Strong bases acid-base reactions

As long as one of the reactants is strong, the acid-base reaction goes to completion. As you learned in Chapter 6, a reaction goes to completion when the limiting reactant is completely consumed. 

Step 3 Take a proton away. Proton transfer between the carboiyl group and the alkoxide ion gives the carboxylate anion. This strongly exothermic acid-base reaction drives the whole reaction to completion. 

N,N,N, N -tetramethyl-l,8,-naph-thalenediamiDe M.P. 51 C. A remarkably strong mono-acidic base (pKg 12-3) which is almost completely non-nucleophilic and valuable for promoting organic elimination reactions (e.g. of alkyl halides to alkenes) without substitution. 

This is an acid-base reaction, in which the base is the oxide ion (p. 89) the acidic oxide SiOj displaces the weaker acidic oxide CO2 in the fused mixture. But in aqueous solution, where the 0 ion cannot function as a strong basefp. 89),carbon dioxide displaces silica, which, therefore, precipitates when the gas is passed through the aqueous silicate solution. In a fused mixture of silica and a nitrate or phosphate, the silica again displaces the weaker acidic oxides N2O5 and P4OJ0 ... 

Consider first the case of adding a strong acid such as HBr to water The equation for the Brpnsted acid-base reaction that occurs between them is... 

In an acid-base reaction, the reaction unit is the proton. For an acid, the number of reaction units is given by the number of protons that can be donated to the base and for a base, the number of reaction units is the number of protons that the base can accept from the acid. In the reaction between H3PO4 and NaOH, for example, the weak acid H3PO4 can donate all three of its protons to NaOH, whereas the strong base NaOH can accept one proton. Thus, we write... 

This type of cement has been further improved by the substitution of -hexyl van ill ate [84375-71-3] and similar esters of vanillic acid [121 -34-6] and/or syringic acid [530-57 ] for eugenol (93—95). These substituted cements are strong, resistant to dissolution, and, unlike ZOE and EBA cements, do not inhibit the polymerization of resin-base materials. Noneugenol cements based on the acid—base reaction of zinc and similar oxides with carboxyhc acids have been investigated, and several promising types have been developed based on dimer and trimer acids (82). 

Step 3 is new to us. It is an acid-base reaction in which the carbocation acts as a Br0n-sted acid, transferiing a proton to a Brpnsted base (water). This is the property of carbocations that is of the most significance to elimination reactions. Car bocations ar e strong acids they are the conjugate acids of alkenes and readily lose a proton to form alkenes. Even weak bases such as water are sufficiently basic to abstract a proton from a carbocation. 

Acid-base reactions in anhydrous HF are well documented. Within the Brpnsted formalism, few if any acids would be expected to be sufficiently strong proton donors to be able to protonate the very strong proton-donor HF (p. 51), and this is borne out by observation. Conversely, HF can protonate many Brpnsted bases, notably water. 

The catalytic effect of protons has been noted on many occasions (cf. Section II,D,2,c) and autocatalysis frequently occurs when the nucleophile is not a strong base. Acid catalysis of reactions with water, alcohols, mercaptans, amines, or halide ions has been observed for halogeno derivatives of pyridine, pyrimidine (92), s-triazine (93), quinoline, and phthalazine as well as for many other ring systems and leaving groups. An interesting displacement is that of a 4-oxo group in the reaction of quinolines with thiophenols, which is made possible by the acid catalysis. 

You need to know the strong acids and bases to work with acid-base reactions. 

When an acidic water solution is mixed with a basic water solution, an acid-base reaction takes place. The nature of the reaction and hence the equation written for it depend on whether the add and base involved are strong or weak. 

Strategy Decide whether the add and base are strong or weak. Then decide which of the three types of acid-base reactions is involved. Finally, use Table 4.2 to derive the proper equation. 

We can use this more general view to discuss the strengths of acids. In our generalized acid-base reaction (52), the proton transfer implies the chemical bond in HB, must be broken and the chemical bond in HB2 must be formed. If the HB, bond is easily broken, then HB, will be a strong acid. Then equilibrium will tend to favor a proton transfer from HB, to some other base, B2. If, on the other hand, the HB, bond is extremely stable, then this substance will be a weak acid. Equilibrium will tend to favor a proton transfer from some other acid, HB2, to base B, forming the stable HB, bond. 

