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December 19, 2005 | APPEARED IN VOLUME 83, ISSUE 51

Chemical safety: LiAlH4 reduction of SiCl4

We would like to report a potential hazard for the synthetic procedure outlined in Physical Review B (1999, 60, 2704). This contribution is widely referenced and describes a procedure for preparing hydride surface-terminated silicon nanoparticles via lithium aluminum hydride reduction of SiCl4 in micellular tetrahydrofuran (THF) solutions. The authors incorrectly report that this reaction produces hydrogen gas that is presumably released into the "controlled-atmosphere glove box." There is no mention of pyrophoric by-products.

We recently attempted to reproduce this reported procedure and performed all our steps on a double-vacuum manifold equipped with argon working gas and an oil bubbler. We used standard experimental techniques for handling air-sensitive compounds. With our experimental design, gas by-products are carried out of the reaction vessel by flowing working gas and are released from the oil bubbler into the ambient atmosphere of the fume hood.

From the article cited, there is no reason to expect any adverse events from the procedural difference of interchanging a glove box for a double manifold. The release of hydrogen gas from the oil bubbler into the atmosphere should have been inconsequential. Furthermore, synthetic chemists well-versed in manipulating air-sensitive compounds often find a double manifold more effective than using a glove box.

Upon addition of a THF LiAlH4 solution to a THF solution of SiCl4, we observed vigorous bubbling consistent with the literature report. To our surprise, a bright orange flame was released from our oil bubbler. It was impossible for the authors of the aforementioned contribution to make this observation because a gaseous reaction by-product was doubtless captured by the glove box circulation system and was never released into the atmosphere. Fortunately, no one was injured when this "controlled burn" occurred in our laboratory.

Subsequent literature searches have revealed that the gas produced is incorrectly identified as hydrogen in the 1999 reference. In fact, the reaction LiAlH4 + SiCl4 t LiCl + AlCl3 + SiH4 occurs in ethereal solutions and has been known for some time to produce pyrophoric silane (J. Am. Chem. Soc. 1947, 69, 1199). While we did isolate some Si nanoparticles from the reaction mixture and confirmed that they were indeed hydride-terminated, we caution other researchers from carrying out this reaction without exercising extreme care.

Jonathan Veinot, Enrico Fok,
Kristy Boates, Janet MacDonald
Edmonton, Alberta

Smalley tribute

I was more than a little disappointed that the Nov. 7 issue of C&EN did not show Richard Smalley's photograph on the cover. Beyond his intellect and unwavering passion for science, beyond the fullerenes and his significant body of scientific work, beyond his education of students, beyond the Nobel Prize, he was distinctive as the most magnetic and eloquent speaker in and for chemistry.

I met with Smalley at Rice University as a prospective graduate student in early 1987. As we climbed the stairs to his laboratory, he asked me with the most penetrating gaze, "Do you know how to program in Fortran?" As I replied that I did, I felt that he would sweep me into his laboratory that very instant and put me to work on a critical scientific problem. In that moment, science was as essential as taking a breath.

Eileen M. Spain
Los Angeles

No substitute for DDT

The article "Fighting Malaria" (C&EN, Oct. 24, page 69) failed to take note of the history involved in the battle against this devastating disease. People have apparently forgotten the spectacular effects achieved by the use of DDT in many underdeveloped countries. In Ceylon (now Sri Lanka), DDT spraying reduced malaria cases from 2.8 million in 1948 to fewer than 20 in 1963. After spraying was stopped in 1964, malaria cases rose again to 2.5 million in 1969. In Zambia, malaria cases dropped from 70% of the population in 1958 to 5% in 1964. By 1984, they had risen to 50-60%. As mentioned in the article, spectacular results were recently achieved by the use of DDT/artemisinin-based combination therapy in a South African province where outpatient cases decreased by 99% and malaria-related deaths by 97%.

In 1972, William D. Ruckelshaus, then-EPA administrator, ignoring the scientific evidence and the consensus of his staff, declared that DDT was a potential human carcinogen and banned its use in the U.S. This led to a worldwide ban, despite the fact that malaria had been essentially eradicated in the U.S. and Europe. This decision was not based on science but on politics. In the years preceding the DDT ban, the National Academy of Sciences, the American Medical Association, the U.S. surgeon general, the World Health Organization, and the Food & Agriculture Organization of the United Nations spoke out in support of the continued use of DDT as a disease fighter and crop protectant. This so-called triumph of the environmentalists to ban DDT has led to the removal of our most effective weapon in the battle against malaria and has resulted in the precipitous rise of malaria-related deaths in the underdeveloped countries.

