Bases table Bronsted-Lowry

Table 8.3 lists the base dissociation constants for several weak bases at 25°C. Nitrogen-containing compounds are Bronsted-Lowry bases, because the lone pair of electrons on a nitrogen atom can bond with H+ from water. The steps for solving problems that involve weak bases are similar to the steps you learned for solving problems that involve weak acids. 

Lewis defined a base as an electron pair donor and an acid as an electron pair acceptor. Lewis electron pair donor was the same as Bronsted-Lowry s proton acceptor, and therefore, was an equivalent way of defining a base. Lewis acids were defined as a substance with an empty valence shell that could accommodate a pair of electrons. This definition broadened the Bronsted-Lowry definition of an acid. The three definitions of acids and bases are summarized in Table 13.3. 

You no doubt noticed that some of the bases in Table 16-1 don t contain a hydroxide ion, which means that the Arrhenius definition of acids and bases can t apply. When chemists realized that several substances behaved like bases but didn t contain a hydroxide ion, they reluctantly acknowledged that another determination method was needed. Independently proposed by Johannes Bronsted and Thomas Lowry in 1923 and therefore named cifter both of them, the Bronsted-Lowry method for determining acids and bases accounts for those pesky non-hydroxide-containing bases. 

A Bronsted-Lowry acid is any substance that is capable of donating a proton, whereas a Bronsted-Lowry base is any substance that is capable of accepting a proton. The loss of a proton by an acid gives rise to an entity that is a potential proton acceptor and thus a base it is called the conjugate base of the parent acid. Examples of acids reacting with bases are given in Table 1.16. The reactions listed in Table 1.16 are spontaneous in the direction that favors production of the weaker acid and base. Compounds that may act as bases and acids are referred to as amphoteric. 

Although the Arrhenius definitions of acid, base, and acid-base reaction are very useful, an alternate set of definitions is also commonly employed. In this system, a Bronsted-Lowry acid is a proton (H+) donor, a Bronsted-Lowry base is a proton acceptor, and a Bronsted-Lowry acid-base reaction is a proton transfer. Table 5.7 summarizes the definitions of acid and base in the Arrhenius and Bronsted-Lowry systems. 

Note that the SO3 molecule, a Lewis acid, accepts an electron pair from the ion, a Lewis base. The Arrhenius, Bronsted-Lowry, and Lewis acid-base models are summarized in Table 18-2. 

Solvent effects are not limited to polarity. Solvent molecules may act as electron pair donors or acceptors, as evidenced by the formation of charge transfer complexes or by the participation of solvent molecules as nucleophiles or electrophiles (Lewis bases or acids) in reactions. Solvent molecules may also behave as acids or bases in the Bronsted—Lowry sense, and they may play important roles in reactions by serving as hydrogen bond donors or acceptors. Kamlet, Taft, and co-workers also developed the parameter a as a measure of the ability of solvent to act as a proton donor in a solvent—solute hydrogen bond and the parameter j8 to describe the ability of solvent to act as a proton acceptor in a solvent-solute hydrogen bond. A compilation of e, IX, Z, Et(30), n, /3, and a values for selected solvents is given in Table 6.1. ... 

In Ghapter 3 we present the first of many A Mechanism for the Reaction boxes, using an example that embodies both Bronsted-Lowry and Lewis acid-base principles. All throughout the book, we use boxes like these to show the details of key reaction mechanisms. All of the Mechanism for the Reaction boxes are listed in the Table of Gontents so that students can easily refer to them when desired. 

Before the introduction of the Bronsted-Lowry theory, many reactions actually involving transfer of a proton were thought to be unique, and were given specific names. Several typical acid-base reactions are listed in Table 13.2 to emphasize their similarity, not to encourage their commitment to memory. 

Table 12.6 Important Bronsted-Lowry Bases Other than Hydroxides...

Look at Table 21.2. For the following acids or ions (shown in the left-hand column) work out which species in the equilibrium are Bronsted-Lowry acids and which are their conjugate bases hydrated Fe ion nitric(lll) (acid) ii carbonic (acid)... 

TABLE 13.4 Relative Strengths of Bronsted-Lowry Acids and Bases... 

The weak bases listed in Table 16.4 all contain an N atom. Not all weak bases contain an N atom, yet so many of them do that it worth noting the following points. For these weak bases, it is the N atom that is protonated when the base reacts with a Bronsted-Lowry acid. The protonation of the N atom is illustrated below for the ionization of CH3NH2 in water. 

The Bronsted-Lowry theory can be applied to acid-base reactions in nonaqueous solvents, where the relative strengths of acids and bases can differ from what they are in aqueous solutions. Indicate whether each of the following would be an acid, a base, or amphiprotic in pure liquid acetic acid, CH3COOH, as a solvent, (a) CHsCOO" (b) H2O (c) CH3COOH (d) HCIO4. [Hint Refer to Table 16.2.]... 

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