Oligomer Oligomeric

Oligomers, oligomeric, oligomerization —, formation by seeding technique 130... 

Off-line coupling of HPLC with FD-MS has been used by several authors [118-121] for the determination of oligomers, oligomeric antioxidants (such as poly-TMDQ), ozonation and vulcanisation products. Pausch [122] reported on rubbers, cyclic polyurethane oligomers, as well as on the determination of the molecular weight distribution (up to 5300 Da) and oligomer analysis of polystyrene. Also the components of an aniline-acetone resin were deduced from FD-MS molecular weights [122]. 

Available products include tea, 1 5 tincture in 45% alcohol, 1 1 liquid extract in 25% alcohol (6), and capsules of 250,455, and 510 mg. The French Pharmacopoeia requires 45% ethanol for the fluid extract and 60% ethanol for the tincture (8). It is recommended that 0.5-1 mL of liquid extract or 1-2 mL of tincture be taken three times a day (6). The tea is made from 0.3-1 g of dried berries infused in hot water and taken three times a day (4,6). A typical therapeutic dose of extract, standardized to contain 1.8% vitexin-4 rhamno-side, is 100-250 mg three times daily. A standardized extract containing 18% procyanidolic oligomers (oligomeric procyanidns) is dosed at 250-500 mg daily (9). 

Vinylpyridine Oligomers. Oligomerizations of 2-vinylpyridine are closely related to polymerizations of methacrylates. Products formed by initiation using lithium and sodium salts of 2-ethylpyridine in THF at —78 °C are predominantly (>95%) isotactic. Methylation of 1,3-di(2-pyridyl)butane anion with... 

Hirata and Nakata Styrene oligomers, oligomeric ethers, polysiloxanes, alkyl phthalates Packed capillary silica ODS Hexane-ethanol Hexane-methanol uv Styrene-oligomers up to 9000 MM... 

Instead of phosgene and its oligomers, oligomeric t-butylcarbonates are also used to convert diamines into diisocyanates. For example, sterically hindered aromatic diamines react with di-f-butyldicarbonate in the presence of dimethylaminopyridine in acetonitrile at room temperature to give sterically hindered aromatic diisocyanates. In this manner 3,6-3, 6 -tetramethyl MDI is obtained in 93% yield (8). Also, aliphatic diamines react with di- -butyltricarbonate at room temperature to give a high yield of the corresponding diisocyanates (9). 

Polyenyne Oligomers Oligomeric a-o-Diynes Oligo(alkynes)... 

Oleochemistry Fettchemie, Oleochemie Oleyl Alcohol Oleylalkohol Oleyl Amine Oleylamin Oligomers Oligomere Oligosylfructoses Oligosylfructosen Olive Olivenbaum Olive Oil Olivenbl Opium Opium... 

Resins. As mentioned above, both furfural and furfuryl alcohol are widely used in resin apphcations. Another resin former, 2,5-furandimethanol [1883-75-6] (BHME), is prepared from furfuryl alcohol by reaction with formaldehyde. It is usually not isolated because oligomerization occurs simultaneously with formation (competing reaction). Both the monomer and oligomers are very reactive owing to difuntionahty, and are used primarily as binders for foundry sand (72) and fiberglass insulation (147,148). 

Oligomeric Vinylphosphonate. A water-soluble oligomer, Fyrol 76 [41222-33-7] is produced by reaction of bis(2-chloroethyl) vinylphosphonate and dimethyl methylphosphonate with elimination of all the chlorine as methyl chloride (127,128). This Hquid, containing 22.5% P, is curable by free-radical initiation, on cotton or other fabrics. Nitrogen components, such as A/-methylolacrylamide or methylolmelamines, are usually included in the finish, which can be durable to multiple launderings (129,130). 

Polymer-type antioxidants have been prepared by Eriedel-Crafts reaction of -cresol andp- and/or y -chloromethylstyrene in the presence of boron trifluoride-etherate (198). The oligomeric product resulting from the alkylation of phenyl-a-naphthylamine using C12—15 propylene oligomer in the presence of AlCl or activated white clays is used as an antioxidant additive for lubricating oils (199). 

Other high molecular weight hydrocarbon polymers are not biodegradable, but oligomers of <7j -l,4-isoprene (83), butadiene (84), and styrene (85), are degradable. And there has been further confirmation of biodegradation of oligomeric ethylene (86). 

Lipase-catalyzed intermolecular condensation of diacids with diols results in a mixture of macrocycUc lactones and liuear oligomers. Interestingly, the reaction temperature has a strong effect on the product distribution. The condensation of a,(D-diacids with a,(D-dialcohols catalyzed by Candida glindracea or Pseudomonas sp. Upases leads to macrocycUc lactones at temperatures between 55 and 75°C (91), but at lower temperatures (<45°C) the formation of oligomeric esters predorninates. Optically active trimers and pentamers can be produced at room temperature by PPL or Chromobacterium viscosum Upase-catalyzed condensation of bis (2,2,2-trichloroethyl) (+)-3-meth5ladipate and 1,6-hexanediol (92). 

Grown Ethers. Ethylene oxide forms cycHc oligomers (crown ethers) in the presence of fluorinated Lewis acids such as boron tritiuoride, phosphoms pentafluoride, or antimony pentafluoride. Hydrogen fluoride is the preferred catalyst (47). The presence of BF , PF , or SbF salts of alkah, alkaline earth, or transition metals directs the oligomerization to the cycHc tetramer, 1,4,7,10-tetraoxacyclododecane [294-93-9] (12-crown-4), pentamer, 1,4,7,10,13-pentaoxacyclopentadecane [33100-27-6] (15-crown-6), andhexamer, 1,4,7,10,13,16-hexaoxacyclooctadecane [17455-13-9]... 

The coiled-coil fibrous proteins have heptad repeats in their amino acid sequence and form oligomers—usually dimers or trimers—through their coiled coils. These oligomeric units then assemble into fibers. 

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