In the distant past – that is, the early 1990s – I sat in a dusty classroom and listened to an organic chemistry professor write on a blackboard that spun in a giant loop. At one point he mentioned capric acid. He didn’t draw the structure and I didn’t ask because I was too busy writing things down.
Later I wanted to know the formula of capric acid. But by now I was in my dorm, far from the chemistry department, where I might have found someone to ask. This was a time before Internet-connected computers became widespread. Smartphones and digital assistants were the stuff of science fiction.
The name wasn’t in my dictionary or in the index of the few expensive textbooks I’d scraped together the money for. So … I’ve resigned myself to not knowing. “The past,” as writer LP Hartley said, “is a foreign land. They do things differently there. ‘
Moving into the past, about 250 years, it was strangely easier – there were few known chemicals to learn. But in the late 18th century things exploded (often literally, health and safety wasn’t what it is today). Swaths of new connections were isolated and named without any unified system in the way.
It was the French chemist Louis-Bernard Guyton de Morveau who first proposed some rules of nomenclature, mainly for acids, bases and salts. One of his key ideas was that the name of the fabric should reflect its nature. For example, if it’s an acid, it must have acid in its name. Seems obvious now, but it wasn’t then. An old name for sulfuric acid, for example, is vitriol oil, and nitric acid once came from aqua fortis (literally “strong water”).
Although some denounced de Morveau’s ideas as “barbaric, incomprehensible, and without etymology” – reminds me of some of my Twitter arguments – they were eventually accepted. But the carbon-based chemistry was still a bit of a mess. In the middle of the 19th century, the number of known organic compounds grew rapidly. They were often named after raw materials, such as acetic acid from the Latin for vinegar, Acetum, But as chemists synthesized more and more substances, it became difficult to make sure that the names were at least unique.
It was another French chemist, Auguste Laurent, who suggested naming compounds based on their longest hydrocarbon chain, and Charles Gerhardt, who came up with the idea of homologous families that gave us alkenes, ketones, carboxylic acids, etc. This eventually led to the Iupac rules we know today. Love them or hate them, they are useful – at least for simpler substances. Look at decanoic acid: the ‘dec’ bit indicates ten carbons and ‘Oic Acid’ means it ends up having COOH. Easy!
Well it would be if people used it. But like my lecturer, they still don’t. Decanoic acid is capric acid. The older name comes from Latin for goat, ‘Capers / capra‘because it has a goat smell. This etymology also gives us the astrological sign Capricorn, which is the tenth sign – that is, ten carbons in the chain. So obvious!
To be fair, if you understand the Latin root, the name is pretty informative. After all, nothing about “decanoic acid” suggests that you get a hint of goat when you open the bottle.
And non-systematic names can come in handy. Take glucose. We all know what it is; we probably learned the empirical formula in high school. (2R, 3S, 4R, 5R) -2,3,4,5,6-pentahydroxyhexanal on the other hand – its systematic name – is rather less well known. Okay, it tells us there are six carbons, five hydroxy groups, and one aldehyde, but no one is going to say that willingly.
Most chemists these days use a combination of ‘old’ and systematic names, everyone gets involved, and we might wonder if that even matters anymore. 25 years ago, apart from deductive leaps in astrological logic, it was difficult to associate a non-systematic name with a substance. But now most of us have powerful computers in our pockets. “Hey Siri, what is capric acid?” You get the answer in seconds. Learning how to systematically name compounds feels like memorizing the periodic table – a nice party trick, but useful? Not special.
Plus, it’s been centuries and chemists still don’t give up systematic names. Outside of chemistry class at school, I find a chemist who calls acetic acid ethanoic acid is just as likely as a squirrel collapsing with a rabbit. It could happen. It’s unlikely.
Maybe it’s time we gave up and just started teaching the old names in schools? They are more interesting, invariably shorter, and anyone who doesn’t recognize something can ask their digital assistant today.