Acids Br0nsted-Lowry

Terms to Understand acid Br0nsted-Lowry base entropy overall formation constant... 

Brpnsted-Lowry acid Br0nsted-Lowry base conjugate acid conjugate base acidity constant Ka pKa organic acid organic base Lewis acid Lewis base... 

In the Br0nsted-Lowry view an acid doesn t dissociate in water it transfers a pro ton to water Water acts as a base... 

The Br0nsted-Lowry approach to acids and bases is more generally use ful than the Arrhenius approach... 

The Lewis definitions of acids and bases provide for a more general view of acid-base reactions than either the Arrhenius or Br0nsted-Lowry pic ture A Lewis acid is an electron pair acceptor A Lewis base is an electron pair donor The Lewis approach incorporates the Br0nsted-Lowry approach as a subcategory m which the atom that accepts the electron pair m the Lewis acid is a proton... 

Achiral (Section 7 1) Opposite of chiral An achiral object is supenmposable on its mirror image Acid According to the Arrhenius definition (Section 1 12) a substance that ionizes in water to produce protons Accord mg to the Br0nsted-Lowry definition (Section 1 13) a sub stance that donates a proton to some other substance According to the Lewis definition (Section 1 17) an electron pair acceptor... 

The acid dissociation constant has the same fonn in Br0nsted-Lowry as in the Aiihenius approach, but is expressed in the concentration of H30" rather than H". The concentration temns [H30 j and [H" ] are considered equivalent quantities in equilibrium constant expressions. 

A Br0nsted-Lowry base is to a hydrogen-ion acceptor as a Brpnsted-Lowry acid is to —... 

Although the concepts of specific acid and specific base catalysis were useful in the analysis of some early kinetic data, it soon became apparent that any species that could effect a proton transfer with the substrate could exert a catalytic influence on the reaction rate. Consequently, it became desirable to employ the more general Br0nsted-Lowry definition of acids and bases and to write the reaction rate constant as... 

Although many other acid-base definitions have been proposed and have been useful in particular types of reactions, only a few have been widely adopted for general use. Among them are those attributed to Arrhenius (based on hydrogen and hydroxide ion formation), Br0nsted-Lowry (hydrogen ion donors and acceptors), and Lewis (electron pair donors and acceptors) [6,67-70]. 

Acid-base reactions concepts of Arrhenius, Br0nsted-Lowry, and Lewis coordination complexes, amphoterism... 

All Br0nsted-Lowry acids are Lewis acids, but in practice, the term Lewis acid is generally reserved for Lewis acids that don t also fit the Bronsted-Lowry definition. The best way to spot a Lewis acid-base pair is to draw a Lewis dot structure of the reacting substances, noting the presence of lone pairs of electrons. (We introduce Lewis structures in Chapter 5.) For example, consider the reaction between ammonia (NH3) and boron trifluoride (BFj) ... 

According to the Br0nsted-Lowry definitions, any species that contains hydrogen can potentially act as an acid, and any compound that contains a lone pair of electrons can act as a base. Therefore, neutral molecules can also act as bases if they contain an oxygen, nitrogen or sulphur atom. Both an acid and a base must be present in a proton transfer reaction, because an acid cannot donate a proton unless a base is present to accept it. Thus, proton-transfer reactions are often called acid-base reactions. 

Brpnsted-Lowry acids are proton donors, and Br0nsted-Lowry bases are proton acceptors. An acid increases the concentration of H,0+ in aqueous solution, and a base increases the concentration of OH. An acid-base pair related through the gain or loss of a single proton is described as conjugate. When a proton is transferred... 

Zeolites may behave as Lewis acids at Al,+ sites, or as Br0nsted-Lowry acids by means of absorbed H+ ions. Because they have relatively open structures, a variety of small molecules may be accommodated within the —O—Al—O—Si— framework. These molecules may then be catalyzed to react by the acidic centers. Coordinatively, unsaturated oxide ions can act as basic sites, and in some catalytic reactions both types of centers are believed to be important. Catalysis by zeolites is discussed further in Chapter 15. 

The usefulness of the Br0nsted-Lowry definition lies in its ability to handle any protonic solvent such as liquid ammonia or sulfuric acid ... 

Use the Lewis definition of acids and truces to explain the examples given tor the Br0nsted-Lowry, Lux-Flood, and solvent system definitions (Eqs 9.1-9.4, 9.S-9.8, 9 9-9.361. 

Acids and bases are defined in accordance with Br0nsted-Lowry theory in terms of their propensity to donate or accept hydrated protons in aqueous... 

A more general theory of acids and bases was devised independently by Johannes Br0n-sted (Denmark) and Thomas M. Lowry (England) in 1923. In the Br0nsted-Lowry approach, an acid is a proton donor, and a base is a proton acceptor. The reaction that occurs between an acid and a base is proton transfer. 

This is a very useful relationship. You should practice writing equations according to the Br0nsted-Lowry definitions of acids and bases and familiarize yourself with Table 1.7 which gives the pXa s of various Brpn-sted acids. 

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