When a strong acid is mixed with a strong base, a neutralization reaction occurs for which the net ionic equation is... 

Using Environmental Examples to Teach About Acids. Acid-base reactions are usually presented to secondary students as examples of aqueous equilibrium (2). In their study of acids and bases, students are expected to master the characteristic properties and reactions. They are taught to test the acidity of solutions, identify familiar acids and label them as strong or weak. The ionic dissociation of water, the pH scale and some common reactions of acids are also included in high school chemistry. All of these topics may be illustrated with examples related to acid deposition (5). A lesson plan is presented in Table I. 

Acid strength may be defined as the tendency to give up a proton and base strength as the tendency to accept a proton. Acid-base reactions occur because acids are not equally strong. If an acid, say HCI, is placed in contact with the conjugate base of a weaker acid, say acetate ion, the proton will be transferred because the HCI has a greater tendency to lose its proton than acetic acid. That is, the equilibrium... 

C06-0067. When 10.00 mL of a solution of a strong acid is mixed with 100.0 mL of a solution of a weak base in a coffee-cup calorimeter, the temperature falls from 24.6 °C to 22.7 °C. Determine q for the acid -base reaction, assuming that the liquids have densities of 1.00 g/mL and the same heat capacity as pure water. 

As described in Chapter 4, acid-base reactions that go to completion can be exploited in chemical analysis using the method of titration. Titrations can be understood in greater detail from the perspective of acid-base equilibria. Protonation of a weak base by a strong acid is a reaction that goes virtually to completion because of its large... 

In solutions neither H+ nor e can exist in a free state they will be donated only if they are accepted within the solution, e.g., by another acceptor, which may be the solvent and thus cause solvation here the mere solvation of electrons is an exceptional case, but may occur, e.g., in liquid ammonia, where according to Kraus82 the strongly reducing alkali metals dissolve while dissociating into cations M+ and solvated electrons e, which, however, are soon converted into NH2" and H2 gas. Further, from the analogy with acid-base reactions and the definition of... 

The reversibility of reactions is another important characteristic in assessing the fate of deep-well-injected wastes. Depending on environmental conditions, reversible reactions readily proceed in either or both directions. Most acid-base reactions exemplify reversible processes. In aqueous solutions, relatively minor changes in such factors as pH or concentration can change the direction of these reactions. Irreversible reactions, typified by hydrolysis, have a strong tendency to go in one direction only. 

Figures 11(a) and 11(b) [112] show the variation of Ni-Ge-P deposition rate and Ge content as a function of aspartic acid and Ge(IV) concentration, respectively. A relatively low P content, ca. 1-2 at%, was observed in the case of films exhibiting a high concentration of Ge (> 18 at%). Like other members of its class, which includes molybdate and tungstate, Ge(IY) behaves a soft base according to the hard and soft acids and bases theory (HSAB) originated by Pearson [113, 114], capable of strong adsorption, or displaying inhibitor-like behavior, on soft acid metal surfaces. In weakly acidic solution, uncomplexed Ge(IV) most probably exists as the hydrated oxide, or Ge(OH)4, which, due to acid-base reactions, may be more accurately represented as [Gc(OH)4 nO ] ".

The net ionic equations for these two reactions are the same because both acid-base reactions involve a strong acid and a strong soluble base forming a soluble salt. 

If the provoked or spontaneous acid-base reactions overcome the radical reactions of the primary radical, the secondary radical is easier to reduce, or to oxidize, than the substrate in most cases. Exceptions to this rule are scarce, but exist. They involve substrates that are particularly easy to reduce thanks to the presence of a strongly electron-withdrawing substituent (for reductions, electron-donating for oxidation), which is expelled upon electron transfer, thus producing a radical that lacks the same activation. Alkyl iodides and aryl diazonium cations are typical examples of such systems. 

A common laboratory application of acid-base reactions is a titration. A titration is a laboratory procedure in which a solution of known concentration is used to determine the concentration of an unknown solution. For strong acid/strong base titration systems, the net ionic equation is ... 

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