ll t Ch 7 (199 3
E ECE IO O Y OGE O I G Y E C EMICA COMMU I Y 19 -1937
n Q n , E t x St t Un v r t
It is well known that hydrogen bonding as a generalized concept was first proposed in the literature by Wendell Latimer and Worth Rodebush in 1920 (1). A footnote in their paper credits "Mr. Huggins of this laboratory [who], in some work as yet unpublished, has used the idea of a hydrogen kernel held between two atoms as a theory in regard to certain organic compounds". At the time Wendell Latimer was a lecturer in G. N. Lewis' chemistry department at the University of California at Berkeley, Worth Rodebush, a postdoctoral fellow, and Maurice Huggins, a first-year graduate student, working on his masters degree. The "unpublished work" referred to was actually done a year earlier when Huggins was an undergradu- ate. He has given several accounts of this work; the most complete and definitive of which appeared in 1980 (2). He W nd ll M t r begins by describing his reaction to advanced courses in organic and inorganic chemistry taught by Professors T. Dale p p r th t r f r r r d f r h r nd t tt n h rt Stewart and William C. Bray. In these courses the students I nt t r f r nd d h f h ld pt r d were introduced to the Lewis theory of chemical bonding (2): n t th t tl nd n dd d d d
r f St rt nd r f r l d d f th n lv d Dr. Huggins, in 1978, was kind enough to send me a pr bl f h tr h pr bl ntr d C ld photocopy of parts of these notes (3 The copy sent me f th b lv d b th ppl t n f th th r p rh p th consists of pages numbered 1-7 and 15-17, with page 17 d f t n ? I th ht l t nd d r d n t b t pr bl obviously not the end of the document. The clearest indication l t n th t d r n bl t In rl M f 1919 of what would be called hydrogen bonding today is a diagram r d t n ppr h d I b rr d I h d n t r tt n th t r on page 17 showing a hydrogen fluoride dimer, with the four atoms arranged in a square, each hydrogen bonded to both fluorines by electron pair bonds. On page 6 an explanation of the keto-enol tautomerism of acetoacetic ester postulates a transition state in which hydrogen is bonded simultaneously by electron pair bonds to a carbon atom and an oxygen atom. There is no indication given that the concept is generally applicable nor is any name given to the idea. For that matter, Latimer and Rodebush themselves do not actually use the terms "hydrogen bond" or "hydrogen bond- ing" in their paper. The closest they come is to describe it as "the hydrogen nucleus held between two octets constitutes a weak 'bond'." The first use of the term in the literature was in Lewis' book, l n nd th Str t r f At nd M l l , in which the section headed "B ivalent Hydrogen" begins (4):
It t th t th t p rt nt dd t n t th r f v l n l n th t n f h t h b n n th h dr n b nd
It is hardly surprising that the idea of hydrogen bonding W rth d b h should have occurred independently to several young chemists ll t Ch 7 (199 at Berkeley at that time. Lewis had been, since 1912, building a strong department and, in doing so, attracted scores of bright young chemists as faculty members and doctoral students (Rodebush and Latimer had obtained doctorates from Berkeley in 1917 and 1919 respectively; Huggins would receive his in 1922). His new ideas on bonding must have been exciting to these young men. The idea of hydrogen bonding would appear to have been a natural outgrowth of the Lewis theory. In hindsight it is somewhat surprising that the idea of the hydro- gen bond met with resistance from the older faculty whose teaching had inspired it. Huggins recounts how Prof. Bray commented on his paper (2):
n th r r v r l nt r t n d n th p p r b t th r n ll n v r t h t t b l v th d th t h dr n t n b b nd d t t th r t t th t
Latimer has stated that Lewis' first response to the Latimer- Rodebush paper was to suggest that the section on hydrogen M r n t d nt t r l bonding be deleted (5). d r n th r t W rld W r Accounts of the history of hydrogen bonding in mono- graphs and textbooks leave the impression that the concept was although there was little unanimity as to the name to be given immediately embraced by the chemical community. A state- the concept. The number of chemists adopting this last attitude ment of George Pimentel and Aubrey McClellan is typical (6): was small during the 1920's but became greater during the early and middle 1930's. By 1937 the concept was so widely r th rl b nn n ll d r n n b r f t d f accepted that it could be mentioned without giving a citation, -b nd n A th n rr n nd p rt n f th and the term "hydrogen bond" had also become by far the most b nd h b pp r nt th v l f r n th n pt f common name. In the remainder of this paper I hope to trace h r d pr t n h r n tr nd l nd t n n r n r t the web of influences by which this general acceptance was achieved, using biographical data, citation analysis, and pre- Actually the Latimer-Rodebush paper was almost completely ferred terminology as tools. ignored for ten years. The first citation of the Latimer-Rodebush paper in connec- Before discussing the complex history of how the concept tion with hydrogen bonding was by Irving Langmuir of the came finally to be accepted, some preliminary distinctions General Electric Company in 1921 (16). Langmuir had been must be made. Latimer and Rodebush introduced the concept instrumental in calling the attention of the chemical commu- of hydrogen bonding to explain certain phenomena which nity to Lewis' ideas about chemical bonding (17). Rather than were already well known: the anomalous boiling point of water accepting the Latimer-Rodebush proposal, Langmuir put forth (7), the vapor phase density of hydrogen fluoride (8), the a competing idea (16): anomalous freezing points (9) and vapor density curves (10) of various liquid mixtures, the basicity constants of ammonia and In d bl l l h ( n nd n p nd the substituted amines (11). Certain other phenomena now h K t t th t th h dr n n l n t d f associated with hydrogen bonding were discovered soon after: f r n d pl t th l tr n n th t f r d pl t n the crystal structures of ice (12) and the HF2 ion (13,14); and h h th t l tr n r n d ff r nt t h h dr n n l the change in stretching frequencies of the -OH bond (15). t