438 research outputs found
Ruthenium catalyzed equilibrium ring-opening metathesis polymerization of cyclopentene
Polypentenamer was synthetized by equilibrium ring-opening metathesis polymerization (ROMP) using well-defined ruthenium catalyst systems. It was found that the equilibrium time is influenced by the catalyst loading or the catalyst activity, however as expected, the overall cyclopentene conversion is determined only by the applied reaction temperature. Equilibrium of the growing chain and monomer was observed and the activation enthalpy and entropy were determined as: ÎH = â5.6 kcal mol^(â1); ÎS = â18.5 cal mol^(â1) K^(â1). So far these values are the lowest which are reported for cyclopentene polymerization catalyst systems. This unique feature of the equilibrium polymerization opens a way for the synthesis of durable, environmentally friendly elastomers where tires can be not only synthetized but also readily recycled by the same transition metal catalyst system
KatalĂzis karbĂ©n-komplexekkel = Catalysis with carbene complexes
RendkĂvĂŒl hatĂĄsos Ășj kobalt-katalizĂĄlt szĂ©n-szĂ©n kötĂ©shez vezetĆ, ĂĄltalĂĄnosan alkalmazhatĂł szintĂ©zis utat fedeztĂŒnk fel karbonsav-szĂĄrmazĂ©kok elĆĂĄllĂtĂĄsĂĄra, amelynek lĂ©nyege egy ketĂ©n intermedier kĂ©pzĆdĂ©se a diazo-csoport szĂ©n-monoxiddal valĂł kicserĂ©lĂ©se ĂĄltal. A karbonsav szĂĄrmazĂ©kok a ketĂ©n intermedierbĆl vezethetĆk le vĂĄltozatos B-H tĂpusĂș reagensekkel. A karbonsav szĂĄrmazĂ©kok 100%-ot megközelĂtĆ kitermelĂ©ssel nyerhetĆk ezen egyszerƱen megvalĂłsĂthatĂł egyreakciĂłedĂ©nyes katalitikus reakciĂłval. A trimetilszilil-diazometĂĄn Co2(CO)8-katalizĂĄlt karbonilezĂ©sĂ©t szobahĆfokon Ă©s lĂ©gköri nyomĂĄson alkalmas preparatĂv mĂłdszerrĂ© fejlesztettĂŒk trimetilszilil-ketĂ©n minden eddiginĂ©l egyszerƱbb elĆĂĄllĂtĂĄsĂĄra. RĂłdium- Ă©s pallĂĄdium-komplexek alkalmas katalizĂĄtoroknak bizonyultak CFC Ă©s HCFC vegyĂŒletek homogĂ©nfĂĄzisĂș katalitikus dehidrohalogĂ©nezĂ©sĂ©re. A kidolgozott mĂłdszerek lehetĆvĂ© teszik e környezetre kĂĄros anyagok hasznos termĂ©kekkĂ© valĂł ĂĄtalakĂtĂĄsĂĄt. | We discovered a very efficient new cobalt-catalyzed carbon-carbon bond-forming synthesis leading to carboxylic acid derivatives. The essence of this high-yield one-pot synthesis is the catalytic substitution of a diazo group by carbon monoxide to form a ketene intermediate, which can be trapped with different B-H type reagents to give various carboxylic acid derivatives in up to 100% yield. The Co2(CO)8-catalyzed carbonylation of trimethylsilyldiazomethane at ambient conditions give trimethylsilylketene in excellent isolated yields, which seems to be the best preparative method so far to obtain this precious synthetic intermediate. Rhodium and palladium complexes proved to be effective catalysts in hydrodechlorination of CFC and HCFC compounds in homogeneous phase. By this way these harmful chemicals can be converted to useful products
Detecting Vital Signs with Wearable Wireless Sensors
The emergence of wireless technologies and advancements in on-body sensor design can enable change in the conventional health-care system, replacing it with wearable health-care systems, centred on the individual. Wearable monitoring systems can provide continuous physiological data, as well as better information regarding the general health of individuals. Thus, such vital-sign monitoring systems will reduce health-care costs by disease prevention and enhance the quality of life with disease management. In this paper, recent progress in non-invasive monitoring technologies for chronic disease management is reviewed. In particular, devices and techniques for monitoring blood pressure, blood glucose levels, cardiac activity and respiratory activity are discussed; in addition, on-body propagation issues for multiple sensors are presented
Concert recording 2016-04-02
[Track 01]. Moondance / John Stevens -- [Track 02]. Turkish march / W.A. Mozart ; translated by Keith Mehlan -- [Track 03]. To a wild rose from Woodland sketches / E. MacDowell ; arranged by J. Lockhart -- [Track 04]. Fantasy movements. Adagio - Allegro vivace ; [Track 05]. Allegro ; [Track 06]. Slowly ; [Track 07]. Very fast & manic ; [Track 08]. Adagio - Allegro / Anthony Plog -- [Track 09]. Saint James infirmary / Joe Primrose ; arranged by Mike Forbes
Guest Artist: Western Brass Quintet
This recital is in partial fulfillment of the graduation requirements for the degree, Master of Music in Performance.
