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Letters

June 8, 2009
Volume 87, Number 23
pp. 4-5

June 8, 2009 Letters

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Chemical Safety Mg3N2 Explosion Risk

Sheldon Crane reported an explosion when using magnesium nitride to convert esters to amides through a protocol similar to that reported in our recent publication (C&EN, April 13, page 2; Org. Lett. 2008, 10, 3623). Our other published procedures for the preparation of dihydropyridines (Org. Lett. 2008, 10, 3627) and pyrroles (Synlett. 2008, 17, 2597) have all proceeded without incident over a large number of experiments.

Although our procedure was not followed exactly and the scale of the reaction was tripled, we were extremely concerned that an accident had resulted. Without knowing the root cause of the explosion, whether it is inherent to the reaction, or due to faulty glassware or contamination of the magnesium nitride (possibly with magnesium azide), or due to the water content of the methanol, we reinvestigated our procedure with different substrates and fresh samples.

Despite having carried out more than 200 magnesium nitride reactions in the past without incident, we also observed explosions when heterocyclic (furan and indole) esters were used as substrates and while following our precise experimental conditions as reported in the supporting information in the initial Organic Letters paper. In view of these results, we must recommend that the procedure be followed only with extreme caution.

We are currently investigating modified experimental procedures to determine whether safer ways of carrying out these reactions can be found. These investigations will center on limiting the scale of the reaction (less than 0.25 mmol) and placing the reaction vessel in an ice-bath for approximately one hour to mitigate any initial exotherm before heating slowly to 80 ºC.

Although not wishing to be bound by any theory, we believe that the explosions were caused by an initial exothermic ammonia-generating reaction and a following or simultaneous runaway reaction between the highly concentrated ammonia and ester substrate.

Steven V. Ley
Cambridge, England



Recycling In Texas

I was very surprised to read that there are areas in the U.S. where polypropylene cannot be recycled (C&EN, March 16, page 30). I live in Irving, Texas, and for at least 10 years we have been able to recycle all plastics except polystyrene. It is interesting that a region that is not particularly "green-friendly" regarding air quality is more advanced in plastic recycling than the Northeast. I am proud of our area for our progress in this area.

Joyce Eckles
Irving, Texas



Priestley House Woes

The loss of a chemical shrine, the Joseph Priestley House, is a very real possibility unless action is taken now. This historic site, designated by ACS as a National Historic Chemical Landmark in 1994, is on a list of museums to be closed on July 1 by the Pennsylvania Historical & Museum Commission (PHMC) because of budget challenges facing the Commonwealth of Pennsylvania (C&EN, April 6, page 9, and June 1, page 32).

Priestley lived and worked at his home in Northumberland, Pa., after he left England (where he discovered oxygen in 1774). He discovered carbon monoxide in his American home, and the location has long been associated with ACS as a focal point for chemists and ACS-related activities. The Priestley house has hosted educational events for for a wide range of people since the 1870s. ACS's highest honor, the Priestley Medal, is named after him.

The Friends of Joseph Priestley House (FJPH) has launched a major effort to prevent the closing of this landmark. We suggest that concerned chemists (and others who recognize Priestley as a key player in early American science, political theory, philosophy, education, and religion) encourage ACS to support, with vigor, the rescue of Priestley House. Furthermore, it is crucial that ACS members and others contact PHMC (e-mail: bfranco@state.pa.us) and indicate their displeasure with PHMC's intended action.

FJPH, a 501(c)(3) not-for-profit organization, also asks concerned individuals and organizations to consider supporting our efforts. We can be reached at 472 Priestley Ave., Northumberland, PA 17857.

Amanda Kessler
William Simpson
William VandenHeuvel
Northumberland, Pa.



Clear Or Colorless Conundrum

I am always delighted to open my issue of C&EN and find a new "What's That Stuff?" item. I post each new article outside my office so students can read about the chemistry behind the materials they use and consume.

I was especially interested to read about "self-darkening eyeglasses"(C&EN, April 13, page 54). Thus, I was a bit dismayed that the author chose to describe these glasses as "dark or clear." If I didn't know better, I might interpret this to mean that, when darkened, the eyeglasses were not clear—and that would seem a dramatic drawback to wearing sight-correcting glasses.

My students struggle with the concept of "clear and colorless," too, and most will initially describe the color of a sodium hydroxide solution as "clear," which, they are reminded, is not a color. After a bit of head-scratching and some prompting, they eventually realize that "colorless" more accurately describes the color (or lack thereof) for this particular solution. This exercise might seem picky, which I don't deny; after all, I know what they mean. But one of my objectives as a teacher is to demand that students be accurate in their descriptions—something that pays benefits to everyone when reading and writing the scientific literature.

Christopher M. Bender
Spartanburg, S.C.

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