lf th t b nd n h t r nd d b h h v Chemists tended to adopt four attitudes toward these d h t l r t n n r rd t h dr n n l "anomalies": some just determined, as precisely as possible, t n b nd h n d r th t th h dr n n l t n t the physical constants or structural parameters and did not p r f l tr n n p r n h f th t t S n th f r t worry about their meaning; some attributed these anomalies to l r f l tr n n ll t nt n nl t l tr n t "association", without speculating on the nature of the forces pr b bl th t th h dr n n th l h ld nl t l tr n causing the association; some proposed theories about the nd th t th f r th d f n t t bl r p h h h v t r d th nature of these forces different from the Latimer-Rodebush d pl t concept of hydrogen bonding; and finally, some accepted the Latimer-Rodebush picture, often at second or third hand, This idea is similar to the "liaison monoelectronique" pro- ll t Ch 7 (199 5 posed, probably independently, by Jean Perrin in 1927 (18) and given to the Latimer-Rodebush paper, Lewis' book, and the maintained by some French spectroscopists till 1937. earlier paper by Lowry. Maurice Huggins published two papers in 1922 (19) in In the meantime, the X-ray determination of the crystal which he expanded on the ideas presented in his 1919 term structures of ice (12), NallF2 (13), and ICHF2 (14) had been paper. Reference to the Latimer-Rodebush paper is made in published. Huggins has claimed that (3): the second paper, but more in the context of their applications of Lewis theory than specifically to hydrogen bonding. One rth r v d n (f r h dr n b nd n ] fr th tr t r f diagram, the same in both papers, shows a hydrogen atom I pr d t d th t h dr n br d ld f r t h v bonded to two other atoms (in NH4OH). In both papers this tr t r n h h h x n rr nd d t tr h dr ll b f r form of bonding by hydrogen is not given any special name but th r th th h dr n n th x n- x n nt r l n In is included, along with examples taken from boron and transi- 19 W ll r h d th t x n t r nd d n h tion metal chemistry, as an example of what we would now call n rr n nt the coordinate-covalent bond. In the second paper, Huggins gave his first indication that he was proposing this form of No such prediction appears in any of Huggins' early published bonding by hydrogen as a general concept (19): papers, and if it appeared in his term paper, it had to be in a section I have not seen. Bragg himself considered that his work It l th nd f r t n h h ft n pr d p l r z t n demonstrated that ice was an ionic structure with 02- sur-
nd th f r t n f l l r r t ( f I-120). rounded tetrahedrally by H+ ions. Friedrich Rinne and cowork- ers and Richard Bozorth established that the HCF2- ion in NaHF2 Only two research groups, both English, made use of the and ICHF2 was linear with the hydrogen atom between two concept of hydrogen bonding in the early 1920's. The first, that fluorine atoms, but no speculation was attempted as to why of Thomas Lowry of Cambridge University, began publishing these atoms adopted such a peculiar arrangement. on this subject in 1923 (20). The initial paper from this group The most commonly accepted theory of the structure of is a survey of the evidence for hydrogen bonding. It is much water during the 1920's was that of Henry Edward Armstrong. more extensive than that given in the Latimer-Rodebush paper, An account of the current version of his theory can be seen in which is cited, along with Lewis' then forthcoming book. one of his papers from 1923 (22): Lowry had corresponded with Lewis in connection with an invitation for the latter to speak at a Faraday Society Sympo- W t r pl x xt r n pr p rt n h h v r th th sium in June 1923 on "The Electronic Theory of Valence" (17) t p r t r f th f nd nt l l l h dr n ( 11 th and presumably was shown the page proofs on this occasion. l l f v r p l rph p rh p The term used to describe this concept (as will be true of future papers by this group during the 1920's) is "coordinated hydro- gen". The second group, that of Nevil Sidgwick at Oxford, published their first paper in 1924 (21). In this paper the "coordination of hydrogen" is used to explain the "abnormal" solubilities and boiling points of certain benzene derivatives. The difference in properties between groups capable of being hydrogen bonded oral° to each other, rather than meta or para, is explained in terms of "chelation". This is what would today As can be seen from the diagrams, the association between be called intramolecular hydrogen bonding. Reference is molecules is assumed to be by way of 0-0 bonds. Armstrong was born in 1848 and retired from teaching at • 0 Imperial College of Science and Technology in London in 1911. From 1890 till a few years before his death in 1937, he was considered one of the leading lights of British chemistry. He was noted for his love of controversy and ridiculed the theories of Arrhenius, van' t Hoff and Ostwald for what he felt was their lack of consideration for the uniqueness of water (23). Naturally, hydrogen bonding did not escape his scorn. In a letter to t r in 1926 Armstrong wrote (24):
h h nd-dr n f r fr n t d nt n t I n t th t n th l t r h h r f r v r ntl n r h n h dr n-b nd d h dr n fl r d d r (3 h br ht f r rd rt n fr f r l f r t rt r d n h h ll t Ch 7 (199 h dr n f r b t I h b t f ll th l zation and association, contrasted the "chemical" theory of x pl t b rt n U n n p ll n E [sic] Sidgwick, in which association consists of the formation of C l f rn n th r d n t r h h h n t d r rd th f nd - coordinate linkages, with the "physical" theory of Debye, in nt l n n f h tr - f r n bv r n th r th n th t f which association is due to the mutual interaction of dipoles. nd l n n pr t r p l t n p n l tr n th f Williams concluded that the "physical" approach, while prom- v l n ising, is not able to account satisfactorily for all the data (29). In 1932, James Speakman, of Sheffield University (30), What may have made Armstrong so vehement was that Lowry cited a paper by Sidgwick's group in pointing out that the had been one of his own students (17). parachor of liquid hydrogen fluoride supports the assumption In 1927, Harris Chadwell, in his review of the molecular that it is a liquid in