Thermal and structural investigation of random ethylene/1-hexene copolymers with high 1-hexene content

Random ethylene/1-hexene copolymers with the 1-hexene content in the range from 2 to 28 mol% were produced with a novel post-metallocene catalyst and analyzed by three techniques, FTIR, ¹³C NMR, and DSC. The 1-hexene content and the sequence distribution in the copolymers were determined by means of FTIR-M and ¹³C NMR. The crystallization behavior of the copolymers was studied by DSC under dynamic and isothermal conditions; the Avrami model was used to analyze the crystallization kinetics. It was found that both the 1-hexene content and the crystallization temperature affect the relative crystallinity. The bulk crystallization rate decreases with the 1-hexene content and reduces exponentially with an increase of T _c. The melting behavior of isothermally crystallized samples was also investigated and it was found that the melting temperatures of the copolymers under equilibrium conditions were related to the composition.     

Solid State NMR Characterisation of Encapsulated Molecules in Mesoporous Silica

Ibuprofen molecules have been encapsulated in mesoporous MCM-41 type-silica functionalised or not by amino groups. They have been characterised by ¹³C and ¹H solid state NMR spectroscopy. The ¹³C MAS single pulse or cross polarization NMR spectra, as well as the ¹H MAS NMR spectra demonstrate an extremely high mobility of the ibuprofen molecules when the matrix is not functionalised. On the contrary, when the silica matrix is functionalized by amino groups, the ¹³C NMR response shows less mobility suggesting the existence of interactions between the amino groups and the carboxylic groups. Benzoic acid as well as benzamide have also been encapsulated and their NMR responses compared to that of ibuprofen.     

Configuration and conformation of methyl 2,3-anhydro-4-deoxy-pyranosides by 1H and 13C NMR spectra

¹³C NMR spectra of 24 methyl 2,3-anhydro-4-deoxy-pento and hexopyranosides have been obtained. ¹H NMR spectra were also recorded for comparison purposes. The ¹³C NMR data can be used for differentiation of the stereo-isomeric epoxide configuration. ¹H and ¹³C NMR spectra give some insight, though still of qualitative nature, into conformation of epoxy compounds.     

13C NMR spectroscopy of copoly(arylenephthalide) derivatives with diphenyloxide and terphenyl fragments in the main chain

¹H and ¹³С NMR spectral assignments have been provided for low‐molecular reference monomers, poly(diphenyleneoxidephthalide) and periodic copoly(arylenephthalide) derivatives such as AB, ABB, and ABBB (where A = terphenylenephthalide and B = diphenyleneoxidephthalide) using ¹H‐¹H COSY, ¹H‐¹³C HSQC and HMBC NMR techniques. Distinctive ¹³C NMR chemical shifts of a main chain have been observed containing fragments of similar structures and lateral phthalate groups being part of various diads. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of ionic liquid counterions on activity and selectivity of ethylene trimerization using chromium-based catalysts in biphasic media

In recent years ionic liquids (ILs) have attracted much interest because of their widespread use in various fields. Several trimerization and oligomerization catalysts have been evaluated in ILs with different organic–inorganic hybrid structures. High catalytic activity and selectivity, easy product separation, and recycling of the catalyst are the advantages of a biphasic catalyst system compared to the homogeneous catalysts. In this study, the influence of IL counter-anions on activity and selectivity of the ethylene trimerization catalysts based on Cr-SNS-R was investigated. All synthesized materials were characterized using Fourier-transform infrared spectroscopy, ¹H NMR, ¹³C NMR, UV–Vis. spectroscopy, thin-layer chromatography, and elemental analysis (CHNS). In ethylene trimerization reaction, the dodecyl substituent in the SNS ligand exhibited better activity and selectivity than the butyl substituent. The results revealed that the presence of BF₄⁻ as a counter-anion in the IL led to an increase in activity and selectivity compared to Br⁻ and I⁻ counter-anions. It was found that the BF₄⁻ counter-anion plays a conclusive role in the development of 1-hexene activity and selectivity to a maximum amount of 71,132 g_1-C6/(g_Cr × h) and more than 99%, respectively. Finally, the catalyst was reused thrice without losing its 1-hexene selectivity.     

