This paper presents a character table of S_4 wr S_2 wreath product group.Using this character table,~1H or ^(13)C NMR spectra analysis of molecula with S_4[S_2]symmetry,especially simplification of the secular determi...This paper presents a character table of S_4 wr S_2 wreath product group.Using this character table,~1H or ^(13)C NMR spectra analysis of molecula with S_4[S_2]symmetry,especially simplification of the secular determinant equation will be easy to carry out. Molecules with S_4[S_2]symmetry,are exemplified by octaphenylcyclo- tetrasiloxane and 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine chromium (Ⅲ)chloride.展开更多
^(199)Hg NHR spectra of 18 Schiff base type arylmercury compounds have been studied.It was further confirmed that in the molecule of XC_6H_4CH=NC_6H_3-2-HgC1-4-CH_3 there exists an intramolecular N→Hg coordination vi...^(199)Hg NHR spectra of 18 Schiff base type arylmercury compounds have been studied.It was further confirmed that in the molecule of XC_6H_4CH=NC_6H_3-2-HgC1-4-CH_3 there exists an intramolecular N→Hg coordination via a four-membered ring.For the series of XC_6H_4CH=NC_6H_3-2-HgCl-4-CH_3(X is a para-or mera-substituent),there is a good linear correlation between δ^(199)Hg and Hammett's o constants.The influence of substituents of C-pheny1 ring on the δ ^(199)Hg can be explained in terms of the intramolecular N→Hg coordination.展开更多
Ⅰ. INTRODUCTION 13C-CPMAS, the combination of magic angle spinning of specimen （MAS） with high power proton decoupling and 1H-13C cross-polarization （CP）, is proved to be a powerful means for research. It enables...Ⅰ. INTRODUCTION 13C-CPMAS, the combination of magic angle spinning of specimen （MAS） with high power proton decoupling and 1H-13C cross-polarization （CP）, is proved to be a powerful means for research. It enables us to have obtained high resolution NMR spectra of展开更多
Dihedral fullerenes are thermodynamically stable molecules with Dnd or Dnh symmetry. Based on experimental findings, two series of dihedral fullerenes with five-fold （C5） and six-fold （C6） symmetry have been studi...Dihedral fullerenes are thermodynamically stable molecules with Dnd or Dnh symmetry. Based on experimental findings, two series of dihedral fullerenes with five-fold （C5） and six-fold （C6） symmetry have been studied using density functional theory （DFT）. The DFT calculations showed that for both series the stabilities increased with increasing fullerene size. Structural analyses indicated that the stabilities are related to specific local geometries. In the case of the more abundant C5 series, the presence of approximately planar pentagons and hexagons on the top bowl favors their formation. That is to say, those fuller- enes with small dihedral angles within the polygons are readily formed, because planar hexagons lead to strengthened conjuga- tion which lowers average bonding energies （ABE） and increases thermodynamic stabilities. Non-planar hexagons at equatorial positions in tube-shaped fullerenes have an adverse effect on the conjugation and inhibit their formation. Calculations also demonstrated that fullerenes in the two series, including C50（D5h）, C60（O6h）, C80（O5d）, C96（D6d）, Cllo（D5h）, and Cl20（D5d）, have thermodynamically stable triplet structures with strong conjugation. The calculated IR and 13C NMR spectra of the fullerenes show some similarities and regular trends due to their homogenous structures. The electronic structures indicate that short dou- ble bonds in hexagons with high electron occupancies are readily attacked by electrophilic agents and can also be coordinated by transition metals. Mechanistic discussions suggested that C2 additions and C2 losses constitute reversible processes at high temperature and C2 additions in pentagonal fusions are crucial to the kinetics of the curvature of structures. C3 additions lead to the formation of large fullerenes of other types.展开更多
The sequence structures of emulsion-processed SBR and solution-processed (by lithium catalyst) SBR were investigated by ^(13)C-NMR spectroscopy. Seventeen peaks within unsaturated carbon region were recorded under the...The sequence structures of emulsion-processed SBR and solution-processed (by lithium catalyst) SBR were investigated by ^(13)C-NMR spectroscopy. Seventeen peaks within unsaturated carbon region were recorded under the adopted experimental conditions. Assignments for these peaks were made by empirical-parameter-evaluation method.展开更多
Suberogorgin（S）, a new reversible anticholinesterase agent, is a tricyclopentapentalane sesquiterpene acid with a rare novel structure. It is important for the exploration of the relationships between its structure ...Suberogorgin（S）, a new reversible anticholinesterase agent, is a tricyclopentapentalane sesquiterpene acid with a rare novel structure. It is important for the exploration of the relationships between its structure and bioactivities and for the development of terpene chemistry to study its structural characteristics. This note is on using 2D NMR techniques to analyse the <sup>1</sup>H and <sup>13</sup>C NMR spectra and the stereochemistry of it.展开更多
Since 1980, the solid-state high resolution NMR techniques have been introduced into mineralogy, and the magic-angle spinning (MSA)NMR technique has been extensively used. Mullite is an important synthetic mineral mat...Since 1980, the solid-state high resolution NMR techniques have been introduced into mineralogy, and the magic-angle spinning (MSA)NMR technique has been extensively used. Mullite is an important synthetic mineral material. The mechanism of展开更多
Several typical exinites in China including alginite, cultinite, suberinite and bituminite are analysed by means of 13C high solution solid state CP MAS TOSS NMR spectra to determine their chemical structures and hydr...Several typical exinites in China including alginite, cultinite, suberinite and bituminite are analysed by means of 13C high solution solid state CP MAS TOSS NMR spectra to determine their chemical structures and hydrocarbon potential. Thermal simulation solid products (TSSP) of hydrogen-rich coals arc studied to discuss the generation and expulsion mechanism of coal-generating hydrocarbon. The preliminary results are quite encouraging, containing useful information about genesis of coal-generating oil and gases.展开更多
An artificial intelligence system for interpretation of proton NMR spectra of polymers is reported in this paper. The system, including spectra data base, knowledge data base and reasoning engine, is based on the char...An artificial intelligence system for interpretation of proton NMR spectra of polymers is reported in this paper. The system, including spectra data base, knowledge data base and reasoning engine, is based on the characteristics of the proton NMR spectra of polymers and the spectra interpretation experiences of specialist. The system can partly simulate human thinking and interpret proton NMR spectra of polymers at different levels of sophistication. The program in the system was written in Turbo Prolog 2.0 and translated into machine language by computer compiler. It has been tested on an IBM PC/XT computer and a satisfactory result was given.展开更多
文摘This paper presents a character table of S_4 wr S_2 wreath product group.Using this character table,~1H or ^(13)C NMR spectra analysis of molecula with S_4[S_2]symmetry,especially simplification of the secular determinant equation will be easy to carry out. Molecules with S_4[S_2]symmetry,are exemplified by octaphenylcyclo- tetrasiloxane and 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine chromium (Ⅲ)chloride.
