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July 2015

What's in a name?

By Ian D. Rae

Naming of elements and chemical substances

The naming of elements after cities or countries was in vogue in the late 19th century – gallium (1875), germanium (1886), polonium (1898), scandium (1876) and thulium (1879) – with francium (1939) coming along later. In the 20th century, it was people – einsteinium (1952/1961), fermium (1954) and mendelevium (1955). Of course, there are some ‘names’ in later years, but like Dr Tom Lehrer (they hadn’t come to Harvard) I’d like to retain my historical perspective.

Place names were given to chemical substances, too, the earliest inorganic ones I could find being Prussian Blue and Paris Green. It was in the domain of organic chemistry, however, that this naming practice was most common. In 1935, Professor J.C. Earl and his student Alan Mackney reported the preparation of an unusual compound that was later shown to be a 1,2,3-oxadiazol-5-one, which exists with separated positive and negative charges and is described as a mesionic structure. By 1946, further members of this group had been prepared and the name sydnone was bestowed on them, denoting the city where they were first prepared. Rolf Huisgen and his students responded in the early 1960s with another class of mesoionic compounds, which they called munchnones, honouring München (Munich).

Natural products were favourite targets of namers. Nickon and Silversmith (Organic chemistry: the name game, 1987) listed a few natural products with names given to them by Dr Maurice Shamma of Pennsylvania State University, reflecting their countries or regions of origin. Most of the names have not been taken up by other researchers, which is a pity because I liked the sound of srilankine, isolated from Alseodaphne semicarpifolia Nees in Shamma’s home country. Something similar led to the name canadine for a tetrahydroberberine alkaloid isolated in 1888 from the plant Hydrastis canadensis. There were local examples, too, such as australine, a tetrahydroxypyrrolizidine with glucosediase-inhibiting properties that was isolated from the seeds of Castanospermum australe (the Queensland black bean) in 1988. Baker and Smith isolated p-allyphenol from Eucalyptus species and referred to it as australol but the name never stuck.

In 1914, Robert Robinson and H.G. Smith reported the isolation of tasmanol form Eucalyptus risdoni Hook, which had been collected on the slopes of Mt Wellington, Tasmania. They thought it was a phenol, but Victor Trikojus and Doug White, who worked on the same sample in 1932, judged it to be an acid because it formed a ‘methyl ester’, among other derivatives. Some of the original oil was still available in 1956, when Birch and Elliott again isolated the compound of interest, showed it to be a β-triketone and so renamed it tasmanone. Later work suggested that the Tasmanian tree was probably E. tasmanica Blakely. Hellyer, Bick, Nicholls and Rottendorf (1963), who collected a sample from the same locality, found that it contained only 0.5% of tasmanone, which explained why only small quantities had been available to earlier researchers. However, the leaf oil of E. camfieldii Maiden growing at Hornsby, New South Wales, contained 40% tasmanone and with these larger quantities the uncertainties left from earlier work could be resolved and the exact structure was published.

It’s easy to see why these names were bestowed and accepted by the chemical community, but there is one substance that I found most elusive – the terpene australene. When I found that it had been isolated from the kauri, Agathis australis, I thought that must have been the initial discovery and act of naming, but further research showed that naming occurred much earlier. In fact, australene had been first identified in the early 1850s by the French chemist Marcelin Berthelot (1827–1907), who isolated it from essence anglais (English oil), which he referred to as essence du pin austral. An isomeric compound, terebenthene, was isolated from French turpentine derived from pin maritime, as well as from Pistacia terebinthus, the source of pistachio nuts. Further investigations, including measurements of optical rotation by Berthelot and others, showed that australene and terebenthene were the

D- and L-isomers, respectively, of a-pinene. They occur very commonly in essential oils and before modern methods of purification and identification many researchers thought that they had isolated a new hydrocarbon, which turned out, upon later investigation, to be just one of these pinenes. Thus, for greater or lesser periods of time, we had terebenthene, eucalyptene, laurene, olibene, massoyene and australene. You will guess that many of these names derive from the plants from which that particular oil was obtained.

The French or Bordeaux turpentine came from Pinus maritime, which grows in southern Europe and especially along the Mediterranean coast. That species name has survived until today and still appears in plant lists, but this is not true of

P. australis, the name of which has disappeared from catalogues. P. australis was the long-leaved pine that grew along the Georgia and the Carolina coasts in the US but once nomenclature settled down it became known as P. pinaster. This pine and some related species were important sources of turpentine in the US, fostered by the American Turpentine Farmers Association in the ‘turpentine belt’ that covered southern states from the Atlantic to the Mississippi.

Watch out for halepensine when all those ‘lone pines’ (Pinus halipensis) are distributed to schools in the ANZAC commemoration.

Ian D. Rae FRACI CChem ( is a veteran columnist, having begun his Letters in 1984. When he is not compiling columns, he writes on the history of chemistry and provides advice on chemical hazards and pollution.

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