which association results from the coordi- structure of water (7), under the heading of "Recent Theories", nation of hydrogen. In 1934, H. M. Glass, W. M. Madgin, and discussed various modifications of Armstrong's theory. The F. Hunter, of the University of Durham, cited Sidgwick's book Latimer-Rodebush theory is mentioned, incongruously, under in arguing that the "coordination of hydrogen" accounts for the the heading "X-ray Analysis of Liquid Water". Incongru- heat of dissociation of quinoline o-chlorophenoxide in ben- ously, since when Latimer and Rodebush wrote, there were no zene solution (31). X-ray data, and Chadwell does not discuss any X-ray evidence Despite the influence of Sidgwick's book, explicit refer- for their approach. The paragraph appears to be an after- ences to hydrogen bonding, whether under the name of coor- thought, inserted at the last minute, possibly to meet a referee's dinated hydrogen or any other name, are rather infrequent comments. during the late 1920's and the early 1930's. Citing all the The lecture by Lowry to which Armstrong referred had papers during this period in which the expected mention of the been recently published in t r ( 5 The work described hydrogen bonding concept is absent, would expand the list of had also appeared in an earlier preliminary communication references to unmanageable size. Most of the papers previous (26). In this work Lowry attributes anomalies in the optical to 1934, and a good proportion even for the period 1934-7 rotary dispersion of tartaric acid to what would now be called listed in the bibliography in Pimentel and McClellan's book intramolecular hydrogen bonding. The citation is to Lewis' (32) are of this character. It will suffice to mention the book and attributes to Lewis the term "bivalent hydrogen" for redetermination of the crystal structure of ice by William the phenomenon. Intramolecular hydrogen bonding is also Barnes (33), in which he came to the conclusion that "The invoked about the same time by Sidgwick (27), under the name structure for ice proposed in this paper is practically identical "chelation" to account for anomalous solubility data for 13- with those of Dennison and Sir William Bragg." keto-esters and p-diketones. In 1925, Sterling Hendricks and Linus Pauling determined In 1927, Sidgwick published his influential book, h the structures of NaN3, K.N3, and KNCO by X-ray diffraction El tr n h r f l n (28), which did perhaps more (34). In the discussion they pointed out that the linear structure than even Lewis' book to spread the new ideas about bonding of the trinitride and cyanate ions is the same as that of the acid to the chemical community. In it, Sidgwick presented what is fluoride ion, HF2-. For this ion they proposed the structure: essentially Lewis' theory, but developed more systematically f:F:H:F.:1-. No reference is made to the Latimer-Rodebush and with a greater wealth of examples. He also had the paper in connection with this structure, nor to Lewis' book, but advantage, as an experimental organic chemist, of being able the structure clearly indicates hydrogen bonding. to speak more directly to that audience than did Lewis. In this Pauling had received his Ph.D. degree from the California book, Sidgwick used the term "coordinated hydrogen" for Institute of Technology (Caltech) in 1925, and when this paper what is now called intermolecular hydrogen bonding and was written he was a National Research fellow. According to "chelation" for in tramolecular hydrogen bonding. The follow- Pauling (35): ing shows how he represented coordinated hydrogen in water: I n d r St rl n ndr t h v b n f r t r d t t d nt t rt d h r d t r th n n h th n n 19 nt t E r p l v n St rl n ndr n r W r t nt r t n p p r t th r As a result of this work, Sidgwick's book (or papers from his group) became the most likely citation given for hydrogen Not long after Pauling himself went to Europe, where he bonding, and the most used term for the phenomenon became studied with Sommerfeld and learned about the new develop- "coordinated hydrogen". This is particularly true of British ments in quantum theory (36). chemists, but also, to a lesser degree, for Americans. For In 1928, Pauling wrote the first paper (36) in a series that example, John Williams, of the University of Wisconsin, in a would lead eventually to his book, h t r f th Ch l 1928 discussion of the relationship between molecular polari- nd. In this paper we see the first use in the literature of the ll t Ch 7 (199 7 term "hydrogen bond" since it was used in Lewis' book. nature of the chemical bond was published in 1931 (38). The Panting, however, had changed his views about the nature of discussion of the hydrogen bond was essentially the same as in the hydrogen bond since the appearance of the paper with the 1928 paper, with the added point that the presence of OHO Hendricks, apparently as a consequence of his exposure to groups in many crystal structures indicates hydrogen bonding quantum theory: involving [0-H'0-1. This strictly electrostatic view of the hydrogen bond was held by Pauling for several years and does C l l t d nd b rv d v l f th h dr n-h l n d t n n not appear to have been definitely repudiated but gradually th h dr n h l d r n r nt nl f r fr h h t n abandoned. In this paper, Pauling credited the discovery of the b n l d d th t p l r p nd f r d fr - nd nd hydrogen bond to Huggins, and to Latimer and Rodebush. th t nd n h d pr v l t t d Cl r nd I r pr b bl Jack Sherman of Caltech, at the time one of Pauling's n n-p l r h n l n r rd n f rth r pp rt d b th graduate students, and previously an undergraduate at Berkeley, x t n f th h dr n b nd h tr t r [ d- f r th d wrote a review of the thermochemistry of ionic compounds in fl r d n nd l r n f r r r l d t b l 1932. In it he states (39): pr n pl f th h r d p r r f nd n t p h n tr t r n h h th pr t n h ld th t fl r d n t th r b h h h v l f r th pr t n ff n t fr n fl r d l tr t t f r ( n l d n p l r z t n f r ll d rpr n b t b xpl n d n th f ll n ll n h h n pt n f th h dr n b nd xpl n th b rv t n th t p nt d t n h l t r th t th n xp t d rr n f rtz t nl t f h h l tr n ff n t (fl r n x n nd n tr n tr t r f r n fl r d pr b bl d t th f r t n f f r h b nd h dr n b nd
