Penta mer

This has been studied much less frequently and appears to be a rather more complex reaction. The first results obtained, for the butyl-lithium, styrene reaction in benzene have already been described. In a similar way the addition of butyllithium to 1,1-diphenylethylene shows identical kinetic behaviour in benzene (26). Even the proton extraction reaction with fluorene shows the typical one-sixth order in butyllithium (27). It appears therefore that in benzene solution at least, lithium alkyls react via a small equilibrium concentration of unassociated alkyl. This will of course not be true for reactions with polar molecules for reasons which will be apparent later. No definite information can be obtained on the dissociation process. It is possible that the hexamer dissociates completely on removal of one molecule or that a whole series of penta-mers, tetramers etc. exist in equilibrium. As long as equilibrium is maintained, the hexamer is the major species present and only monomeric butyllithium is reactive, the reaction order will be one-sixth. A plausible... 

Steam cracking of various petroleum fractions is gaining widespread use for the production of olefins. These olefins are produced essentially for use as feed stock for numerous petrochemical processes, but the by-product butylenes and propylenes are sometimes used as feed stock for aviation and motor alkylation units. Ethylene is the most important of the olefins produced from this type of cracking, and propylene is second in importance. These two olefins are normally charged to either alkylation or polymerization units for the production of petrochemicals or petrochemical intermediates. Polyethylene and propylene dimers, trimers, tetramers, and penta-mers are some of the more important polymers produced, while ethybenzene, dodecylbenzene, cumene, diisopropylbenzene, and alkylated... 

Evidence of oligomers appears at short contact time. Figure 3 shows plateaus corresponding to the trimer, tetramer and penta-mer of propylene at conditions of 2.7 WHSV, 400°F, 500 psig at which propylene conversion if 67%. This contrasts with the smooth curve at 0.4 WHSV, 98% propylene conversion. 

Chitobiase degrades only small N-acetyl-D-glucosamine oligomers (up to penta-mers), and the released N-acetyl-D-glucosamine monomers retain their Cl anomeric configuration. 

The phosphonitriles represent a mixture of cyclic trimers, tetramers, penta-mers, etc., together with linear oligomers. Depending on reaction conditions, the yield of trimers and tetramers can be increased to about 90%. If PCls is replaced by R2PCI3, the corresponding compounds with the monomeric unit (NPR2)n are formed. 

The optical properties of these oligomers have been investigated [67]. Up to the penta-mer the dispersion in benzene obeys the one term Drude equation but the hexamer and mainly the heptamer show anomalous curves which are highly dependent on the solvent [68] and on temperature [69, 70]. These anomalous dispersion curves were only observed in aromatic hydrocarbons [68]. The authors attribute it to the formation of an ordered helical structure via intramolecular weak hydrogen bonding between urethane linkages. 

An increase in the specific rotation of low-molecular weight polypeptides may be caused also by their intermolecular association (75). Such an effect should be concentration dependent, and indeed in dioxane the specific rotations of the penta- and hexamer were found to increase with their concentration, and ultracentrif-ugation studies (77) proved indeed that these oligomers are associated. However, the specific optical rotations of the dimer, trimer and tetra-mer, as well as of the hepta- and nonamer were concentration independent, and hence the abnormally high specific rotation of the hepta- and nonamers indicates that they are probably helical. 

Initially, some linear libraries of penta-, hexa-, octa and decamers with structure (A )ra-/J- -/J- -TentaGelS (where ft = /1-alanine and s = e-aminocaproic acid) were tested. For each position 19 natural amino acids (cysteine was avoided) were used, and the active ligand structures are shown in Figure 8.13. Some recurrent motifs emerged, such as FDW and QDPR, especially for 5- and 6-mers, and WXXGF for 8- and 10-mers. 

S-Alkylation. A stirred soln. of mer/-bicyclo-3,5-epidithio-l,4-diphenyl-2,4-penta-diene-l-thione in nitromethane treated with methyl iodide, and refluxed overnight 3-(2-methylthio-l-phenylvinyl)-5-phenyl-l,2-dithiolium iodide. Y 90%. F. e., also N-analogs, s. E. Klingsberg, J. Org. Chem. 33, 2915 (1968). 

Octahedral tricarbonyls can be facial (fac), or meridional (mer) tetracar-bonyls can be cis or trans (the labels refer to the orientation of the noncarbonyl ligands) but there are only single isomers of penta- and hexacarbonyls. In each case there is a characteristic pattern of IR bands that allow us to identify each type Fig. 10.10 shows the spectra expected for the two tricarbpnyl isomers. ... 

Duneres Piperidein 20,134, II 67. N-Methyl.cinohdloipon-nitril 22,12. 2.2.3.Trimethyl-6-[x-ainino.ieopropyl]. pyrrolenin Mer 5-Amino.2.2.3.5.e.penta> methyl-2.5-dihydro.pyridin 88 16%. 2-FropyI-l.bntyl.unidazol 88, 83. 

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