Exercises Reaction Types

Because this topic only appears as Free Response questions, no multiple-choice questions are included in this chapter. As you work through these, don t try to memorize them. The reactions change every year, and they are very diverse. Make sure you are learning how to write your answers and also the major principles that guide all reactions. Learning these will help you better predict the products of any reaction. 

Give the formulas to show the reactants and the products for the following chemical reactions. Each occurs in aqueous solution unless otherwise indicated. Represent substances in solution as ions if the substance is extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction. In all cases a reaction occurs. Balancing the equations is worth one point. As you work through the book, think of a possible question 1. 

A clean piece of magnesium ribbon is burned in nitrogen gas. 

A beaker of ammonium sulfate solution is added to a saturated solution of barium hydroxide. 

A sample of solid calcium fluoride is mixed with dilute sulfuric acid. 

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UCLEOPHILIC DISPLACEMENT OFFERS EXCITING OPPORTUNITIES to relate reactivity in the gas phase to reactivity in solution—perhaps to a greater extent than any other reaction type (1-4). The nature of that relationship, and the reasons for it, are developed in this and several other chapters in this volume, for example, by Brauman, Caserio, and McDonald. Exploring the relationship is not just an academic exercise this relationship is clearly fundamental to any general treatment of reactivity. Reaction in the gas phase reveals intrinsic or solvent-free reactivity (5). In different solutions, this intrinsic reactivity is variously transformed, through the differing action of the solvents. Viewed thus, the intrinsic reactivity is the element common to each, and as such, it plays the central role. 

These exercises review types of organometallic reactions and the 18-electron rule. 

Insertion into C—H bonds is also a reaction type common to nitrene chemistry. This is observed in the formation of the cyclopropylamine 615 from reaction with 1-ethoxy-l-trimethylsilyloxycyclopropane. Details have been reported of the use that can be made of the addition of the same nitrene to the chiral silyloxyalkene 616. This leads to an asymmetric synthesis of the amine 6YT. Insertion of a nitrene into C—H bonds is also reported for the photodecomposition of/7-trimethylsilylbenzoyl azide in hydrocarbons Reports have been made concerning the non-specificity of this particular nitrene. Apprently, some control can be exercised on its reactivity by using a micellar system. Under conditions of this type, using N, A-dimethyloctylammonium propionate as the micellar material, only the formamidine 618 is obtained ... 

Step 1 of our general equation-writing procedure is to classify the reaction type." In this exercise, we provide the chemical formulas of reactants in a reaction. Without writing the formulas of the products or balancing the equation, classify the following as... 

The reaction follows a free radical mechanism and gives a hydroperoxide a compound of the type ROOH Hydroperoxides tend to be unstable and shock sensitive On stand mg they form related peroxidic derivatives which are also prone to violent decomposi tion Air oxidation leads to peroxides within a few days if ethers are even briefly exposed to atmospheric oxygen For this reason one should never use old bottles of dialkyl ethers and extreme care must be exercised m their disposal... 

The main by-pioducts of this type of reaction are sulfides. By exercising careful control of stoichiometry, these can be rninimized quite readily. By-products are disposed of by incineration or by reprocessing for fuel value. 

Charge Transport. Side reactions can occur if the current distribution (electrode potential) along an electrode is not uniform. The side reactions can take the form of unwanted by-product formation or localized corrosion of the electrode. The problem of current distribution is addressed by the analysis of charge transport ia cell design. The path of current flow ia a cell is dependent on cell geometry, activation overpotential, concentration overpotential, and conductivity of the electrolyte and electrodes. Three types of current distribution can be described (48) when these factors are analyzed, a nontrivial exercise even for simple geometries (11). 

StevensJohnson syndrome isa serious and sometimes fatal hypetsenslivity reaction. The nurse must be alert for lesions on the skin and mucous membranes , a diagnostically important symptom of this syndrome. The lesons appear as red wheats or blisters , often starting on the face, in the mouth, or on the lips neck, and extremities This syndrome, which also may occur with the administration of other types of drugs can be fatal. The nurse must notify the primary health care provider and withhold the next dose of the drug. In addition, the nurse must exercise care to prevent injury to the involved areas... 

Two objectives have dominated the thinking behind the dangerous reaction chapters the means to supplement the often inadequate safety documents available in this area and to provide for university teachers (and other lecturers and trainers) an aid which will enable them to integrate the study of safety into their chemical reactivity courses. Safety is often missing from this type of exercise, although there are exceptions. 

The long-running dispute over the mechanism of base hydrolysis of cobalt(III)-ammine and -amine complexes, SVj2 versus SVjlCB (better termed Dcb), was several years ago resolved in favor of the latter (73). Recent activity on reactions of this type has concentrated on attempting to locate the precise site of deprotonation of the complex, an exercise successfully accomplished for the complexes syn,anti-[Co (cyclen)(NH3)2]3+ and syn,[Pg.80]

Indeed, the oxidation of Fe(CN)g by O2 (as well as by H2O2 and BrOj) proceeds via the rds of dissociation of the hexa- to the penta-cyano complex. The value of k in (8.90) is 5.6 X lO M s at pH > 3.8. Traces of Fe from decomposition of the cyano complex promote catalytic oxidation (Prob. 19). A large number of complexes of the type Fe(CN)5X" for both Fe(II) and Fe(III) have been studied and cross-reaction redox kinetics abound. Care has to be exercised in the use of FeiCN) . Daylight can induce changes in the complex even within an hour and catalytic effects (traces of Cu Sec. 3.1.4) have to be considered. In addition, the sensitivity of the values of and rate constants to medium effects lessen the value of the iron-cyano complexes as reactant partners for the demonstration of Marcus relationships. Nevertheless, they, with other inorganic complexes, have been extensively employed to probe the peripheral characteristics of metallopro-teins. 

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