Brensted-Lowry acid

I Table 13.4 Relative Strengths of Brensted-Lowry Acids and Bases ... 

Amphiprotic species Capable of acting as either a Brensted-Lowry acid or base, 354,372-373,623... 

The strength of a Brensted-Lowry acid is quantified in terms of the magnitude of the equilibrium constant for the ionization reaction in which the solvent acts as the base, e.g. for the aqueous system, the general reaction is ... 

Brensted-Lowry acid proton donor Bronsted-Lowry base proton acceptor J. N. Bronsted of the University of Copenhagen published his definition of acids and bases in 1923. 

Brensted-Lowry Acids and Bases and Conjugate Pairs Lewis Acids and Bases Titration and Neutralization Hydrolysis... 

Like Other Brensted-Lowry acids discussed in Section Z7, carbo) acids dissociate sligblly in dilute aqueous solution to ve H ,0 and boxy late anions, RCO. The exact, extent of dissociation is given by an ity constant. A ... 

A Brensted-Lowry acid is a substance that donates a hydrogen ion (H ), and a Brensted-Lowry base is a substance that accepts H. (The name proton is often used as a synonym for H because loss of the valence electron from a neutral hydrogen atom leaves only the hydrogen nucleus— a proton.) When gaseous hydrogen chloride dissolves in water, for example, an acid-base reaction occurs. A polar HCl molecule donates a proton, and a water molecule accepts the proton, )rielding hydronium ion (HjO ) and chloride ion (Cl ). 

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,... 

Figure 18.8 Proton transfer as the essential feature of a Brensted-Lowry acid-base reaction. A, When HCl dissolves in water, it acts as an acid by donating a proton to water, which acts as a base by accepting it. B, In aqueous solution, NH3 acts as a base by accepting a proton from water, which acts as an acid by donating it. Thus, in the Bronsted-Lowry sense, an acid-base reaction occurs in both cases.

The Brensted-Lowry acid-base definition does not require that bases contain OH or that acid-base reactions occur in aqueous solution. It defines an acid as a species that donates a proton and a base as one that accepts It. An acid and a base act together in proton transfer. When an acid donates a proton, it becomes the conjugate base when a base accepts a proton, it becomes the conjugate acid. In an acid-base reaction, acids and bases form their conjugates. A stronger acid has a weaker conjugate base, and vice versa. Thus, the reaction proceeds in the net direction in which a stronger acid and base form a weaker base and acid. 

Proton Transfer and the Brensted-Lowry Acid-Base Definition... 

TABLE 6.8 Hydrated Metal Ion Brensted-Lowry Acidities (298 K)... 

We explore the fact that the ions of a soluble ionic compourxt can serve as Brensted-Lowry acids or bases. 

You have reviewed the Bronsted-Lowry definition of acids and bases and the meanings of pH and pTQ. You have learned to identify the most acidic hydrogen atoms in a molecule based on a comparison of pIQ values. You will see in many cases that Brensted—Lowry acid-base reactions either initiate or complete an organic reaction, or prepare an organic molecule for further reaction. The Lewis definition of acids and bases may have been new to you. However, you will see over and over again that Lewis acid—base reactions which involve either the donation of an electron pair to form a new covalent bond or the departure of an electron pair to break a covalent bond are central steps in many organic reactions. The vast majority of organic reactions you will study are either Bronsted-Lowry or Lewis acid—base reactions. 

Earlier we noted a major shortcoming of the Arrhenius acid-base definition many substances that yield OH ions when they dissolve in water do not contain OH in their formulas. Examples include ammonia, the amines, and many salts of weak acids, such as NaF. Another limitation of the Arrhenius definition was that water had to be the solvent for acid-base reactions. In the eariy 20 century, J. N. Br0n-sted and T. M. Lowry suggested definitions that remove these limitations. (Recall that we discussed their ideas briefly in Section 4.4.) According to the Brensted-Lowry acid-base definition,... 

Boyle s law The gas law stating that, at constant temperature and amount of gas, the volume occupied by a gas is inversely proportional to the applied (external) pressure V /p (144) Brensted-Lowry acid-base definition A model of acid-base behavior based on proton transfer, in which an acid and a base are defined, respectively, as species that donate and accept a proton. (587) buffer (See acid-base buffer.)... 

A Figure 16.2 When a proton is transferred from HCl to H2O, HCl acts as the Brensted-Lowry acid and H2O acts as the Brensted-Lowry base. 

Brensted-Lowry acid 95 Brensted-Lowry base 95 cations 125 conjugate acid 95... 

In the Lewis acid-base definition, an acid is any species that accepts a lone pair to form a new bond and yield an adduct therefore, there are many more Lewis acids than Arrhenius or Brensted-Lowry acids. Lewis acids include metal ions and molecules with either electron-deficient atoms or polar multiple bonds. 

The Bronsted-Lowry definitions of acids and bases provide a basis for studying proton-transfer reactions. Suppose that a Bronsted-Lowry acid gives up a proton the remaining ion or molecule can re-accept that proton and can act as a base. Such a base is known as a conjugate base. Thus, the species that remains after a Brensted-Lowry acid has given up a proton is the conjugate base of that acid. For example, the fluoride ion is the conjugate base of hydrofluoric acid. 

Brensted-Lowry acid a substance that donates a proton to another substance dcido de Bronsted-Lowry una... 

Carboxylic acids—Strong organic Brensted-Lowry acids... 

Brensted-Lowry acid (Section 2.7) A substance that donates a hydrogen ion (proton H" ") to a base. 

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