Sequence Distribution of cis-1,4- and trans-1,4-Units in Polyisoprenes

1976 ◽  
Vol 49 (5) ◽  
pp. 1269-1275
Author(s):  
Y. Tanaka ◽  
H. Sato
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectroscopy ◽  
13C Nmr Spectra ◽  
Sequence Distribution ◽  
Isomeric Structures ◽  
Nmr Signals

Abstract Recently 13C NMR spectroscopy has been successfully applied to investigate the sequence distribution of 1,2- and 1,4-units or cis-1,4- and trans-1,4-units in polybutadienes. As for polyisoprenes, however, few investigations have been made on the sequence distribution of isomeric structures using this technique, although Duch and Grant have assigned the 13C NMR signals of cis-1,4- and trans-l,4-homopolyisoprenes. In previous work we have found new signals attributed to cis-trans linkages in the 13C NMR spectra of cis-trans isomerized polyisoprenes and assigned the signals using diad sequences of cis-1,4- and trans-l,4-units. We have also studied the 13C NMR spectra of hydrogenated polyisoprenes containing various amounts of 1,4- and 3,4-units and the sequence distribution of 1,4- and 3,4-units were discussed for n-BuLi-catalyzed polyisoprenes. In this work we have investigated the sequence distribution of chicle polyisoprene and cis-trans isomerized 1,4-polyisoprenes containing various ratios of cis-1,4- and trans-1,4-units.

Sequence Distribution of Polyisoprenes

1976 ◽  
Vol 49 (5) ◽  
pp. 1259-1268 ◽  
Author(s):  
Y. Tanaka ◽  
H. Sato
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Polymer Chains ◽  
Absolute Amount ◽  
Mechanical And Thermal Properties ◽  
13C Nmr Spectra ◽  
Pyrolysis Gas ◽  
Sequence Distribution ◽  
The Difference ◽  
Isomeric Structures

Abstract Isoprene can be polymerized into four types of isomeric structures; cis-1,4, trans-1,4, 3,4, and 1,2, depending on catalysts and polymerization conditions. So far, the difference of mechanical and thermal properties among polyisoprenes has been discussed chiefly on the basis of amounts of these isomeric structures. However, it is quite reasonable to expect that the polymer properties are affected not only by the composition of isomeric structures but also by the distribution of isomeric structures, the arrangement of head and tail linkages, and the degree of branching. This idea was adopted by Hackathorn and Brock as an explanation of the poor crystallizability of lithium polyisoprene; i.e. head-to-head and/or tail-to-tail linkages of 1,4- and 3,4-units prevented the crystallization of the polymer. Pyrolysis-gas chromatography has been applied to the investigation of the sequence distribution of 1,4- and 3,4-units in polyisoprenes. This method is based on the structural relationship between the isoprene dimers and the diad sequences of 1,4- and 3,4-units. However, it is difficult to discuss the slight differences in the yield of each dimer because the absolute amount of the dimers is small (∼30%) compared to the isoprene monomer (∼65%). Ozonolysis has been used to measure the amount of head-to-head, head-to-tail, and tail-to-tail linkages of the 1,4-unit in polyisoprenes. This method, however, is limited to the detection of these linkages of 1,4-units. In a previous paper, we have investigated 13C NMR spectra of chicle and cis-trans isomerized polyisoprenes and determined the sequence distribution of cis-1,4- and trans- 1,4-units in these polymers. We have also studied 13C NMR spectra of hydrogenated polyisoprenes prepared with n-BuLi-Et2O catalysts and found that 1,4- and 3,4-units were distributed randomly along the polymer chains regardless of the amounts of 3,4-units. In the present investigation we prepared various types of polyisoprenes and discussed the distribution of 1,4-and 3,4-units, arrangements of head and tail linkages, the branches of polymer chains, and the tacticity of polyads of 3,4-unit by the use of 13C NMR spectra of hydrogenated polyisoprenes.

Synthesis of Phosphatidylcholines Possessing Functionalized Acids at sn-2, and 13C–14N and 13C–31P Couplings in Their 13C NMR Spectra

Synlett ◽  
2020 ◽  
Vol 31 (07) ◽  
pp. 718-722
Author(s):  
Masao Morita ◽  
Shun Saito ◽  
Riku Shinohara ◽  
Ryohei Aoyagi ◽  
Makoto Arita ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectroscopy ◽  
13C Nmr Spectra ◽  
Epoxy Acids ◽  
Acid Acid ◽  
Standard Base ◽  
Acid Labile

Although 4-Me2NC5H4N (DMAP) is a standard base for esterification of (2-Me-6-NO2-C6H3CO)2O (MNBA), N-methylimidazole (NMI) was examined for the condensation of acids with 1-stearoyl-lysophosphatidylcholine because of the non-tailing nature of NMI on silica gel. Acids tested were EPA, α-linolenic acid, TBS ethers of 18-HEPE and ricinoleic acid, acid-labile epoxy acids, and a phenyldiynyl acid. The condensation proceeded well with these acids, and chromatographic separation of resulting phosphatidylcholines and remaining NMI was easily performed. During the characterization of the products by 13C NMR spectroscopy, 13C–14N and 13C–31P couplings were observed.