No reference is given to any earlier workers for the concept of Pauling covered hydrogen bonding in lectures on the nature of the hydrogen bond. the chemical bond from 1927-1928 at Caltech and in lectures An alternative candidate for the first mention in print of the on the applications of quantum mechanics at Berkeley begin- term hydrogen bond since Lewis' book is a volume by Arthur ning in the spring of 1929. The view of hydrogen bonding in Buswell of the University of Illinois entitled The Chemistry of these lectures, at least from the period 1929-1931, is the same Water and Sewage Treatment (37): as that presented in his 1928 and 1931 papers (35,40). In 1933, Pauling analyzed the X-ray diffraction data on t r nd d b h n n xt n n f th th r f v l n NH4HF2 (41): h v d pl bl t n t th n h h th l l r r t b b lt p h t v r l n t n n In pr d t n tr t r f r I-1 1-1 th f ll n p- h h h dr n n l t v l n b nd b h r n t p r t n f l tr n th d ff r nt t h r t n ld b t 1 W xp t l n r r p n nd K th th n d r d h dr l f r d th - d t n l t 1 1 A° W f rth r xp t h dr n b nd b t n n tr n nd f r rr nd n fl r n n h fl r n n h ld b ppr x t l t tr h dr ll rr n d b t th n tr n n t d t n f 3 A° n If n d r th f r l tr n p r f th x n h ll d p d t rd th rn r f t tr h dr n t ld pp r th t d bl r The hydrogen bond in this compound is assumed to be com- tr pl h dr n b nd ht x t It h p d th t th th r f th pletely ionic. n t t t n f t r ll b bj t d t xp r nt l nv t t n Pauling and L. 0. Brockway determined the structure of formic acid by X-ray diffraction in 1934 (42). Formic acid and Buswell had obtained a Ph.D. from ColumbiaUniversity in other carboxylic acids had long been known to form dimers, 1917 and since 1920 held joint appointments as Professor of and Latimer and Rodebush had suggested in 1920 that this was Sanitary Chemistry at the University of Illinois and as Chief of due to hydrogen bonding. The results of this determination the State of Illinois Water Survey. At Illinois he was a confirmed this suggestion. In this paper Paining retreated colleague of Worth Rodebush, with whom he would later slightly from the purely ionic picture of the hydrogen bond, collaborate on some papers on hydrogen bonding. It is doubtful indicating that resonance between ionic and covalent forms of that Buswell's book exerted much influence on academic the carboxylic acid group may contribute to the stability of the chemists; I have found only one citation to it with reference to hydrogen bond. hydrogen bonding. The citation is from a review article by In 1935, Pauling published a paper on the structure and Rodebush. entropy of ice (43). In it he pointed out that the residual entropy A more complete pr nt t n f l n views on the of ice can be accounted for by a structure in which each oxygen ll t Ch 7 (199 atom is attached to two hydrogen atoms in the same molecule, of deuterated compounds. Differences between the vapor and to two other hydrogen atoms in other water molecules by pressures of deuteroacetic acid (49), deuterochloric acid (50), hydrogen bonds, such that the hydrogens in the O-H-0 linkage and deuterocyanic acid (51), and the vapor pressures of the are not symmetrically located between the two oxygens. Since corresponding "light" compound were attributed to stronger the discussion implies discrete water molecules, rather than hydrogen bonding in the deutero compound. Thus, there is a ionic bonding between H+ and 0-, it would appear that Pauling 5% difference in the vapor pressure of the acetic acids, for had quietly abandoned his insistence on the purely ionic nature which hydrogen bonding is important, and little difference for of the hydrogen bond. HC1 and HCN, where hydrogen bonding is much weaker. In 1936, A. E. Mirsky and Pauling (44) proposed that Rodebush, in 1936, published a review on the subject of protein molecules are held in definite configurations by hydro- hydrogen bonding and coordination (52), pointing out the gen bonding between amino and carboxylic side chains; the similarities and differences (mainly that the hydrogen bond is process of denaturation would be one in which these hydrogen much weaker than the coordination of metal ions) between the bonds are broken. William Astbury and H. J. Woods (45) had two concepts. He pointed out that it was only then, 15 years previously proposed that bonding between protein chains is after the introduction of the concept, that definite proof of the due to the attraction between =NH and =CO groups. The hydrogen bond has appeared, pointing specifically to the X-ray following diagram shows their proposed structure: studies of Panting and the disappearance of the O-H vibrational frequency in the IR in hydrogen bonding situations (of this more later). William Claussen and Joel Hildebrand (53) reported on the vapor pressures of hydrogen and deuterium fluoride in 1934, citing the above-mentioned papers (49-51) of Lewis:
S n th h dr n b nd h b n r rd d b l r l r p n bl f r th d ff r n n v p r pr r b t n th rr - The dotted lines between the CO and NH groups might indicate p nd n l ht nd h v p nd t rr d t th t p r - that they had hydrogen bonding in mind, even though they do n f th t h dr n fl r d n h h th b nd p rt l rl not use any of the names then current for the concept. The fact tr n ld b nt r t n that the same dotted lines are used between the alpha-hydro- gens in CHR groups, leaves some doubt that they intended The results of this investigation supported Lewis' contention. anything so specific. Four years earlier, G. H. Cady and Hildebrand (54) had studied Several of the pioneers of hydrogen bonding returned to the the freezing points of water-hydrogen fluoride mixtures and concept in the 1930's, after a decade or more of pursuing other explained the results in terms of molecular compounds be- research interests. In 1931, Huggins proposed a mechanism tween Hp and HF without reference to hydrogen bonding. for the high specific conductances of the hydroxide and hydro- Hildebrand had been a faculty member at Berkeley since gen ions in liquid water involving the transfer of protons from 1913. He was one of the first of the young faculty members