Tribute To A Numerical Inorganic Icon: Kenneth Wade
Apr11

Tribute To A Numerical Inorganic Icon: Kenneth Wade

University of Durham chemistry professor Kenneth Wade, famously known for the borane electron-counting rule that bears his name, passed away on March 16 at age 81. Chemists at the University of Nottingham, led by big-haired chemistry professor Martyn Poliakoff, have prepared a lovely video tribute to Professor Wade as part of their Periodic Table of Video series. Chemists use electron-counting rules to determine bonding patterns in different classes of compounds, such as the familiar octet rule for first- and second-row elements, the 18-electron rule for transition metals, and the Hückel 4n + 2 rule for aromatic compounds. However, these rules don’t readily apply to electron-deficient molecules such as boranes that utilize multicentered bonding–a pair of electrons shared between more than two atoms–so other rules have been devised. In 1971, building on the collective observations of other chemists, Wade formulated his n + 1 rule. Wade’s rule states that a cage molecule with a geometry based on a closed polyhedron constructed of triangles with n vertices will possess n + 1 skeletal bonding electron pairs. Wade’s rule and its corollaries have been refined and extended by a number of researchers. When coupled with spectroscopic studies and theoretical calculations, these rules have been successful in showing the structural interconnections between boranes, carboranes, other heteroboranes, carbocations, organometallic complexes, and transition-metal cluster compounds. Hats off to Professor...

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Printed Icon Lives On
Apr20

Printed Icon Lives On

Back in the April 2 issue of C&EN, we at Newscripts lamented the news that Encyclopaedia Britannica was no longer going to be issued in print format. Although the venerable encyclopedia will still be available online, we considered that the loss of the printed icon would be detrimental to tactile learning gained by leafing through the meaty volumes. In particular we noted that in the 1967 edition, the section on chemistry spans more than 50 pages. “Yes, that is a loss,” comments Newscripts reader Robert B. “Brad” Spencer of Madison, Wisc., who is proud owner of five sets of Encyclopaedia Britannica, including a reprint of the first edition from 1771. Spencer sent along this scan (below) of the beginning of the article on “Chemistry” from the first edition. The article has no chemical element symbols—they hadn’t yet been established. It is also absent any formulas or equal signs, and the “long s” was still in use in English.  “Chemistry was a recognized field of interest at the time,” Spencer observes. “But it was still largely an outgrowth of alchemy.” This first article states that the four principles (or elements) are earth, water, air, and fire, Spencer notes.  “Not that long ago the belief in these was still dominant,” he says. “But also notice what follows: a statement that our senses cannot possibly determine the principles of which they are composed, so we should, in essence, give up.  As we know, there were already at that time individuals who were not so pessimistic about the ability to dig deeper, and they began a marvelous understanding of chemical reality.” Thanks for sharing...

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Dark-Colored Sodas May Have Toxic Backwash, Or Not
Mar09

Dark-Colored Sodas May Have Toxic Backwash, Or Not

The Center for Science in the Public Interest (CSPI) has made a claim that “caramel coloring” used to improve the eye appeal of colas and other dark-colored soft drinks contains the carcinogenic by-products 2-methylimidazole and 4-methylimidazole (shown) and thus might be a cause of thousands of cancers in the U.S. The nonprofit consumer advocacy organization made its announcement via a regulatory petition filed with the Food & Drug Administration on Feb. 16. Besides being used in colas, the artificial coloring, which can range from yellowish to black, is used in some baked goods, precooked meats, soy and Worcestershire sauces, chocolate-flavored products, and even whiskey and beer. It’s typically made by pyrolyzing sugar with the aid of ammonium and/or sulfite compounds, a process that forms many derivative chemicals. This browning process is similar to, but distinct from, the Maillard reaction between a sugar and an amino acid. CSPI wants FDA to revoke regulations allowing the types of caramel coloring made using ammonium compounds, which contain the imidazoles. “Carcinogenic colorings have no place in the food supply, especially considering that their only function is a cosmetic one,” CSPI Executive Director Michael F. Jacobson said when announcing the petition. CSPI is invoking the Delaney Clause, an amendment to the Food, Drugs, & Cosmetic Act of 1938, to state that FDA is obligated to ban caramel coloring–the clause stipulates that FDA “shall not approve for use in food any chemical additive found to induce cancer in man, or, after tests, found to induce cancer in animals.” The issue of the toxicity or nontoxicity and possible regulatory control of the imidazole compounds has been bouncing around for a few years. CSPI based its petition on a pair of 2007 studies (1 and 2) published by the National Toxicology Program (NTP), a unit of the National Institute of Environmental Health Sciences. The studies conclude that 2- and 4-methylimidazole, compounds known to be in cigarette smoke, caused cancer in rats and mice. But NTP has not listed the imidazole compounds as being carcinogenic. CSPI also cites a paper by researchers at the University of California, Davis, who detected 4-methylimidazole in five brands of cola. The UC Davis researchers extrapolated their data to the NTP studies and concluded that “the amounts ingested from these beverages may not be significant.” Nonetheless, CSPI’s press announcement suggests that the amount of the compound in colas is large enough to be cause for concern, although the amount in soy sauce and other products is likely small enough to not be a problem. Caramel coloring is largely unregulated in the U.S., but California state health officials have added 4-methylimidazole to the state’s list...

