Bransted-Lowry acids

The acidic and basic properties of aqueous solutions are dependent on an equilibrium that involves the solvent, water. The reaction involved can be regarded as a Bransted-Lowry acid-base reaction in which the H20 molecule shows its amphiprotic nature ... 

Arrhenius acid, Bransted-Lowry acid Arrhenius acid, Bransted-Lowry acid Arrhenius base, Bransted-Lowry base Arrhenius acid, Bransted-Lowry acid amphoteric hydroxide (can act as either an acid or base)... 

The acids (proton donors) and bases (proton acceptors) are labeled below their formulas. Remember that a proton, in Bransted-Lowry acid-base theory, is H+. 

Write a balanced net ionic equation for the reaction of each of the following ions with water. In each case, identify the Bransted-Lowry acids and bases and the conjugate acid-base pairs. 

Acid and base behavior can be observed in solvents other than water. One commonly used solvent is dimethyl sulfoxide (DMSO), which can be treated as a monoprotic acid "HSol." Just as water can behave either as an acid or a base, so HSol can behave either as a Bransted-Lowry acid or base. 

Write balanced equations for the reactions of (a) H3PO4 and (b) B(OH)3 with water. Classify each acid as a Bransted-Lowry acid or a Lewis acid. 

Carboxylic acids react as Bransted-Lowry acids— that is, as proton donors. 

A Bransted-Lowry acid-base reac tion... 

Bransted-Lowry acid/acido de Bransted-Lowry... 

Identify the Bransted-Lowry acid, the Bronsted-Lowry base, the conjugate acid, and the conjugate base in this reaction ... 

Bransted-Lowry acid-proton donor Bransted-Lowry base-proton acceptor... 

In this example, the initial products of nucleophilic substitution bear a positive charge. They readily lose a proton to form neutral products. The overall process with a neutral nucleophile thus has three steps the first two constitute the two-step 8 1 mechanism (loss of the leaving group and attack of the nucleophile), and the third Is a Bransted-Lowry acid-base reaction leading to a neutral organic product. 

We will consider more general definitions of acids and bases in Chapter 13 (Bransted-Lowry) and Chapter 15 (Lewis). 

Cations. The ammonium ion, NH,+, behaves as a weak acid in water a 0.10 M solution of NH4CI has a pH of about 5. The process by which the NH4+ ion lowers the pH of water can be represented by the (Bransted-Lowry) equation ... 

A very similar equation can be written to explain why solutions of zinc salts are acidic. Here it appears that the hydrated cation in water solution contains four H20 molecules bonded to a central Zn2+ ion. The Bransted-Lowry equation is... 

A1C13, or S02 in an inert solvent cause colour changes in indicators similar to those produced by hydrochloric acid, and these changes are reversed by bases so that titrations can be carried out. Compounds of the type of BF3 are usually described as Lewis acids or electron acceptors. The Lewis bases (e.g. ammonia, pyridine) are virtually identical with the Bransted-Lowry bases. The great disadvantage of the Lewis definition of acids is that, unlike proton-transfer reactions, it is incapable of general quantitative treatment. 

B) From the foregoing, it is clear that the Arrhenius or solvents theory cannot work for aprotic solvents most adequate here is the Bransted-Lowry or proton theory, in which an acid is defined as a proton donor and a base as a proton acceptor, and under conditions such that the acid by donating its proton is converted into its conjugate base, and the base by accepting a proton is converted into its conjugate acid. This mutual relationship is illustrated by the following equilibrium reaction ... 

When water acts as a Bronsted-Lowry acid, it donates a proton to another species, thereby converting to the hydroxide ion. HjO + H O OH + H3O" base acid conjugate conjugate base acid 1 point given for correct Bransted-Lowry concept of water being able to donate a proton, resulting in a hydroxide ion. 

According to the Arrhenius theory, acids (HA) are substances that dissociate in water to produce H + (aq). Bases (MOH) are substances that dissociate to yield OH aq). The more general Bransted-Lowry theory defines an acid as a proton donor, a base as a proton acceptor, and an acid-base reaction as a proton-transfer reaction. Examples of Bronsted-Lowry acids are HC1, NH4+, and HSO4- examples of Bronsted-Lowry bases are OH-, F-, and NH3. 

In the Bransted-Lowry theory, every acid-base reaction creates its conjugate acid-base pair. In the above reaction HCl is an acid which, after giving up a proton, becomes a conjugate base, Cl . Similarly, water is a base which, after accepting a proton, becomes a conjugate acid, the hydronium ion. 

Some acids can give up only one proton. These are monoprotic acids. Examples are (H)C1,(H)N03, HCOO , and CH3COO(H). The hydrogens circled are the ones donated. Other acids yield two or three protons. These are called diprotic or triprotic acids. Examples are H2S04, H2C03, and H3P04. However, in the Bransted-Lowry theory, each acid is considered monoprotic, and a diprotic acid (such as carbonic acid) donates its protons in two distinct steps ... 

This reaction is essentially an acid-base process, which is most conveniently explained in terms of the Bransted-Lowry theory of acids and bases (see Section 1.23). 

Acids are compounds that ionise to release hydrogen ions, or protons, to their surroundings. Bases are compounds that can accept hydrogen ions. This is called the Bransted-Lowry definition of acids and bases (named after yet another Scandinavian chemist, Johannes Nicolaus Bronsted, and Thomas Martin Lowry, who was British). There are other ways of explaining acidity and basicity, but the Bransted-Lowry theory works most of the time, and will be used throughout this book. 

The Bransted-Lowry concept of acids and bases will be discussed in detail in Chapter 7. 

We then learn the more general Bransted-Loivry definitions for acid and base. A Bronsted-Lowry acid is a proton donor and a Bronsted—Lowry base is a proton acceptor. 

The Bransted-Lowry Theory of Acids and Bases COAL 2 Given the equation for a Br0nsted-Lowry acid-base reaction, explain how or why it can be so classified. 

Section 17.2 The Bransted-Lowry Theory of Acids and Bases... 

These compounds are both Bransted-Lowry adds and Lewis acids. 

In equations (5.11) and (5.12), the acid molecules are acting as proton donors and the water molecules are acting as proton acceptors. Accoring to the Bransted-Lowry theory, an acid is a proton donor. 

Describe an acid-base reaction in the context of Bransted-Lowry theory, and identify conjugate acid-base pairs. 

In 1923, the same year that Bransted and Lowry came up with their idea of what acids and bases were, an American chemist named Gilbert Newton Lewis began to work on his own acid-base theory. Lewis defined acid as any substance that accepted an electron pair. A base, on the other hand, is any substance that donates an electron pair. 

Earlier in this chapter we considered Arrhenius s concept of acids and bases An acid is a substance that produces H+ ions when dissolved in water, and a base is a substance that produces OH- ions. Although these ideas are fundamentally correct, it is convenient to have a more general definition of a base, which covers substances that do not produce OH- ions. Such a definition was provided by Bransted and Lowry, who defined acids and bases as follows ... 

What is the Lowry-Bransted acid in (a) HCl dissolved in water (b) HCI (unionized) dissolved in benzene (c) Which solutionis the more strongly acidic ... 

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