Acetylene block technique

Hutchins, S. R. (1992). Inhibition of alkylbenzene biodegradation under denitrifying conditions by using the acetylene block technique. Applied and Environmental Microbiology, 58(10), 3395-8. 

Indirect methods used to estimate DNF include the acetylene block method (S0rensen, 1978), metabolite stoichiometry (Dollar et al., 1991), or stable isotope tracers (Nielsen, 1992). Acetylene (C2H2) blocks the terminal step of DNF, the conversion of N2O to N2, and the DNF rate is estimated by quantifying the production of N2O on a gas chromatograph with an electron capture detector. Problems with the acetylene block technique include blockage of NTR (which means that rates of coupled NTR—DNF cannot be obtained), inefficacy at low N03 concentration, and interference by H2S. Sulfide appears to alleviate the acetylene block of nitrous oxide reductase and permit full reduction of N2O to N2. 

Welsh, D. T., CastadeUi, G., Bartoli, M., Poli, D., Careri, M., de Wit, R., and Viaroh, P. (2001). Denitrification in an intertidal seagrass meadow, a comparison of N-isotope and acetylene-block techniques DissimUatory nitrate reduction to ammonia as a source of N2O Mar. Biol. 139, 1029-1036. 

Copolymerizations of benzvalene with norhornene have been used to prepare block copolymers that are more stable and more soluble than the polybenzvalene (32). Upon conversion to (CH), some phase separation of nonconverted polynorhornene occurs. Other copolymerizations of acetylene with a variety of monomers and carrier polymers have been employed in the preparation of soluble polyacetylenes. Direct copolymeriza tion of acetylene with other monomers (33—39), and various techniques for grafting polyacetylene side chains onto solubilized carrier polymers (40—43), have been studied. In most cases, the resulting copolymers exhibit poorer electrical properties as solubiUty increases. 

At last, the inhibition technique takes advantage of the property of acetylene to block the reduction of N O to N after it is injected into the sediment. The total amount of N O produced is then the measure for the denitrification rate as it is easy to determine by gas chromatography (Andersen et al. 1984) or by microsensors (Christensen et al. 1989). The advantage of this method is that analyses can be carried out rapidly and sensitively. Problems are (a) N O reduction is sometimes incomplete, (b) a homogenous distribution of in the pore water is difficult to maintain, (c) inhibits nitrification in the sediment meaning that the coupled system (nitrification / denitrification) might be seriously affected due to the applied method, and... 

Since the discovery of the elegant coupling techniques of the Wittig reactions, novel retinoid syntheses with acetylenic building blocks have been employed only for the design of specific synthetic retinoids, for example, in the synthesis of the acetylenic retinoids (427), (429), and (430) (Chauhan et al, 1982). 

Maleic anhydride grafting (cont.) poly(styrene-co-divinylbenzene), 694 poly(styrene-co-isobutylene), 675, 689 poly(styrene-co-nfialeic anhydride), 676, 679 poly(vinyl acetate), 676, 694 poly(vinyl acetate-co-vinyl fluoride), 678 poly(vinyl alkyl ethers), 675, 679, 692, 701 poly(vinyl chloride), 683, 692, 693, 695, 702 poly(vinylidene chloride), 691 poly(vinyl toluene-co-butadiene), 689 radical—initiated, 459-462, 464-466, 471, 475, 476 radiation—initiated, 459, 461, 466, 471, 474 redox-initiated, 476 rubber, 678, 686, 687, 691, 694 to saturated polymers, 459-466, 475, 476 solvents used 460-463, 465, 466, 469, 474-476 styrene block copolymers, 679 tall oil pitch, 678, 697 terpene polymers, 679, 700 thermally-initiated, 462, 464-467, 469, 476 to unsaturated polymers, 459, 466-474 vapor-phase techniques, 464, 474, 475 to wool fibers, 476 Maleic anhydride monomer acceptor for complex formation, 207-210 acetal copolymerization, 316 acetone CTC thermodynamic constants, 211 acetone photo-adduct pyrolysis, 195, 196 acetylacetone reaction, 235 acetylenic photochemical reactions, 193-196 acrylamide eutectic mixtures, 285 acylation of aromatic acids, 97 acylation of aromatics, 91, 92 acylation of fused aromatics, 92, 95, 97, 98 acylation of olefins, 99 acylation of phenols, 94-96 acylic diene Diels-Alder reactions, 104-111, 139 addition polymer condensations, 503-505 adduct with 2-cyclohexylimino-cyclopentanedi-thiocarboxylic acid, 51 adducts for epoxy resins curing, 507-510 adduct with 2-iminocyclopentanedithiocarboxylic acid, 51... 

---