Polymerization of 1-hexene catalyzed by Cp*TiMe3-B(C6F5)3; a mechanistic and structural study

2001 ◽  
Vol 79 (5-6) ◽  
pp. 1012-1018 ◽  
Author(s):  
Michael C Murray ◽  
Michael C Baird
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Monomer Unit ◽  
Gel Permeation Chromatography ◽  
Active Species ◽  
Methyl Groups ◽  
Molecular Weights ◽  
H Nmr ◽  
Gel Permeation ◽  
Cp Ti

Solutions of the Ziegler–Natta system Cp*TiMe3 – B(C6F5)3 in toluene catalyze the polymerization of 1-hexene to mixtures of atactic poly-1-hexenes and complex oligomeric materials, which were characterized by 1H and 13C{1H} NMR spectroscopy and gel permeation chromatography (GPC). The polymer molecular weights and the relative proportions of polymers and oligomers vary with temperature, monomer:catalyst ratios, and degree of dilution and may generally be rationalized in terms of a conventional Ziegler–Natta mechanism. The 13C{1H} NMR spectra of the polymers exhibit resonances suggesting significant degrees of 2,1-insertions during propagation, while experiments utilizing Cp*Ti(13CH3)3 verify that initiation in toluene involves predominantly via 1,2-insertion of the first monomer unit but that 2,1-insertions occur up to 15–20% of the time in CH2Cl2. NMR experiments involving Cp*Ti(13CH3)3 demonstrate that both methyl groups in the presumed active species Cp*TiMe+2 are incorporated into polymerKey words: titanium, polymers, polymerization, Ziegler–Natta

New Arylidene—Siloxane Polyesters

2003 ◽  
Vol 15 (3) ◽  
pp. 231-242 ◽  
Author(s):  
Carmen Racles ◽  
Vasile Cozan ◽  
Maria Cazacu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Nmr Spectroscopy ◽  
Liquid Crystalline ◽  
Gel Permeation Chromatography ◽  
Polymer Structure ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
H Nmr ◽  
Gel Permeation ◽  
Thermotropic Liquid Crystalline Behavior

New siloxane-containing polyesters with arylidene mesogenic moieties were prepared by copolycondensation reactions between bis(hydroxybuthyl)siloxanes, 2,6-bis(4-hydroxybenzylidene)cyclohexanone, and diacid chlorides such as sebacoyl and terephthaloyl. The polymer structure was confirmed by IR and 1H-NMR spectroscopy. They were characterized by gel permeation chromatography and ultraviolet analyses. The thermotropic liquid crystalline behavior was investigated by differential scanning calorimetry and polarized optical microscopy.

Synthesis and characterization of 4- and 6-arm star-shaped poly(ε-caprolactone)s

e-Polymers ◽  
2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Michael A. R. Meier ◽  
Ulrich S. Schubert
Keyword(s):  
Ring Opening ◽  
Analytical Techniques ◽  
Gel Permeation Chromatography ◽  
Laser Desorption ◽  
Ring Opening Polymerization ◽  
Molecular Weights ◽  
H Nmr ◽  
Flight Mass Spectrometry ◽  
Gel Permeation

AbstractStar-shaped poly(ε-caprolactone) (PCL) polymers were synthesized and fully characterized by gel permeation chromatography, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) as well as 1H NMR spectroscopy. First a series of four-armed PCLs with different molecular weights was prepared and analyzed with the mentioned analytical techniques revealing that the applied ring-opening polymerization was controlled and defined star-shaped polymers could be synthesized. Subsequently, also the synthesis of six-armed PCL polymers was investigated with the conclusion that also these starshaped polymers could be prepared in a controlled fashion.

Magnetic resonance imaging (1H) and spectroscopy (1H, 31P) of growing chicken embryos

1993 ◽  
Vol 73 (4) ◽  
pp. 953-965 ◽  
Author(s):  
A. Lirette ◽  
Z. Liu ◽  
D. C. Crober ◽  
R. A. Towner ◽  
U. M. Oehler ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Surface Coil ◽  
Nmr Imaging ◽  
Chicken Embryos ◽  
H Nmr ◽  
Imaging And Spectroscopy ◽  
Two Peaks

Nuclear magnetic resonance (NMR) imaging and spectroscopy techniques were used to observe in vivo anatomical and metabolite changes, respectively, in developing chicken embryos. Proton (1H) NMR images of the eggs revealed major changes in yolk shape from day 2 to day 6. Embryos were visible from day 6 to hatching, and good embryonic anatomical images were obtained. Two peaks were observed from 1H-NMR spectroscopy of fertilized eggs: one for lipid methylene protons, and one for water protons. Water peak to lipid peak ratios did not vary significantly (P > 0.05) from day 2 to day 21 of incubation. Localized 31P-NMR spectra of developing embryos were obtained with either a 31P surface coil or a double-tuned 31P/1H volume coil. The surface-coil method gave a greater signal to noise ratio by a factor of four. The 31P-NMR spectra indicated two peaks at day 2; these were attributed to phosphomonoesters and phosphodiesters. The three peaks characteristic of ATP appeared on day 11 and increased in size until hatching. From day 19, phosphocreatine was detectable. There appeared to be a good correlation between 31P-metabolite changes detected by in vivo 31P-NMR spectroscopy and literature values for biochemical analyses of developing chicken embryos. The advantage in using NMR imaging and spectroscopy techniques is that anatomical and metabolic changes can be obtained in vivo, non-invasively and repeatedly as an embryo develops. Key words: NMR, MRI, embryo, poultry

scholarly journals NMR Spectroscopy as a Tool for Studying Asphaltene Composition

