Many Processes in Chemistry Are Acid-Base Reactions

1 I Many Processes in Chemistry Are Acid-Base Reactions 

Common acids and bases include aspirin (acetylsalicylic acid) and milk of magnesia (magnesium hydroxide). Besides providing the basis of many medicinal and household products, though, acid-base chemistry is important in industrial processes and essential in sustaining biological systems. Before we can discuss acid-base reactions, we need to know more about acids and bases themselves. 

The first definitions of acids and bases were formulated in the late nineteenth century by the Swedish chemist Svante Arrhenius. According to Arrhenius, an acid is a substance that yields hydrogen ions (H ) when dissolved in water. For example, HCl fits the Arrhenius definition of an acid because, when dissolved in water, HCl dissociates into R (aq) and Cr(fl )  

Arrhenius defined a base, on the other hand, as a substance that yields hydroxide ions (OH ) when dissolved in water. For example, when sodium hydroxide is dissolved in water, it dissociates into Na (ag) and OH (a ) 

In contrast, bases have the following characteristic properties  

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Lewis acid-base reactions in which a metal cation combines with a Lewis base result in the formation of complex ions. Thus, we can define a complex ion as an ion containing a central metal cation bonded to one or more molecules or ions. Complex ions are crucial to many chemical and biological processes. Here we will consider the effect of complex ion formation on solubihty. In Chapter 22 we will discuss the chemistry of complex ions in more detail. 

Proton-transfer reactions are among the most common of all reaction types. Although the transfer of a proton is a very simple particulate-level process, its macroscopic applications are countless. You will learn about many additional acid-base reactions throughout your studies in biology and chemistry. 

We shall also see that such apparently unrelated processes as oxidation of fuels, respiration, and photosynthesis are actually all closely related, for in each of them an electron, sometimes accompanied by a group of atoms, is transferred from one species to another. Indeed, together with the proton transfer typical of acid-base reactions, processes in which electrons are transferred, the so-called redox reactions, account for many of the reactions encountered in chemistry and biology. 

I he present review deals with the state of the art of this important type of Catalysis. gi ing almost. M)() references on the topic. It focuses on ba.se catalysis mainly, though acid-ba.se bifiinctional catalysis is also briclly discussed. A classification ofbase catalysts depending on their composition is given together with some of the test reactions for base characieri/ation of solids. Moreover, many applications in Fine Chemistry processes arc discussed. I inally. some of the facts that, to our mind, will contribute to further development iti base catalysis are mentioned. 

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