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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Dallas: A Structural Analysis
Mar20

Dallas: A Structural Analysis

If you haven’t been to an ACS national meeting in Dallas—the last one, if memory serves, was in 1998—there’s a few interesting things to see. This is a summation after spending some time walking the streets here the past week. Located on the Trinity River, Dallas was first settled in the early 1840s when Texas was its own country. A few homesteaders moved into this area and built small log cabins. There’s a reconstructed cabin near the convention center. Dallas is now the ninth largest city in the U.S., with about 1.2 million residents, swollen by an additional 10,000 souls this week with the ACS meeting. Dallas has a compact downtown with a surprising structural diversity when it comes to the architecture of its buildings. The Magnolia Hotel, which dates from 1922, features a neoclassic beaux-arts style common in those days and was once home to Magnolia Petroleum Co., which was one of the forerunners of ExxonMobil. The building is famous for its Pegasus sign placed on the roof. This is the iconic red winged pony you see today on gas pumps. Next door to the Magnolia is the Adolphus Hotel, another beaux-arts building, which opened in 1912. It was built by Adolphus Busch, renowned founder of the Anheuser-Busch company. Another Dallas classic is the original Federal Reserve Bank Building, constructed in 1921, another example of the beaux-arts style. The much larger new Reserve Bank Building is a glass and stone box that is not as easy on the eyes. Yet some of the modern buildings in town have an appreciated distinctive look, such as the polygonal glass Wells Fargo Building. It might at first glance look like a shard of glass, but to the country chemist in the big city it is reminiscent of a crystal of some exotic metal salt. Among the other interesting sights in town, there’s the giant eyeball. This is a 30-foot-tall ocular oddity set up in a park (maybe it is an empty lot) adjacent to the Joule Hotel on Main Street. The big eye got its start as part of a pop culture arts project in Chicago before joining the hotel’s modern art collection. But that still doesn’t explain why someone would create it. I wonder how they moved it here from Chicago? For ACS meeting-goers, another point of interest in Dallas this week has been Pioneer Park, which is adjacent to the convention center. The park features an art installation of a herd of oversized longhorns crossing a stream, pressed on by a pair of cowpokes. Oddly there’s also a cemetery right outside the convention center, where some of Dallas’ founding fathers rest in peace. It was...

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Going Green On St. Patrick’s Day
Mar18

Going Green On St. Patrick’s Day

On a sunny St. Patrick’s Day in Dallas, green chemists gathered in several venues at the ACS national meeting to discuss how to encourage more chemists to live green. One well-attended symposium in the Division of Organic Chemistry that mixed academic and industry scientists focused on transition-metal catalyzed reactions with a green twist. UCLA’s Neil Garg spoke about nickel-catalyzed cross-coupling reactions that are inherently green for their atom economy, that is, most or all of the atoms in the starting materials end up in the products. Garg carried out the work in part using a grant from the ACS Green Chemistry Institute’s Pharmaceutical Roundtable, an industry group made up of pharmaceutical companies that are working together to develop more efficient reactions that are kind to the environment and don’t cost a pretty penny. Shu Kobayashi of the University of Tokyo took a deeper look at using immobilized catalysts that are easily recovered and reused to help reduce waste. And symposium organizer Bruce Lipshutz from UC Santa Barbara discussed his efforts to carry out organic chemistry without using organic solvents. About 85% of the waste in a chemical reaction comes from using organic solvents, Lipshutz noted. His group has developed a micellar reaction system that allows just about any kind of organic reaction to run in water at room temperature. That is about as green as you can get. The green session was followed by a panel discussion in which journal editors and directors of green chemistry institutes, including yours truly, fielded questions from the audience. The questions focused on the challenges for pursuing green chemistry and barriers that seem to be impeding broader adoption of green practices. Among the points discussed, one that stood out is that chemists need to adopt a different way of thinking as they approach their work. The panel suggested that as academics go about teaching students and writing journal articles, and as industrial chemists help mentor their junior colleagues, they need to take the time to explain why a certain reaction pathway is taken and the difference between choosing one solvent over another. They should provide tangible numbers to show how beneficial a green process can be. These explanations are necessary, even if they seem obvious or simplified, because chemists too often assume everyone knows and understands the nuances of green chemistry, when actually many still don’t. Or many chemists simply don’t give green options consideration at all and stick with what they know--business as usual. The panelists advocated for journal editors to apply gentle pressure to their authors to describe these green attributes in research papers to help nudge the adoption of green...

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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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