New Reagents Lead to Safer Chemistry

May 23, 2012 at 12:49 am Leave a comment

C&EN, aka Chemistry & Engineering News, is the weekly news magazine of the American Chemical Society. Every page contains something different from its neighbors, whether its an announcement of a merger between two chemical companies, a report on a new chemical discovery, a letter to the editor, or an obituary for some chemist. Here are three articles from recent issues that show how diverse ‘green chemistry’ can look:

  • Taming Diazomethane (Mar 26, 2012, p. 26) describes a new iron-porphyrin catalyst for creating diazomethane and using it to make cyclopropanes. Diazomethane (or H2C=N=N, for those of you who don’t recognize the name) is a fearsome reagent. It is highly poisonous. It is a gas, so it is hard to confine, even in a fume hood. And it is an explosive. I made it once in graduate school and my lab mate, who already had made it once himself, warned me, “use brand new glassware, get a new reagent kit, and follow the instructions exactly.” Apparently a damaged or scratched glass surface is enough to set off an explosion. As shown in the figure, the researchers have found a substitute for diazomethane that reacts with the catalyst to accomplish the same overall reaction, the addition of CH2 to an alkene, that is much less hazardous to the experimenter and his or her lab mates. (See Science, DOI: 10.1126/science.1218781 for additional details.)

  • Into the Blue (Apr 2, 2012, p. 18) Describes a new business collaboration between a giant dyeing company, DyStar, and a small Swiss start-up, RedElec Technologie. Indigo, the dye molecule responsible for the lovely blue color of my jeans, is insoluble in water. In order to attach indigo to the denim, indigo is reduced to a yellow soluble substance, leucoindigo. The denim is dipped into this solution and then set in the air to re-oxidize, i.e. turn blue. Two of the environmental problems associated with the dyeing process are the release into wastewater of excess reducing agents and unbound indigo when the denim is initially rinsed. The chemists at RedElec Technologie think they have solved the latter pollution puzzle by reducing indigo to leucoindigo electrochemically. This approach had been tried unsuccessfully in the past, but the company has developed a new electrode material that is more efficient at transferring electrons to indigo molecules and holds up better over prolonged use.

  • Ever-Cleaner Auto Exhaust (May 21, 2012, p. 10) Dangerous and toxic chemistry is not limited to the lab or the factory. Anyone who grew up in Los Angeles during the period between 1950-1980 can remember how the skies would turn from blue to brown each day with photochemical pollution, most of it from automobiles. And, if you grew up in an inland area, like I did, you also may have experienced an asthma-like cough that would follow you home from the schoolyard and leave you short of breath through dinner and into the night. The introduction of catalytic converters in the 80’s, a smallish device that was attached to each car’s tailpipe, improved this picture a bit. The catalyst inside the converter reduced the emission of toxic gases by chemically altering them before they could leave the tailpipe (unfortunately, by this point in time, the growing number of cars and miles driven/day was already threatening to overwhelm any possible improvements in the treatment of auto exhaust). This article describes the latest improvements in catalytic converters.
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Entry filed under: In the News.

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