Aluminum cation reaction with base

As described above for the amorphous aluminosilicates the acid strength of a zeolite increases with increasing Si Al ratios. Species with particularly high ratios have been prepared by removing some of the aluminum by reaction with materials such as silicon tetrachloride. On the other hand, the basic character of these materials increases with increasing numbers of A104 species so aluminum-rich zeolites are better bases, particularly when the Na" " is replaced with a large cation such as Cs. 52... 

Aluminum chloride coordinates with 1-chloropropane to give a Lewis acid/Lewis base complex, which can be attacked by benzene to yield propylbenzene or can undergo an intramolecular hydride shift to produce isopropyl cation. Isopropylbenzene arises by reaction of isopropyl cation with... 

To probe this question, diatomic bromine is mixed with aluminum chloride (AlClg), a Lewis acid-Lewis base reaction forms the complex Br+AlClgBr as the product before there is any reaction with benzene. This cationic bromine atom is so reactive, however, that even a weak base like benzene will react. Benzene donates two electrons to Br to form a new C-Br bond, which disrupts the aromatic system of benzene and forms a carbocation, 40. 

The isomorphic substituted aluminum atom within the zeolite framework has a negative charge that is compensated by a counterion. When the counterion is a proton, a Bronsted acid site is created. Moreover, framework oxygen atoms can give rise to weak Lewis base activity. Noble metal ions can be introduced by ion exchanging the cations after synthesis. Incorporation of metals like Ti, V, Fe, and Cr in the framework can provide the zeolite with activity for redox reactions. 

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