Brpnsted-Lowry acidity

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

When water acts as a Brpnsted-Lowry acid, it donates a proton to another species, thereby converting to the hydroxide ion. 

The hydrogen ion accepts the lone pair of electrons from the ammonia to form the ammonium ion. The hydrogen ion, because it accepts a pair of electrons, is the Lewis acid. The ammonia, because it donates a pair of electrons, is the Lewis base. This reaction is also a Brpnsted-Lowry acid-base reaction. This illustrates that a substance may be an acid or a base by more than one definition. All Brpnsted-Lowry acids are Lewis acids, and all Brpnsted-Lowry bases are Lewis bases. However, the reverse is not necessarily true. 

What is the value of when water acts as a Brpnsted-Lowry acid Write the expression for if water acts as a diprotic acid. 

The carboxylic acids, like all Brpnsted-Lowry acids, can lose a hydrogen ion. The result is a carboxylate ion, shown in Figure 9-4. 

In this reaction, hydrochloric acid (HCl) donates a proton to water (H2O), making it the Brpnsted-Lowry acid. Water, which accepts the proton, is the Bronsted-Lowry base. This makes hydronium (H3O+) the conjugate acid and chloride (Cl ) the conjugate base. Water can act as the base in this reaction and as an acid in the example problem because it s composed of both a hydrogen ion and a hydroxide ion therefore, it can either accept or donate a proton. 

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... 

Distinguish Lewis acids and bases from Brpnsted-Lowry acids and bases. Give an example of each. 

Identify the Brpnsted-Lowry acids among the reactants in the following reactions ... 

Brpnsted-Lowry acid A proton (hydrogen ion) donor. 

In 1923, Brpnsted and Lowry defined acids and bases on the basis of the transfer of protons. A Brpnsted-Lowry acid is any species that can donate a proton, and a Brpnsted-Lowry base is any species that can accept a proton. These definitions also include all the Arrhenius acids and bases because compounds that dissociate to give H30+ are proton donors, and compounds that dissociate to give OH are proton acceptors. (Hydroxide ion accepts a proton to form H20.)... 

The strength of a Brpnsted-Lowry acid is expressed as it is in the Arrhenius definition, by the extent of its ionization in water. The general reaction of an acid (HA) with water is the following ... 

How can we look at a structure and predict whether a compound will be a strong acid, a weak acid, or not an acid at all To be a Brpnsted-Lowry acid (HA), a compound must contain a hydrogen atom that can be lost as a proton. A strong acid must have a stable conjugate base (A ) after losing the proton. 

Some of the terms associated with acids and bases have evolved specific meanings in organic chemistry. When organic chemists use the term base, they usually mean a proton acceptor (a Brpnsted-Lowry base). Similarly, the term acid usually means a proton donor (a Brpnsted-Lowry acid). When the acid-base reaction involves formation of a bond to some other element (especially carbon), organic chemists refer to the electron donor as a nucleophile (Lewis base) and the electron acceptor as an electrophile (Lewis acid). 

In this case, no proton has been transferred, so this is not a Brpnsted-Lowry acid-base reaction. Instead, a bond has formed between the C = 0 carbon atom and the oxygen of the CH3—O group. Drawing the Lewis structures helps to show that the CH3—O group (the nucleophile in this reaction) donates the electrons to form the new bond to acetaldehyde (the electrophile). This result agrees with our intuition that a negatively charged ion is likely to be electron-rich and therefore an electron donor. 

Hydrogen bromide provides the proton, so it is the Brpnsted-Lowry acid in the reaction. Water receives the proton, so it is the Brpnsted-Lowry base. The conjugate acid-base pairs are HBr/Br and H20/H30+. 

BECAUSE a conjugate base is formed once a Brpnsted-Lowry acid accepts a proton. 

A Brpnsted-Lowry acid donates an H+ ion a Br0nsted-Lowry base accepts H+. 

Reactions (a) and (c) are reactions between Brpnsted-Lowry acids and bases the stronger acid and stronger base are identified. Reactions (b) and (d) occur between Lewis acids and bases. 

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

A Br0nsted-Lowry acid must contain a hydrogen atom. This definition of an acid is often familiar to students, because many inorganic acids in general chemistry are Brpnsted-Lowry acids. The symbol H-A is used for a general Br0nsted-Lowry acid. 

Examples of Brpnsted-Lowry acids and bases are given in Figure 2.1. 

Acidity is measured by an equilibrium constant. When a Brpnsted-Lowry acid H- A is dissolved in water, an acid-base reaction occurs, and an equilibrium constant can be written for the reaction. 

A Lewis acid must be able to accept an electron pair, but there are many ways for this to occur. All Brpnsted-Lowry acids are also Lewis acids, but the reverse is not necessarily true. Any... 

Furthermore, when the substitution product bears a positive charge and also contains a proton bonded to O or N, the initial substitution product readily loses a proton in a Brpnsted-Lowry acid-base reaction, forming a neutral product. 

A hydroxide nucleophile is needed to synthesize an alcohol, and salts such as NaOH and KOH are inexpensive and commercially available. An alkoxide salt is needed to make an ether. Simple alkoxides such as sodium methoxide (NaOCH3) can be purchased, but others are prepared from alcohols by a Brpnsted-Lowry acid-base reaction. For example, sodium ethoxide (NaOCH2CH3) is prepared by treating ethanol with NaH. 

The cyclopentadienyl anion is readily formed from cyclopentadiene by a Brpnsted-Lowry acid-base reaction. 

Proton transfer reaction (Section 2.2) A Brpnsted-Lowry acid-base reaction a reaction that results in the transfer of a proton from an acid to a base. 

In 1923, the Danish chemist Johannes Brpnsted proposed a broader definition of acid. Surprisingly, the same year, the British scientist Thomas Lowry happened to make exactly the same proposal independently. Their idea was to apply the name acid to any species that can donate a proton. Recall that a proton is a hydrogen atom that has lost its electron it is a hydrogen ion and can be represented as Ht Such molecules or ions are now called Brunsted-Lowry acids. A reaction showing hydrochloric acid, a representative Brpnsted-Lowry acid, is depicted in Figure 7. 

The reaction shows HCl acting as an Arrhenius acid, forming a hydro-nium ion. Because the reaction also involves a proton transfer, hydrochloric acid is also a Brpnsted-Lowry acid. All Arrhenius acids are, by definition, also Brpnsted-Lowry acids. 

Every Brpnsted-Lowry acid has a conjugate base, and every Brpnsted-Lowry base has a conjugate acid. Table 3 lists many such acid-base pairs. 

When ammonia dissolves in water, water is a Brpnsted-Lowry acid in the forward reachon. Because the NH3 molecule accepts a H+ ion to form the ammonium ion (NH4+), ammonia is a Brpnsted-Lowry base in the forward reachon. 

Now look at the reverse reachon. The ammoiuum ion gives up a H+ ion to form the molecule ammoiha and thus acts as a Brpnsted-Lowry acid. The ammonium ion is the conjugate acid of the base ammonia. The hydroxide ion accepts a H+ ion to form a water molecule and is thus a Brpnsted-Lowry base. The hydroxide ion is the conjugate base of the acid water. 

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