one water molecule to another through the formation of tempo- brought in by Lewis to build up the department, and had rary hydrogen bonds. This paper is the first use by Huggins of collaborated with Latimer on the Reference Book of Inorganic the term hydrogen bond (46). In 1936 he wrote reviews of Chemistry. Consequently it is surprising to find that it took hydrogen bridges in ice and liquid water (47) and in organic Lewis' renewed interest in hydrogen bonding for him to accept compounds (48). In the second paper he repudiates the the concept in his own work. Considering that it took 14 years accepted name for the concept (48): for the hydrogen bonding concept to cross the hall (figura- tively) at Berkeley, it is perhaps understandable that it took as h r t r pr f r th t r "h dr n br d " t th xpr n long as it did to win acceptance from the chemical community "h dr n b nd" ntr d d b t r nd d b h b l v n t at large. b t t th rd b nd ( n h tr nl f r t n t n In 1933, John D. Bernal and K. H. Fowler discussed the f n r r (n rl l t l tr n h ld n t th r t theory of water and its ionic solutions. Bernal, a crystallogra- t dr n b nd l nf n n t t th pher at Cambridge University (in 1937 he would move to
l tr n p r b nd b t n t t n th l l Birbeck College, University of London) is probably best known for his work on the structures of proteins. Their In this Huggins was fighting a lost cause, as by that year almost explanation for the high mobility of the Hp+ and OH ions was everyone else who was making use of the concept had adopted essentially the same as that proposed by Huggins in 1931, but the term "hydrogen bond". no citation of Huggins' article was given. In comparing the Lewis, by 1934, had turned his attention to the preparation association of water with that of other liquids, they stated that: ll t Ch 7 (199 9
"In BF the cohesion is better regarded as due not to dipoles but hydrogen bond is due primarily to unusually strong dipole to 'the H-bond'." In concluding they state (55): interactions (60). The current view also allows for some contribution from It l r th t th d h r d v l p d f th r t ll rr t ll covalency in stronger instances of hydrogen bonding (such as l nd th lv t n b r f f rth r ppl t n p rt l rl n HF2-). These days this is generally described in terms of three- ph l nd h l ppl t n f th h dr n b nd center orbitals. The equivalent for the chemist of the 1930's would be "resonance". We have already seen that Pauling The term "hydrogen bond" does not otherwise occur in the invoked resonance as contributing to the stability of the formic main discussion of the structure of water and ice, but it is clear acid dimer (42). Sidgwick, in 1934, on quantum mechanical that this is what they have in mind. No citation of previous grounds, abandoned the theory that the hydrogen atom in the workers is given for the concept, but Lewis' work with deu- hydrogen bond has four shared electrons ( 1 terium compounds is mentioned in a discussion of the mobility of D+ in heavy water. h l t n f th d ff lt pr v d d b th th r f r n n In 1935, Bernal and H. D. Megaw published a major paper th h dr n t b n v l ntl tt h d t n nd n th r f th on the function of hydrogen in intermolecular forces (56). In t t n th t tr t r it they attributed the "so called hydrogen bond" to Huggins and Pauling. The major thrust of the paper was a distinction Bernal and Megaw (56) suggested that oscillation of the between ordinary hydrogen bonding and bonding between two hydrogen atoms between positions in which it is bonded to hydroxyl groups, which they consider different enough to give each oxygen in turn might be equivalent to electronic ex- a separate name: "the hydroxyl bond". Bernal's papers influ- change. They proposed this speculation rather tentatively, enced many British and Continental chemists during the middle however, and concluded that the hydrogen bond is primarily 1930's, as judged by the number of citations. The conception due to electrostatic attraction. of the hydroxyl bond was much commented on and debated. In 1937, Albert Sherman (62), a Berkeley graduate and the Rodebush (52) remarked that the "hydroxyl bond" did not twin brother of Jack Sherman who had worked with Pauling, appear to differ in any significant way from the hydrogen bond, considered that the hydrogen bond is stabilized by resonance and after the initial impression caused by Bernal 's papers died structures in which the hydrogen atom is bonded to either down, this view came to be generally accepted. oxygen, and that this stabilization energy should show up in Other crystallographers were, in the meantime, following thermochemical data for compounds in which it occurs. He Pauling's lead, finding hydrogen bonding in various crystal pointed out that such stability is not found in therrnochemical structures. As early as 1930, J. West, of the University at data for nitro derivatives of benzene and argued that hydrogen Manchester (57 suggested that the X-ray analysis of potas- bonding is not present in these compounds, despite the indica- sium dihydrogen phosphate could best be fit by placing the tion from IR spectra that it is present. This analysis is flawed hydrogen atoms on a line joining two oxygen atoms of adjacent by the fact that he did not allow for the possibility of intermol- PO,' groups, giving each hydrogen a coordination of two. ecular as well as intramolecular hydrogen bonding, but the There is, however, no suggestion in this paper that this conclu- value (about 2 kcal/mole) that he predicted for the effect is of sion can be generalized to other structures. the right order of magnitude. IR and Raman spectra of water, In 1933, William H. Zachariasen of the Physical Labora- the alcohols, amines, and related compounds were studied tory of the University of Chicago came to the same conclusion intensively in the 1920's and early 1930's. It was recognized with regard to the position of the hydrogen atoms in sodium that the characteristic stretching frequency of the OH or NH bicarbonate (5 In this paper Zachariasen suggested that this group appeared in the spectra of these compounds in the vapor arrangement is due to the hydrogen bond and credits Pauling