Bromine puts the Purple in Tyrian Purple

Althouse commenter Palladian wrote an interesting comment a while back about Tyrian purple dye:

The ancient purple, Tyrian purple, is more akin to the color of a fresh Welch's grape juice stain on a white cotton shirt, only much more intense. Tyrian purple is made from the fresh mucous secretion of a big sea snail that is variously known as Murex brandaris and Haustellum brandaris. It requires harvesting and killing 10,000 of these gastropods to produce one gram of the dye, hence the astronomical price and rarity of the color. Link.

Palladian didn't mention bromine in his comment but I remembered his post after I started thinking about organobromine compounds.* He didn't give a pretty picture either, so here it is:

So what?  Well, it's bromine that gives it its striking color. Why do I say that?  Take away the two bromines and replace them with hydrogens and you get a dye called indigo:

I am interested in this stuff because I'm trying to understand and explain how organic dyes are used in DNA sequencing and also in OLED devices (futuristic electronic devices).  Subtle changes like changing substituents like bromine (or more commonly chlorine and fluorine) are important to those technologies.
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*Bromine is rare in natural compounds and, unlike chloride and iodide, bromide is not an essential element for humans. Due to its high water solubility, the world's bromide is mostly trapped in the oceans, where it cannot easily escape without help. Significant amounts of bromide are also trapped in fresh water brines and brackish waters, which is why Dow Chemical is in Michigan. Link

Bromine Has A Hangover

Most of the world's bromide is dissolved in the sea, but chloride still outnumbers it by about 500 to 1. Originally dubbed "muride" from the Latin word muria meaning brine,* bromide was renamed after bromos which means stench (of male goats) in Greek.

Elemental bromine is a nasty red liquid (bromine and mercury are the only two liquid elements at ambient temperature and pressure). An electron short of an octet and tranquil stability (as bromide), the fuming element can still suck the electron out of many a juicy nucleophile, as I wrote back here. But its power for doing so is less than chlorine's and much less so than fluorine's power. Bromine can still "oxidize" iodide back to iodine, though.

Bromine's usefulness is diminishing. Its greatest ex-use was as ethylene dibromide--an additive for leaded gasoline (it scavenged the lead). Film photography used to rely on silver bromide, but digital photography is killing off that use. Bromide used to be a mild sedative and hangover cure--until it was outlawed for over-the-counter sales around 1995. The main use for the element today is for making fire retardants--as organobromides which are ubiquitous in electronic products.
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*Cf. Muriatic acid, the original name for hydrochloric acid: link

Bromine swings both ways when coupling with double bonds

Here's a little chemical example of my favorite dictum: polarization followed by attack, followed by depolarization.

In certain solvents, molecular bromine, Br₂, cracks apart into plus and minus ions: bromide and bromonium (note the cool use of the "ium" suffix for the positively charged ion):

Br—Br  —>  Br^-  +  Br⁺

Now Br₂ will add to ethylene to make ethylene dibromide, a useful pesticide, but the bromine and ethylene can't simply couple because it's forbidden. Instead, bromonium ion approaches ethylene, sucking at and polarizing her most available electrons (recall I deduced that ethylene was female here). Bromonium's negatively charged doppelgänger (umpolung!) then backside attacks the polarized ethylene, after which her electrons collapse into bromonium's clutches and the partners relax. Here's a visual:

Michigan is still well endowed with bromides

Herbert Henry Dow (1866-1930)

I just ordered an old biography about Herbert H. Dow. I don't own a kindle, so I tend to collect books. I have lots of older books too.

Herbert Dow based his eponymous company in Midland, Michigan because he found lots of bromide ion in the water there. I learned that when I visited there--years ago--to help a company evaluate some technology they were buying from Dow.

Dow originally invented a process for producing bromine from bromide and the story of him beating the Germans at their own game fascinates me. I want to read more.

What Is The World's Smelliest Chemical?

Wikipedia corrals some of the suspects here: link  I thought I'd put their mugshots up here. Please vote for your favorite in the comments or suggest your own "worst."

(1) Spermidine, the essence of "funky spunk." 

Spermidine is related to aptly-named cadaverine and putrescine.

(2) Trimethylamine, the essence of "fish taco:"

(3) Butyric Acid, the essence of vomit:

(4) Skatole, an indole & the essence of poop:

(5) Mercaptans--methyl and butyl thiols--the essence of skunk:

R = methyl and butyl

(6) Hydrogen sulfide, H₂S, the essence of rotten eggs and bad farts:

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Runner's up which did not make Wiki's list:
(a) Cacodyl, named from the Greek, meaning "evil-smelling."
(b) Bromine, from Greek βρῶμος, brómos, meaning "stench (of he-goats)"
(c) Cyclohexane thiol: This is technically covered under (5), but to my nose smells like the essence of armpit B.O.