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Pyrrole, chemical structure

The DSC and TGA plots of the oxidized polymer (VIII) showed that the Tm is 130°C and the weight loss of 20% and 80% was observed at 455°C and 600°C, respectively, compared to 400° and 482°C for the original polymer VII indicating the oxidized polymer was more stable to heat. This observation was consistent with the chemical structure of the oxidized polymer, which consisted of a repeating aromatic pyrrole structure and, therefore, should be more thermodynamically stable. The thermal data of the polymers are tabulated in Table II. [Pg.136]

Since the corresponding endoperoxide precursors are all too unstable for isolation, the diimide reduction constitutes an important chemical structure confirmation of these elusive intermediates that are obtained in the singlet oxygenation of the respective 1,3-dienes. However, the aza-derivative 14 and the keto-derivative 15 could not be prepared,17> because the respective endoperoxides of the pyrroles 18) and cyclopentadienones suffered complex transformations even at —50 °C, so that the trapping by the diimide reagent was ineffective. [Pg.131]

The chemical structure of 2,5-hexanedione suggested that it could react with lysine side-chain amino groups in proteins to form pyrroles (see Figure 2-7). In vitro experiments showed that this was, in fact, the case, and that the modified proteins can undergo secondary reactions to yield oxidized and polymeric products (DeCaprio et al. 1982 Graham et al. 1982). Oral administration of 2,5-hexanedione produced evidence that this process can take place in vivo as demonstrated by the detection of 2,5-dimethylpyrrole adducts in serum and axonal cytoskeletal proteins (DeCaprio and O Neill 1985). When a series of... [Pg.121]

Tables I through VIII summarize the occurrences of alkaloids from ants and other insects. Each table presents chemical structures as well as specific sources of particular types of alkaloids e.g.. Table I covers piperidines and pyridines. Table II, pyrrolidines, pyrroles, and indolizidines. Tables I through VIII summarize the occurrences of alkaloids from ants and other insects. Each table presents chemical structures as well as specific sources of particular types of alkaloids e.g.. Table I covers piperidines and pyridines. Table II, pyrrolidines, pyrroles, and indolizidines.
The data shown in Table 2 illustrate the general paucity of comparative toxicity data within an isosteric series of chemicals. In this Table a variety of toxic end-points observed for benzene and naphthalene have been compared with those of their simple heterocyclic analogues, and it is clear that it is almost impossible to derive chemical structure-biological activity relationships from the published literature for even such a simple series of compounds. Even basic estimates of mammalian toxicity such as LD50 values cannot be accurately compared due either to the absence of relevant data or the noncomparability of those available. Thus in a field where there are little comparative data on the relative toxicity to mammals of pyrrole, thiophene and furan for example, it is difficult to relate chemical structure to biological activity in historical heterocyclic poisons such as strychnine (3) and hemlock [active agent coniine (4)]. [Pg.114]

Structure-property correlations in primary expls have been addressed via IR spectroscopy (Ref 55). The time for deflagration to detonation as a function of chemical structure for the compd methylnitrotetra-pyrrole was investigated and the presence of the nitro group confirmed by IR analysis... [Pg.422]

The base unit of polypyrrole is pyrrole, the structure of which is a five member hetero-aromatic ring containing a nitrogen atom, as shown in Fig. 13a. Polypyrrole is synthesized from the pyrrole monomer by mild oxidation, using chemical or electrochemical technique. After the oxidation of the monomer, a black solid polymer is precipitated from the solution. The polypyrrole structure in its oxidized form is shown in Fig. 13b. Film thicknesses on the order of 1-1.5 pm, using in situ deposition, were obtained for our application [19]. [Pg.128]

The solvent hexane causes a different type of neurotoxicity, involving swelling and degeneration of motor neurones. This leads to paraesthesia and sensory loss in the hands and feet, and weakness in toes and fingers. Hexane has been widely used in industry as a solvent, and there have been many cases of neuropathy reported from different parts of the world. The toxicity is due to the metabolite 2,5-hexanedione which arises by co-1 oxidation at the 2- and 5-positions to 2,5-hexanediol, and then further oxidation to the diketone (figure 4.9). The 2,5-hexanedione then reacts with protein to form pyrrole adducts. The v-diketone structure is important, as 2,3- and 2,4-hexanedione are not neurotoxic. Methyl -butyl ketone also causes similar neurotoxic effects and is also metabolized to 2,5-hexanedione. The lipophilicity of the molecule allows distribution to many tissues including the nervous system. Thus, chemical structure and metabolism are important prerequisites for this toxicity. Exposure to the solvent carbon disulphide in industry causes neuronal damage in the central and peripheral nervous system. [Pg.365]

Porphyrins are a class of biologically important heterocyclic compounds with a characteristic chemical structure that includes four pyrrole groups (five-membered organic rings each containing a nitrogen atom) linked on opposite sides... [Pg.732]

We report here the result of an electrochemical study of the effect of gamma irradiation on a poly(pyrrole)-coated Pt electrode. The effect of the irradiation on the chemical structure of poly(pyrrole) was followed by changes in its vibrational spectrum. The results were interpreted, together with ESR spectroscopic data obtained with irradiated and nonirradiated samples of poly (pyrrole). [Pg.435]

Figure 1.15 Chemical structure of self-doped poly(pyrrole-co(3-(pyrrol-lyl)pro-panesulfonate). (Chemical Communications, 1987, 621, N. S. Sundarsan, S. Basak, M. Pomerantz, J. R. Reynolds. Reproduced by permission of the Royal Society of Chemistry.)... Figure 1.15 Chemical structure of self-doped poly(pyrrole-co(3-(pyrrol-lyl)pro-panesulfonate). (Chemical Communications, 1987, 621, N. S. Sundarsan, S. Basak, M. Pomerantz, J. R. Reynolds. Reproduced by permission of the Royal Society of Chemistry.)...

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See also in sourсe #XX -- [ Pg.753 ]




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