Adds and Bases

When an acidic water solution is mixed with a basic water solution, an acid-base reaction takes place. The nature of the reaction and hence the equation written for it depend on whether the add and base involved are strong or weak. 

Strategy Decide whether the add and base are strong or weak. Then decide which of the three types of acid-base reactions is involved. Finally, use Table 4.2 to derive the proper equation. 

For each of the following reactions, indicate the Brensted-Lowry adds and bases. What are the conjugate acid/base pairs ... 

The product of the reaction, the binding agent, is a complex salt, and powder in excess of that required for the reaction acts as the filler. Each cement system is a particular combination of add and base. The number of potential cement systems is considerable since it is a permutation of all possible combinations of suitable adds and bases. 

Thus, adds and bases do not react directly but as solvent cations and anions. Since emphasis is placed upon ionization interactions, inherent addity and basidty is neglected, as are interactions in the non-ionic state. The theory is a simple extension of the Arrhenius theory and suffers from... 

Lewis (1938) was not content with a purely conceptual view of adds and bases, for he also listed certain phenomenological criteria for an add-base reaction. The process of neutralization is a rapid one, an add or base displaces a weaker add or base from its compounds, adds and bases may be titrated against each other using coloured indicators, and both adds and bases have catalytic effects. 

Yatsimirskii (1970) attempted to quantify HSAB theory and produced hardness indices for adds and bases. These indices were obtained by plotting the logarithms of the equilibrium constants for the reactions of bases with the proton (the hardest add) against similar values for the reactions with CHjHg (one of the softest adds). For adds, the hydroxyl ion (the hardest base) and the chloride ion (a soft base) were chosen. 

Add (Nafion or molybdic add)- and base (diamine-based or guanidine residues)-catalyzed reactions in the same pot Sol-gel immobilization of both catalysts... 

Slonczewski JL et al. Add and base regulation in the proteome of Escherichia coli. Novartis Foundation Symp 1999 221 75-83. 

Addition of salts, adds and bases tend to make the laevo-rotary acid more dextro-rotary. With rising temperature, the pure add and also the solutions become more laevo-rotary. These changes cannot be due to dectrolytic dissociation, because the effect of hydrochloric acid is quite marked up to rdatively high concentrations and it would take relatively little acid to force back the dissociation of malic acid to a negligible value. Another reason is that we get a similar change with the concentration with malic ester in alcoholic solution. 

The change with the concentration cannot be due to the reversible formation and decomposition of a lactone of the ordinary type because we get the effect with ethyl malate as well as with malic add. The change cannot be due to a reversible conversion of laevo-malic acid into dextro-malic add, because then a solution of equivalent amounts of dextro- and laevo-malic acids would become optically active on addition of salts, adds and bases. Hydrochloric add or sodium hydroxide imparts no activity to a solution of d/-malic add. The changes on adding electrolytes to a solution of dextro-malic add are equal and opposite in sign to the changes in laevo-malic acid under the same conditions. 

Amino acids are classified as acidic or basic according to their R groups because in proteins, these are the only groups that can dissociate. The a-amino and a-carboxyl groups are in peptide bonds and lose their acid-base character. This system of classification can be confusing since the words add and base are used in a way slightly different than discussed in the section above. 

You must remember these points and also know which adds and bases are strong and which are weak. 

You can find some Information about the Bronsted-Lowry theory of adds and bases at www. brlghtredbooks.net... 

To find out more about conjugate adds and bases, visit www.brlghtredbooks.net... 

Besides concave pyridines, concave 1,10-phenanthrolines and concave benzoic acids, a large number of other concave adds and bases are conceivable containing other acidic or basic groups in the concave position. The central question for such new concave reagents is how can the new functionality be incorporated into the bimacrocyclic structure, and how can a concave orientation be assured ... 

For discussions of field effects on add and base strength and on reactivity, see Chapters 8 and 9, respectively. 

Normality is sometimes used in acid-base or ion-exchange chemistry. With respect to adds and bases, the equivalent mass of a reagent is the amount that can donate or accept 1 mole of H+. With respect to ion exchange, the equivalent mass is the mass of reagent containing 1 mole of charge. 

McDaniel and coworkers have presented a graphical means of portraying some of the ideas discussed in this chapter. For the reaction of hard and soft adds and bases... 

The "equilibrium boxes" for the solvents (Fig. 10-1) indicate the range over which differentiation occurs outside the range of a particular solvent, all species are leveled. For example, water can differentiate species (i.e., they are weak adds and bases) with pKa s from about 0 to 14 (such as acetic acid). Ammonia, on the other hand, behaves the same toward acetic acid and sulfuric acid because both lie below the differentiating limit of —12. The extent of these ranges is determined by the autoionization constant of the solvent (e.g, —14 units for water). The acid-base behavior of several species discussed previously may be seen to correlate with Fig. 10.1.11... 

Condensations of aldehydes and ketones are catalyzed homogeneously by adds and bases, but solid bases are preferred, such as anion exchange resins and alkali or alkaline earth hydroxides or phosphates. 

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