文摘^(199)Hg NHR spectra of 18 Schiff base type arylmercury compounds have been studied.It was further confirmed that in the molecule of XC_6H_4CH=NC_6H_3-2-HgC1-4-CH_3 there exists an intramolecular N→Hg coordination via a four-membered ring.For the series of XC_6H_4CH=NC_6H_3-2-HgCl-4-CH_3(X is a para-or mera-substituent),there is a good linear correlation between δ^(199)Hg and Hammett's o constants.The influence of substituents of C-pheny1 ring on the δ ^(199)Hg can be explained in terms of the intramolecular N→Hg coordination.
文摘Ⅰ. INTRODUCTION 13C-CPMAS, the combination of magic angle spinning of specimen （MAS） with high power proton decoupling and 1H-13C cross-polarization （CP）, is proved to be a powerful means for research. It enables us to have obtained high resolution NMR spectra of
文摘Dihedral fullerenes are thermodynamically stable molecules with Dnd or Dnh symmetry. Based on experimental findings, two series of dihedral fullerenes with five-fold （C5） and six-fold （C6） symmetry have been studied using density functional theory （DFT）. The DFT calculations showed that for both series the stabilities increased with increasing fullerene size. Structural analyses indicated that the stabilities are related to specific local geometries. In the case of the more abundant C5 series, the presence of approximately planar pentagons and hexagons on the top bowl favors their formation. That is to say, those fuller- enes with small dihedral angles within the polygons are readily formed, because planar hexagons lead to strengthened conjuga- tion which lowers average bonding energies （ABE） and increases thermodynamic stabilities. Non-planar hexagons at equatorial positions in tube-shaped fullerenes have an adverse effect on the conjugation and inhibit their formation. Calculations also demonstrated that fullerenes in the two series, including C50（D5h）, C60（O6h）, C80（O5d）, C96（D6d）, Cllo（D5h）, and Cl20（D5d）, have thermodynamically stable triplet structures with strong conjugation. The calculated IR and 13C NMR spectra of the fullerenes show some similarities and regular trends due to their homogenous structures. The electronic structures indicate that short dou- ble bonds in hexagons with high electron occupancies are readily attacked by electrophilic agents and can also be coordinated by transition metals. Mechanistic discussions suggested that C2 additions and C2 losses constitute reversible processes at high temperature and C2 additions in pentagonal fusions are crucial to the kinetics of the curvature of structures. C3 additions lead to the formation of large fullerenes of other types.
文摘The sequence structures of emulsion-processed SBR and solution-processed (by lithium catalyst) SBR were investigated by ^(13)C-NMR spectroscopy. Seventeen peaks within unsaturated carbon region were recorded under the adopted experimental conditions. Assignments for these peaks were made by empirical-parameter-evaluation method.
基金Project supported by the National Natural Science Foundation of China.
文摘Suberogorgin（S）, a new reversible anticholinesterase agent, is a tricyclopentapentalane sesquiterpene acid with a rare novel structure. It is important for the exploration of the relationships between its structure and bioactivities and for the development of terpene chemistry to study its structural characteristics. This note is on using 2D NMR techniques to analyse the <sup>1</sup>H and <sup>13</sup>C NMR spectra and the stereochemistry of it.
文摘Since 1980, the solid-state high resolution NMR techniques have been introduced into mineralogy, and the magic-angle spinning (MSA)NMR technique has been extensively used. Mullite is an important synthetic mineral material. The mechanism of
基金Project supported by the"85-102"Chinese National Key Science and Technology Project
文摘Several typical exinites in China including alginite, cultinite, suberinite and bituminite are analysed by means of 13C high solution solid state CP MAS TOSS NMR spectra to determine their chemical structures and hydrocarbon potential. Thermal simulation solid products (TSSP) of hydrogen-rich coals arc studied to discuss the generation and expulsion mechanism of coal-generating hydrocarbon. The preliminary results are quite encouraging, containing useful information about genesis of coal-generating oil and gases.
文摘An artificial intelligence system for interpretation of proton NMR spectra of polymers is reported in this paper. The system, including spectra data base, knowledge data base and reasoning engine, is based on the characteristics of the proton NMR spectra of polymers and the spectra interpretation experiences of specialist. The system can partly simulate human thinking and interpret proton NMR spectra of polymers at different levels of sophistication. The program in the system was written in Turbo Prolog 2.0 and translated into machine language by computer compiler. It has been tested on an IBM PC/XT computer and a satisfactory result was given.
