Furan special

The potential of these transformations has not been fully exploited. The method is certainly valuable both for the purpose of studying the structure of furan polymers which might be of interest but cannot be prepared easily by conventional techniques and for preparing polymers in which a certain proportion of the hydroxyl groups of poly(vinylalcohol) are substituted with a furan moiety which gives the new product some special property. 

A special case of amide formation was observed in the reaction of a furan-2-carboxylic acid with two moles of CDI and subsequent conversion with amines, hi this reaction, besides formation of the imidazolide, addition of imidazole also takes places.1-1411... 

Electronic products become e-waste when they are deemed at the end of their useful life. Nonfunctioning or obsolescent TVs, computers, printers, photocopiers, cell phones, fax machines, home appliances, lighting equipment, games and such, when no longer wanted, come to constitute e-waste. These electronic products contain many materials requiring special end-of-life handling, most prominently lead, mercury, arsenic, chromium, cadmium, and plastics capable of releasing dioxins and furans. 

There are several systematic nuclear magnetic resonance studies of the interaction between the substituents and the protons and ring atoms of five-membered heterocycles. In some 2-substituted furans, thiophenes, selenophenes, and tellurophenes there is a linear correlation between the electronegativity of the chalcogen and several of the NMR parameters.28 As there also is a good correlation between the shifts of the corresponding protons and carbons in the four heterocycles, the shifts of unknown selenophene and tellurophene derivatives can be predicted when those of thiophene are known. This is of special interest for the tellurophene derivatives, since they are difficult to synthesize. In the selenophene series, where a representative set of substituents can be introduced in the 2- as well as in the 3-position, the correlation between the H and 13C shifts and the reactivity parameters according to Swain and Lupton s two-parameter equation... 

Hanssen, and Nair,127 and by Chadwick et a/.128 All deal with mono-, di-tri-, and sometimes tetra-substituted furans where the substituents are variously selected from halogen, ester, acid, aldehyde, and ketonic functions. Here we consider only some more special situations. 

The anodic oxidation of furans has been studied from both synthetic and theoretical points.285 Because of the many possibilities for delocalization, tetraphenylfuran is a special case but it does allow certain basic processes to be monitored by cyclic voltammetry.286 In nitrobenzene two steps are seen ... 

Dioxins, furans and heavy metals can be released as air borne pollutants in the ash, which needs to be landfilled with special care (i.e. mixed with cement) due to a danger of ground water contamination. 

The D. pulchra furanone compounds generally consist of a furan ring structure with a substituted alkyl chain at the C-3 position and a bromine substitution at the C-4 position (Fig. 5). The substituent at the C-5 position may vary in terms of side chain structure. The natural furanones are halogenated at various positions by bromine, iodine, or chlorine [128]. D. pulchra produces at least 30 different halogenated furanones which are stored in specialized vesicles and are released at the surface of the thallus at concentrations ranging from 1 to 100 ng/cm2 [132]. Field experiments have demonstrated that the surface concentration of furanones is inversely correlated with the degree of colonization by marine bacteria [133]. 

The most recent entrant-to the. club of commodity chemicals is 1,4-butanediol (BDO), a petrochemical used in some of the more specialized applications such as chemical intermediates for the production of tetrahydro-furane and gama-butyrolactone, polybutylene terephthalate, and the more familiar polyurethanes. Traditionally, the Reppe process was the primary route to BDO, based bn acetylene and formaldehyde feeds. More recently, the share of BDO from butane and propylene oxide based production has grown rapidly. 

Current work is focused on the benzoheteropines with the fused pyrrole (or indole), thiophene or furan rings, i.e., ortho-fused 6 + 7 + 5 ring systems with carbons only on the six-membered ring, one heteroatom on the five-membered ring and one or more heteroatoms on the seven-membered ring. The variety of heteroatoms is limited to nitrogen, oxygen and sulfur. Several examples of the related cyclic systems with the other heteroatom distribution or peri-fusion are briefly summarized in Section 4.3. The current first specialized review covers synthetic, reactivity and structural aspects reported from the late 1989 until 2007. 

Benzoheteropines with fused pyrrole, furan, and thiophene rings, of great interest because of their biological activity, are surveyed by Dr. D.O. Tymoshenko of the Albany Molecular Research Institute, New York. These compound classes were considered in both the first and second editions of Comprehensive Heterocyclic Chemistry as part of a host of related multi-atom heterocyclic systems. Other specialized reviews have appeared. However, the present survey is the first comprehensive treatment. 

Among the facts supporting this mechanism (which is an A-Se2 mechanism because the substrate is protonated in the rate-determining step) are (1) lsO labeling shows that in ROCH=CH2 it is the vinyl-oxygen bond and not the RO bond that cleaves 497 (2) the reaction is subject to general acid catalysis 498 (3) there is a solvent isotope effect when D2O is used.498 Enamines are also hydrolyzed by acids (see 6-2) the mechanism is similar. Ketene dithioacetals R2C=C(SR )2 also hydrolyze by a similar mechanism, except that the initial protonation step is partially reversible.499 Furans represent a special case of enol ethers that are cleaved by acid to give 1,4 diones. Thus... 

The metabolism of several furan derivatives, e.g. furan-2-carboxylic acid and furan-2-carbaldehyde (furfural), was studied in 1887 by Jaffe et al. (1887CB2311), and most of this early work has been summarized (B-47MI10900). The metabolism of furfural (127 Scheme 12) is of special interest since it yields furfuracryluric acid (furylacryloylglycine) (128) as... 

A special instance of Brown s method is the dehydration of ce-(4-ethoxynaphthyl)benzoin (163) in the presence of SnCl2 + HC1 + AcOH instead of the normal reduction of the carbonyl group, cyclodehydration occurs, giving l,2-diphenyl-5-ethoxynaphtho[2,l-6]furan (164).416 The reaction also occurs under the influence of H2S04 in AcOH or of A1C13 in anisole. 

These methods have been applied to the synthesis of dihydronaphtho-[1,2-6], [2,1-6], and [2,3-6] furans and their substituted derivatives,491,496-499 and of the furoxanthone (234).500 A special case is the preparation of the benzofuran (235) as shown.501... 

When butanolides are methylated it is again the carbonyl oxygen atom that is attacked. In this case the substrate is behaving like any other ester and no special furan feature seems to be involved. The products are exemplified by the simplest furylium cation (101) which is considered to adopt the conformation shown (80CJC164). 

Kim, S.-C., 2001. Emission characteristic of dioxins/furans and major air pollutants from incinerators. J. Environ. Toxicol, (in Korean) Special Lecture in The Korean Society of Environmental Toxicology 2001. 

To better understand the structure and the inner workings of an environmental laboratory, we need to familiarize ourselves with laboratory functional groups and their responsibilities. Figure 4.2 shows an example of a typical full service environmental laboratory organization chart. A full service laboratory has the capabilities to perform analysis for common environmental contaminants, such as VOCs and SVOCs (including petroleum fuels and their constituents, pesticides, herbicides, and PCBs), trace elements (metals), and general chemistry parameters. Analysis of dioxins/furans, explosives, radiochemistry parameters, and analysis of contaminants in air are not considered routine, and are performed at specialized laboratories. 

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