New Oenotheralanosterol A and B Constituents from the Oenothera biennis Roots

Two new compounds oenotheralanosterol A and B along with four known compounds have been isolated from the roots of Oenothera biennis. Their structures have been elucidated with the help of 300 MHz NMR using 1D and 2D spectral methods viz: ¹H and ¹³C NMR, ¹H‐¹H COSY, ¹H‐¹³C HETCOR and DEPT aided by EIMS, ESI Mass and IR spectroscopy.     

Chimie des complexes de metaux de transition avec des hydrocarbures cyanes : III. Quelques observations sur la conformation et la reactivite de complexes dicyclopentadienyles du molybdene et du tungstene

A new class of cyclic telluronium salts has been prepared. All the salts are stable in solution in CHCl₃ or dimethylsulphoxide (DMSO). Conductivity measurements in DMSO and dimethylformamide (DMF) have shown that considerable ion pairing occurs in solution. Infrared, ¹H, ¹³C, ¹²⁵Te NMR, and mass spectra are reported and discussed.     

Effect of 1-Hexene Comonomer on Polyethylene Particle Growth and Kinetic Profiles

Summary: The polymer growth and the microstructure of the final polymer are greatly affected by mass transfer, especially in the early stages of polymerization. In the present work, the catalytic system (nBuCp)₂ZrCl₂/MAO immobilized over SiO₂-Al₂O₃ has been tested in ethylene-1-hexene copolymerizations using different amounts of comonomer. The catalytic activity shows a positive comonomer effect up to 1-hexene concentration of 0.724 mol/L since larger amounts of 1-hexene lead to a decrease in the activity. Copolymer properties analyzed by ¹³C NMR, GPC, CRYSTAF and DSC point to the presence of important amorphous regions in the growing polymer chains as the 1-hexene concentration increases. In order to study the incorporation of 1-hexene during ethylene polymerization, several experiments were performed with 0.194 mol/L of 1-hexene, 5 bar of ethylene pressure and different polymerization times. The incorporation of 1-hexene decreases slightly at polymerization times above 20 minutes. From cross-sectioned SEM images it can be concluded that the presence of 1-hexene helps catalyst fragmentation which could be related with the filter effect proposed by Fink.     

Configurations and conformations in acyclic,unsaturated hydrocarbons. A 13C NMR study

¹³C NMR (CMR) spectra of a number of di- and trisubstituted ethylenes have been measured. Very consistent values are found for the differential shieldings of allylic carbons in a number of linear, (Z)- and (E)-disubstituted ethylenes. The discrepancies between the several structural elements are explained tentatively by assuming different rotational preferences in the (Z)-isomers, the (E)-isomers, or both. The results obtained for some branched olefins are qualitatively in agreement with conclusions reached in previous ¹H NMR (PMR) investigations, with the possible exception of 2,5-diMe-3-hexene. Differential shieldings in trisubstituted ethylenes are larger than in disubstituted ethylenes, probably as a consequence of steric interaction between geminal substituents. It is confirmed, that API's recent relabelling of the isomers of 3-Me-2-hexene was justified. Furthermore, the (E)-configuration is assigned to the high-boiling isomer of 3,4,4-triMe-2-pentene. On the other hand, the high-boiling isomer of 3-Et-4-Me-2-pentene is shown to be the (Z)-isomer. For the isomeric pair of geraniol and nerol, the (E)-configuration is assigned to the former and the (Z)-configuration to the latter, in agreement with our recent PMR investigations.     

脯氨酸类N-酰胺衍生物的核磁共振研究

脯氨酸类衍生物结构独特,鲜有报道利用核磁共振（nuclear magnetic resonance,NMR）技术对氨基酸的手性进行鉴别.利用多种NMR技术:1H NMR、1H-1H同核位移相关谱（1H-1H COSY）、1H-1H质子全相关谱（1H-1H TOCSY）、1H-1H核Overhauser效应谱（1H-1H NOESY）、13C NMR、无畸变的极化转移增强法（DEPT135°）、1H-13C检出1H的异核单量子相干（1H-13C HSQC）和1H-13C检出1H的异核多键相关（1H-13C HMBC）,对脯氨酸类N-酰胺衍生物两种构象异构体的1H和13C NMR进行了全归属,确定了室温下在二甲基亚砜（DMSO）中L型和D型的顺反异构体以相同的比例同时存在.     