scholarly journals Assessment of the triacylglycerol fraction of olive oil by 1D-NMR spectroscopy: exploring the usefulness of DEPT tool on the peak assignments of 13C NMR spectra

2019 ◽  
Vol 245 (11) ◽  
pp. 2479-2488
Author(s):  
Raquel Garcia ◽  
Arona Pires ◽  
Nuno Martins ◽  
Teresa Carvalho ◽  
Anthony J. Burke ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Olive Oil ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectra ◽  
Triacylglycerol Fraction

Organoboranes and tetraorganoborates studied by 11B and 13C NMR spectroscopy and DFT calculations

2015 ◽  
Vol 70 (6) ◽  
pp. 421-424 ◽  
Author(s):  
Bernd Wrackmeyer
Keyword(s):  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
13C Nmr ◽  
Quantum Chemical ◽  
13C Nmr Spectroscopy ◽  
Coupling Constants ◽  
Line Widths ◽  
Nmr Signals ◽  
C Nmr ◽  
Extract Information

AbstractCare should be taken on recording the sometimes elusive 13C NMR signals for boron-bonded carbon atoms, since it is easy to extract information about coupling constants 1J(13C,11B) by measuring the respective line widths of 13C(B-C) and 11B NMR signals. This information can be confirmed by quantum-chemical calculations [B3LYP (6-311+G(d,p) level of theory] of nJ(13C,11B) in organoboranes and tetraorganoborates. For the latter, the signs for n = 2, 3, 4 were experimentally determined.

Hochauflösungs-13C-NMR-Spektroskopie, VI [1]. Strukturabhängigkeit der 13C,H-Kopplungskonstanten in 6.6-disubstituierten Fulvenen / High Resolution 13C NMR Spectroscopy, VI [1]. Structure Dependence of the 13C,H Coupling Constants in 6,6-Disubstituted Fulvenes

1980 ◽  
Vol 35 (12) ◽  
pp. 1572-1574 ◽  
Author(s):  
Siegmar Braun ◽  
Ulrich Eiehenauer
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectroscopy ◽  
High Accuracy ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Structure Parameters ◽  
Structure Dependence ◽  
C Nmr

In order to study the structure dependence of the 13C,H couplings in the fulvene system the 1H-coupled 13C NMR spectra of 6,6-disubstituted fulvenes (R = R′ = C6H5, CH3, cyclopropyl and N(CH3)2) were recorded and the interesting couplings determined with high accuracy by complete analysis. They have values typical for unsaturated five membered rings with vastly localised double bonds like cyclopentadiene-1,3 and spiro[2.4]heptadiene- 4,6 and show characteristic correlations with structure parameters.

scholarly journals Qualitative and Quantitative Analysis of Heavy Crude Oil Samples and Their SARA Fractions with 13C Nuclear Magnetic Resonance

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 995
Author(s):  
Ilfat Rakhmatullin ◽  
Sergey Efimov ◽  
Vladimir Tyurin ◽  
Marat Gafurov ◽  
Ameen Al-Muntaser ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Crude Oil ◽  
Functional Groups ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectra ◽  
Sara Fractions ◽  
Nuclear Magnetic

Nuclear magnetic resonance (NMR) approaches have unique advantages in the analysis of crude oil because they are non-destructive and provide information on chemical functional groups. Nevertheless, the correctness and effectiveness of NMR techniques for determining saturates, aromatics, resins, and asphaltenes (SARA analysis) without oil fractioning are still not clear. In this work we compared the measurements and analysis of high-resolution 13C NMR spectra in B0 ≈ 16.5 T (NMR frequency of 175 MHz) with the results of SARA fractioning for four various heavy oil samples with viscosities ranging from 100 to 50,000 mPa·s. The presence of all major hydrocarbon components both in crude oil and in each of its fractions was established quantitatively using NMR spectroscopy. Contribution of SARA fractions in the aliphatic (10–60 ppm) and aromatic (110–160 ppm) areas of the 13C NMR spectra were identified. Quantitative fractions of aromatic molecules and oil functional groups were determined. Aromaticity factor and the mean length of the hydrocarbon chain were estimated. The obtained results show the feasibility of 13C NMR spectroscopy for the express analysis of oil from physical properties to the composition of functional groups to follow oil treatment processes.

Isolierungen und 11C-NMR-Spektroskopie von Indoleninalkaloiden / Isolation and 13C NMR Spectroscopy of Indolenine Alkaloids

1982 ◽  
Vol 37 (4) ◽  
pp. 494-498 ◽  
Author(s):  
Mohammad Ataullah Khan ◽  
Hans Horn ◽  
Wolfgang Voelter
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectroscopy ◽  
H Nmr ◽  
First Time

The indolenine alkaloids raucaffricine and perakine were isolated from Rauwolfia caffra Sonder and their PFT 13C{1H}-NMR spectra studied for the first time. The interpretations of their spectra were accomplished in correlating with those of quinuclidine, indole, methyl-α-D-galactopyranoside, methyl-β-D-galactopyranoside, methyl-2,6-di-O-methyl-α-D-galactopyranoside and methyl-3-O-methyl-β-D-galactopyranoside.

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