Polyfunctional reagents

Optimization of the ATP—hemoglobin reaction conditions produced a preparation having a markedly reduced oxygen affinity. Five fractions from a reaction mixture, when isolated, were found to have P q values ranging from 1.1 to 5.0 kPa (8 to 38 torr), most withUtfle cooperativity (118). These results are consistent with those found with other polyfunctional reagents that react on the surface of hemoglobin. 

Suitable chemistry must be chosen to allow the use of polyfunctional, unprotected reagents. In general, acylations and other reactions with electrophiles of a support-bound substrate will require the protection of functionalized side chains, both in the substrate and in the reagent. Protected, polyfunctional reagents are, however, rare and expensive, and protections/deprotections add further synthetic steps to the synthesis. Nucleophilic transformations, on the other hand, often enable the direct use of highly functionalized, unprotected reagents. Hence, nucleophilic transformations (e.g. 

A convenient route to the 1,3-selenazole nucleus uses a polyfunctional reagent such as the vinylphosphonium salt (110), which with sodium hydrogen selenide gives the ylide (111) (Scheme 33). Cyclization of (111) yields the phosphonium derivative (112). A variety of compounds have been prepared by this method [182-184],... 

In addition, the polyfunctional reagents bearing two vicinal amino groups—for example, cthylcncdi- R N—23 amines - or o-arylendiamines—-may produce cyclic... 

Polysaccharide cross-linking frequently occurs when it is acetalated, esterified, or etherified with bi- and polyfunctional reagents, e.g., P0C13, polyphosphates, dianhydrides of tetraioic acids, dialdehydes, dicarboxydiamides, vinyl monomers, and so on. Usually such compounds have enhanced water-binding capacity, lower aqueous solubility, and shear force stability. 

The special criteria of validation for an analytical method are directly related to the characteristics of the analytical method. For UV/Vis spectrometry, the reaction between the analyte and reagent must be fast, reproducible, and quantitative. The solution of the product resulting from the reaction must have at least 10,000 times the value of molar absorbtivity. In this regard, higher values can be obtained by using a polyfunctional reagent (e.g., Arsenazo III). For atomic absorption spectrometry and ICP, reproducibility of the flame and plasma, respectively, are essential for the quality and reliability of the analytical information, as well as for the validation criteria of the method. 

Reactions of diamines, diols, dihaloalkanes, and other polyfunctional reagents with polymer networks have been carried out for many purposes. If both groups of the reagent react with the polymer, a new cross-link is formed (Equation 2). If only one group reacts, the difunctional molecule is monosubstituted (Equation 3). Whether one or both groups react depends upon the DF of the polymer, shell dffusive or... 

Cross-linked starches are obtained by the reaction of starch (R—OH) with bi- or polyfunctional reagents, such as sodium trimetaphosphate, phosphorus oxychloride, epichlorohydrin or mixed anhydrides of acetic and dicarboxylic acids (e. g., adipic acid) ... 

Although side reactions which cause additional crosslinking are difficult to detect in polymers that are already crosslinked, they undoubtedly occur when polyfunctional reagents are used since the polymer chains can move fairly freely within the crosslinked network, and thus, reactive sites in close proximity to one another can interact easily. In our study (Ref. 16, 18) of the reaction of excess malononitrile with a 20% chloromethylated crosslinked polystyrene resin in the presence of base and tetrabutyl ammonium hydroxide, we routinely obtained conversions of more than 95% (calculated from N and Cl analyses for a monosubstitution) indicating that although a small amount of additional crosslinking might have occurred, and indeed probably did occur, the reaction was nevertheless of practical value. 

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