Kemp Recital HallApril 7, 2015Tuesday Evening7:30 p.m
Guest Artists Recital: Western Brass Quintet: Donald Bullock, Trumpet; Stephen Jones, Trumpet; Neil Sanders, Horn; Russell Brown, Trombone; Robert Whaley, Tuba; September 27, 1976
Hayden AuditoriumMonday EveningSeptember 27, 19768:00 p.m
Student Brass Quintet: Robert Fund, Trumpet; Jim Cassens, Trumpet; Peter Johnson, Horn; David Kotowski, Trombone; Brian Frederiksen, Tuba; October 15, 1973
Hayden AuditoriumMonday EveningOctober 15, 19738:15 p.m
Synthesis of recyclable tire additives via equilibrium ring-opening metathesis polymerization
Linear <i>trans</i>-polypentenamers
are highly desired
materials among synthetic tire additives due to their comparable physical
properties to natural rubber. <i>trans</i>-Polypentenamer
can be prepared by equilibrium ring-opening metathesis polymerization
(ROMP) using well-defined ruthenium catalyst systems. This unique
feature of the equilibrium polymerization reaction opens a way for
the synthesis of durable, environmentally benign elastomers where
polymers including synthetic tire additives can be synthesized and
readily recycled using the same transition metal catalyst system.
The addition of silica fillers significantly improves the physical
properties of the composite materials in comparison to the use of
polymeric material. It is also known that the structural effects and
the polymerâfiller surface interaction are of prime importance.
Herein, we report on the synthesis of silica filler compatible recyclable
polypentenamer copolymers via equilibrium ROMP of cyclopentene <b>1</b> and 4-(triethoxy)Âsiloxy cyclopentene <b>11</b>. It
has been demonstrated that polypentenamer tire additives can be synthesized
via equilibrium ROMP affording polymers with high yields (>80%)
at
0 °C and can be readily depolymerized at 40 °C and/or under
diluted conditions using the same metathesis catalyst systems. Furthermore,
the polypentenamer can also be synthesized in neat at room temperature
and at very low (10<sup>5</sup>) monomer/catalyst ratio. This methodology
is based on the synthesis of polyolefins utilizing a ruthenium-based
metathesis catalyst via equilibrium ROMP of cyclopentenes and their
silylated derivatives
One-pot Synthesis of 1,3-Butadiene and 1,6-Hexanediol Derivatives from Cyclopentadiene (CPD) via Tandem Olefin Metathesis Reactions
A novel tandem reaction of cyclopentadiene (CPD) leading
to high value linear chemicals via ruthenium catalyzed ring opening cross metathesis (ROCM), followed by cross metathesis (CM) is reported. The ROCM of cyclopentadiene (CPD) with ethylene using commercially available 2nd gen. Grubbs metathesis catalysts (1âG2) gives 1,3âbutadiene (BD) and 1,4âpentadiene (2) (and 1,4âcyclohexadiene (3)) with reasonable yields (up to 24â% (BD) and 67â% (2+3) at 73â% CPD conversion) at 1â5â
molâ% catalyst loading in toluene solution (5â
V% CPD, 10â
bar, RT) in an equilibrium reaction. The ROCM of CPD with cisâbutene diol diacetate (4) using 1.00 â 0.05â
molâ% of 3rd gen. Grubbs (1âG3) or 2nd gen. HoveydaâGrubbs (1âHG2) catalysts loading gives hexaâ2,4âdieneâ1,6âdiyl diacetate (5), which is a precursor of 1,6âhexanediol (an intermediate in polyurethane, polyester and polyol synthesis) and heptaâ2,5âdieneâ1,7âdiyl diacetate (6) in good yield (up to 68â% or TON: 1180). Thus, convenient and selective synthetic procedures are revealed by ROCM of CPD with ethylene and 4 leading to BD and 1,6âhexanediol precursor, respectively, as key components of commercial intermediates of highâperformance materials
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