There is no economical substitute for DDT for application in the malaria-infested regions of the world. Other chemicals are too expensive and do not function nearly as well in the massive spraying programs required for effective control of mosquitoes. The long-term effectiveness and persistence of DDT in the environment are virtually unique. There is also little or no evidence that DDT-resistant strains of mosquitoes have developed since the ban. In addition, the presence of low levels of DDT and DDE in humans and animals has not been shown to cause significant health effects. For example, a review of recent studies has concluded that DDT and DDE have no significant estrogenic activity. Also, attempts to associate the presence of residues of DDT and DDE with breast cancer have failed to produce statistically significant results.

Billions of dollars have been committed to the development of antimalarial drugs and vaccines. Although some promising results have been obtained, it is unlikely that development and production of adequate supplies of these compounds can be achieved in the next few years. Virtually none of this money is being used to develop strategies for killing and repelling the mosquitoes that cause the disease. Funding such an effort based on the use of DDT would give us time to develop drugs and vaccines and in the process save millions of lives. A current bill in Congress, the Senate version of H.R. 3057, has the potential to add DDT to the arsenal for fighting malaria. It should be supported.

Albert Z. Conner
Wilmington, Del.

Morrison & Boyd

How delighted I was to read about my old friend, Morrison & Boyd's "Organic Chemistry," the book that convinced me to remain in chemistry.

I had planned to transfer to the School of Pharmacy after my second year at Long Island University in 1974 when I took introductory organic chemistry, using the brand-new, golden-covered 3rd Edition of M&B. I fell in love with organic chemistry, and that, as well as the discovery that my scholarship was not transferable to other schools at LIU, convinced me to become an organic chemist. Over 32 years later, my worn copy of M&B still sits on my office shelf, used most recently only five days ago. You keep your friends.

Jaan Pesti
Yardley, Pa.

Getting serious about energy

The Aug. 1 editorial in C&EN leaves several important questions regarding nuclear energy unanswered. Since nuclear power is more prevalent in France, how does France and how do other countries deal with the radioactive waste issue? Surely, they have no vast, relatively unoccupied regions of the country in which long-term storage facilities can be constructed.

Do they reprocess their waste? If so, why don't we?

Frederick Ehrgott
Killingworth, Conn.

Are women making progress?

I have been watching the inclusion of women into chemistry since I was an undergraduate student in the 1970s. As I recall, my small class at Notre Dame was 20% women, and there were no women on the faculty. Your recent story (C&EN, Oct. 31, page 38) recounts the proportion of women in top chemistry departments, now at 13%, showing that this proportion has hardly changed over the past four years. Your story also shows a greater proportion of women at the assistant professor level, suggesting the overall rates will increase, but this has been the situation for some time.

Your story missed an important question: What have the relative promotion rates been for women versus men over the past four years, and what has been the proportion of women in the applicant pool? Only by understanding whether or where women are not advancing in the enterprise will we have much chance at improving their representation in positions of authority and control.

Andrew L. Waterhouse
Davis, Calif.

Organic rip-off

The public has been brainwashed into believing that all synthetic chemicals are "bad" and are probable carcinogens. In reality, there is no difference between synthetic chemicals and natural substances when tested in the standard animal cancer test. Nearly half of all chemicals, whether natural or synthetic, test as carcinogens. This strongly suggests that the standard animal cancer tests are completely unreliable.

The amount of synthetic pesticide residue in plant foods is insignificant when compared with natural pesticides produced by the plants themselves. Of all dietary pesticides, 99.9% are natural toxins produced by the plants to defend themselves against fungi and animal predators.

Bruce Ames, professor of biology at the University of California, Berkeley, points out that Americans are focused on synthetic chemicals that may cause cancer in humans, even at levels of parts per quintillion, while many of these same people are unaware that there are more than 1,000 natural chemicals in a cup of coffee. Only 22 of these have been tested in the standard animal cancer test, and 17 showed up as carcinogens. Thus, there are more cancer-causing chemicals in a single cup of coffee than you are likely to get from synthetic pesticides in a year. Ames says: "I don't want to scare people away from drinking coffee. The problem isn't the coffee-it is the high-dose animal tests."

The organic food industry is not only robbing the public's wallet but, because of the exorbitant prices of organic foods, depriving many people of having adequate amounts of fruits and vegetables. The end result may well be increasing one's risk for cancer by reducing fruits and vegetables in the diet. The reduced exposure to synthetic chemicals is insignificant.

Philip Sweetser
Hyde Park,Vt.

Executive Compensation Information Available

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