Bronsted-Lowry acid-base

The species shown in red, HB and HA, act as Bronsted-Lowry acids in the forward and reverse reactions, respectively A and B (blue) act as Bronsted-Lowry bases. (We will use this color coding consistently throughout the chapter in writing Bronsted-Lowry acid-base equations.)... 

Preparation of the alkynide anion involves simple Bronsted-Lowry acid-base chemistry. 

In the Bronsted—Lowry acid—base theory, there is competition for an H+. Consider the acid—base reaction between acetic acid, a weak acid, and ammonia, a weak base ... 

Under the Bronsted-Lowry acid-base theory, acids are proton (H+) donors and bases are proton acceptors. 

This is a classic Bronsted-Lowry acid-base pair. Water (H2O) loses a proton to ammonia (NH3), forming a hydroxide anion. This makes water the proton... 

O Jamie L. Adcock, "Teaching Bronsted-Lowry Acid-Base Theory in a Direct Comprehensive Way," /. Chem. Educ., Vol. 78,2001, 1495-1496. 

It follows from this equation that the products of a Bronsted-Lowry acid-base reaction, BH+ and A-, are themselves acids and bases. The species BH+ produced when the base B accepts a proton from HA can itself donate a proton back to A-, meaning that it is a Bronsted-Lowry acid. Similarly, the species A- produced when HA loses a proton can itself accept a proton back from BH+, meaning that it is a Bronsted-Lowry base. Chemical species whose formulas differ only by one... 

For the following reaction in aqueous solution, identify the Bronsted-Lowry acids, bases, and conjugate acid-base pairs ... 

The second reactant is HF, and the first product is its conjugate base F -. The second product is H2S, and the first reactant is its conjugate base HS-. Therefore, the Bronsted-Lowry acids, bases, and conjugate acid-base pairs are as follows ... 

Related ammonium salts derived from amines, such as [CH3NH3]C1, [(CH3)2NH2]C1, and [(CH3)3NH]C1, also give acidic solutions because they too have cations with at least one dissociable proton. The pH of a solution that contains an acidic cation can be calculated by the standard procedure outlined in Figure 15.7. For a 0.10 M NH4C1 solution, the pH is 5.12. Although the reaction of a cation or anion of a salt with water to produce H30+ or OH - ions is sometimes called a salt hydrolysis reaction, there is no fundamental difference between a salt hydrolysis reaction and any other Bronsted-Lowry acid-base reaction. 

Bronsted-Lowry acid-base reactions always result in the transfer of a proton from an acid to a base. 

Problem 6.15 Draw an energy diagram for the Bronsted-Lowry acid-base reaction of CH3CO2H with "OCICHglg to form CH3CO2" and (CHglgCOH. Label the axes, starting materials, products, AH°, and Eg. Draw the structure of the transition state. 

Preparation of alkoxides—A Bronsted-Lowry acid-base reaction... 

Treatment of indene with NaNH2 forms its conjugate base in a Bronsted-Lowry acid-base reaction. Draw aii reasonable resonance structures for indene s conjugate base, and explain why the pKa of indene is lower than the pK of most hydrocarbons. 

A broader definition of acids and bases, which will be useful in quantitative calculations in this chapter, was proposed independently by Johannes Bronsted and Thomas Lowry in 1923. A Brensted-Lowry acid is defined as a substance that can donate a hydrogen ion, and a Bronsted-Lowry base is a substance that can accept a hydrogen ion. In a Bronsted-Lowry acid-base reaction, hydrogen ions are transferred from the acid to the base. When acetic acid is dissolved in water,... 

Most of the acids considered up to now have been uncharged species with the general formula HA. In the Bronsted-Lowry picture there is no reason why the acid should be an electrically neutral molecule. When NH4CI, a salt, dissolves in water, NH4 ions are present. These ionize partially by transferring hydrogen ions to water, a straightforward Bronsted-Lowry acid-base reaction ... 

The alkylammonium cation is called the conjugate acid of the amine. Write down the general equation for a Bronsted-Lowry acid/base reaction, labelling the acid and the base, and the related conjugate base and acid. 

The nucleophile, the ammonia molecule, is also acting as a base, while the electrophile, the proton, is also acting as an acid. So a base may also be thought of as a nucleophile, because both are electron rich species and seek positive centres. The above reaction between the ammonia and the proton may be classified as a Bronsted-Lowry acid/base reaction. It may also be classed as a Lewis acid/base reaction, depending on whether one views the ammonia as a proton acceptor or as a donor of a lone pair of electrons. 

Nucleophiles with a high charge density, such as hydroxide ions, tend to react more readily with electrophiles with a high charge density, such as protons. Thus, hard nucleophiles tend to react with hard electrophiles. The reaction of a hydroxide ion with a proton is also typical of a Bronsted-Lowry acid/base reaction. 

In this case, the hard hydroxide anion has removed the hard proton on the hydroxyl group to form an alkoxide ion in a simple Bronsted-Lowry acid/base reaction. Suggest what is the next step in this reaction, remembering that overall there is retention of the stereochemistry at the carbon bonded to the chlorine atom. 

Some important reaction types not shown here are redox, combustion, Bronsted-Lowry acid-base, and Lewis acid-base. We will cover these types later in this book. Reaction types are not mutually exclusive, so one reaction can fall into more than one type. 

For a Bronsted-Lowry acid-base conjugate pair, the stronger the conjugate acid, the weaker the conjugate base. 

We can describe Bronsted-Lowry acid-base reactions in terms of conjugate acid-base pairs. These are two species that differ by a proton. In the preceding equation, HF (acid2) and (basc2) are one conjugate acid-base pair, and H2O (bascj) and H30 (acidj) are the other pair. The members of each conjugate pair are designated by the same numerical subscript. In the forward reaction, HF and H2O act as acid and base, respectively. In the reverse reaction, H30 acts as the acid, or proton donor, and F acts as the base, or proton acceptor. 

Arrhenius and Bronsted-Lowry acid-base neutralization reactions all have one thing in common. They involve the reaction of an acid with a base to form a salt that contains the cation characteristic of the base and the anion characteristic of the acid. Water is also usually formed. This is indicated in the formula unit equation. The general form of the net ionic equation, however, is different for different acid-base reactions. The net ionic equations depend on the solubility and extent of ionization or dissociation of each reactant and product. 

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. 

Bronsted-Lowry acid-base reaction A chemical reaction in which a proton, H" ", is transferred. 

Bronsted-Lowry Acid A substance that donates protons, H, in a Bronsted-Lowry acid-base reaction. 

Given a Bronsted-Lowry acid-base equation, identify the Bronsted-Lowry acid and Bronsted-Lowry base. 

The position is similar in basic catalysis. The hydroxyl ion has no strong claims to uniqueness, being merely the anion of a weak acid. According to the Bronsted-Lowry acid-base definition, a base is any species which has a tendency to accept a proton. This obviously includes anions like OH-, CH3COO, HPCL , as well as uncharged basic molecules like ammonia and the amines. Catalysis by all these species was first found in the decomposition of nitramide (Bronsted and Pedersen, 15), and subsequently in many other reactions. 

In the Bronsted-Lowry acid-base definition, a base is any species that... 

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