analyses carried out by passing ordinary ether and Dabit's ether through porcelain pipes convinced them that Dabit's ether contained more carbon, more oxygen, and less hydrogen than alcohol which "is almost the opposite in the case of ordinary ether." They conclnded that
elucidate its exact relations with alcohol and acetic acid. The chemical properties which characterized i t were also yet to he discovered. This was to be the work of Justus von Liebig. To Fonrcroy and Vauquelin however belong the honor of the discovery of acetaldehyde. 3. Liebig.-From 1800 to 1821, there appears to be a lacuna in the histom of acetaldehvde , broken onlv by Humphry Davy's discovery of lampic acid.' In his great humanitarian research which led to the discovery of the Davy lamp, for which he asked no profit other than the knowledge of having served his fellows, Davy prepared and desaihed what was in reality an impwe form of acetaldehyde. This work was carried out in the year 1815 or shortly thereafter. Davy ohserved that when alcohol or ether was placed in the flameless lamp (a platinum spiral suspended in the vapors of an inflammable liquid mixed with air), a pungent vapor which made the eyes smart was generated. This substance came to he called lampic acid and was later examined by Daniell and Phillips. Daniell condensed it to a liquid and observed that when this condensate was heated a pungent, choking, volatile liquid was first distilled. He noted that its vapors when inhaled would seize or grip the breathing organs. This is one of the unusual and characteristic properties of acetaldehyde. Daniell conclnded that the substance was neither an acid nor an ether. Later Liehig was to show that this liquid was acetaldehyde. In 1821, Professor J. W. Dohereiner published in Schweigger's Journal fur Chemie und P h y ~ i k ,that ~ he had obtained a new material, which he named "oxygen-ether," by the distillationof a mixture of alcohol with chromic acid or a mixture of manganese dioxide and sulfuric acid. This liquid was heavier than water hut on distillation i t gave another fluid lighter than water which he called "light oxygen-ether." This latter was a mixture consisting largely of acetaldehyde and acetal. The residue from the distillation or "heavy oxygen-ether" was soon shown by Gay-Lussac to he the long-known wine-oil, a mixtnfe of diethyl sulfate and hydrocarbons. The "light oxygen-ether" was according to this chemist a mixture of alcohol, sweet wine-oil, and ether. In the next year Dobereiner published his pmcednre for making "oxygen-ether" together with a picture of his apparatus.$ He stated that the "light ether" smelled like "ktric ether." All this had been done before and more thoroughly by Fonra o y and Vauquelin, but Dobereiner apparently did not know of their work. The close rapport between the German and French chemists which prevailed in the early days of Liebig's Annalen was probably not yet established. In 18231° Dljbereiner puhlisheh the fact that "light ~~
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Dabit's ether was indeed formed by thp removal 01 hydrogen from alcohol by oxidation hut "this liquor does not resemble common sulfuric ether in any way: it is an entirely new compound that citizen Dabit has discovered but he has not examined its properties carefully enough." Fourcroy and Vauquelin thus showed that a new compound was formed when alcohol was oxidized by manganese dioxide and sulfuric acid and that this compound apparently contained more carbon, more oxygen, and less hydrogen than alcohol. This was indeed the case. All that now remained to be done was to determine the chemical structure of this new compound and
TIE~IG, "Ueber die Producte der Oxydation des Alkohols,"
Ann., 14, 160 (1835). D~BEREINER, "Verschiedene Untersuchungen," Schwciggn's Journal fur Chemie zrnd Phyrik. 32, 26%9 (1821). DOBEFSINER,"Apparat zur Darstellung des Sauerstoffaethers," ibid., 34, 1 2 P 5 (1822). lo D~BEREINER, "Ueber dem Sauentoffaether und ein news HXZ," i&d., 38, 327-30 (1823).
