Fast bases

Cl azoic diazo component Amine stmctuie CAS Registry Number Cl number Fast base or salt... 

Biosensors are the analytical systems, which contain sensitive biological elements and detectors. Plant cells as a possible biosensors have natural structure that determinates their high activity and stability. Criteria in the screening of the plant cells as biosensors for allelopathy should be as under (i) Reaction is fast based on the time of response, (ii) Reaction is sensitive to small doses of analysed compounds or their mixtures and (iii) Methods of detection viz., biochemical, histochemical, biophysical (in particular, spectral changes in absorbance or fluorescence) are easy in laboratory and in the field conditions. The search of biosensors in active plant species is suitable to determine the mechanisms of action of biologically active substances or external factors of the environment (Roshchina and Roshchina, 2003 Roshchina, 2004 2005 c)). 

As the range of components available for use in the azoic dyeing process expanded, research was simultaneously targeted on improvements designed to make the process more attractive to the commercial dyer. The necessity for the dyer to diazotise the Fast Base was removed with the introduction of stabilised diazonium salts [111], known as Fast Salts. Stabilisation was achieved by a judicious selection of the counter-ion to the diazonium cation various anions have found use in commercial Fast Salts and some examples are listed in Table 4-4. Particularly effective is the diazonium tetrachlorozincate, which can be readily prepared by adding an excess of zinc chloride solution to a solution of the diazonium salt. The precipitated complex diazonium salt is usually admixed with an inert diluent, which enhances its stability, and in use the dyer only needs to dissolve the powder in water to prepare the necessary diazonium salt solution. 

The DLVO theory, a quantitative theory of colloid fastness based on electrostatic forces, was developed simultaneously by Deryaguin and Landau [75] and Verwey and Overbeek [76], These authors view the adsorptive layer as a charge carrier, caused by adsorption of ions, which establishes the same charge on all particles. The resulting Coulombic repulsion between these equally charged particles thus stabilizes the dispersion. This theory lends itself somewhat less to non-aqueous systems. 

However, the substituent effect is opposite to that for the SN1 route as discussed above, but fits an addition-elimination path. The kinetics at 65° may be explained by a fast base-catalysed addition forming the a J8-adduct (240), followed by its rate-determining solvolysis. Decreasing the temperature or substitution by electron-donating substituents... 

Trinitroso derivative 27 underwent in CD30D/D20 solution fast base-catalyzed H/D exchange on the whole set of methylene hydrogens, and nitroso groups can be subsequently removed by reduction with Ni/Al alloy <2002TL771>. 

Ml those fast bases yield red or maroon shades with hydroxynaphthoic acid, after diazotization as described in the following paragraph. 

There are a number of Fast Bases which are adsorbed by the fibre at 100°C (212°F) and with these no advantage is gained by increasing the temperature further because the degree of exhaustion tends to decrease. 

Cationic Carbamoyi Poiymors. Poly(acrylamide) reacts with formaldehyde [50-00-0], CH2O, and dimethylamine [124-40-3], C2H7N, to produce aminomethylated polyacrylamide (a Mannich reaction). This reaction has been studied extensively (110-114). A wide range of substitution can be produced in solution or in water-in-oil emulsion. nmr studies (114) have verified that the Mannich substitution reaction follows second-order kinetics. The formation of the formaldehyde-dimethylamine adduct is very rapid. The high rate of Mannich substitution at high pH indicates a fast base-catalyzed condensation mechanism. The Mannich reaction is reversible and pH dependent. At low pH, the rate of substitution is very slow. 

Two dye components are needed for dyeing with azo dyes which are synthesised on the fibre a diazonium salt and the coupling compound, abbreviated as the naphthol . Diazonium components are aromatic amines, the fast bases, which must be previously diazotised or stabilised diazonium salts, the fast salts. Coupling components are arylamides of aromatic o-hydroxyacids and of acylacetic acids. Perkavec and Perpar [54] report the TLC-separation of these products. 

The fast bases can be separated on silica gel G using the solvents 1. n-butanol-acetic acid-water (64 + 16 + 20) or 2. n-butanol-pyridine-water (25 + 50 + 25). 4-Dimethylaminobehzaldehyde (Rgt. No. 72) is used for visualisation, hi /-values obtained are in Table 136. 

Table 136. JiRf-values of the fast bases [54] details in text...

The anomalously fast base hydrolysis of the rra//s-[Co(en)2Cl2] and trans-[Co(ddn)Cl2]+ions (ddn = /J,5-2,3,2-tet = / ,5 -l,9-diamino-3,7-diazanonane)has been shown to arise mainly from the unusually high lability of their conjugate bases. Using deuteriated complexes the extent of replacement of the labelled amine protons... 

For the success of the whole process, fast, base-catalyzed racemization of the wrong enantiomer (4R)-4 in the extract, and feeding the racemate back into the SMB unit proved to be cmcial. The most important operating parameters for the pilot scale performance are given in Table 7.1 [51]. An impressive, nearly 100% recovery of the target enantiomer (45 -4 was achieved. 

An important consequence of these side reactions is the presence of water, irrespective of the fact that anionic polymerization starts in anhydrous conditions. Water is able to hydrolyze N-acyl lactams, p-ketoamides, p-ketoimides, and the imide branching points via fast base-catalyzed reactions. During these hydrolytic reactions, carboxylates, amine... 

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