Amyl Butyrate/Pentyl Butyrate (From vomit to Juicy Fruit!)
18th July 2006
Esters are a continuing source of fascination for me. Chemically, they’re unremarkable. If you heat an alcohol and carboxylic acid together under conditions that allow it to eliminate water (say, by doing the reaction in the alcohol or acid under concern, if one’s liquid), they will form a compound called an ester. Usually you add a trace of additional acid as a catalyst - a drop of hydrochloric acid solution is common.
What’s remarkable, though, is the smell. Pentanol (amyl alcohol, in old-school chemspeak, rarely used, but I learned this ester as “amyl butyrate”) is unremarkable, and it smells like most low-molecular weight alcohols - a bit like ethanol, a bit like lighter fluid. Butyric acid, however, is Satan’s own carboxylic acid - it is a sort of B.O./vomit/Sex Panther odor.
When transesterified, however, the resulting compound smells uncannily like Juicy Fruit gum. The funny thing about esters is that so many of them smell good. Fruit aromas are common.
See you tomorrow.
July 19th, 2006 at 6:03 pm
I agree, esters are interesting compounds. I was a Lab Tech for Undergraduate Organic Chemistry Labs. We performed one lab that produced isopentyl acetate from acetic acid and isopentyl alcohol. It smelt exactly like ripe bananas!
July 21st, 2006 at 6:00 pm
My Chemistry teacher did the one that smells of vomit. Unsurprisingly, he;s now banned from doing any experiments like that and is only allowed to play with esters without the fume cupboard on! We had one smelling of pear drops the other day - lovely!
September 23rd, 2006 at 3:21 am
[…] Curiously, while butyric acid itself smells vile, butyric acid esters smell pretty nice–in the case I linked to, like Juicy Fruit gum. (Such nice scents are fairly typical of esters; they’re a very large and versatile part of the artificial-flavoring artist’s arsenal.) […]
September 28th, 2006 at 1:00 pm
Found this website while searching for information about
a set of stencils which smelled absolutely horrid. Love
your website, which I mentioned in a post on another site:
Years ago, one could find, and likely purchased at least
one particular brand of stencil by the name of Timely or Flowchart symbols by Timesaver. These plastic green
stencils featured various shapes such as oval, square, circles, etc. Great for crafts, engineering, etc.
To abbreviate, I keep all of my stencils in one box. Recently
I opened the box to the smell of vomit or, to be honest, animal feces. As the lid was shut and the box in my own clothing closet, it was highly unlikely there was either of the two offensive items in my stencils.
The stencils in question were about two dozen of the same green plastic. I cleaned them with dish soap. Still smelled something horrid. Used Clorox Clean Up. Still the smell. So I called the company; Timely, and sure enough, was told the following.
The thermoplastic used in these stencils contains Cellulose Acetate Butyrate (CAB). Many other items are manufactured with this chemical such as tool handles, panels for illuminated signs, steering wheels, goggles, bathroom
fittings, decorative trim for cars and consumer durables, drawing stencils, pens, pneumatic system traps, blister packaging, and laminating with aluminium foil.
A polite way to describe the disadvantages of using such plastic? “Attacked or swollen by many solvents including chlorinated and aromatic hydrocarbons, alcohols and ketones. ” In other words, they smell absolutely horrid
when stored in a closed location, even a desk drawer.
So if any of you have smelly stencils, or the stencils I mentioned, you would be well advised to take them out of storage and put them where they can get air flow, or you will find yourself sickened and possibly tossing out many
expensive stencils.
And for those who always like to know more, this is a very interesting website featuring this particular molecule of the day:
[HYPERLINK@www.moleculeoftheday.com] omit-to-juicy-fruit/