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Tetrabromobisphenol A (Now with bromine!)

By moleculeoftheday on June 26, 2007.

Bisphenol A is one ingredient that makes polycarbonate and epoxies work the way they do. A lot of people have fretted and expressed some concern about bisphenol A bioaccumulating - I can just about guarantee you're toting some around in your fat. More persistent and toxic to aquatic life is a derivative of bisphenol A - tetrabromobisphenol A.

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Hanging a lot of halogens off of a compound is a pretty good way of making a flame retardant - we used to make amazing fire extinguishers with stuff called Halon (that link's highly recommended). I am told they were so good you could set up flame sensors and fill a room with them before a fire barely became visible (I'm talking lighting a match). They also required a low enough concentration that they could be used to extinguish a fire, while keeping enough oxygen in a room to support life.

Sadly, they destroy ozone quite effectively, so they were pretty comprehensively banned. Now we flood rooms with suffocating amounts of CO2. Halon may be the most effective fire suppressant the world will ever know - it is hard to conceive of something that works by as effective a mechanism.

Anyway. Tetrabromobisphenol A is like a solid halon - the idea is you mix a few percent in with your regular bisphenol A and make a flame-retardant polymer. There are the aforementioned tox and persistence problems, however. Always a trade-off...

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Speaking of bromine, I have a request: Inspired by some old 19th c. short stories, I was looking for information about potassium bromide (seems like in those days, everyone was taking bromides and "sleeping draughts"), and Google failed me. What do you know about potassium bromide, especially its use as a sedative, how it works, and why it fell from favor as a drug? What are some modern uses of this molecule?

Well, I don't know why it works, though I would imagine that an excess of bromide ions would cause depolarization similar to chloride ion?? Anyways, the drug has plenty of nasty side effects. It was apparently used for epilepsy (and is still for German people and American dogs). It was replaced by the barbiturates, which themselves fell out of favor with the arrival of benzodiazepines, which as a class have a much higher therapeutic index.

Actually, there is finally a replacement for Halon. Check out www.phostrex.com; Eclipse Aviation is using it as the engine fire-suppressant in the Eclipse 500 very-light jet.

that phostrex, upon a bit research is PBr3 - best not breathe that stuff in at any point. Probably gives off HBR and one of the phosphoric acids ....