The reaction of 2-methyl pent-2-ene with primary alcohols (C1-C18) at 95°C over an Al-montmorillonite gave yields of 20–90% of ethers of the type R-O-C(CH3)2C3H7. Lower yields were produced if secondary alcohols were employed, and tertiary alcohols gave only a trace of this ether. When a variety of alkenes was reacted with butan-1-ol at 95°C over a similar catalyst, no reaction occurred unless the alkene was capable of forming a tertiary carbonium ion immediately upon protonation. In this case the product was the tertiary ether t-R-O-nC4H9. However, at a reaction temperature of 150°C a variety of products were formed including (1) ether by the attack of butanol on the carbonium ions produced either directly from protonation of the alkenes or by hydride shift from such an ion, (2) alkenes by the attack of n-C4H9+ ions (derived from protonation and dehydration of butanol) on the alkene, (3) di-(but-1-yl) ether by dehydration of the butanol, and (4) small amounts of alcohol by hydration of the alkene. The differences in reactivity below and above 100°C are related directly to the amount of water present in the interlayer space of the clay and the degree of acidity found there. Although the clay behaves as an acid catalyst, the reactions are far cleaner (more selective) than comparable reactions catalyzed by sulfuric acid.

When 1-hexene was adsorbed by Cr3+-montmorillonite at room temperature, all evidence of C=C(str) vibrations was lost. Protonation of the alkene occurred, and the secondary carbocation formed was bound at a site on the primary coordination sphere of the interlayer cation. Some of the hydrogen atoms of these primary-sphere water molecules were involved in strong hydrogen bonds to the silicate sheets, whereas others did not form such bonds, but were free and directed into the interlayer space. These latter hydrogen atoms were labile and protonated the alkene molecules.