Acid base system

Still another type of adsorption system is that in which either a proton transfer occurs between the adsorbent site and the adsorbate or a Lewis acid-base type of reaction occurs. An important group of solids having acid sites is that of the various silica-aluminas, widely used as cracking catalysts. The sites center on surface aluminum ions but could be either proton donor (Brpnsted acid) or Lewis acid in type. The type of site can be distinguished by infrared spectroscopy, since an adsorbed base, such as ammonia or pyridine, should be either in the ammonium or pyridinium ion form or in coordinated form. The type of data obtainable is illustrated in Fig. XVIII-20, which shows a portion of the infrared spectrum of pyridine adsorbed on a Mo(IV)-Al203 catalyst. In the presence of some surface water both Lewis and Brpnsted types of adsorbed pyridine are seen, as marked in the figure. Thus the features at 1450 and 1620 cm are attributed to pyridine bound to Lewis acid sites, while those at 1540 

A new dimension to acid-base systems has been developed with the use of zeolites. As illustrated in Fig. XVIII-21, the alumino-silicate faujasite has an open structure of interconnected cavities. By exchanging for alkali metal (or NH4 and then driving off ammonia), acid zeolites can be obtained whose acidity is comparable to that of sulfuric acid and having excellent catalytic properties (see Section XVIII-9D). Using spectral shifts, zeolites can be put on a relative acidity scale [195]. An important added feature is that the size of the channels and cavities, which can be controlled, gives selectivity in that only 

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Weltin, E. Galculating Equilibrium Goncentrations for Stepwise Binding of Ligands and Polyprotic Acid-Base Systems, ... 

Fig. 23. Representative protecting groups for phenolic and carboxylic acid-based systems, (a) The polymer-based protecting groups are fisted in order of increasing activation energy for acid-catalyzed deprotection, (b) Acid-labile monomeric dissolution inhibitors, a bifunctional system based on protected bisphenol A. (c) Another system that combines the function of dissolution inhibitor and PAG in a single unit.

Phosphoric Acid-Based Systems for Cellulosics. Semidurable flame-retardant treatments for cotton (qv) or wood (qv) can be attained by phosphorylation of cellulose, preferably in the presence of a nitrogenous compound. Commercial leach-resistant flame-retardant treatments for wood have been developed based on a reaction product of phosphoric acid with urea—formaldehyde and dicyandiamide resins (59,60). 

Scheme VIII has the form of Scheme II, so the relaxation time is given by Eq. (4-15)—appjirently. However, there is a difference between these two schemes in that L in Scheme VIII is also a participant in an acid-base equilibrium. The proton transfer is much more rapid than is the complex formation, so the acid-base system is considered to be at equilibrium throughout the complex formation. The experiment can be carried out by setting the total ligand concentration comparable to the total metal ion concentration, so that the solution is not buffered. As the base form L of the ligand undergoes coordination, the acid-base equilibrium shifts, thus changing the pH. This pH shift is detected by incorporating an acid-base indicator in the solution.

Drago and co-workers have correlated a large body of enthalpies of adduct formation in Lewis acid-base systems, including some solvents as reactants, with this four-parameter equation ... 

C17-0037. Outline the procedure for working an equilibrium problem for a weak acid-base system. 

As in electroanalysis both ionic and possible electrode aspects are of major interest, both aspects of solutes in non-aqueous solvents have to be considered this can best be done by dividing the theory of the solutions concerned into two parts, viz. (1) the exchange of ionic particles (ionotropy), which leads to acid-base systems, and (2) the exchange of electrons only, which leads to redox systems. 

The generalization was based on the introduction of the concept of donor-acceptor pairs into the theory of acids and bases this is a fundamental concept in the general interpretation of chemical reactivity. In the same way as a redox reaction depends on the exchange of electrons between the two species forming the redox system, reactions in an acid-base system also depend on the exchange of a chemically simple species—hydrogen cations, i.e. protons. Such a reaction is thus termed proto lytic. This approach leads to the following definitions ... 