1H and 13C NMR studies on 1,3,2-dioxarsolanes

The ¹H and ¹³C NMR spectra of a series of 1,3,2-dioxarsolanes have been obtained at 2.1 T and some at 9.4 T. The chemical shifts and spin-spin coupling constants have been obtained from complete spectral analyses of the ¹H and proton-coupled ¹³C spectra. The spectral data are interpreted on the basis of two rapidly interconverting half-chair conformers with a pseudoaxial substituent at arsenic. Unique assignment of syn/anti or cis/trans geometries have been made from ¹H or ¹³C NMR spectroscopy alone. The syn and trans isomers of the 4-methyl- and 4,5-dimethyl-1,3,2-dioxarsolanes, respectively, appear to be conformationally biased towards the forms with pseudoequatorial methyl groups. The general trends in the geminal and vicinal ¹H? ¹H and ¹³C? ¹H coupling constants are interpreted in terms of stereospecific, electronegativity and lone-pair effects of the oxygen heteroatoms and conformational factors. The NMR data on the 1,3,2-dioxarsolanes are discussed with reference to related 1,3-dithoxa- and 1,3-dithia- five-membered rings with As, P, S or C at the 2-position.     

Demonstration of methylene-ether bridge formation in melamine-formaldehyde resins

¹H and ¹³C NMR have been used for the quantitative determination of methylene-ether bridges in melamine-formaldehyde (MF) resins. The amount of methylene-ether bridges was determined by ¹³C NMR from the number of monomethylolated amino groups consumed in the condensation reactions and is in agreement with that calculated from the condensation water contents. This latter method, which involves a combination of ¹H and ¹³C NMR, is based on the amount of condensation water released during the formation of both methylene and methylene-ether bridges. © 1995 John Wiley & Sons, Inc.     

Synthesis, Characterization And Biphasic Catalysiswith RuCl(η5-C5H5)(TPPMS)2

A synthetic route is reported for the water soluble complex RuCl(h⁵- C₅H₅)(TPPMS)₂(1), (TPPMS = (C₆H₅)₂P(C₆H₄-m-SO₃Na) and characterized by UV-Vis, FTIR, ¹H, ¹³C NMR and GC-MS. Complex 1 is a good catalytic precursor in biphasic media (toluene/ water) for 1-hexene hydrogenation under moderate reaction conditions (e.g. 500 psi H₂, 100°C) giving good yields of n-hexane, and smaller amounts of cis-2-hexene and trans-2-hexene. Other organic substrates (cinnamaldehyde, crotonaldehyde, cyclohexene, acetone and butylaldehyde) are hydrogenated.     

Structure elucidation,complete NMR assignment and PM5 theoretical studies of new hydroxy‐aminoalkyl‐α,β‐unsaturated derivatives of the macrolide antibiotic josamycin

Four new hydroxy‐aminoalkyl derivatives of α,β‐unsaturated macrolide‐josamycin (2–5) have been synthesised and their structures have been studied by means of ¹H and ¹³C NMR and FT‐IR methods. Complete assignment of resonances in the ¹H and ¹³C NMR spectra has been made on the basis of ¹H? ¹³C HSQC, ¹H? ¹³C HMBC, ¹H? ¹H COSY, ¹H? ¹H NOESY 2D experiments. Spectroscopic data indicated that for the derivatives 3 and 4 some equilibrium between two different structures exists in contrast to derivatives 2 and 5. The lowest‐energy structures of the new derivatives of josamycin have been calculated and visualised by PM5 method at semi‐empirical level of theory, taking into account the NMR and FT‐IR data. The most significant differences between the structures of josamycin and its newly synthesised derivatives' were found in the conformation of the macrolide aglycone part and in the mutual orientation of the 4‐O‐isovalerylmycarosylmycaminose moiety relative to the aglycone part. PM5 semi‐empirical calculations indicated that the structures of the new macrolide derivatives are stabilised by rather weak intramolecular hydrogen bonds in agreement with spectroscopic data. Antimicrobial properties of the new derivatives 2–5 as well as those having an acetate group at C‐3 (6 and 7) were determined and compared to that of the parent macrolide antibiotic josamycin (1). Copyright © 2010 John Wiley & Sons, Ltd.     