phase, but was absent, or displaced, in the liquid phase or in with the idea. In 1935, Zachariasen reported the X-ray analysis solutions. In the condensed phase it had long been recognized of liquid methyl alcohol (59): that the position and intensity of this band varied with the temperature and the solution concentration. These effects in O r n l th tr n l nd t th pr n f h dr n b nd water were often interpreted in terms of Armstrong's model for b t n x n t f n hb r n l l Ev r h dr n water, in which changes in temperature or solute concentration t th l n d t t x n t ; nd bt dl t l n d r were attributed to the changing proportions of the various tr n l t n f th x n t th n t th th r t ld t ll polymers of "hydrone". For the alcohols and amines the b j t f bl t t l b t h dr x l r p t r ll f h t equivalent explanation in terms of different degrees of associa- h r t r z th n t r f th h dr n b nd h ld pl tion was offered. Some workers, noting the fact that changes th t r d p l b nd n were seen in the OH or NH vibrational frequencies, drew the conclusion that association was through these bonds, but This is the first clear indication of the current view that the before 1935, no connection was made with the Latimer- 1 ll t Ch 7 (199
Rodebush concept of hydrogen bonding (63). bonding (71): The first clear recognition that these changes were due to hydrogen bonding appeared in 1935. A paper (64) published It b n v d nt n th t th t r " t n" nd r h h inNature on 26 January 1935 by a research group in the Bureau h v l p d ll d p rt r fr n r l b h v r t b of Chemistry and Soils of the Department of Agriculture in bd v d d nt t n r n fr th nt r t n f d p l Washington, D.C., attributed the lack of the characteristic OH nd th t d t th f r t n f d f n t h l b nd Of th absorption in such molecules as salicyaldehyde, o-nitrophe- p rh p th t nt r t n r th h dr n b nd r br d nol, and 2,6-dinitrophenol to the presence of "chelated" hydro- b t n x n n tr n r fl r n t p f h l gen. Reference is given to Sidgwick's book. It is noteworthy nt r t n that one of the members of the group, Sterling Hendricks, had previously worked with Pauling on the crystal structure of the Among the scientists who also gave papers at this meeting were HF2- ion (34). Independently, in a paper presented to the Bernal (72) and Errera (73). The record of this meeting, Academy of Sciences in Paris on 18 February 1935, Jacques appearing in print early in 1937, was much cited by chemists Errera and Pol Mollet of the University of Brussels (65) came and physicists during the remainder of the year. Interestingly, to the same conclusion with regard to the IR spectra of the citations are as often to the "General Discussions" follow- salicyaldehyde and o-chlorophenol. They also cited Sidgvvick's ing the papers as to the papers themselves (74). book for the concept, calling it "covalence de coordination". As an example of the shift of opinion during 1937, we might At about the same time (paper submitted 20 March 1935), point to two French spectroscopists, René and Marie Frey- Hendricks reported the results of an X-ray diffraction determi- mann. They had been working on the IR spectra of alcohols, nation of the structure of oxalic acid. He concluded (66): amines, and related compounds since 1931, and René Frey- mann had written his doctoral thesis (75) on the subject. In one h p r t n - = 55 A° pr b bl t d th of René's earlier papers (76), he studied the spectra of alcohols "h dr n b nd" b t n t x n t in non-polar solvents and attributed the shift in the OH stretch- ing frequency on changing concentration or temperature to The following year the group at the Bureau of Soils (67) "les associations moléculaires", envisioned as in the following adopted the term "hydrogen bond" for the concept, citing diagram: Huggins, Latimer and Rodebush, Sidgwick, and Panting for the previous history of the concept. The absence of the characteristic OH stretching frequency is proposed as a defi- nite test for the presence of hydrogen bonding. A paper (68) from the same group later that year, extending the application of the criterion to phenols, states that "The authors are much In a paper presented to the Academy of Sciences in Paris by indebted to Professor Linus Panting for discussion of this type René on 28 December 1936 (77), he considers association as of spectra and helpful advice as to its interpretation." It is involving "des liaisons monoelectroniques" of Perrin: tempting to speculate that it was the presence in the group of Hendricks and Oscar Wulf, both of whom had worked with Palling, which led them to look at hydrogen bonding as a possible explanation of the anomalies. By 1936, Errera (69) was also using the term "hydrogen Another paper, by Marie, presented 25 January 1937 (78), bond", though he was still citing Sidg-wick's book for the also proposes "liaison monoelectronique" to account for shifts concept. Before the papers of Errera and the group at the in IR spectra of amines. However, in a joint paper submitted Bureau of Soils, papers using the concept of hydrogen bonding on 25 February 1937 (79), they review the evidence for"liaison had largely been confined to crystallographers, British physi- hydrogéne". Although the papers presented at the Faraday cal organic chemists of the Sidgwick school, and a few chem- Society meeting are not cited as references, the timing of this ists with associations with Berkeley. During 1936 and 1937 an paper and the abrupt shift in their view of the nature of increasing number of spectroscopists, both chemists and physi- association makes it likely that they were influenced by reports cists, began publishing papers making use of the concept. from other French scientists who had attended the meeting. Another significant event leading to general acceptance of The Freymanns were not the first French scientists to use the concept was a Meeting of the Faraday Society on the the term "hydrogen bond": it appeared (untranslated from Structure and Molecular Forces in Liquids and Solutions held English) in a paper submitted a month earlier (30 January at Edinburgh on 24-26 September 1936 (70). Hildebrand gave 1937) by Ch. Sannié and V. Poremski (80) on the Raman the keynote lecture for the section on the structure of solutions, spectra of organic acids. in the course of which he stressed the importance of hydrogen By 1937, the term "hydrogen bond" was also used by Japa- ll t Ch 7 (199 11 nese chemists. The earliest use of the term I have been able to theory: namely that Lewis, Latimer, Rodebush, and Huggins find is in a paper by S. Mizushima, Y. Uehara, and Y. Morino did not have any program of experimentation which made use (81) of the Imperial University of Tokyo. The first instance I of hydrogen bonding and consequently did not influence the have found of the occurrence of "Wasserstoffbriicke", the greater number of chemists who were experimentalists rather German equivalent of "hydrogen bond", is in a book published than theorists. We see this influence of an experimental pro- in 1938 (82). However, at the Edinburgh meeting, K. L. Wolf gram in spreading acceptance of hydrogen bonding repeatedly of the University of Wiirzburg wrote (83): during the 17 year history described in this paper. Lowry, and particularly Sidgwick, primarily influenced the new British ... t f ll th t th r r r d t p r t pl t l th -O school of physical organic chemists; Pauling influenced crys- b nd n (d nt ll t th d p l f r fr th t t f p r tallographers; Lewis, when he began research on deuterium, l h l t pl t d t n l p r l l h l where he could apply the concept of hydrogen bonding to his own work, influenced Hildebrand. Hendricks, a crystallogra- Since many participants at the meeting (including Hildebrand) pher and Pauling's student, probably influenced the spectro- were drawing distinctions between hydrogen bonding and scopists at the Bureau of Soils, who in turn, influenced other dipole forces, it cannot be claimed that Wolf would have spectroscopists. Finally, the Edinburgh meeting of the Fara- agreed that he was talking about hydrogen bonding. But his day Society, bringing together theorists and experimental sci- estimate of the heat of dissociation shows that he recognized entists using different techniques, diffused the "new" ideas that the forces between -OH dipoles are greater in magnitude throughout the community of chemists and chemical physi- than ordinary dipole forces. cists. Why did the acceptance of the hydrogen bonding concept by the chemical community take as long as it did? Rodebush References and Notes gave one answer in his 1936 review (52): that it was only after 15 years that definite evidence for hydrogen bonding was A n l d nt M th n f r t t Ch t n h forthcoming. The group at the Bureau of Soils proposed nt nt n f r t n n h n r th n th b nn n f h dr n another explanation (67): b nd n ( nf rt n t l n v r f n h d l d h t r t th n t l l tt r t n n 197 ; th n t n l h h lp d th nd n f h dr n t t t h b n r n z d nd d r b d th f n l t f th l t r t r rv I ld l l t th n r nd r h v r t r p rt l v l n nd r f r h dr - n l n h n r d r t f r nf r t n th n b nd h l t r n rd n t n r th r n t n nt r- v r l r l tt r nd t Cl ff rd M d f th W ll p r l l r t n nd th " rth ff t" h v r lt pl t K rr br r t Or n St t Un v r t h h lpf ll nt f n n r fl t th rph h r t r f th n pt nd t ph t p f t r l fr th l n Ar h v n ll t S tt p rt ll n rr l t d pp r n n th l t r t r d r n th p t n n nd h t ff f nt r-l br r l n l br r n t E t x t nt -f v r St t Un v r t h r d t r l l t t ph t p f th j rn l n t n r ll t n These explanations may be partially true; still, most of the 1 W M t r nd W d b h " l r t nd I n z t n textbook examples for the existence of hydrogen bonding were fr th St ndp nt f th h r f l n " . A . Ch . already known when Latimer and Rodebush wrote their paper, S ., 1920, 42, 1 19-1 33 or were discovered soon afterwards. And most chemists who M n " h dr n nd nd Oth r used the terms "association" or "intermolecular association" n n " Ch l h, 1980, - 9 or "secondary valence" do not appear to have anything as 3 M L. n " r p r Ch 1 M 1919 S definite as the hydrogen bond in mind. Sp l t n rd n M l l r Str t r " Unp bl h d p p r It is more likely the case that the true explanation lies in two G l n nd th Str t r f At nd M l factors: first, despite the general acceptance of the Lewis l , v r Y r 19 p 1 9 ( pr nt f 19 3 d t n theory by the late 1920's, most chemists were not yet accus- 5 ld br nd "W nd ll M t h ll t r" r. M . tomed to think in terms of electronic effects; they had learned t. A d. S ., 1958, 3 - 37 early in their chemical education that "association" explained G C nt l nd A M Cl ll n h dr n nd, the properties now explained by hydrogen bonding, so that r n S n r n 19 p they did not question whether the concept of association had 7 M Ch d ll " h M l l r Str t r f W t r" Ch . any real content. This is similar to the unthinking acceptance v., 1927, 4, 375-39 of the octet rule by chemists in the 1950's, so that the synthesis S n " dr n l r d nd It S l t n " Ch . of xenon compounds came as a shock. v., 1931, 8, 13- 3 A second reason is similar to that proposed by Robert 9 E nn " t n v n M l l r ht n n h Kohler (17) to explain the delay in the acceptance of the Lewis d r S d th d " h . Ch ., 1890, 6, 37- 73 1 ll t Ch 7 (199
1 W rn t " rt l n n St ff h n z C n t nt n r f A t v t (C r p rt I h - ö n tt ln nd z h n ö tt l d pfr " t n f Q n l n -Chl r ph n x d n nz n nd p- h . Ch ., 8 , 8, 11 -139 hl r b nz n " . Ch . S ., 4, - 3 11 S M r nd W n ll " h St t f A n n 3 f r n ( pp 3 7- 7 A S l t n" . Ch . S ., 2, 0 , 1 35-1 7 33 W rn " h Cr t l Str t r f I t n °C nd 1 W r " h Cr t l Str t r f I " r . h . S . -1 3°C" r . . S . nd n, A, 2 , 2 , 7 - 93 nd n, 22, 4, 9 -1 3 3 S ndr nd l n " h Cr t l Str t r f 13 r " r n nt b r f r ln" h Ch S d nd t r n tr d nd t C n t nd th 22, 00, ; h n nt h l nd . nh rdt "Ob r t r f th r n tr d Gr p" . A . Ch . S ., 2 , 4 , 9 - f nb l h r h z r K n tr t n d tr h dr fl r d 919 nt r r nd n d r At b r h nd Ob r d rönt n r ph - 35 l n p r n l n t n 17 M 19 9 h Erf r h n d r r nd n " Kr t ll r., 2 , 8, 9- 3 l n " h Sh r d-El tr n Ch l nd" r . t. A d. S ., 28, 4, 359-3 1 M z rth " h Cr t l Str t r f t dr - 37 A M ll h Ch tr f W t r nd S r t n l r d " . A . Ch . S ., 2 , 4 , 1 - 13 nt, Ch l C t l C Y r 19 pp - 15 C ll n "Ch n n th Infr -r d Ab rpt n Sp tr 3 l n " h t r f th Ch l nd Appl t n f W t r th p r t r " h . v., 2 , 26, 771-779 f lt Obt n d fr th Q nt M h n nd fr h r 1 I n r " p f l n " S n , 2 , 4, 59- 7 f r n t S pt b l t t th Str t r f M l l " . A . 