I have a hunch I know what that smell actually is caused by.
Sweat on its own does not smell, well it may contain pheromones, but not a consciously perceptible smell.
When bacteria act on it, there gets produced a lot of propionic acid and valeric (possibly isovaleric acid also, I can't remember). Propionibacter is a common commensal organism on the skin surface, and produces propionic acid as a metabolite, a waste product, and its volatile.
I think this has a lot to do with it, because I've smelled propionic acid, its produced as a byproduct if the conditions are not strictly anhydrous (the rxn in question works anyway and is pretty tolerant), in the synthesis of the heroin analog dipropionylmorphine, especially when propionyl chloride/bromide is used for the acylation reaction. I've never done it with propionic anhydride, as the halide doesn't require heat, it reacts very quickly, in the cold or at room temperature whilst acylation reactions such as the synthesis of regular, bog standard vanilla H, requires heat. Although unlike doing it the acyl halide (propionyl chloride for dipropionylmorphine, and acetyl chloride for diamorphine/H) way, with an anhydride there is no requirement for addition of a base, such as potassium carbonate, or better yet something like Hunig's base (diisopropylethylamine)
https://en.wikipedia.org/wiki/N,N-DiisopropylethylamineThe base has to be added in order to suck up the proton released during the reaction of the acyl halide with the phenolic hydroxyl groups of morphine, during which it comes off as HCl gas, is absorbed as its formed into the solvent, and makes the result overacidic, so its there to neutralize that proton and bind the acid as a salt, from which the desired compound being esterified is then recovered and purified.
When making H, it ends up smelling strongly of vinegar at first, from the acetic acid produced during hydrolysis of either acetic anhydride or acetyl chloride/bromide. The acetyl group is the carboxylate moiety formed from the second simplest of the carboxylic acids, the first and simplest of the series being formic acid, HCOOH, acetic acid, or in dilute solution, vinegar, is CHCOOH, and propionic acid CH3CH2CO2H is the next, derived from the 3-carbon alkane propane. And the aftermath of such a completed esterification with either propionic anhydride or propionyl chloride results in propionic acid as a byproduct.
And funnily enough 'goatish' was the very first thought that came into my mind the first time I ever caught the odour of propionic acid. Propionyl chloride itself just stings like a bugger if the nose catches traces, due to its hydrolysing and producing hydrochloric acid. But once it does, there is a very distinctive smell of, well, goatlyness, in a goatey, goatish kind of way. I thought to myself hmm..is that right? its been a long time since I had cause to detect the smell of a goat, years and years ago in my first spesh ed school, we were taken on an outing to a petting zoo/farm type place where the kids are allowed to get to become familiarised with the fauna kept there, and a goat took a liking to my coat, and tried to stick its head through a wire fence and eat my jacket. Little fuckers will eat anything given the chance. I got out of the way after it took a chomp, and took my coat back intact, although a bit goat-slobberier than it was when I got on the minibus to school at the start of the day, but otherwise not the worse for wear.
And whilst at the time, propionyl chloride and propanoic/propionic anhydride were not reagents I had yet become familiar with in my lab, and whislt nowadays I do not have a particularly compelling reason to interact with all things goaticious, that is the thought that immediately poked its way into my prefrontal cortex and amygdalae the first time I had reason to handle the stuff. And tiny traces once or twice got into my mouth, just by tertiary transfer from gloves to fingertips to mouth after handling a pippette being used to transfer aliquots of propionyl chloride into some acetone for something. And it really lingers, in a nasty ass kind of way, and is quite persistent in a bitterish, rancid taste that is strongly reminiscent of the stink of stale sweat, goat, or, more like it, sweaty, stale goat.
The valeric acid, is produced by feet bacterial commensals in particular, and is responsible for the unpleasant cheesy pong of rank feet. And also, its found in large quantities in the plant valerian, and its extracts, often used as a herbal sedative, and as well, as an oneirogenic (dream enhancer, inducer of vivid and lucid dreaming) drug; and if you've never smelled the plant (particularly the roots) or the pills, tinctures or other extracts it smells strongly and quite unpleasantly of cheesy feet.
I've been wanting to try (di)valeroyl and diisovaleroylmorphine for a while now, and although I've never actually caught the smell of/handled valeric anhydride/isovaleric anhydrides or valeroyl/isovaleroyl chloride or bromide those too should behave similarly and smell disgustingly of rancid feet.
So-the mystery behind the stench of the great unclean, and of the unwashed sweaty teenage armpit, and of rancid goat, can now, with the aid of a basic primer lesson in heroin, and heroin analogue-related clandestine chemistry be considered case, closed.
And hopefuily the armpits of sweaty teenagers everywhere will, too, be considered closed:P
Plu
