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Ammonia's effect on nicotine in cigarette smoke elucidated The first empirical study of ammonia's ef fect on nicotine in cigarette smoke has shown that ammonia boosts nicotine's im pact by converting it to its volatile, freebase form [Environ. Sci. Technol, 31, 2428 (1997)]. The study, conducted at Oregon Graduate Institute of Science & Technology, Portland, appears to validate the view that ammonia compounds are added to cigarettes to make nicotine more available to smokers. "Free-base nicotine is absorbed much more rapidly and efficient ly" than other forms of nicotine, explains Jack E. Henningfield, an associate professor of behavioral biology and psychiatry at Johns Hopkins University and an editor of former Surgeon General C. Everett Koop's 1988 report on nicotine addiction. But "the tobacco industry [has] argued that there weren't empirical data showing that such treatment of cigarettes [with ammonia] ac tually released more free-base nicotine," he notes. Environmental chemist James F. Pankow, who led the Oregon research team, says the process of converting nicotine "is analogous to what occurs" when cocaine is smoked as its free-base form.^
kene epoxidation. The catalytic mechanism is similar to that of dioxygenase enzymes, which activate dioxygen without reducing it, making it possible to use dioxygen's oxi dizing power most efficiently. John T. Groves and Robert Quinn of the depart ment of chemistry at the University of Mich igan, Ann Arbor, demonstrated such activ ity with a ruthenium-porphyrin complex [J. Am. Chem. Soc, 107, 5790 (1985)]. But Neumann and Dahan point out that inor ganic catalysts such as their polyoxometa late are much less subject to decomposi tion than organometallic complexes.^
Electron flow in DNA: Slower than wire, faster than proteins
Dev., 1, 264 (1997)]. In classic FriedelCrafts acylation, thionyl chloride (a corro sive and irritating reagent) is used to make an acid chloride, which is then used to acylate an aromatic substrate in a chlorinated hydrocarbon solvent in the presence of aluminum trichloride. The new method eliminates the need for thionyl chloride, aluminum trichloride, and the chlorinated solvent. In a case study, senior organic lec turer Timothy P. Smyth and graduate stu dent Brian W. Corby reacted TFA anhy dride and 2-phenylbutanoic acid to form the mixed anhydride, which was then used to acylate AfAklimethyl-2-phenoxyethylamine in the presence of phosphoric acid catalyst in a solvent mixture of TFA and its anhydride. The product they ob tained in high yield is an intermediate in the synthesis of the anticancer drug ta moxifen. After workup, they recovered TFA anhydride by distilling the solvent mixture from phosphorus pentoxide. Phosphoric acid residue was neutralized with calcium hydroxide.^
New experimental results suggest that al though DNA appears to conduct electrons faster than proteins, DNA does not neces sarily behave like a molecular wire. The researchers—chemistry professor Fred erick D. Lewis of Northwestern Universi ty, Evanston, 111., and his colleagues there Bottleneck identified and at Argonne National Laboratory—have in activating AZT created systems of DNA hairpins with stilbene dicarboxamide bridges. This allows Using a combination of kinetics studies them to study the rates of fluorescence and X-ray crystallography, a team of Ger quenching in DNA over known distances man researchers has uncovered a reason [Science, 277, 673 (1997)]. Previously, the that the widely used AIDS drug AZT (3'researchers reported that hairpins with de- azido-3' (TFA) and the acylating acid has been properties of AZT. The other choice is (H20)](ZnW9034)2}11_ may activate dioxy shown by chemists at the University of more novel: to modify the enzyme so that gen by a nonradical mechanism. They Limerick, Ireland, to be a viable alternative it will be better able to accommodate AZT have now demonstrated that this happens to the usual Friedel-Crafts reagent used on as a substrate and introduce the gene for and have used the complex to catalyze al a large scale in industry [Org. Proc. Res. the modified enzyme into infected cells. Λ AUGUST 4, 1997 C&EN 29
