Performing a Finkelstein reaction with a benzosulfonate ester. 

What is the Finkelstein reaction? Finkelstein Reaction is a HalEx (Halogen Exchange) reaction what lets to change a bromine or chlorine to an iodine atom on an organic molecule. The trick is, that sodium iodide is well soluble in acetone, while the sodium chloride and sodium bromide is nearly insoluble. What happens is simple: R-X + NaI = R-I + NaX. The reaction is based on an equilibrium what only goes one direction, since the NaX gets removed from the reaction since it precipitates.

So why I am using a benzosulonate ester? It acts similarly to a bromide/chloride/halogen and it also does the reaction, the only difference that it has a much higher molecular weight, so it’s not as volatile as a bromide, while the iodide what is produced, could be distilled out easily from the reaction mixture. And also another short note: I use another solvent than acetone, since the acetone would also distill out with those conditions. 

This chalky yellowish-white tape residue probably looks familiar to a lot of you. We are all too well-acquainted with this gunk, which can range from being relatively simple to flake off (with a micro spatula, for instance) to devilishly difficult to remove by any means, depending on its age and on the surface it’s applied to. In the case of this volume, covered in copiously tooled pigskin, we’ve found that a quick application of thick klucel-g in ethanol, gently swabbed about with a brush, will effectively loosen the stuff so that it can be wiped away with a soft cotton cloth, leaving very little behind. It’s a very large book and the residue covers about half its surface area, so even this solvent-enhanced residue reduction is going to take quite some time!

A ferrofluid is a fluid that becomes strongly magnetized in the presence of a magnetic field. Essentially, they’re nano-scale particles of magnetic iron suspended in an organic solvent. Put them near a magnet and things get really awesome really fast. (Source: Business Insider)

Some deuterochloroform with a little added tetramethylsilane for NMR spectroscopy.

Deuterated chloroform (CDCl3), is an isotopologue of chloroform (CHCl3) in which the hydrogen atom (“H”) is replaced with a deuterium (heavy hydrogen) isotope (“D”), therefore it’s much more expensive. Deuterated chloroform is a common solvent used in NMR spectroscopy of organic molecules.

chemical fumes

Yesterday I noticed the smell of ethyl acetate leaking from the undergrads’ bench and advised them to use it in the hood. This started a big conversation about chemical odors.

I discovered that my olfaction is (somewhat) keener than average people since I was young, and while it’s been going slowly downhill since I started working with smelly chemicals more than 4 years ago, I’d say it’s still pretty decent. My colleague Tom always jokes about how bad his sense of smell is especially after he started working in the lab.

So returning to ethyl acetate, a commonly-used solvent in organic chemistry. My first contact with this chemical is probably from a bubble-blowing paste I used to play when I was like 5 years old. And in middle school science lab I synthesized it by Fischer esterification where students were directed to detect the presence of it by the characteristic smell. To me, ethyl acetate has a fruity smell (some friends of mine said it reminded them of durian) which can be detected in small concentrations in the air. It is not particularly unpleasant, but it gets strong and unbearable pretty easily. It can get to a point where I can even sense a vinegary odor from the amount of acetic acid from the hydrolysis of it on contact with atmospheric moisture! For this reason I always have words about people using ethyl acetate outside the fume hoods.

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