Reactions of the Conjugated Dienes Butadiene and Isoprene Alone and with Methanol Over Ion-Exchanged Montmorillonites

Abstract

Abstract--The reactions of simple conjugated dienes over divalent and trivalent transition metal-exchanged montmorillonites yield, in the absence of nucleophiles, a variety of products. Some of these products are a result of Diels-Alder cycloaddition reactions, whereas others are indicative of carbocation intermediates, i.e., other dimers, oligomer8, and isomerization products of these intermediates. The reactions in sealed cells between 20 ~ and 150"C show trends in the yields of the various product groups. Dimers of butadlene and isoprene formed by cycloaddition (i.e., 4-vinylcyclohexene and the monoterpene p-menthadiene (limonene)) were formed at low temperatures (20-50~ As the temperature was raised, the total yield of dimers increased and higher oligomers were formed along with isomerization products of the dimers and oligomers. The products of cycloaddition, however, did not increase markedly. The type of solvent used for the reaction was found to influence the reactivity, e.g., the use of 1,4-dioxan rather than chloroform led to a reduction in total conversion and also to a markedly higher degree of selectivity. In the presence of a suitable nucleophile (methanol), both dienes gave the 1,4-addition product predominantly, which suggests that an allylic carbocation intermediate was involved. The use of an interlayer-supported nickel complex, [HNi(P(OEt)3)4] § produced the only large scale polymerization observed in this work.

A Study of the Catalytic Properties of Synthetic Aluminosilicates of Different Morphologies in Cracking Reactions of the Byproducts of Isoprene Synthesis

“…Over the past few years of development, the composition of existing catalysts based on natural clays was entirely determined by the composition of the resulting BP of the decomposition products (for example, [14][15][16][17][18][19][20]). General regularities were derived, according…”

Esterification of succinic anhydride to di-(p-cresyl) succinate over Mn+-montmorillonite clay catalysts

“…Among smectite clays, montmorillonites, both in natural and exchanged forms, possess both Lewis and Brønsted acidities, which enable them to function as efficient catalysts in organic transformations. Montmorillonite clay exchanged with metal ions (M n+ -mont) are efficient catalysts in many organic transformations such as Diels-Alder reaction [9,10], polymerization [11], benzylation of aromatics [12], etherification [13,14], and acetalization reactions [15].…”

Ab Initio Molecular Orbital Study of the Acidity of Hydrated Lithium Hydroxide

“…Even "small" clay/metal cation systems are large by ab initio standards. For example, a single unit cell of a 2:1 smectite has a molecular formula of Na(H 2 O) 8 (Al 4 Si 8 O 20 (OH) 4 ), 12 which is much too large for even the simplest ab initio calculation. As calculations making use of advances in computer technology are carried out on larger clusters to model clay frameworks, there is a need for accurate ab initio molecular orbital calculations on small, fundamental systems to provide benchmarks for the more approximate calculations on larger systems.…”

“…2 Clays can also act as both Brønsted and Lewis acids and are a naturally occurring source of inorganic catalysts that facilitate a number of organic reactions. [3][4][5][6] Clays are also important in areas of environmental concern, for example, in controlling the migration of pesticides through soil. 7,8 The interaction of alkali metal cations with water has been well established as an important topic in solution, surface, and biological chemistry.…”

“…Of special interest are their uses as catalytic materials for the conversion of various hydrocarbons into useful chemical and petroleum products . Clays can also act as both Brønsted and Lewis acids and are a naturally occurring source of inorganic catalysts that facilitate a number of organic reactions. − Clays are also important in areas of environmental concern, for example, in controlling the migration of pesticides through soil. , …”