![]() ![]() Table 3.5 lists some materials that react with water. Table 3.4 indicates some chemical categories susceptible to water reactivity. For fire protection purposes, a material is considered water reactive if a gas or at least 30 cal/g of heat is generated when it is mixed with water (NFPA 704 2001), using a two- drop mixing calorimeter (Hofelich et al. If you are uncertain as to whether a material is water reactive, a chemist or other expert should be consulted or a simple test can be performed. If you are certain that NO water-reactive substances are present, then go to Question 10. Table 10.7 shows the main reactions that proceed by the Sn2 mechanism (if R = primary or, often, secondary alkyl) Table 10.8 shows the main reactions that proceed by the tetrahedral mechanism. Table 10.6 is an approximate listing of groups in order of SnI and Sn2 reactivity. Table 9 summarizes the effect of various substituents on the physical properties of resulting siloxane homopolymers. The properties that can be changed or modified by the variations in the siloxane backbone include the low temperature flexibility ( glass transition temperature, crystallization and melting behavior), thermal, oxidation, and radiation stability, solubility characteristics and chemical reactivity. Īlthough each of these cyclic siloxane monomers can be polymerized separately to synthesize the respective homopolymers, in practice they are primarily used to modify and further improve some specific properties of polydimethylsiloxanes. Table 10-5 summarizes the nucleophilic parameters. The Edwards equation is thus an oxibase scale of nucleophilic reactivity. Since H measures proton basicity and En the electron-donation ability, this treatment models nucleophilicity as a combination of electron loss and electron pair donation. (10-17), parameters a and b measure the sensitivity of the reaction to these nucleophilic parameters. ![]() Ĭhemistry in three dimensions is known as stereochemistry At its most fundamental level stereochemistry deals with molecular structure at another level it is concerned with chemical reactivity Table 7 2 summarizes some basic definitions relating to molec ular structure and stereochemistry. Table 2.4 lists the results for nitration in 95% and 100% acid of a selection of less completely investigated compounds. 2.1 illustrates the variation with acidity of the second-order rate constants of the nitration of a series of compounds of widely differing reactivities. ![]() Although the proportion of nitric acid present as nitronium ions does not change between 90% and 100% sulphuric acid, the rate constants for nitration of most compounds decrease over this rai e. ![]()
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