Adds, definition strong

Olefins can add to double bonds in a reaction different from those discussed in 5-15, which, however, is still formally the addition of RH to a double bond. This reaction is called the ene synthesis44,1 and bears a certain similarity to the Diels-Alder reaction (5-47). For the reaction to proceed without a catalyst, one of the components must be a reactive dienophile (see 5-47 for a definition of this word) such as maleic anhydride, but the other (which supplies the hydrogen) may be a simple alkene such as propene. There has been much discussion of the mechanism of this reaction, and both concerted pericyclic (as shown above) and stepwise mechanisms have been suggested. The reaction between maleic anhydride and optically active PhCHMeCH=CH2 gave an optically active product,441 which is strong evi-... 

In the presence of such a plethora of definitions, one can well ask which is die "best" one. Each concept, properly used, has its strong points and its weaknesses. One can do no better than to quote the concluding remarks of one of the best discussions of add-base concepts.15 Actually each approach is correct as far as it goes, and knowledge of the fundamentals of all is essential."... 

When K[PtX(acac)2] (X = Cl, Br) is treated with a strong proton add the uncoordinated 0,0 site is protonated and complex (170) is formed.1606,1607 If the alkyl groups on the 0,0 -bonded acac ligand are non-equivalent, exchange can be observed. Although the mechanism has not been definitively proven, a dissociative mechanism is favored.160 This proposal correlates with the observations that the 0,0 -bonded chelate complex Pt(acac)2 will react with tertiary phosphines and nitrogen bases with substitution of one of the oxygen-bonded chelate arms.1609,1610 A variety of products are formed as outlined in Scheme 17. 

One method used for the preparation of [Pt(en)2]Cl2 or [Pt(en)3]Cl4 is the direct reaction between ethylenediamine and PtCU or PtCLt, respectively. The technique is to add slowly the solid platinum salts to the liquid ethylenediamine. This addition is accompanied by a vigorous evolution of heat, which is to be expected whenever a strong acid is added to a strong base. Recall (Section 2.1) that in terms of the Lewis definition of acids and bases, the formation of coordination compounds involves an acid-base reaction. In this particular case, the platinum ions are the acids and ethylenediamine is the base. Metal dimethylsulfoxide complexes have been prepared and characterized. One method used to prepare some of these complexes is a direct reaction (12) in the absence of any added solvent. 

Acids and bases are essential substances in home, industry, and the environment. In aqueous solution, water combines with the proton released from an acid to form the hydrated species represented by H3O (aq). In the Arrhenius definition, adds contain H and yield H3O in water, bases contain OH and yield OH" in water, and an acid-base reaction (neutralization) is the reactfon of H and OH to form HgO. Acid strength depends on [HsO j relative to [HA] in aqueous solution. Strong acids dissociate completely and weak acids slightly. The extent of dissociation is expressed by the acid-dissociation constant, K. Weak acids have values ranging from about 10 to Many acids and bases can be classified qualitatively as strong or weak based on their formulas. 

Understand the nature of the hydrated proton, the Arrhenius definition of an acid and a base, and why all strong acid-strong base reactions have the same A// xn describe how acid strength is expressed by K, classify strong and weak adds and bases from their formulas ( 18.1) (SP 18.1) (EPs 18.1-18.12)... 

Figure 10.15 A shows the steps and relative rates involved in the addition with the strongly basic amines. The addition step has three possible pathways (step 1) direct addition, general-acid catalyzed addition, or specific-acid catalyzed addition. Because the amines are good nucleophiles, they add directly at all pHs, but below pHs around 4 this direct addition becomes rate-determining. This is because there is a low concentration of unproton-ated amine present at low pHs. In some circumstances, enforced general-acid catalysis of the first step is found (see Section 9.3.6 for the definition of enforced catalysis). At the high pHs...

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