17 E K hl r r "Irv n n r nd th O t t h r f Ch . S ., , , 13 7-1 l n " t.St d. h .S ., 2, 4, 39- 7; " h - n r . . Sh r n "Cr t l En r f I n C p nd nd h r f l n nd th Ch l C n t 19 -19 "; t. h r h l Appl t n " Ch . v., 2, , 93-17 St d. h . S ., , 6, 31- l n Ar h v Or n St t Un v r t x 9 b; Ad- 8. . rr n " l n t p d dd t n" C pt. nd., v n d In r n Ch tr t r t C l f rn In t t t f 2 , 8 , 557-5 1 hn l 193 -31; x 1 r l t r n Appl t n 19 M n "At Str t r " S n , 22, , 59- f Q nt M h n 19 9-1933 ; "El tr n Str t r f At " . h .Ch ., 22,26, 1 - 1 l n " h Cr t l Str t r f A n dr n 5 l r d " . Kr t ll r., , 8 , 3 -391 M r nd r "St d f El tr v l n l n nd r " h Str t r f th rt II C rd n t d dr n" . Ch . S ., 2 , 2 , 111- C rb x l Gr p I h Inv t t n f r A d b th 1 ffr t n f El tr n " r . t. A d. S ., 4, 20, 33 -3 1 S d nd K C ll "Abn r l nz n 3 l n " h Str t r nd Entr p f I nd f Oth r r v t v " . Ch . S ., 24, 2 , 5 7-53 Cr t l W th S nd n f At Arr n nt" . A . E Ar tr n " h Or n f O t Eff t I Ch . S ., , , - dr d n Ch n n A S l t n " r . . S . n A E M r nd l n "On th Str t r f t v d n, A, 2 , 0 , 1 - 1 n t r d nd C l t d r t n " r . t.A d.S ., 6, 22, 3 C E nn b r "A tr n nr Ed rd" n C C 39- 7 G ll p d t n r f S nt f r ph , l I S r bn r 5 W A tb r nd W d " - St d f th Y r 197 p - 9 Str t r f r W l nd l t d br h M l l r E Ar tr n " dr n - A r t t" t r , Str t r nd El t r p rt f r K r t n" h l. r n . . 26, , 553-55 S . nd n, A, , A2 2, 333-39 5 M r "Opt l t t r p r n" t r , 26, M n " h l f dr n nd n C nd t n , 71- 75 b dr n nd dr x l I n " . A . Ch . S ., , , 319 - M r nd C A t n " h t t r p r n f 3191 rt r A d" t r , 24, 4, 3 31 7 M n " dr n r d n I nd d W t r" 7 S d " h Str t r f th En l f r f 13- . h . Ch ., 6, 40, 7 3-731 K t - t r nd 13- t n " . Ch . S ., 2 , 2 , 9 7-9 9 M n " dr n r d n Or n C p nd " S d h El tr n h r f l n , Oxf rd . Or . Ch ., 6, , 7- 5 Un v r t r nd n 19 7 9 G nd W S h tz "S r p rt f r 9 W W ll " h l t n t n l r z t n nd t t A d" . A . Ch . S ., 4, 6, 93- 95 A t n" r . t. A d. S ., 28, 4, 93 -93 5 G M n ld nd W S h tz " h p r 3 C Sp n "C rd n t n f dr n n A t d r r f d nd S l d t hl r A d" . A . Clz . S ., d " t r , 2, 2 , 4, 6, 9 - 95 31 M Gl W M M d n nd nt r "E l br 51 G nd W S h tz " h p r r r f d nd S l d t n A d" . A . Ch . S ., 193 6, 1 73 Err r "Str t r f d St d d n th Infr r d" 5 W d b h " h dr n nd nd C rd n t n" r n . r d S ., 1937 33 1 -1 9 Ch n. v., 193 , 59- 5 7 "G n r l n" r n . r d S ., 1937 33 1 1-3 53 W Cl n nd ld br nd " h p r r r - 1 f dr n nd t r l r d " .A .Ch . S ., 193 6, 75 r nn " h r h r l pr h nfr r " Ann. 1 h . ( r , 1933 20, 3-3 3 5 G C d nd ld br nd " r z n nt f th 7 r nn "Eff t d l d l t n t d l t p r t r r l S t W t r- dr n l r d " . A . Ch . S ., 193 2, b nd d b rpt n nfr r t n l l r " C pt. 3 3-3 nd., 193 , 39- 1 55 rn l nd l r "A h r f W t r nd I n 77 r nn "Sp tr d b rpt n d n l pr h nfr - S l t n th rt l r f r n t dr n nd dr x l r d l t n d l h l d n l th r l d x n f r t n I n " . Ch . h ., 1933 , 515-5 d x n " C rnpt. nd., 1937 204, 1- 3 5 I3 l nd M " h n t n f dr n n 7 M r nn "Sp tr d b rpt n d n l pr h nfr - Int r l l r r " r . . S . nd n, A 1935 , 3 - r d l n d n t d l h l r t n d p rn n " C pt. nd., 1937 204, 1- 3 57 W t "A Q nt t t v -r An l f th Str t r f 79 M r nn nd r nn "Int rpr t t n d d v r t h dr n h ph t (K O " Kr t ll r., 193 pr pr ét h p r l h p th d l l n h dr n p tr 4, 3 -33 d b rpt n nfr r " ll. S . Ch ., 1937 4, 9 -95 5 W h r n " h Cr t l tt f S d r- C S nn nd r " h r h r l n t t t n b n t CO3" . Ch . h ., 1933 , 3 - 39 d p pt d 1 S r l tr t r d d r n nd 59 W h r n " h d Str t r f M th l Al h l" n d l f n t n d d n l d t l r d r v " ll. S . . Ch . h ., 1935 3 15 -1 1 Ch ., 1937 4, - 93 S f r x pl A C tt n nd G W l n n Adv n d 1 S M z h rn Y U h r nd Y M r n " h O br t n In r n Ch tr , 5th Ed W l Y r 19 p 9 Sp tr n th h t r ph Infr r d" ll. Ch . S . p n, 1 S d " h h r f n n nd th C rd - 1937 1 13 -135 n t n f dr n" Ann. p. r r. Ch ., 193 31 K hlr h r S l n ff t Er änz n b nd A Sh r n " h t r f th dr n nd I h l , . Spr n r rl n 193 p 117 f n n G n r l C n d r t n " . h . Ch , 1937 4 , 3 K W lf "On A t n t f M x n nd M b l- 117-1 t G p " r n r d S ., 1937 33 179-19 3 S r f r n - 5 7- 9 nd 75- f r r f r n t th rl r r G E lb rt W lf S ndr nd U dd l "A The Editor regrets to report that Dr . Denis Quane passed away Sp tr p M th d f r t t n S r f Ch l t n" on 21 September 1990 shortly after correcting the final proofs t r , 1935 , 1 7-1 for this article. Dr. Quane was an Associate Professor of 5 En- r nd M ll t "I r ntr lé l r t Chemistry at East Texas State University, where he had been p tr d b rpt n nfr r " C p . nd., 1935 200, 1 - teaching a course in the history of science since 1982. 17 S ndr " h Or nt t n f th Ox l t Gr p n Ox l A d nd S f It S lt " Kr t ll r., 1935 91 - 7 G E lb rt W lf S ndr nd U dd l ph W ll M ll r ( 86 8 " h dr n nd t n Ox n At n S Or n C p nd " . A . Ch . S ., 193 8, 5 -555 Fat hi Habashi, Universite Laval W lf U dd l nd S ndr " h Eff t f Orth S b t t t n n th Ab rpt n f th O Gr p f h n l n Today most students of chemistry have probably never heard th Infr r d" . A . Ch . S ., 193 8, 7- 3 of Joseph William Mellor, though his monumental 16-volume 9 Err r nd M ll t "Int r l l r r nd - Comprehensive Treatise on Theoretical and Inorganic Chem- Ab rpt n nd n Al h l t 3 " t r , 193 8, istry is still to be found on the shelves of most chemistry 7 S p n "Str t r nd M l l r r n r libraries and he was, without a doubt, one of the most prolific d nd S l t n " r n . r d S ., 1937 , 1- 79 and influential textbook authors of his time. His biography in 71 ld br nd "Int r l l r r n S l t n " r n . the Obituary Notices of the Fellows of the Royal Society r d S ., 1937 , 1 -151 appears to have been accidentally overlooked by the standard 7 rn l "An Att pt t M l l r h r f d biographical indices (1) and he does not appear in any of the Str t r " r n . r d S ., 1937 33 7- standard biographical dictionaries of prominent scientists (2,