Aluminum chloride-monomethanolate

Modified aluminum chloride catalysts (aluminum chloride sludges, aluminum chloride monomethanolate, aluminum chloride-nitroalkane... 

It follows from the above discussion that the chain mechanism requires that markedly different products be obtained in the alkylation of isobutane with 1- and 2-butene, respectively. The former should yield dimethyl-hexanes and the latter, trimethylpentanea, as the major products. Such has been showm (Schmerling, 14d) to be the case when aluminum chloride (particulary when modified to diminish side reactions) was employed as catalyst. The product of the alkylation with 1-butene in the presence of aluminum chloride monomethanolate contained about 60% by w eight dimethylhexanes and 10% trimethylpentanes, whereas the 2-butene product contained 65% trimethylpentanes and only 4% dimethylhexanes. The difference in composition was apparent also in the A.S.T.M. octane numbers of the 125° end-point gasolines. That from 1-butene had an octane number of only 76.1 that from 2-butene, 94.1. 

When isobutane was alkylated with 1- or 2-butene in the presence of aluminum chloride monomethanolate, very little or no n-butane was formed despite the fact that appreciable amounts of 2,2,4-trimethylpentane were produced (Schmerling, 14d). Similarly, no n-butane or n-pentane, respectively, was obtained by the alkylation of isobutane with 2-butenc and with 2-pentene in the presence of sulfuric acid although trimethylpentanes were formed in both cases (McAllister et al., 12 cf. Marschner and Carmody, 24). This apparent discrepancy in the alkylation mechanism may be explained readily. The n-alkylcne is converted not into n-alkane, but into isoalkane. The resulting isobutane cannot, of course, be differentiated from that charged the resulting isopentane, on the other hand, can be and was actually found in substantial yield. In other words, the proton transfer reaction is accompanied by rearrangement of the carbon skeleton of the carbonium ion. 

Aluminum chloride loses its activity when dissolved in excess methanol but yields a catalyst when converted to its monomethanolate (AICI3—CH3OH). On the other hand, the dimethanolate has no catalytic activity. Nitroalkanes (such as nitromethane) form 1 1 addition complexes with aluminum chloride that modify its reactivity and are used for more selective alkylations.90... 

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