Technology, says the work older in 14 cities. It finds a 1% increase is very nice, beautifully pre in hospital admissions for cardiovascusented, and represents real lar disease and a 2% increase for pulmoprogress toward meeting nary disease and pneumonia for each the Barton Challenge. lO-jig/m3 increase in PM10. That challenge was conThe American Lung Association says ceived by Roberts in 1998 the study "confirms the need for strong in honor of the late Sir Defederal clean air health standards" and rek H. Barton's ground"dispels industry criticisms of earlier breaking research in selecstudies" linking particulate pollution to tive oxidation of aliphatic health problems. and alicyclic hydrocarbons The Environmental Protection Agen(C&EN, Jan. 4, 1999, page cy says, 'This important new study fur24). The competition will ther confirms the scientific basis for award $5,000 to the first EPA's measures to protect public health person or research group from particulate matter." The agency Royal Institution team of (from left) Raja, Thomas, and to produce adipic acid by a says it will review the study as it conducts Sankar pose In front of portrait of Michael Faraday. chemical or biochemical a new evaluation of the health effects oxidation of w-hexane with an 85% yield from particulates. That evaluation, re- important chemical feedstock for the quired under the Clean Air Act, is sched- manufacture of polyamides such as ny- based on the w-hexane consumed. "I have heard a lot of speculative talk uled for completion in 2002. lon and urethanes The Health Effects Institute, which Chemistry professor Sir John Meurig about space-selective catalysts for air funded the study, is an independent, non- Thomas, senior research fellow Gopi- oxidations of alkanes with the hope of profit corporation that studies health ef- nathan Sankar, and postdoctoral re- making adipic acid, and it is great to see fects of pollutants from motor vehicles search fellow Robert Raja at the Royal that Thomas, group actually has it goand other sources. Its money comes from Institution of Great Britain used an alu- ing," Roberts tells C&EN. Adipic acid is mainly manufactured EPA and auto and engine manufacturers minophosphate molecular sieve with cobalt(III) ions located on the inner walls in a two-step process involving the nitric and marketers. The report can be downloaded from of cages inside the sieve to convert the acid oxidation of a cyclohexanonethe Internet at http://www.healtheffects. linear alkane to adipic acid in up to 33% cyclohexanol mixture generated from yield at low temperature [Angew. Chem. cyclohexane using a homogeneous coorg/news.htm. balt-based catalyst. Cheryl Hogue Int. Ed., 39, 2313 (2000)]. Thomas and coworkers show, in an"Our molecular sieve catalyst is, to our knowledge, the first inorganic, het- other paper, that cyclohexane can be Novel Catalytic Routes erogeneous catalyst that can selectively directly oxidized by air to adipic acid oxidize both terminal carbons of n-hex- by free-radical, shape-selective catalyLead To Adipic Acid sis using an aluminophosphate molecuane simultaneously," Sankar says. The Royal Institution group points lar sieve containing iron (III) ions [AnBy using a molecular sieve catalyst and out that linear alkanes are notoriously gew. Chem. Int. Ed., 39, 2310 (2000)]. air as an oxidant, chemists in London difficult to oxidize. w-Hexane, for exam- The team on this project, which inhave selectively oxidized the terminal ple, is not attacked by boiling nitric acid, cludes postdoctoral research fellow methyl groups of w-hexane to produce concentrated sulfuric acid, potassium Markus Dugal, notes that a heterogeneous catalyst that functions with air adipic acid [HOOC(CH2)4COOH], an permanganate, or chromic acid. "Using our catalyst, the or oxygen as the oxidant allows facile alkane oxidation proceeds separation and recycling and simultaby a free-radical mecha- neously avoids the use of hazardous or nism," Thomas explains. corrosive reagents. "The molecular sieve con"I consider the w-hexane oxidation strains the w-hexane mole- report the most spectacular of the two cule in a spatially restricted papers," remarks Herman van Bekenvironment that ensures kum, professor of organic chemistry that the molecule points to and catalysis at Delft University, the the catalytically active co- Netherlands. "End-on oxidation of nbalt center that generates paraffins is a breakthrough. Nature thefreeradicals. The mole- can do this, but until now, scientists cule is perpetually im- have been unable to. There is still a lot mersed in an abundant of work to do before a process is develquantity of oxygen which oped. For example, stability of the catcan move in and out of the alyst might be a major issue. However, pores readily." it seems afinebeginning and for many John D. Roberts, emeri- researchers a start of another way of tus professor of chemistry thinking." n-Hexane molecule Is constrained In shape-selective cage. at California Institute of Michael Freemantle JULY 3,2000 C&EN
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