Aluminium chloride, reaction + silica

The product distribution in the reaction of benzene with dodecene was determined for a number of catalysts (Table 5.1-4). As can be seen, the reaction with the zeolite H-Beta gave predominantly the 2-phenyldodecane, whereas the reaction in the pure ionic liquid gave a mixture of isomers, with selectivity similar to that of aluminium chloride. The two supported ionic liquid reactions (H-Beta / IL and T 350 / IL) again gave product distributions similar to aluminium(III) chloride (T350 is a silica support made by Degussa). 

The surface of silica is highly reactive and hydroxyl groups exchange hydrogen for deuterium with D20 [14—16] but not with D2. They can be replaced by Cl from Cl2 or CC14 [16] and they react with silanes and aluminium chloride [15,19], Surface alcoholates are formed when silica is contacted with primary or secondary alcohols [20] either by the reaction with hydroxyl groups... 

The procedure for preparing supported aluminium chloride relies on the small but significant solubility of aluminium chloride in aromatic hydrocarbons (typically toluene) and the slow reaction of the dissolved A1C13 with the surface hydroxyls of a commercial silica gel or acid-treated clay (Figure 1). One mole equivalent of HC1 is produced during the catalyst preparation consistent with the formation of mostly -OAlCl2 units on the surface and the use of hot solvent is essential so as to force the reaction and to ensure that the HC1 is driven from the system. 

In some cases the heterogeneous version of a catalyst can be prepared by direct reaction of that catalyst with a suitable support material. Thus reactive Lewis acids such as aluminium chloride will react with hydroxylated materials such as silica gel to give directly bonded surface species such as -OAICI2.20 Another single-step route to the supported catalyst is via sol-gel techniques, typically to produce an organically modified mesoporous silica. This is based on the co-polymerisation of a silica precursor and an organosilicate precursor (Figure 1.5). 

An important fact to remember is that an interaction of a metal precursor with an oxide support modifies the support and very often a part of the support dissolves [33]. So, for example, aluminium from AI2O3 appears in the liquid phase as chloride, oxychloride, hydroxynitrate, etc. The same holds for oxides of V, Ta, Nb, Ti, Zr and others. On the other hand, silica can be partially dissolved when NH3-containing precursors are used. When water or another solvent is removed upon drying, the species formed from the support can appear on the surface of the precursor crystallites and finally, after reduction, on the metal. (Note, a high temperature reduction would remove a volatile AICI3, a low temperature reduction would not.) For certain reactions this could be a way of creating promoters from the support. 

To a stirred solution of 100 mg (0.38 mmol) of 1.1.10c in 5 mL of methylene chloride were added 500 mg of pyridinium chlorochromate (PCC) on aluminium oxide (6.1 mmol PCC/7.5 g AI2O3). The reaction mixture darkened from orange to black and after 24 h additionally 500 mg of PCC/alox were added. After completion (62 h, TLC control) the mixture was filtered through a small silica gel column and washed with 50 mL of CH2CI2. The solvent was removed under reduced pressure, yielding 79 mg (80%) of a colorless viscous oil, [a]j3 = -70.1° (1.0, MeOH). 

The preparation of cyclopropyl ketones can be achieved in good yields, and with a minimum of ring-cleaved by-products, from the reaction between an acid chloride and cyclopropyltrimethylsilane in the presence of aluminium trichloride. The same authors have generated cyclopropanesulphonic acid for the first time. Cyclopropyl ketones can also be obtained by treatment of the corresponding hydrocarbon with ozone adsorbed on silica. This dry ozonolysis method is widely applicable and yields are generally good. 

Silicone oils (product may be diluted by hydrocarbons, ethers, ketones or chlorohydrocarbons, although this does not, however, appear as a specific claim) Aluminium oxides, titanium dioxides, plus various silicas. These react with silicone oil in situ, with the reaction being catalyzed by an acid-condensation reagent (1) Dimethyl polysiloxane -1-silica -t- aerogel -t- AICI3 diluted by toluene. (2) Dimethyl polysiloxane -1-alumina -t- SnCU diluted by toluene. (3) Dimethyl polysiloxane -1-precipitated silica -1-phosphorous nitrile chloride + poly(ethylene glycol) stearate 1-30... 

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