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Other oligomers

Efforts towards the preparation of porphyrin-functionalized polythiophenes have centered on complexes 38-41, in which thiophenes are tethered to porphyrin cores (Chart 5.9) [50], The syntheses employed either porphyrin formation using MacDonald-type conditions (38-40) or Wittig coupling to produce 41. No electronic properties of these materials have yet been reported. [Pg.299]

The bis-ruthenium species 45 (Chart 5.12) has been prepared and characterized via an X-ray crystal structure [54]. No splitting is observed in the reduction waves, suggesting that the interaction between metal centers is weak, but the thiophene oxidation is shifted positive due to the electron-withdrawing nature of the metal groups. [Pg.301]


Furfural reacts with ketones to form strong, crosslinked resins of technical interest in the former Soviet Union the U.S. Air Force has also shown some interest (42,43). The so-called furfurylidene acetone monomer, a mixture of 2-furfurylidene methyl ketone [623-15-4] (1 )> bis-(2-furfurylidene) ketone [886-77-1] (14), mesityl oxide, and other oligomers, is obtained by condensation of furfural and acetone under basic conditions (44,45). Treatment of the "monomer" with an acidic catalyst leads initially to polymer of low molecular weight and ultimately to cross-linked, black, insoluble, heat-resistant resin (46). [Pg.79]

Uses. Besides polymerizing TFE to various types of high PTEE homopolymer, TEE is copolymerized with hexafluoropropylene (29), ethylene (30), perfluorinated ether (31), isobutylene (32), propylene (33), and in some cases it is used as a termonomer (34). It is used to prepare low molecular weight polyfluorocarbons (35) and carbonyl fluoride (36), as well as to form PTEE m situ on metal surfaces (37). Hexafluoropropylene [116-15-4] (38,39), perfluorinated ethers, and other oligomers are prepared from TEE. [Pg.349]

Cmde diketene obtained from the dimeriza tion of ketene is dark brown and contains up to 10% higher ketene oligomers but can be used without further purification. In the cmde form, however, diketene has only limited stabHity. Therefore, especiaHy if it has to be stored for some time, the cmde diketene is distiHed to > 99.5% purity (124). The tarry distiHation residue, containing trike ten e (5) and other oligomers, tends to undergo violent Spontaneous decomposition and is neutralized immediately with water or a low alcohol. Ultrapure diketene (99.99%) can be obtained by crystallization (125,126). Diketene can be stabHized to some extent with agents such as alcohols and even smaH quantities of water [7732-18-5] (127), phenols, boron oxides, sulfur [7704-34-9] (128) and sulfate salts, eg, anhydrous copper sulfate [7758-98-7]. [Pg.479]

Similar reactions lead to other oligomers depending on the size of the R groups and the conditions of the reaction, e.g. cyc/o-(Me2AlNMe2)2 (structure 1) and the imido-clusters (PhAlNPh)4, (HAlNPr )4 or 6,... [Pg.265]

The well-known condensation between 2-furaldehyde and acetone in a basic medium yields what is usually called furfurylidene acetone monomer composed of a mixture of 2-furfurylidene methyl ketone, di-2-furfurylidene ketone, mesityl oxide and other oligomers derived from further condensation reactions135. This mixture is then polymerized by the action of an acidic catalyst in the first phase of the reaction a polymer of low molecular weight is produced which on further treatment cross-links to a black insoluble and heat-resistant material136. ... [Pg.80]

Some remarkable chemistry is observed when silenes react with heteroatom systems, in particular carbonyl compounds (]>C=0) and imines Q>C=N—R). The reaction with ketones was first described by Sommer (203), who postulated formation of an intermediate siloxetane which could not be observed and hence was considered to be unstable even at room temperature, decomposing spontaneously to a silanone (normally isolated as its trimer and other oligomers) and the observed alkene [Eq. (14)]. Many efforts have been made to demonstrate the existence of the siloxetane, but it is only very recently that claims have been advanced for the isolation of this species. In one case (86) an alternative formulation for the product obtained has been advanced (204). In a second case (121) involving reaction of a highly hindered silene with cyclopentadienones,... [Pg.29]

