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Letters

January 10, 2011
Volume 89, Number 2
pp. 2-3

January 10, 2011 Letters

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October 28, 2011

Speedy Homemade-Explosive Detector

Forensic Chemistry: A new method could increase the number of explosives detected by airport screeners.

Solar Panel Makers Cry Foul

Trade: U.S. companies complain of market dumping by China.

Novartis To Cut 2,000 Jobs

Layoffs follow similar moves by Amgen, AstraZeneca.

Nations Break Impasse On Waste

Environment: Ban to halt export of hazardous waste to developing world.

New Leader For Lawrence Livermore

Penrose (Parney) Albright will direct DOE national lab.

Hair Reveals Source Of People's Exposure To Mercury

Toxic Exposure: Mercury isotopes in human hair illuminate dietary and industrial sources.

Why The Long Fat?

Cancer Biochemistry: Mass spectrometry follows the metabolism of very long fatty acids in cancer cells.

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Chemical Safety: Synthesis Procedure

WE ARE WRITING to report on an accident that occurred in the chemistry department at Northwestern University on Dec. 3, 2010. Unfortunately, one of our advisees was seriously injured. The accident—a reaction mixture detonation—occurred during an attempt to synthesize 2-(tert-butylsulfonyl)iodosylbenzene, a partially soluble form of iodosylbenzene that is particularly convenient for use as an oxygen source in studies of catalytic chemical oxidations, such as olefin to epoxide reactions. The synthesis had been performed about a dozen times previously at Northwestern without incident.

The synthesis procedure was a modified version of a procedure first described by Dainius Macikenas and coworkers (J. Am. Chem. Soc., DOI: 10.1021/ja991094j), which in turn had been adapted from a tested “Organic Syntheses” preparation (Sharefkin, J. G. and H. Saltzman, in “Organic Syntheses”; H. C. Baumgarten, Ed.; New York: John Wiley & Sons, 1973; Collection Vol. 5, page 660). One modification was the use of a higher H2O2/iodobenzene ratio (25 instead of 2.8) while maintaining a similar H2O2 concentration. Likely more relevant was a second modification: the use of 35% by weight (freshly opened) hydrogen peroxide, rather than the 30 wt % solution indicated in the Macikenas procedure and used previously at Northwestern.

We do not know with any certainty what caused the explosion. However, the procedure entails combining aqueous H2O2 with acetic anhydride to form peracetic acid. The water component of the aqueous H2O2 solution should serve to remove excess acetic anhydride. We speculate that if some acetic anhydride remained after conversion of the majority to peracetic acid (the desired intermediate compound) or acetic acid (side product), the anhydride could have combined with peracetic acid to form diacetyl peroxide. This organic peroxide is known to be a shock-sensitive explosive.

If our reasoning is correct, the amount of diacetyl peroxide that potentially can form is greater in the modified reaction. Presumably, the less water initially present the greater the chance of forming the unstable organic peroxide. For a given amount of H2O2, the number of moles of water present in 35 wt % hydrogen peroxide is about 21% less than the number present in 30 wt % hydrogen peroxide. It is sobering to realize that even with 35 wt % hydrogen peroxide, the combined number of moles of water and hydrogen peroxide likely exceeded the number of moles of acetic anhydride initially present—and yet an explosion occurred. It is unclear what the margin of error is with regard to water and hydrogen peroxide concentration versus acetic anhydride concentration. However, we believe that at least some diacetyl peroxide is formed under all reaction conditions.

We emphasize that the above “explanation” and discussion are speculative. Nevertheless, there is support from the patent literature. (See, for example, U.S. Patent No. 3,079,443, “Production of a Solution of Diacetyl Peroxide in Acetic Anhydride.”) In the patented process the coreactant is aqueous H2O2.

At least until the cause of the explosion can be determined, we strongly encourage researchers to consider using alternative, nonperoxide, routes to 2-(t-butylsulfonyl)iodosylbenzene, iodobenzene diacetate, and related compounds (J. Am. Chem. Soc., DOI: 10.1021/ja1069773). More generally, we recommend that aqueous H2O2 and acetic anhydride never be combined—despite the fact that, until now, this has been a commonly used reagent combination in oxidation chemistry.

Joseph T. Hupp and SonBinh T. Nguyen
Evanston, Ill.



Lessons Of Kickball

When I was a kid, my family moved many times. At each new school, I would go out to the kickball field during recess and wait to be picked. Because the team captains didn’t know me, I would endure a week or two disappointed that I wasn’t picked. Finally, there would be a shortage of kids, and a team captain would reluctantly add me to their team. At that point, I was elated and tended to play well. Eventually I would become a team captain, and I would be picking my own team. Then my family would move again, and the process would be repeated.

Now I am an adult and a professional chemist and in a very similar situation. I’m unemployed and waiting to be picked. The team captains don’t know me, and so I have been turned away many times, dejected. I’m mature enough to know that there may never be a “shortage of kids” and waiting for one would be foolish. I know that there are things I can do to grab a team captain’s attention, and I practice them almost daily. But as in my younger days, I know that I must be patient.

One day I will be picked, and I’ll be elated, and I’ll kick a home run, and then all the other kids will like me. Maybe one day I’ll be a team captain again.

Frederick J. Lakner
San Diego



Polymers... Or Slime

In the Dec. 13, 2010, issue of C&EN (page 13) the caption on picture (1) says, “A girl … makes polymers from glue and borax.” To my best knowledge, it is more likely that the girl is making a slime using glue and borax. The glue can be polyvinyl acetate-based such as the commonly used white glue. The glue contains polymer (polyvinyl acetate) itself. The nature of the slime that the girl is making is more like a gel (that is, the polyvinyl acetate cross-linked with borate) than a “polymer.”

Leiming Li
Sugar Land, Texas



Political Climate Changes

The Government & Policy article predicting a tough time for climate science in the new Republican-controlled House of Representatives came as no surprise (C&EN, Nov. 29, 2010, page 30). A Pew poll (http://people-press.org/report/?pageid=1549) in 2009 found that only 6% of scientists considered themselves Republicans; 55% are Democrats, with an overwhelming 81% leaning toward the Democrats. Fifty-two percent of scientists view themselves as liberals.

Attitudes vary within the scientific community, but even including industrial scientists, 47% are Democrats and only 10% are Republicans. In the sciences overall, 47% of chemists are Democrats, and the figure rises to 60% in the geosciences.

I personally view the Republicans as broadly antiscience, and this will not change in our lifetimes. I also suspect that, worldwide, scientists are more liberal than the general population.

Earl Evleth
Paris



Chemical & Engineering News
ISSN 0009-2347
Copyright © 2011 American Chemical Society
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