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Compounds pass the smell test

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10:11am, September 13, 2006
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A vile-smelling but versatile class of compounds may find a role in more chemistry laboratories with the introduction of easily made, inoffensive versions.

Isonitriles, chemicals characterized by a triple bond between a carbon and a nitrogen atom, are useful in many reactions. But many chemists have shunned them because of their pungency, says Michael C. Pirrung of the University of California, Riverside. "It makes your nose burn," he says. Moreover, the primary way to make the chemicals is difficult and uses highly toxic gas.

Pirrung frequently uses isonitriles in his research, and he wanted to simplify the production method. So, he and Subir Ghorai developed a one-pot reaction using materials found in most chemistry laboratories.

The researchers started with a compound called an oxazole. They added a strong base, followed by an organic acid. The resulting isonitriles contained chemical groups called esters, which typically produce fruity and flowery smells. While the motivation behind the work "was to gain easier access to isonitriles," Pirrung says, it turned out that the reaction also produced better-smelling compounds.

Each of the nine isonitriles that he and Ghorai made had a different ester and a different—and pleasant—aroma, ranging from mild cherry to taffy to soy. The researchers describe the isonitriles in the Sept. 13 Journal of the American Chemical Society.

When Pirrung and Ghorai tested the compounds in reactions, they found that the new versions worked as well as or better than the stinky isonitriles.

Now that isonitriles can be easily made and are better smelling, "I hope there will be people inspired to do things with them," says Pirrung.

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