ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2013-06-25
    Description: The Journal of Organic Chemistry DOI: 10.1021/jo400900x
    Print ISSN: 0022-3263
    Electronic ISSN: 1520-6904
    Topics: Chemistry and Pharmacology
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The spontaneous free radical copolymerizations of a series of electron-rich olefins with acrylonitrile (AN) complexed to zinc chloride (ZnCl2) have been investigated in solution. With styrene (St) and 2-vinylnaphthalene, an alternating copolymerization occurred without added initiator at 40°C. Using p-methylstyrene as the electron-rich olefin, no-initiator spontaneous alternating copolymerization was observed at 30°C. Copolymer formed in an amount equal to that of the ZnCl2 used. With p-methoxystyrene (pMeOSt) and with isobutyl vinyl ether (IBVE), the copolymerizations were conducted in the presence of ethyldiisopropylamine (EDIA) to inhibit cationic homopolymerization of these monomers. The copolymerization with pMeOSt proceeded to high yield, but the copolymers were rich in pMeOSt and the rates were slow presumably due to competitive complexation of ZnCl2 with the methoxy-substituent. Using IBVE only low yields of a random copolymer were obtained, and again competitive coordination with ZnCl2 appears responsible. The small molecules accompanying these spontaneous copolymerizations were shown by GC/MS to possess cyclobutane and Mayo adduct structures. The mechanism of these spontaneous copolymerizations cannot be decided on the basis of the small molecules formed, but the increases of copolymer molecular weight with time at constant yield speaks for a diradical mechanism.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The free radical copolymerization of a vinyl-terminated hydrocarbon macromonomer, namely poly-l-butene with molecular weight 1,000, with methyl acrylate (MA) led to copolymers with broad molecular weight distributions, and even bimodal character. In the presence of alkylaluminum chloride Lewis acids, higher incorporation of MA was obtained. The polymer MW and mole% MA in the copolymer increase with their decreasing Lewis acid strength. The best result was obtained in the presence of 25 mole% Et2AlCl versus MA at 60°C which led to 82% of the polyhydrocarbon chains being derivatized and unimodal MW distribution. For the copolymerization of the polyhydrocarbon macromonomer and AN, the best results were obtained without Lewis acid in toluene using a free radical initiator at 125°C. The model compound 2,2,4-trimethyl-1-pentene copolymerizes with both MA and AN in standard free radical conditions and the copolymerization parameters were determined.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reactions of the mildly electron-poor olefin methyl acrylate (MA) with three electron-rich substituted hydrocarbon 1,3-dienes, namely 2,3-dimethyl-1,3-butadiene (DMB), 4-methyl-1,3-pentadiene (MPD) and isoprene (IP) were investigated in 1,2-dichloroethane in the presence of various amounts of zinc chloride at different temperatures. ZnCl2 complexes with the ester group of MA and increases the MA's electron-poor character and therefore its tendency towards reactions with electron-rich dienes. In the absence of ZnCl2, no reaction occurs between the investigated dienes and MA under the used reaction conditions. Both alternating copolymers and [4+2] cycloadducts formed spontaneously in the presence of ZnCl2 even at room temperature. The structure of the diene and its nucleophilicity control the product distribution. For the DMB and IP systems, raising the reaction temperature and increasing the ZnCl2 concentration enhance the overall reaction rate and in most cases also favor the cycloaddition over the copolymerization. IP is less reactive than DMB. With MPD only copolymer is formed because the two terminal methyl groups retard the concerted [4+2] cycloaddition. These results are in agreement with a postulated mechanism involving competition between the formation of a π-allyl 2-hexene-1,6-diradical, capable of initiating free radical copolymerization, and concerted [4+2] Diels-Alder cycloaddition.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new monomers, methyl 3,3-difluorocyclobutene-1-carboxylate (MDFC) and methyl 3,3,4,4-tetrafluorocyclobutene-1-carboxylate (MTFC), were synthesized. Under free radical conditions, MDFC gave homopolymer; MTFC did not. Copolymerizations of these monomers showed them to behave as very electron-deficient monomers, MTFC more so than MDFC. MDFC copolymerized with various vinyl ethers and styrenes to give high yields of almost 1:1 copolymers. Acrylonitrile copolymerized in lower yield with less incorporation of MDFC; trimethylethylenetricarboxylate did not copolymerize. Bicyclobutane-1-carbonitrile copolymerized well. MTFC copolymerized with the very electron-rich monomers t-butyl vinyl ether and p-methoxystyrene, leading to alternating and nearly alternating copolymers, respectively, and even styrene tended to give almost 1:1 copolymers. Acrylonitrile gave only polyacrylonitrile, and trimethylethylenetricarboxylate did not react with MTFC under free radical conditions. The reaction of MTFC with the electron-rich monomers t-butyl vinyl ether and p-methoxystyrene occurred spontaneously via charge transfer complexes. Thermally, the copolymers were rather stable, those of MTFC more so than those of MDFC.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A process that uses terephthalic acid and excess 1,4-butanediol for the production of polybutylene terephthalate was investigated and the reaction conditions were maximized for fast reaction and minimal loss of butanediol by dehydration to tetrahydrofuran. For best results a mixed catalyst was selected: butylstannoic acid and titanium tetrabutoxide (0.05 and 0.025 mole %, respectively, versus terephthalic acid) with a starting material ratio of butanediol: terephthalic acid of 1.7 at 210°C. The mixture cleared at 2.5 hr with a loss of 6% of butanediol. HPLC analysis showed that the clearing point corresponds to the disappearance of terephthalic acid and monohydroxybutyl terephthalate from the reaction mixture. Thus the polycondensation conditions can be applied before the clearing point with the result that the reaction is faster and tetrahydrofuran formation is minimized. Tetrahydrofuran is formed from butanediol in the reaction mixture by acid catalysis. Excess butanediol results in the formation of larger amounts. End group cyclization of terephthalate esters accounts for the slow tetrahydrofuran formation in the absence of excess butanediol.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Azoxyarylene compounds can be quantitatively formed by oxidative coupling of N-arylhydroxylamines in the presence of a copper-pyridine catalyst and dioxygen. This new method was utilized to synthesize a poly(azoxy arylene). Polymer 5 obtained has a weight average molecular weight of 6,500 and a number average molecular weight of 4,400.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A simple synthetic procedure for vinyloxy phosphorus monomers involves the reaction of the enolate of acetaldehyde, obtained from the cycloreversion of tetrahydrofuran in the presence of n-butyllithium, with chlorophosphites or phosphorochloridates leading to vinyl phosphites or vinyl phosphates, respectively, in high yield and purity.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerizability of a variety of mono- and multi- nitriles in the presence of free radical initiators at high temperature is determined by the concentration of available cyano-groups. Mononitriles do not polymerize, but multinitriles do so readily. If alkyl substituents are introduced in a molecule that easily polymerizes, this concentration and the ability to polymerize are lowered; if several or bulky substituents are introduced, the polymerization is completely prevented. Multinitriles containing ester groups undergo decarbomethoxylation in these polymerizations. The polymers are black and highly insoluble. From the few reactions that were attempted on these polymers, we can conclude that the structure is probably not the simple conjugated imine structure proposed by earlier investigators, but more experiments are needed to prove this point. The black polymers had conductivities less than 10-9 Ω-1 but, after heating at 700°C, conductivities in the range from 10-3 to 10-6 Ω-1 are observed.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...