Published online 4 December 2007 | Nature | doi:10.1038/news.2007.341

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103-year-old chemical reaction pops up again.

Annulenes are common; but replacing carbon with nitrogen in a 12-membered ring might be harder than thought. LAGUNA DESIGN / SCIENCE PHOTO LIBRARY

There was something strangely familiar about results published in two high-profile chemistry journals recently: as one researcher has since pointed out, they accidentally replicated an experiment that was done more than a century ago. The resulting ruckus has highlighted how accidental chemical conclusions can get past peer review, and stands as a reminder of how easy it is to miss similarities to old results.

The results were those from two groups who claimed to have made an unusual organic compound: a 12-membered nitrogen-containing ring of a class of molecules called annulenes. This chunky compound, they said, would have special properties and could be useful as a surfactant, among other things. One paper was published in 20061; the second builds on it, and was published this year2.

But when Manfred Christl, a chemist at the University of Würzburg, read the papers he recognized the reaction conditions as those used some 103 years earlier by German chemist Theodor Zincke, in a reaction that took his name3. That reaction creates a salt half as big as the claimed annulene ring (the annulene ring is a ‘dimer’ or double-molecule version of the monomer salt).

Christl got in touch with the authors to let them know his thoughts. Since then, Isao Yamaguchi, at Shimane University, Japan, and colleagues have retracted their work in Organic Letters4. “I reflect that I lacked a knowledge about the reaction pointed out by Dr Christl,” says Yamaguchi.

“It’s good for older folk to point out to us young punks that ‘you need to do your homework better’.” Michael Haley



Fredric Menger at Emory University in Atlanta, Georgia, and colleagues say a correction will be published for their paper, published in Angewandte Chemie in August. In Menger’s case, the mistake arose partly because of an effect that happens with mass spectrometry (MS) — a technique used to determine the mass of a molecule. “Our MS mass was twice that of the monomer because, apparently, dimers form in the gas phase of the mass spectrometer, a point that we did not realize at the time,” says Menger. Christl's own notes are also published in Angewandte Chemie5.

Whoops

It is not unusual for scientists to retract results. The most recent, high-profile case in chemistry was in March 2006, when Dalibor Sames, a chemist at Columbia University, New York, retracted six full papers because a number of results about C–H bonds produced by one of his graduate students could not be reproduced.

But the Menger/Yamaguchi case highlights another problem – lack of knowledge of old literature.

“We are so reliant on electronic databases nowadays, I bet there are many current students that have no idea that the print version of Chemical Abstracts [a database of all chemical reactions ever published] even exists,” says Michael Haley, a chemist at the University of Oregon, Eugene. “It’s good for older folk to point out to us young punks that ‘you need to do your homework better’,” he says.

“I am sure this happens a lot and is probably becoming increasingly common as we fail to keep up with the literature,” agrees Andrew Holmes of Melbourne University, Australia, who worked with annulenes as a graduate student and was forced to retract a paper of his own in 1996 after being unable to reproduce results.

Christl also criticizes the peer-review process that let both Yamaguchi's and Menger's papers be published in the first place; he bemoans the lack of time that people have to do a thorough job. “Reading the literature is a luxury that not many respected scientists can allow themselves anymore,” he says.

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Haley sees this episode as a useful warning to scientists: “referees need to do their job and examine manuscripts carefully,” he says. “It’s a good call to arms, a warning sign.”

Menger adds there is much in his paper that is correct and useful; the theoretical work on the structure of 12-membered annulene is still valid and the compounds he made are still useful surfactants, he notes. His research will not be affected, he says, except “we will probably be more careful in the future combing the ancient literature.”