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Sustainability Is Where You Find It
Dec21

Sustainability Is Where You Find It

At Pacifichem, the conference is set up so that you tend to want to just drift around and stick your head into one meeting room for a talk and them skip out to another session for a different talk. Doing that one afternoon, I came across a talk by Rogers E. Harry-O’kuru of the U.S. Department of Agriculture’s National Center for Agricultural Utilization Research, in Peoria, Ill., who was speaking about novel synthetic products that could be made from milkweed. Milkweed, which literally is a weed in agricultural areas, can ideally be cultivated on unused farmland, Harry-O’kuru said. The plant produces a fibrous “seed floss,” which equips the seeds for wind dispersal, that can be used as a hypoallergenic fill material for pillows and jackets, he noted. The seeds also contain a highly unsaturated oil that can be converted to polyoxiranes and polyhydroxy triglycerides to use as base materials in creams and lotions or as lubricants, he said. What struck me about Harry-O’kuru’s lecture is the ingenuity of people to turn whatever they have at hand into useful products that potentially cost little and can help improve the environment. These talks have applications globally, especially in developing countries. I then noticed a handful of other talks strung together by the common theme of sustainability: Kyoung S. Ro of USDA’s research center in Florence, S.C., gave an interesting talk on gasification of blended animal manures to produce synthesis gas and activated carbon. Pig and chicken poop mixed with sawdust and wood chips can be converted to syngas, which can be burned to generate electricity or further upgraded to dimethyl ether that can be used as a diesel fuel substitute. The whole process can be carried out in a transportable reactor, with the char left behind purified and used as activated carbon filter material in the reactor. Guillermo Toriz of the University of Guadalajara, in Mexico, gave a talk on the diversified uses of agave, the plant that is used to make tequila. The waxing and waning popularity of tequila has led to a severe overproduction of agave in Mexico, Toriz said, which has obliterated the price for farmers from about $2.00 per kilogram to about 5 cents per kilogram, making it uneconomical to harvest. Toriz described some new uses for agave that could help farmers: Enzymatic production of high-fructose-content agave syrups, using fructans (fiberlike polysaccharides) in agave as food additives and prebiotics that help promote growth of beneficial bacteria in the human gut, and using esterified fructans to make microspheres to encapsulate and deliver drugs to the colon. Janusz Kozinski of the University of Saskatchewan described the use of supercritical water as a medium for...

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Dressed Up With No Place To Go

Here at Pacifichem, the Alternate Energy Technology topical area featured a number of sessions on improving coal technologies to curb carbon dioxide emissions and using biomass as a source of energy. I have attended quite a few conferences, workshops, and symposia during the past decade that focused on these topics. The message is always the same: We need to develop alternative technologies to generate electricity and transportation fuels as our supply of petroleum and other fossil fuels runs out, and it would be nice to curb carbon dioxide emissions to save the planet at the same time. Based on current trends in global energy consumption, even with significant incremental technology changes–that is, business as usual–atmospheric carbon dioxide levels will still more than double by 2100 and impact global temperatures. Exactly how the planet will react is uncertain, but the prospects aren’t good. Scientists and engineers participating in these gatherings acknowledge that there is no one solution to this future-of-energy scenario, and of the emerging technologies such as solar, wind, electric vehicles, and more, none are yet concrete nor are they affordable.  The message is: We know what has to be done, we have a pretty good idea how to do it, but no one wants to pay for it.  It’s getting to be a tiresome refrain. The U.S. budget provides more than $1 billion annually for energy research. More than $400 million of that is dedicated to coal, which is an indicator of the reality of energy consumption–the U.S. has lots of coal and natural gas, an estimated 250 years or more supply, and we are going to use it up first and set a regulatory policy in order to do it. Coal-rich countries such as China are in the same policy boat. It is not a bad policy, because coal is cheaper for now. It just means alternative energy technologies are not going to be adopted very quickly, and we are unlikely to do much about the cost of environmental control quickly, because no one wants to pay for it, hence the reason global agreements on carbon capture and sequestration to curb carbon dioxide emissions are languishing. We have to continue research in all areas to be able to move when the time comes, however. That is the essence of being sustainable. But that does nothing to satisfy the need for instant gratification that today’s global society has come to expect–that one can have what they want when they want it from a blue electronic screen or by sliding a card. So it is with alternative energy technologies. It’s really an ideal that is dressed up with no place...

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