Pyridine-pyridine connections via a Stille reaction have been well precedented for the syntheses of bipyridine, terpyridine, tetrapyridine and other oligomers of pyridine [73-75]. These reactions are exemplified by the synthesis of tetrapyridine 84 [75] from terpyridyl chloride 83 and 2-tributylstannylpyridine. [Pg.201]

Among the oligomers, the cyclic trimer has been postulated to be uniquely stable [53, 54], This could be due to either a mechanism favouring the formation of trimer (kinetic control) or to the trimer having a lower energy than other oligomers (thermodynamic control), thus decreasing its rate of further reaction. [Pg.52]

Breaking down Adding of other oligomers Elongated... [Pg.164]

Substraction spectra were obtained by setting the aliphatic C-H stretching band at 2969 cm l at about zero. The spectrum comparing AO/60 PHBA/diol polyol and unmodified polyester (Fig. 3) is typical. The aliphatic OH band at about 3535 cm"l has been largely replaced by a phenolic OH band at about 3365 cm"l. Subtraction spectra of the other oligomers (Fig. A) yield similar conclusions. [Pg.337]

The said tendency also holds for the oligomerization lFf-l,2,4,3-triazaphospholes are monomeric and the 2//-isomers are so too, although for some of them (mainly with RO or RS as 5-substituents) tetramers (or other oligomers) are reported to exist in a temperature controlled equilibrium with the monomers <87TL6049, B-90MI 422-01, 91CC23, 93CJC1200>. Finally, 4//-1,2,4,3-triazaphospholes are not known at all as such, but only in the form of their 2,3-dihydro derivatives, i.e. their tetramers and adducts (see Section 4.22.9.3). [Pg.805]

Primary structure of a protein is simply amino acids sequence of the peptide chain. The secondary structure is a result of the different conformations that the chain can take. The tertiary structure refers to the three dimensional shape that results from twisting, bending and folding of protein helix. The quaternary structure refers to the way in which these amino acid chains of a complex protein are associated with each other (oligomer, dimers, trimers, etc.). [Pg.102]

Quinodimethane derivatives of terthiophene and other oligomers showed an absorption maximum at 583-688 nm (02JOC6015 03OL1535). Bis(dicyanoethylene) oligothiophene derivatives have been characterized and the compound with four thienyl rings showed an absorption band at 790 nm (02JA12380). This type of compounds was used in thin film transistors (see below) (02JA4184). [Pg.149]

The synthesis of the first n-type sexithiophene conductor, a,co-diperfluorohexylsexithiophene (374) has been described (00AGE4547) the synthesis of other oligomers of the same shape has been reported (04CM4715). [Pg.247]

In the absence of monomer, GTP catalysts are destroyed by the initiator. A one to one molar mixture of bifluoride and MTS, for example produces methyl isobuterate, trimethylsilylfluoride, trimethylsilylmethoxide, methyl 2,2,4-trimethyl-3-oxopentanoate, and other oligomers [19, 26]. Seebach has shown that ester enolates generate ketenes at room temperature [27] (Scheme 16). These reactions support the dissociative mechanism wherein... [Pg.14]

The largest proportion of TFE is used for the polymerization into a variety of PITH homopolymers. It is also used as comonomer in the copolymerization with hexaflu-oropropylene, ethylene, perfluorinated ether, and other monomers and also as a comonomer in a variety of terpolymers. Other uses of TFE are to prepare low-molecular-weight polyfluorocarbons, carbonyl fluoride oils, as well as to form PTFE in situ on metal surfaces,13 and in the synthesis of hexafluoropropylene, perfluorinated ethers, and other oligomers.14... [Pg.18]


See other pages where Other oligomers is mentioned: [Pg.330]    [Pg.442]    [Pg.235]    [Pg.67]    [Pg.477]    [Pg.835]    [Pg.887]    [Pg.281]    [Pg.536]    [Pg.136]    [Pg.300]    [Pg.164]    [Pg.17]    [Pg.269]    [Pg.150]    [Pg.262]    [Pg.308]    [Pg.453]    [Pg.106]    [Pg.460]    [Pg.136]    [Pg.397]    [Pg.330]    [Pg.235]    [Pg.157]    [Pg.70]    [Pg.59]    [Pg.379]    [Pg.656]    [Pg.79]    [Pg.20]    [Pg.228]   


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