2019 ◽  
Vol 92 (3) ◽  
pp. 323-329 ◽  
Author(s):  
Jelena Parlov Vuković ◽  
Predrag Novak ◽  
Tomislav Jednačak
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Analytical Techniques ◽  
Complex Mixtures ◽  
Aggregation Process ◽  
Molecular Architecture ◽  
Valuable Data ◽  
Molecular Weights ◽  
Nmr Techniques ◽  
Oil Components

Asphaltenes are the most polar oil components with molecular weights between 500 and 1000 Da, which primarily consist of carbons and hydrogens, some heteroatoms, such as nitrogen, sulphur, oxygen and traces of nickel, vanadium and iron. Owing to their extreme complexity, it is almost impossible to completely identify all the compounds present in asphaltene samples. Various analytical techniques and approaches were used to characterize asphaltenes but their structure and composition are still a matter of thorough investigations. NMR spectroscopy can reveal useful information on asphaltene molecular architecture and aggregation process. In that respect, one- and two-dimensional NMR techniques have widely been employed. Although NMR spectra of these complex mixtures are difficult to interpret, they still can provide valuable data, especially in combination with statistical methods. Some distinctive examples of using NMR spectroscopy to study asphaltenes are given in this review.

scholarly journals Assessment of 1H NMR Spectroscopy for Specific Metabolite Fingerprinting of Angelica sinensis

2008 ◽  
Vol 3 (5) ◽  
pp. 1934578X0800300
Author(s):  
Dongmin Su ◽  
Jinglan Han ◽  
Shishan Yu ◽  
Hailin Qin
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Authentic Sample ◽  
Angelica Sinensis ◽  
Metabolite Fingerprinting ◽  
H Nmr ◽  
Pure Compounds ◽  
Polar Extracts

The 1H NMR fingerprints of fractionated non-polar extracts (CSPD A) from the roots of Angelica sinensis of six different specimens were assigned by comparison with the 1H NMR spectra of the isolated pure compounds. The 1H NMR fingerprints showed exclusively characteristic resonance signals of the major constituents of the plant. The 1H NMR fingerprint established for an authentic sample of A. sinensis can be used for authenticating A. sinensis species.

Morpholines-(IV)

1971 ◽  
Vol 26 (11) ◽  
pp. 1140-1143 ◽  
Author(s):  
Riaz F. Abdulla ◽  
Alok N. Bannerji
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Beta Lactams ◽  
Aryl Substituent ◽  
Open Chain ◽  
H Nmr

Cyclodehydrohalogenation-beta-Lactams-Morpholin-3-ones-H'-NMR SpectroscopyN-Aryl-N-chloroacetyl-2-chlorophenacylamines (2) give morpholinones 3, or beta-lactams 4, depending upon the N-aryl-substituent. N-Phenyl-N- (2,3-dibromo-3-phenylpropionyl) -4-nitrophenacylamine did not undergo base-catalysed cyclization but gave, instead, the α,β-unsaturated, open-chain amide 5. N-Aryl-N-chloroacetyl-aminomethyl-2-naphthylketones afford only beta-lactams. The first attempt at the synthesis of a 2-chloro-3-oxo-morpholine resulted in the isolation of the 2-hydroxyderivative. The H1-NMR spectra of some more 3-oxo-morpholines have been recorded.

scholarly journals Purification and characterization of two human erythrocyte arylamidases preferentially hydrolysing N-terminal arginine or lysine residues

1978 ◽  
Vol 175 (3) ◽  
pp. 1051-1067 ◽  
Author(s):  
K K Mäkinen ◽  
P L Mäkinen
Keyword(s):  
Substrate Inhibition ◽  
Gel Filtration ◽  
Deae Cellulose ◽  
Gel Permeation Chromatography ◽  
Ph Optimum ◽  
Preparative Scale ◽  
Molecular Weights ◽  
Gel Permeation ◽  
Lysine Residues ◽  
Enzyme I

Two arylamidases (I and II) were purified from human erythrocytes by a procedure that comprised removal of haemoglobin from disrupted cells with CM-Sephadex D-50, followed by treatment of the haemoglobin-free preparation subsequently with DEAE-cellulose, gel-permeation chromatography on Sephadex G-200, gradient solubilization on Celite, isoelectric focusing in a pH gradient from 4 to 6, gel-permeation chromatography on Sephadex G-100 (superfine), and finally affinity chromatography on Sepharose 4B covalently coupled to L-arginine. In preparative-scale purifications, enzymes I and II were separated at the second gel-permeation chromatography. Enzyme II was obtained as a homogeneous protein, as shown by several criteria. Enzyme I hydrolysed, with decreasing rates, the L-amino acid 2-naphtylamides of lysine, arginine, alanine, methionine, phenylalanine and leucine, and the reactions were slightly inhibited by 0.2 M-NaCl. Enzyme II hydrolysed most rapidly the corresponding derivatives of arginine, leucine, valine, methionine, proline and alanine, in that order, and the hydrolyses were strongly dependent on Cl-. The hydrolysis of these substrates proceeded rapidly at physiological Cl- concentration (0.15 M). The molecular weights (by gel filtration) of enzymes I and II were 85 000 and 52 500 respectively. The pH optimum was approx. 7.2 for both enzymes. The isoelectric point of enzyme II was approx. 4.8. Enzyme I was activated by Co2+, which did not affect enzyme II to any noticeable extent. The kinetics of reactions catalysed by enzyme I were characterized by strong substrate inhibition, but enzyme II was not inhibited by high substrate concentrations. The Cl- activated enzyme II also showed endopeptidase activity in hydrolysing bradykinin.

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