Volume 75, Issue 10

Following the first IUPAC Polymer Conference on the Mission and Challenges of Polymer Science and Technology (IUPAC PC2002), this article highlights and summarizes the historical development of polymer science and technology and the recent advances that have occurred and are occurring in the subject. It highlights the mission and challenges for the future, particularly as reflected in the papers presented at the conference and in the con- ference’s concluding panel discussion. The important role of IUPAC in defining and leading developments in polymer science and technology is also described. The central role of polymer science and technology and its close interactions with chemical, physical, and biological sciences are defined and discussed. The 21 st century is shown to be the Age of Polymers.

This article reviews heteronuclear NMR techniques that are used to characterize the 3D structures and internal molecular dynamics of proteins in solution. Applications to several proteins that have been studied in our laboratory are presented. Topics discussed include sequential assignments, the use of nuclear Overhauser enhancement spectroscopy (NOESY) and residual dipolar coupling restraints to determine protein structure, and the use of relaxation measurements to obtain information about protein internal motions. Also discussed are recent computational approaches directed at increasing the efficiency of structure determination, as well as new methods for studying large proteins.

In the course of the last 20 years, our view on rotaxanes and catenanes has completely changed. Copper(I)-templated strategies, in particular, have allowed us to prepare catenanes on a real preparative scale, in a few chemical steps from commercially available compounds. A particularly significant improvement was the introduction of the recently developed ring-closing metathesis reaction, using Grubbs catalyst. The dynamic properties of rotaxanes and catenanes has been exploited to construct molecular systems for which one component can be set in motion under the action of an external signal, while the other components can be considered as motionless (artificial molecular “machines ”and “motors ”). A particularly representative example is that of a rotaxane dimer, whose overall length can be controlled chemically: A metal exchange reaction (Cu I /Zn II ) triggers a reversible contraction/stretching process of the same molecular assembly, in a way reminiscent of the functioning of biological muscles.

One of the challenges in polymer physics is to predict the structure and properties of polymeric materials from their microstructures and processing conditions by integrating various theories and simulation methods. We have been involved in such a challenge through a governmental project involving computational modeling of polymeric materials. This article discusses how we tackled the challenge and describes the system we developed.

Reaction of pyridine and substituted pyridines with N 2 O 5 in an organic solvent gives the N-nitropyridinium ion. When this is reacted with SO 2 /HSO 3 – in water, 3-nitropyridine is obtained (77 % yield). With substituted pyridines, the method gives good yields for 4-substituted and moderate yields for 3-substituted pyridines. The reaction mechanism is not an electrophilic aromatic substitution, but one in which the nitro group migrates from the 1-position to the 3-position by a [1,5 ] sigmatropic shift. From 4-aminopyridine, imi- dazo [4,5- c ] pyridines have been synthesized. From 3-nitropyridine, 5-nitropyridine-2-sulfonic acid is formed in a two-step reaction. From this, a series of 2-substituted-5-nitro-pyridines has been synthesized. 3-Nitropyridine and 4-substituted-3-nitropyridines have been substituted with ammonia and amines by the vicarious substitution method and by the oxidative substitution method in the position para to the nitro group. High regioselectivities and yields have been obtained in both cases to afford a series of 4-substituted-2-alkylamino-5-nitropyridines.

Indoles that are substituted at the 2- or 3-position with electron-withdrawing groups (nitro, phenylsulfonyl) undergo nucleophilic addition, 1,3-dipolar cycloaddition, and Diels–Alder reactions to give a variety of indoles, pyrroloindoles, and carbazoles. New methods for the synthesis of furo[3,4- b ]indoles and the novel ring system furo[3,4- b ]pyrrole are described for the first time. Diels–Alder reactions of furo[3,4- b ]pyrroles afford indoles after dehydration of the primary cycloadducts. Efficient syntheses of both 2- and 3-nitroindoles from indole are reported, and the first generation and successful electrophilic trapping of a 2,3-dilithioindole has been achieved.

The synthetic potential of lithio 3-halo-1-azaallylic anions as building blocks in organic chemistry and especially in heterocyclic chemistry will be highlighted by the synthesis of functionalized imines, obtained after reaction of 3-halo-1-azaallylic anions with het- eroatom-substituted electrophiles. Thus, the latter generated functionalized imines are suitable building blocks for the synthesis of a whole range of heterocycles and physiologically active compounds, including agrochemicals and pharmaceuticals. 3-Halo-1-azaallylic anions were used in the synthesis of N -alkyl-3,3-dichloroazetidines, 2,3-disubstituted pyrroles, piperidines, 2-substituted pyridines, 2-alkoxytetrahydrofurans,etc., from which a large range of useful and interesting chemicals can be produced, e.g., 2-azetines and 9-alkyl- 2-phenyl-3a-beta,4,6,7,8,9,9a-beta,9b-beta-octahydro-1 H -pyrrolo [3,4, h ]quinoline-1,3-diones. The utility of the present methodology is demonstrated by the synthesis of the pheromone (S)-manicone, the sulfur-containing flavor compound 2-[(methylthio)methyl ]-2-butenal, and some agrochemical and pharmaceutical compounds.

The unique availability of substituted cyclohexa-1,4- and 1,3-dienes, notably enol ethers, from Birch reduction of anisoles, permits many novel synthetic reactions of general utility. The total synthesis of several natural products derived from polyketides have been accomplished using a Diels–Alder and Alder–Rickert process. The strategies of the synthesis are discussed.

The ring opening of different three-, four-, five-and six-membered oxygen-, nitrogen- and sulfur-containing saturated heterocycles using lithium and a catalytic amount of an arene (naphthalene or DTBB) yields a series of functionalized organolithium compounds, which, by reaction with different electrophiles, allow the preparation of polyfunctionalized molecules in only one synthetic operation.

This document is part of an ongoing effort to standardize transmission of laboratory data across cultural and linguistic domains, without attempting to standardize the routine language used by clinicians and laboratory practitioners. It comprises a general introduction and an alphabetic list of properties. The list is based on the syntax for properties recommended by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the International Union of Pure and Applied Chemistry (IUPAC). The nomenclature is primarily from the Working Party on Terminology of the International Society of Blood Transfusion (ISBT).

The IUPAC/IUPAP Joint Working Party on the priority of claims to the discovery of new elements has reviewed the relevant literature pertaining to several claims. In accordance with the criteria for the discovery of elements, previously established by the 1992 IUPAC/IUPAP Transfermium Working Group, and reinforced by the 1999 IUPAC/IUPAP Joint Working Party, it was determined that the claim by the Hofmann et al. research collaboration for the discovery of element 111 at Gesellschaft für Schwerionenforschung (GSI) has fulfilled those criteria. For elements 112, 114, and 116, the collaborations of Hofmann et al. and of Oganessian et al. produced high-quality data with plausible interpretations. However, confirmation by further results is needed to assign priority of discovery for these elements. The working party was not persuaded that other collaborations have satisfied the discovery criteria.

A joint IUPAC–IUPAP Working Party (JWP) confirmed the discovery of the element with atomic number 110. In accord with IUPAC procedures, the discoverers proposed a name and symbol for the element. The Inorganic Chemistry Division recommended this proposal for acceptance, and it was adopted by the IUPAC Council at Ottawa, 16 August 2003. The recommended name is darmstadtium with symbol Ds.