B Lewis acids

Answer (a) Bronsted acids, HN()2, H2P04 Bronsted bases, HP042 and N02 (b) Lewis acid, H+ Lewis bases, HP042 and NOz ]... 

From this sort of data it can be concluded that the cobalt(III) ion in this complex is a soft, or class b, Lewis acid. It has been suggested previously that the cobalt(III) ion in vitamin B12 was also a class b acid (138). The kinetic order, which presumably corresponds closely to the order of thermodynamic stability, suggests that for at least some ligands jr-bonding may be important. In this connection it is noteworthy that methylcobaloxime forms a complex with CO (139). 

The properties of elastomers are much improved by strain-induced crystallization, which occurs only in polymers with high stereoregularity. The polymerization of butadiene using completely soluble catalysts composed of a) rare earth carboxylates, b) Lewis acids and c) aluminum alkyls leads to polymers with up to 99 % cis-1,4 configuration. These polymers show more strain-induced crystallization than the commercial polybutadienes and consequently their processability is much improved. 

Fig. 12. Score plots used for selecting test items in the Fischer indol synthesis. Selected items (a) ketones, (b) Lewis acids, (c) solvents are marked with dots. For identification numbers in the score plots, see Refs. [51, 55,61]...

Mueller, E., Zeeh, B. Lewis acid-catalyzed reaction of carbonyl compounds with tertbutyl isonitrile. Liebigs Ann. Chem. 1966, 696, 72-80. 

Cationic polymerization takes place in the presence of any of the following catalyst (a) protic acid such as HBr, HCl, triflicacid, etc., (b) lewis acid such as ZnClj, AICI3, etc., and (c) alkilating or acylating agents such as EtjO BF, etc., as shown in Figure 7.4 [12]. 

Scheme 14 A Azido-Schmidt reaction. B Lewis acid-mediated reactions of alk)4azides with a, 8-unsaturated ketones [49]...

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