Translators
1
Frank F. Kluge Division of Language and Literature and David F. Larder Division of Natural Sciences Notre Dame University Nelson, British Columbia, c a n a d o
A. M. Butlerov: I
On
the Chemical
Structure of Substances
In the present state of sffain of chemistry which has provided us with a great number of unexpected and interesting facts, it is generally felt that our theoretical knowledge cannot accommodate all these new deta. Indeed, the presently almost universally accepted "type" method of explaining facts is scarcely sufficient any Longer, even though if it sprang up only a few years ago and has had great influenceon the development of chemistry (Note ($)I. Lately some facts have been discovered which support theories held in earlier days. Thus, the formation of the hydroxy-ethyl bases discovered by Wurtz supports the theory of Berzelitts who regarded the alkaloids as quarternary ammonium compounds, and the ethylene theory of the ethyl derivatives appears to be correct up to a certain point if one thinks of the formation of dcohol from ethylene and water, the formation of ethyl iodide from ethylene and hydrogen iodide, etc. But the majority of the older theories as well as the now prevalent one explain only a certain number of facts, i.e., mainly those on which these specific theories are based. The number of facts explained is much larger for the new theory. A new theory is usudly more comprehensive than its predecessors. It is preferred since it evaluates facts from a different viewpoint and shows analogies which had been overlooked earlier. But all this does not exclude the correctness of the earlier theories as long as one stays within thelimits on which they were based. Unfortunately, this is too often forgotten by each new theory or, to be more exact, by its promoters! However, a t the same time it has to be remembered that the new theory has very important merits. I t has eliminated many a theoretical assumption from the field of chemistry and has taught us to put the facts as such first. In connection with this concepts such as "atom." "eauivalent." and "molecule" were develoned and acceptedby thk sciences, i.e., quantities have been discdvered which permit proper comparisons [Note ($)I. The original "type" formulas serve exclusively to describe substitutions or double decompositions; they only indicate the direction in which each compound breaks down if certain double decompositions take place. They show the atomicity of the residue (radical) and the often far removed analow which one substance shows with the other ones classified undeFthe same type. We know, however, that far each substance there exists not only one but several directions in which this substance can decampose and that also, with the change of direction, often the atomicity of the radicals varies. From this it is necessary to assume not one hut several rationd (in the sense of Gerhardt) formulas for the same substance. Furthermore we know that the radicals which appear in the "type" formulas result from stepwise chemical processes. So there can be scarcely any doubt that for carhon compounds a whole series of processes is possible each time B C (1 at.) joins the compound. To the extent that increasing numbers of facts favor this opinion and refer to the formation of one and the same substance it seems to be necessary to divide the formula of that substance more and more, a t least, if one wants to express all these factors by it [Note (4)l. This is elso the reason for inventing the expression "mixed types" which is used off and on but which, by no means, can be called either simple or convenient. These andogies expressed by type formulas me act-
ually correct, at least as long as one ascribes to them only a limited importance. However, they are-as remarked earlieractually very farfetched. Besides these objections to type formulas still another much more serious one can be raised. We know by now that besides double decomposition, when two reacting molecules form two new ones, real combination, direct addition, is also possible. In such a. case two molecules unite to form one single new molecule. The latest discoveries speak more and more in favor of the fact that in each case of double decomposition, an analogous case of direct combination can also occur. Into this category belongs the previously mentioned formation of alcohol andethyl iodide, the direct union of fumarie acid with bromine, of carbonic acid with ethyl sodium, that of the nitriles with hydrogen, the formation of P-hydroxy propionic acid from acrylic acid and alcohol, and so on. I t can be predicted that the number of such cases will soon increase. On the other hand the original 'type" method of denoting them does not give any account of these processes. Recently an ides. is making a comeback which had earlier been propounded for a long time but was later forgotten.. .the theory of mechanical types.. . [Note (6)l. The reason for this revival, in my opinion, is that now, in connection with the idea of mechanical types, the meaning of the atomicity of elements has become much clearer and as a, further consequence the meaning of the atomicity of the complex groups has become much clearer. Since these theories allow a. deeper insight into the nature of chemical compounds and are much more applicable, bhey have, quite understandably, been readily accepted. Until now these theories went hand in hand with the older "type" theory. On the other hand I will scarcely be proven wrong in stating that the time has come when Gerhardt's theory [of types] must make way for the ides. of stomicity. Many chemists have already expressed their opinions on this subject in one or the other way and all of them can more or less be traced back to one and the same theory, that of atomicity. Indeed, everyone taking s. closer look at the meaning of the mechanical types must admit that it. must he t o t d y subordinated to the meaning of atomicity. Among thesamemechanied typesme counted all substances which contain either one and the same element or, according to the atomicity, analogous polyatomic ones. Thus only that chemical process of the molecule which is caused by this specific element is actually expressed. Thereby different types can be assumed for such compounds, containing more than one polyatomic constituent. In this way it is, for example, possible to classify methylamine under the types: CH, or NHs or methylsmmanium chloride to the types: CHc or NHGI, or also HC1, and to compare it either with all or onlv individual com~oundsclassified under this type. In other words the mechanical tvne shows onlv certain rels-
however, becomes much more inlportant because it has been derived from facts. Lately the opinion has been propounded' that
' FOSTER, "Report. de Chimie Pure,"
1861, p. 273.
Volume 48, Number 5, May 1971
/
289
~ l < , m i r i tisy n definite and unchangeable property of the elements which, in ihe present st,ate of science, can serve as a basis for a ~ atomicity as n st,~rtingpoint it seems gimrrd ~ I I P O I Taking indwd lo he possible lo go rather far in our chemical speculations. 111 ngrecnirllt with Gerhardt we deny a t the present time the ~xtssihilily of nccounting for the at,omic arrangement in the intcri f I n l . I t seems to he quite natural that chemistry, wl8ir.h drsls rnrly with snhstances during the course of their transfcmmticnn, is unnhlo to make any statements about their mechaniKII strwturr, at least BP long as there is no assistance from physiw1 investigation. But on the other hand Laurent has already sh