oxygen-ether" produces a yellow-brown resin when treated with alkali or sulfuric acid. This appears to he the first published description of an aldehyde resin. From this insignificant starting point one might write the history of the synthetic resin industry. Liebig who was acquainted with Dobereiner soon began to study the new compound. His first work appeared in 183211 in the new Annalen. In this paper he showed that "light oxygen-ether" was a mixture containing a water-soluble volatile fluid which minified when treated with alkali forming the resin previously ohsenred by Dobereiner. About this time the latter investigator found that his "light oxygen-ether" formed a crystalline compound with ammonia and communicated this discovery to Liebig, sending him three grains of the new compound. It was the study of this compound (aldehyde-ammonia) which led to Liehig's discovery of the true nature of acetaldehyde. The results of his research were published in 183512 and it was in this paper that the new compound was first called aldehyde. This name was derived from the term al(koho1) dehyd(roxydatus). In the paper is given a full account of the chemical and physical properties of acetaldehyde. Its relation to alcohol, acetic acid, and aldehyde ammonia is clearly elucidated. The chemical formula of the new compound is given as determined by Liebig's improved method of making combustions. The method of detecting aldehyde with ammouiacal silver nitrate is also set forth. Dohereiner's "light oxygen-ether" was shown to be a mixture of acetaldehyde, acetal, and minor impurities. In Liehig's classic paper on acetaldehyde, there is only one serious mistake. Liebig believed that there was an intermediate oxidation product between aldehyde and acetic acid. He thought that this compound was the acidic constituent of lampic acid and named it aldehydic acid. He was almost inclined to call it acetous acid. That he was uncertain, however, in regard to this hypothetical compound is clearly shown in his statement that "in the lack of better facts, the theories expressed are only to act as clues to future research." Heintz and Wislicenus later showed that this body was a mixture of acetic acid and aldehyde. Liebig's table setting forth the related chemical formulas for acetaldehyde, aldehydic acid, and acetic acid is shown below. The hypothetical hydrocarbon from which it was believed they were derived is also shown. The formulas appear somewhat confugng because the atomic weights C = 6 and 0 = 16 were employed. The formula for acetaldehyde is correct as will be seen by translating it into modern terms. Licbig's Formuh Name 6Hs Unhekannte Kohlenwasserstoffverbindung CHa HsO Aldehyd (C,HsOd C4HsOz HnO Aldehydsaure ( C ~ B O S ) C&08 H 3 0 Essigsaure Hydrat (CfiOS -
+ +
"
+
LIEBID, "Ueber Verbindunga, wwelche durch die Einwirkungen des Chlors auf Alkohol, Ather, Blbildige Gas, und Essiggeist entstehen," Ann., 1, 182 (1832). LIEBIG, "Ueber die Producte der Oxydation des Alkohols," ibid., 14, 13347 (1835).
"
In Liebig's paper, metaldehyde, the crystalline polymer of acetaldehyde, is also described. The other polymer of acetaldehyde, paraldehyde, was later recognized by Fehling. ma With the appearance of Liebig's paper in 1835, the account of the early history of acetaldehyde is complete. Although many discoveries in acetaldehyde chemistry
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were still to be made, the foundation upon which this work was to be built up had been laid for all time. There followed this, however, a controversy which is so typical of Liehig and so characteristic of the early days of the Annalen that i t cannot be left unmentioned. A short time after the publication of-the above-mentioned paper, Dobereiner published a short article on the chemistry of platinum. In this paper, he made the following statement: "These two products (aldehyde and acetal) were likewise prepared by J. W. Dobereiuer and analyzed by Liebig." A similar statement was also made in Gmelin's "Einleitung in die Chemie." As can he seen Liehig's part in aldehyde chemistry was
thus reduced to insignificance. Anyone familiar with the temperament of Justus von Liebig can picture the resultant explosion. A paper entitled, "Wer ist der Entdecker des AldehydsB" (Who is the Discoverer of Aldeh~de?),'~ soon made its appearance in the Annalen. Liebig began his paper with the following quotation: "Wenn diess die Freuv.de sagen, was kann uns Schlimmeres won unsern Feindes geschehen?" (If our friends say this, what worse can be done by our enemies?) In this polemic one can see what Berzelius meant when he wrote to Mitscherlich, "It is his (Liebig's) misfortune that the devil drives him when he takes his pen in hand."I4 The whole story of aldehyde research as concerned Dobereiner and Liebig was set forth in this paper in terms of biting sarcasm. The properties which Dobereiner attributed to "light oxygen-ether" are compared with the properties of pure acetaldehyde. "Oxygen-ether" boiled a t 75"C., aldehyde a t 21.8'C.; "oxygen-ether" was not miscible in water, aldehyde was miscible in all proportions. The paper ends with a characteristic counterblast to the impious Dobereiner.
form in which formaldehyde exists in its aqueous solutions together with a number of polymethylene glycols having the type formula, Methylene glycol is stable only in aqueous solution and when attempts are made to isolate it, solid polymerized
Doherein& has had in the discovery of acetaldehyde about the same position as Newton's apple in the discovery of gravity and the laws of free fall.
No wonder Liebig's pen was the fear and wonder of his contemporaries. Although we must accord the honor of having first ascertained the exact chemical nature of acetaldehyde to Liebig, neither he nor Dobereiner was right in this contention. Fourcroy and Vauquelin were the true discoverers of acetaldehyde. At least such appears to be the case in the light of our present information. FORMALDEHYDE
As we have already stated, with the publication of Liebig's great work on acetaldehyde in 1835, the groundwork for the comprehension of the aldehydic nature was clearly laid. In the years that followed, other aliphatic aldehydes were discovered and were easily recognized as falling in the group of organic compounds of which acetaldehyde was the best-known member. Aldehydes whose existence had already been observed were now comprehended and classified. Propionaldehyde, butyraldehyde, and isovaleraldehyde, among others, were discovered before 1860.. Formaldehyde, however, remained unknown. The ease with which methanol passes on oxidation from fodaldehyde to formic acid and hence to carbon dioxide and water, made it difficult to isolate. It is possible that many chemists tried to prepare it but they were apparently unsuccessful. 1. Butlerow.-Strangely enough formaldehyde was not first prepared by oxidizing methanol but in a research whose object was the preparation of methylene glycol, CH1(OH)2. We know today that this is the $8 LIBBIG, "Wer ist der Entdecker des Aldehyds?" Ann., 22, 273-7 (1837). 14 W I L L ~ T ~ ~ "Hundert ER, Jahre Liebig's Annden." 2. angew. C h m . , 45, 217 (1932).