13C?1H coupling constants in 9, 10-dihydroanthracene

The ¹H and ¹³C NMR spectra of 9,10-dihydroanthracene have been obtained at 2.1 and 9.4 T using selective decoupling of the methylene protons. Complete spectral analyses of the experimental spectra have provided the chemical shifts and coupling constants. The ¹³C? ¹H coupling constants in 9, 10-dihydroanthracene and biphenylene have been well accounted for by MNDO theoretical calculations of the molecular geometries and bond orders in these compounds.     

Structural Study on NMR and X-Ray of Lactucopicrin—A Guaianolide Ester

The guaianolide ester is a potent inhibitor of cancer cells. Lactucopicrin, a guaianolide, shows analgesic, antitussic, and sedative activities. In order to investigate its structure, ¹H and ¹³C NMR and 2D NMR have been carried out at a proton field strength of 400 MHz and a carbon field strength of 100 Mhz in DMSO-d ₆ at 20°C. Resonances for all protons and carbons have been assigned. The results of HMQC and HMBC experiments suggest that the structure of lactucopicrin is as shown in Fig. 1. Its stereostructure is verified by the X-ray experiment. ¹H and ¹³C NMR of lactucopicrin are reported. Its 2D NMR and X-ray are reported for the first time.     

13C, 15N and 113Cd NMR and Molecular Orbital Studies of Novel Bile Acid N-(2-aminoethyl)amides and Their Cd2+-complexes

Lithocholic acid N-(2-aminoethyl)amide (1) and deoxycholic acid N-(2-aminoethyl)amide(2) have been prepared and characterized by¹H, ¹³C and ¹⁵N NMR. The accurate molecular masses of 1 and 2 have been determined by ESI MS. The formation of the Cd²⁺-complexes (1+Cd and 2+Cd) in CD₃OD solution have been detected by ¹H,¹³C, ¹⁵N and ¹¹³Cd NMR. The ¹³C NMR chemical shift assignments of 1 and 2 and their Cd²⁺-complexes are based on DEPT-135 and z-GS ¹H,¹³C HMQC experiments as well as comparison with the assignments of the related structures. The ¹⁵N NMR chemical shiftassignments of the ligands and theirCd²⁺-complexes are based on z-GS¹H,¹⁵N HMBC experiments. ¹³C NMR chemical shift differences between 1and its 1:1 Cd²⁺-complex based on ab initiocalculations at Hartree-Fock SCI-PCM level using3-21G(d) basis set are in agreement with theexperimental shift changes observed onCd²⁺-complexation.     

Reactions of (E)-4-Stilbenethiole with Dibromoalkanes

New substituted stilbenes have been prepared by reactions of (E)-4-stilbenethiole with dibromoalkanes. ¹H and ¹³C NMR spectra of new compounds have been assigned unambiguously on the basis of a combination of homo- (¹H?¹H COSY) and heteronuclear (¹ H?¹³C COSY-HETCOR) two-dimensional methods, chemical shifts, and spin-coupling constants.     

Triterpenoids from Abies species

From an acid fraction of an ethereal extract of Siberian fir needles two new stereoisomeric acids, the molecules of which have a modified lanostane carbon skeleton, have been isolated in the form of methyl esters. The structures of the molecules of these substances have been established by the use of¹³C and¹H NMR,¹H-¹H and¹³C-¹H two-dimensional NMR spectra, circular dichroism, and chemical transformations as (24Z)- and (24E)-8(14 → 13)-abeo-17,13-friedo-lanosta-8,14(30),24-triene-3,23-dion-26-oic acids.     

Synthesis,characterziation, semi-empirical quantum-mechanical study and biological activity of organotin(IV) complexes with 2-ethylanilinocarbonylpropenoic acid

Seven different organotin(IV) complexes have been synthesized by reacting 2-ethylanilinocarbonylpropenoic acid with R₂SnCl₂/R₃SnCl under reflux conditions. The organotin(IV) complexes along with ligand have been characterized by different techniques including elemental analysis, FT-IR and multinuclear NMR (¹H and ¹³C). IR data show that complexation occurs through -COO site and the ligand is bidentate which is also confirmed by the semi-empirical quantum-mechanical study. ¹H and ¹³C NMR data confirm the tetrahedral geometry of complexes in solution. The complexes as well as the ligand were also checked for various