Fused tetramates

Polymerization reactions, in addition to those previously mentioned, have been reported in the Russian literature which involve unsaturated compounds of all kinds. However, recent original work has not exceeded in industrial importance the polymerization of butadiene over metallic sodium as developed by Lebedev. In studies of the effect of temperature on this polymerization, Lebedev established the limits of formation of a cyclic butadiene dimer, vinylcyclohexene, while a lower temperature was necessary for polymer formation. Slobodin and co-workers established that at 300-400° over Florida earth, 1,3-butadiene gave the above dimer as well as dimethylcyclohexadiene and also trimers and tetramers with fused rings (379,382). 

Minerals which also contain iron will yield ferrous ions when fused with zinc chloride and they too give a red color with dimethylglyoxime and ammonia (compare page 267). Consequently, in such cases it is best to test for ferrous silicates as outlined on page 563 and if the response is positive the ammoniacal suspension should be warmed with hydrogen peroxide prior to the centrifuging. Ferric hydroxide is precipitated, while the nickel tetram-mine ions remain in solution. 

Tandem indicates that two monomers have been fused to produce a one peptide chain dimer, while dimer or tetramer indicates that the protein is an obligate oligomer. 

Finally, Osuka and coworkers also performed the synthesis of fused tetrameric porphyrin sheets with [)-P, meso-meso, [3-P triply links using 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ), and Sc(OTf)3 as oxidants (Fig. 2Id) [165]. The square structure of these planar tetramers was very well characterized by STM measurements [165]. 

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