Acetals, functional groups among

As can be seen from Table 4.2. most functional groups are only weak acids and/or weak bases. They are too weak to behave as acids or bases in aqueous solution and therefore are said to be neutral. There are three exceptions to this rule among the common functional groups. Carboxylic acids (p/Za 5) and substituted phenols (pKa 10) are weak acids. Amines, like ammonia, are weak bases. The pH of a 0.1 M solution of acetic acid (CH3CO2H) is about 3. Phenol is a weaker acid and the pH of a 0.1 M solution is about 5.5. And the pH of a 0.1 M solution of CH3NH2 is about 11. 

Numerous complexes of nickel(II) and nickel(O) catalyze the addition of the Si-H bond to olefins. Among such catalysts are nickel-phosphine complexes, e.g., Ni(PR3)2X2 (where X=C1, I, NO3 R=alkyl and aryl), Ni(PPh3)4, and Ni-(CO)2(PPh3)2, as well as bidentate complexes of NiCl2-(chelate) and Ni(acac)2L (I phosphine), and Ni(cod)2(Pr3)2 [1-5]. A characteristic feature of nickel-phosphine-catalyzed olefin hydrosilylation is side reactions such as H/Cl, redistribution at silicon and the formation of substantial amounts of internal adducts in addition to terminal ones [69]. Phosphine complexes of nickel(O) and nickel(II) are used as catalysts in the hydrosilylation of olefins with functional groups, e.g., vinyl acetate, acrylonitrile [1-4], alkynes [70], and butadiynes [71]. 

The data in Table 10.4 show that even among carboxylic acids (where the ionizing functional group is kept constant), acidities can vary depending on what other groups are attached to the molecule. Compare, for example, the of acetic acid with those of mono-, di-, and trichloroacetic acids, and note that the acidity varies by a factor of 10,000. 

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