Molecular engineered layer structures MELS

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

Organic phosphonates represent another class of anchoring agents, which react with zirconium hydroxide to form pillared structures. These are also referred to as molecularly engineered layered structures (MELS). Layered compounds of organic phosphonates of zirconium with the formula of Zr(RP03)2 have been rec-... 

Tetravalent metal phosphonates, or MELS (for Molecularly Engineered Layered Structures), provide a novel class of materials that combine many of the properties of incn-ganic metal oxides with the organic functionality more commonly found in functionalized polymeric resins. Early development work on these materials was carried out by Alberti and co-woikers [ref. 1] and Dines et al. [ref. 2]. Synthesis and characterization of related zirconium phosphates that also contain phosphonate groups as pillars have been described by Clearfield [ref 3]. There is a substantial patent estate for tetravalent metal phosphonates, and exclusive rights to this estate are owned by Catalytica [ref 4]. 

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