formaldehyde or the monomeric gas are obtained. Butlerow sought to prepare methylene glycol or methylene alcohol as he called it and obtained formaldehyde. He has left ,us a description of polymerized formaldehyde, formaldehyde solution, formaldehyde gas, and most of the fundamental facts of formaldehyde chemistry.16 Unfortunately, he did not realize the full meaning of his experiments. Butlerow treated methylene iodide with silver acetate and obtained methylene acetate, proving its stmc-
-
" B u n ~ ~ o w"Ueher ,
Ann.. 1 1 1 , 242-52 (1859).
einige Derivate des Iodmethylens,"
ture by the manner of synthesis. He noticed the odor that they were incorrect." Unfortunately, Hofmann of formaldehyde which is produced when this com- reasoned that since thioformaldehyde had a solid pound hydrolyzes in the nostrils. He hydrolyzed the polymer which he had found to be a trimer, the polyester with alkali but was unable to isolate the expected mer of formaldehyde was also a trimer. Hence he glycol. By the action of silver oxalate on methylene named it trioxymethylene. Today we know that iodide he then obtained a polymerized formaldehyde, trioxymethylene, (CH,O)a, is quite another substance probably polyoxymethylene, possibly paraformalde- possessing a chloroform-like odor and melting a t 60°C. hyde. By analysis he showed that this new com- and yet the misnomer "trioxymethylene" is still appound had the formula (CHzO).. By a mistake made plied to the polymers of formaldehyde-paraformalin the determination of the density of the vapor ob- dehyde and polyoxymethylene. tained by vaporizing this material, he concluded that With Hofmann's discovery of formaldehyde, our the compound was dioxymethylene, (CH20)z. He also history is complete. The story of how the present obtained the new compound by the action of silver oxide technical methods of manufacturing formaldehyde deon methylene iodide, a method of synthesis which veloped has been ably told by Gunther Bugge.18 supplied him with additional evidence of its structure. Those who are interested may turn to his work. Bugge, He showed that his compound reduced silver oxide, like most chemical historians, however, seems to underformed a crystalline compound on reacting with am- estimate the importance of Butlerow's work. Textmonia (hexamethylenetetramine) and even remarked books as a rule never mention him in connection with that these and other reactions are those which one the discovery of formaldehyde. Butlerow proved that might expect for the unknown "formyl-aldehyde." he had prepared a formaldehyde polymer and though 2. Ilofmann.-August Wilhelm Hofmann, profes- he never knew he had depolymerized it, in vaporizing sor of chemistry and student of Liebig, was the first it and dissolving it in water he did state in clear to prepare formaldehyde by the oxidation of methyl language all the fundamental facts of formaldehyde alcohol and to prove its structure. To Hofmann, the chemistry seven years before the appearance of Hofteacher, i t seemed had pedagogy that the first member m a d s paper on "methyl-akfehyd." The fact that of the aldehyde family should be missing. Accordingly formaldehyde solutions contain methylene glycol was he set out to prepare it and succeeded. His paper, almost implicit in Butlerow's work. Later investi"Zur Kenntniss des Methylaldehyds,"!"egins as fol- gators drew the necessary conclusions and it was soon lows: " 'The aldehyde of the methyl group is unknown,' accepted as a theoretical possibility and used in interall chemical textbooks announce it, and for twenty preting formaldehyde reactions. I t was not proved, years, every year have I dutifully made this statement however, until recent years when the absorption spectra to my students." That time, however, was now a t an and the Raman spectra made this pos~ible.'~ end. In this history we have tried to show how the chemHofmann prepared formaldehyde by passing a mix- istry of aliphatic aldehydes as we know it today came ture of methyl alcohol vapor and air over a heated into existence. Similar histories coeval with this one platinum spiral, making it in somewhat the same might be written for many other compounds and manner by which it is now manufactured industrially groups of compounds. These stories and their interin tank-car lots. By the action of hydrogen sulfide on relationships make up the history of organic chemits acid solution, he also made tritbioformaldehyde, istry. Many interesting paths and by-paths await the (CH&&, and identified it. At a later date he prepared student of chemical history in this field. polymerized formaldehyde by evaporating the solution. " HoaaaANN, "Zur Kenntniss des ~ethyl$dehyds. 11," Ber.. He identified the polymer as identical with Butlerow's (1869); see also Zentr., 1869, I , 289-94. "dioxymethylene" and as a result of this Butlerow 2, '15240 8 Bucce, "Aus der friihen Geschichte der Forrnaldehyddarchecked his vapor density measurements and found stellung," Chem. Afifiaratur, 18, 157-60 (1931). -
:.
16
HOFMANN, "Zur Kenntniss des Methylaldehyds." Ann.,
145, 357 (1868).
1' WALKER."Formaldehyde and its polymers," Ind. Eng. C h m . , 23, 1220 (1931).
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