Phosphoric acid-based systems, for cellulosics, 11 488 Phosphoric acid esters, 24 159 Phosphoric acid fuel cells (PAFC), 13 858— 860 12 203-204, 216-219 19 626 effects of carbon monoxide and sulfur in, 12 219... 

Our goal in this chapter is to help you understand the equilibrium systems involving acids and bases. If you don t recall the Arrhenius acid-base theory, refer to Chapter 4 on Aqueous Solutions. You will learn a couple of other acid-base theories, the concept of pH, and will apply those basic equilibrium techniques we covered in Chapter 14 to acid-base systems. In addition, you will need to be familiar with the log and 10 functions of your calculator. And, as usual, in order to do well you must Practice, Practice, Practice. 

We have referred to the influence of hydrogen bonding in one-component systems and mentioned the two-component system benzoic acid-pyridine (108). A variety of acid-base systems in addition to the latter are known to give 1 1 complexes. Pfeiffer gives in his book (88) a wealth of information from the older literature on such complexes, as well as on two-component organic-inorganic systems and charge-transfer complexes. 

Lewis acid-base systems lone-pair interaction in, 16 100 PES of, 16 94... 

All these electrolytes are neutral in Bronsted acid-base properties. Although rather exceptional, an acid, a base, or a pH buffer may be added to the supporting electrolyte of neutral salts. The acid-base system to be selected depends on the purpose of the measurement. We often use trifluoromethanesulfonic acid (CF3S03F1) as a strong acid acetic acid, benzoic acid, or phenol as a weak acid an amine or pyridine as a weak base and tetraalkylammonium hydroxide (ILtNOH) as a strong base. Examples of buffer systems are the mixtures of picric acid and its R4N-salt and amines and their PlCl04-salts. Here, we should note that the acid-base reactions in aprotic solvents considerably differ from those in water, as discussed in Chapter 3. 

The use.of the terms "acids" and "bases") 8)G.B.L.Smith, "Acid-Base System" in Kirk Othmer, 1( 1947), 128-137 9)R.P.Bell, "Acids and Bases. Their Quantitative Behavior,"Wiley,NY(1952) 10)R.P. Bell, Acid-Base Catalysis and Molecular Structure, 151-210 in "Advances in Catalysis" 4, Academic Press,NY(1952)... 

The general treatment of acid-base systems begins with charge and mass balances and equilibrium expressions. There should be as many independent equations as chemical species. Substitute a frac-... 

Ion pairing in acid-base systems. This problem incorporates ion-pair equilibria 13-12 and 13-13 into the acid-base chemistry of Section 13-1. 

The most effective buffering system contains equal concentrations of the acid, HA, and its conjugate base, A-. According to the Henderson-Hasselbalch equation (2.6), when [A-] is equal to [HA], pH equals pKa. Therefore, the pKa of a weak acid-base system represents the center of the buffering region. The effective range of a buffer system is generally two pH units, centered at the pKa value (Equation 2.9). 

The logarithmic form lends itself to graphical presentation. For example, in a system containing a number of acid-base systems of known total concentrations, the concentration of each individual species is a unique function of the master variable log [H ], which may be represented in a logarithmic diagram. In Figure 1, for a system with total phosphate... 

The base used may be hydroxide, alkoxide, carbonate, alkyl lithium, or alumina (13, 20, 24, 41, 49). The reaction is the reverse of the vinylidene synthesis by protonation of the n-acetylide, and the two complexes form a simple acid-base system. For the iron complexes in Eq. (2), the pK has been measured at 7.78 (in 2 1 thf-H20) (24). 

Perfluoroalkanesulfonic Acid-Based Systems. CnFn+1S03H-... 

Figure 2.12. Hq acidity function values for various perfluoroalkanesulfonic acid-based systems. (0)CF3S03H-SbF5 (ref. 14) (+)C4F9S03H-SbF5 (ref. 14) ( )CF3S03H(CF3S03)3B (ref. 84).

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