Professor D. L. H. Williams

Daniel Lyn Howell Williams, chemist: born Ammanford, Carmarthenshire 6 August 1936; Assistant Lecturer in Chemistry, University College Swansea 1961-62; Lecturer in Chemistry, Durham University 1963-77, Senior Lecturer 1977-85, Reader 1985-91, Professor 1991-2001 (Emeritus), Head of Department of Chemistry 1992-95; married 1961 Lona Tayson (one son, one daughter; marriage dissolved), 1995 Gill Humphrys; died Newcastle upon Tyne 1 September 2006.

When D. L. H. Williams was in his first job - and perhaps the most junior member of staff - at University College, Swansea, he was made an offer he could not refuse. Would he like to deliver the undergraduate lectures in Chemical Thermodynamics? His stomach dropped, but that there was nothing to do but to get his head down and get on with it. Later he said that this was about the best thing that could have happened to him. After this ordeal by fire, he felt that he could tackle almost anything.

Williams, a physical organic chemist and Emeritus Professor of Chemistry at Durham University, became renowned for his work in the field of nitrosation reactions and latterly for his contributions to pathways for in vivo formation of nitric oxide (NO).

Daniel Lyn Howell Williams was born in Ammanford, Carmarthenshire, in 1936 and brought up bilingually. He attended Ammanford Grammar School before studying Chemistry at University College London. He chose to study for his doctorate in the field of physical organic (mechanistic) chemistry, largely the creation at UCL of Christopher Ingold and Edward Hughes, into whose orbit his research adviser, Peter de la Mare, an Aucklander, had earlier been drawn. The research was concerned with the pathways and intricacies of allylic rearrangements and from the number and quality of the publications that accrued, it was evident that a promising research career lay ahead for Williams.

He stayed on at UCL for a further year to work with Hughes (a native of Criccieth), to probe the mechanism of the benzidine rearrangement which had troubled chemists for over half a century, and whose sphinx-like character partially resisted this determined pan-Welsh scrutiny.

Williams spent 1961-62 as an Assistant Lecturer at Swansea before going to Durham in 1963, as Lecturer in Chemistry. There he developed an interest in nitrosation by entities such as XNO, in which X is variable, and was not helped by the instability of the parent nitrous acid, HONO. Like a medieval map-maker he patiently, doggedly, determinedly and with much low-key forensic skill, charted the terrain and waters. He pursued the mechanistic details of the nitrosation of four different elements - carbon, nitrogen, oxygen and sulphur - with nitrosation agent nitrous acid (HONO), esters (e.g. CH ₃ONO), nitrosothiols, and oxides of nitrogen with a variety of catalysts, for instance thiourea, which forms a very useful adduct (NH ₂) ₂ CSNO ⁺.

Williams was led to consider the physiological chemistry of the "parent" entity NO (nitric oxide), an extremely unstable gas in air. Nitric oxide mediates vascular tonus (blood vessel relaxation), affects neurotransmission, and is involved in pathogen suppression and the regulation of blood pressure; excess nitric oxide can lead to toxic shock. So part of Williams evolved into a physical organic biochemist. Biochemistry is but chemistry proceeding under severely restricted conditions, most evidently that of temperature. Latterly he was concerned with important compounds in which the NO group is bonded to sulphur.

Further details are to be found in his books Nitrosation (1988) and Nitrosation Reactions and the Chemistry of Nitric Oxide (2004). A very readable synopsis, "A Chemist's View of the Nitric Oxide Story", was published by Williams in the Royal Society of Chemistry journal Organic and Biomolecular Chemistry in 2003.

Williams pursued a longstanding collaboration with a group at Santiago de Compostela, and also, more recently, one at the Middlesex Hospital, and he was supported throughout by one-to-one colloquia with one of his former teachers, John Ridd, at UCL, who shared similar interests.

A successful university teacher surmounts three challenges - research, teaching and administration. Lyn Williams's high-quality research is manifest from the number of his publications (and associated books) whose significance is attested by their incidence of citation.

His teaching at all levels was excellent: he had an enviable repartee with his classes. On certain Monday mornings gentle barbs went thither or hither according as to whether Wales had won (or otherwise) in the then Five Nations. He had a facility for putting students at ease; but, having induced calm, he was no soft touch. His penchant for administration led to his appointment as Head of Department at Durham from 1992 to 1995. He ran a happy ship.

And yet, to a casual observer, Williams never seemed to get out of second gear. Supremely well organised, he was the antithesis of Churchill's allusion to "Every train should be given a sporting chance of getting away . . ." I don't think that Lyn Williams ever missed a train, or an appointment, and I doubt that he ever came close.

His keen interest in choral music led to his appearance on Sunday Night at the London Palladium as a member of the London Welsh Male Voice Choir, c 1960; he was later a founder (and long-time) member of the Northern Sinfonia Chorus. He played the organ regularly at his local church and during research visits to Santiago de Compostela he was given permission to play the organ in the cathedrals both there and at Burgos.

A keen club cricketer and former UCL first team squash player, Williams was axiomatically a Welsh rugby fan; when John Taylor achieved his legendary try conversion in the last minute from the touchline against Scotland at Murrayfield (in the early Seventies), Williams's quiet elation was such that he playfully renamed the ground ("maes" being "field" in Welsh) "Maesmurray".

David Morris