Mills, William Hobson

MILLS, WILLIAM HOBSON

(b. London, England, 6 July 1873; d. Cambridge, England, 22 February 1959)

organic chemistry.

Although Mills was born in London, his father, William Henry Mills, an architect, and his mother, Emily Wiles Quincey Hobson, came from Lincolnshire and returned there in the autumn of 1873; thus he always regarded himself as a Lincolnshire man. He was educated first at Spalding Grammar School and then at Uppingham School, where an accident in the snow caused the severing of an Achilles tendon and limited his outdoor activities, although in his mature years he could walk and cycle with considerable vigor. He entered Jesus College, Cambridge, in October 1892 and in due course obtained a first class in the natural sciences tripos, part I, in 1896 and in part II (chemistry) in 1897.

Mills then began research in the Cambridge University Chemical Laboratory under T. H. Easterfield (later Sir Thomas Easterfield); when the latter accepted the professorship of chemistry at Wellington, New Zealand, in 1899, Mills continued the work alone and was elected to a fellowship (tenable for six years) at Jesus College in 1899.

In October 1899 Mills went to Tübingen to work under Hans von Pechmann for two years, during which period he met N. V. Sidgwick of Oxford University; the two chemists, so similar in their interests, became friends for life. In 1902 Mills was appointed head of the chemical department of Northern Polytechnic Institute in London. In 1912 he returned to Cambridge, having been appointed to the demonstratorship to the Jacksonian professorship of natural philosophy and to a fellowship and lectureship at Jesus College. In 1919 he was appointed university lecturer, and in 1931 the university recognized the high quality of his work by creating a personal readership in stereochemistry, which he held until his retirement in 1938.

The major part of Mills’s scientific work was devoted to stereochemistry and the cyanine dyes. Only brief mention of some of the highlights in each of these divisions will be made.

Stereochemistry . Certain types of oximes were known to exist in two or more isomeric forms, for which an explanation had been suggested by Hantzsch and Werner. This explanation was not accepted by many chemists, and Mills sought decisive experimental evidence for its accuracy. After investigating several compounds, Mills and B. C. Saunders (Journal of the Chemical Society [1931], 537) prepared the o carboxyphenylhydrazone of β-methyl-trimethylene-dithiolcarbonate, which they resolved into optically active forms. Optical activity could arise in this compound only if the Hantzsch-Werner theory were correct.

It had been recognized that a spirocyclic compound consisting of two carbon rings linked together by a common carbon atom might show optical activity if the rings possessed appropriate substituents to ensure molecular dissymmetry. Mills and C. R. Nodder idid., 119 [1921], 2094) synthesized and resolved into optically active forms the first such compound, the kelodilactone of benzophenone-2,4,2′,4′-tetraearboxylic acid.

It had also long been recognized that a suitably substituted allene compound (3) would be dissymmetric;

but the synthesis of such a compound, bearing acidic or basic groups for resolution, had defied synthesis. P. Maitland and Mills, after about six years of persistent work, synthesized αγ-biphcnyl-αγ-di-α-naphthylallyl alcohol, which by a stereospecific dehy

dration using dextro and levo camphorsulfonic acid, was converted into the optically active forms of αγ-biphenylαγ-di-α-naphthyl allene (5).

By extensions of these general methods, Mills and E.H. Warren (ibid., 127 [1925], 2507) showed that the nitrogen atom of a quaternary ammonium salt had the tetrahedral configuration and was not situated in the center of a square-based pyramid. Furthermore, Mills and T. H. H. Quibell (ibid. [1935], 839) produced stereochemical evidence that the four-coordinated platinum atom had the planar, as distinct from the tetrahedral, configuration.

The fact that a biphenyl molecule, having suitable substituents in the 2,2′ 6,6′ positions. could show optical activity at first puzzled chemists. Mills was the first to point out in a simple diagram (Chemistry and Industry, 45 [1926], 884) that the size of these substituents could obstruct the free rotation of the two phenyl groups about their common axis, C₆H₅—C₆H₅, and such molecules could thus show optical activity. He became greatly interested in this subject of “restricted rotation” and later applied it to suitably substituted derivatives of naphthalene, quinoline, and benzene (with K. A. C. Elliott, et al. in Journal of the Chemical Society [1928], 1291; [1932], 2209; [1939], 460).

Cyanine Dyes . In 1914 photographic plates and films were normally prepared with a silver bromidesilver iodide emulsion, which was sensitive only in the ultraviolet, violet, and blue regions. In 1905, however, a German firm had synthesized a “photographic sensitizer” which, when incorporated into the emulsion, extended the sensitivity well into the red region, When in 1914-1915 the Western Front became essentially two parallel bands of heavily entrenched positions, it became imperative to detect as early as possible each day any work on these positions which the enemy had carried out during the previous night. The photographic reconnaissance of the British Royal Flying Corps (later the Royal Air Force) was under a great disadvantage, for their silver bromide-silver iodide plates were at their least sensitive in the red light of the early morning. The British authorities sent an urgent request to W. J. Pope, the head of the Cambridge University chemical department, to investigate the structure and the synthesis of Pinacyanol, which the Germans were using.

Pope enlisted the help of Mills and other workers, notably F. M. Hamer. This small team showed that Pinacyanol had the structure shown in Figure 6 and

developed a rapid synthesis of this compound and of other novel sensitizers such as the isoeyanines. After the war Pope and Mills stated: “Throughout the war practically all the sensitizing dyestuffs used by the Allies in the manufacture of panchromatic plates were produced in this (i.e. the Cambridge ) Laboratory” (Photographic Journal, 60 [1920], 183, 253). Mills and his co-workers subsequently continued the investigations of the various new types of sensitizers.

Mills was elected a fellow of the Royal Society in 1923 and received its Davy Medal in 1935. He was president of the Chemical Society for the years 1942-1943 and 1943-1944; his presidential addresses, entitled “The Stereochemistry of Labile Compounds” and “Old and New Views on Some Chemical Problems,” respectively form the last of his chemical publications.

Retirement allowed Mills to devote himself to the study of natural history, in particular to the many subspecies of British bramble. His collection of Rubi is housed in the botany department of Cambridge University and is composed of about 2,200 specimens mounted in sheets and arranged in systematic order: he had specimens of 320 of the 389 “microspecies” of Rubus fructicosus.

BIBLIOGRAPHY

In addition to the works cited in the text see F. G. Mann’s much fuller account of Mills and his work (with a photograph and a bibliography containing 73 entries) in Biographical Memoirs of Fellows of the Royal Society, 6 (Nov. 1960), 201.

Frederick G. Mann