Scavangers

Before coupling, excess nitrous acid must be destroyed. Nitrite can react with coupling components to form nitroso compounds causiag deHterious effects on the final dyestuff. The presence of nitrite can be detected by 4,4 -diamiQO-diphenyHnethane-2,2 -sulfone [10215-25-5] (Green reagent) or starch—iodide. Removal of nitrite is achieved by addition of sulfamic acid or urea [57-13-6], however, sulfamic acid [5329-14-6] has been more effective ia kinetic studies of nine nitrous acid scavangers (18). 

A commercial polystyrene supported version is available — scavanger resin (for diol substrate). 

The reaction occurs in one step, but an equivalent excess of iminoether must be used as HCl scavanger. 

Scanning tunneling microscopy (STM), 787. 1157 bioelectrochemistry and, 1159 electrochemistry and. 1158 electrodeposition and. 1310 nanotechnology, 1345 piezoelectric crystal, 1158 tunneling current. 1157 underpotential deposition, 1313, 1315 Scavanger electrolysis, electrodeposition, 1343 Schlieren method, diffusion layer. 1235 Schmickler, 1495,1510 Schrodinger equation, 1456, 1490 Schultze 923,1497.1510 Screw dislocation, 1303, 1316, 1321, 1326 Secondary reference electrode, 815, 1109 Self-consumed electrode, 1040 Semiconductors... 

Treatment of nonfluorinated benzylic alcohols with sulfur tetrafluoride results in extensive polymerization. However, at low temperatures and in the presence of a hydrogen fluoride scavanger, such as triethylamine or pyridine, sensitive substrates such as benzylic alcohols,47 furfuryl alcohol (6), and 2-phenylcthanol (8)48 give the expected fluoro derivatives, albeit in low yield. 

Sulfur tetrafluoride undergoes addition across the carbonyl groups of glyoxal to form 1,2-difluoroethane-l,2-diol orthosulfite 13 the reaction occurs at room temperature in the presence of a hydrogen fluoride scavanger, such as sodium fluoride.75... 

The scavenging ability of this novel resin as an allyl cation scavanger was demonstrated in the palladium catalysed O-Alloc deprotection of the O-Alloc benzyl alcohol (Scheme 7.42). Benzyl alcohol was obtained in high yield with only small traces of byproduct, thereby eliminating the need for further purification. The relevant C-allylation of the resin was observed by the presence of C-allyl signals in die corresponding MAS-probe H NMR. 

For technical applications, knowledge of the irradiation behaviour of the Levextrel-TBP resin is important. A detailed study carried out at the Radiochemistry Institute of the Technical University, Munich(21,22), showed that with gamma irradiation the formation rate of dibutyl phosphoric acid (HDBP) and of "non-removable" acidic radiolysis products ("do-bads") is 2 to 5 times lower with Levextrel-TBP resin than with pure TBP the effect is attributed to the "scavanger" action of the aromatic groups in the matrix material. In summary, a high radiation resistance of the resin has become evident. 

Ivanov, B. B. and Robey, F. A. (1996) Effective use of free thiols as scavangers for HF coctails to deprotect bromo- and chloroacetylated synthetic peptides. Pept. Res. 9, 305-307. 

Oya Y, Yamamoto K, Tonomura A The Biological Activity of Hydrogen Peroxide. 1. Induction of Chromosome-type Aberrations Susceptible to Inhibition by Scavangers of Hydroxyl Radicals in Human Embryonic Fibroblasts. Mutat. Res. 1986 172(3) 245-53. 

Sodium hypochlorite solution is strongly alkaline (pH = 11.55) and the free caustic present in the solution acts as a stabiliser. Soda-ash scavanges free hydrochloric acid forming a non-volatile salt and maintain its alkalinity. Stability of sodium hypochlorite solution is also improved by storing it in a dark room below 30°C and free from contaminations of any heavy metal salts. The decomposition of sodium hypochlorite can be represented by the following reactions ... 

A number of protozoal parasites such as Trypanosoma, Plasmodium, Ldslinmnin, Crithidia and Toxoplasma spp. have been shown to contain at least one of the three major anti-oxidant enzymes superoxide dismutase, catalase and glutathione peroxidase [32]. Thus, many of these parasites are able to quench or scavange the oxidants... 

O-Donor Ligands. Previous studies of the charge-transfer photochemistry of [Fe(H20)J and [Fe(H20)5Cl] have been complicated by the complexity of hydrolytic equilibria and the requirement for scavangers to render the primary photochemical process observable. However, using Bu OH as a scavanger, it has been shown that the former yields OH radicals on irradiation at 254 nm and the latter yields Q- radicals on irradiation at 350 nm. Studies on solutions of FeX3(X = NO3 or CIO to which 0.5—2.0 equivalents of base were added have established the existence of [(H20)5Fe0Fe(H20)3] . Structural studies of... 

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