13C-NMR study of cresyl benzoates

The proton-decoupled ¹³C FT—NMR spectra of para-, meta- and ortho-cresyl benzoates have been recorded and the observed signals have been assigned following the substituent additivity rule. The important features of diagnostic value of these spectra are discussed.     

1H- and 13C-NMR Investigations of Heptafulvenes

¹H- and ¹³C-NMR spectra of a series of 8-R¹-substituted as well as of 8,8-R¹, R²-disubstituted heptafulvenes, varying from inversely polarized ( 3l ) to unpolar ( 3h ) and polar heptafulvenes with electron-withdrawing groups ( 3d , e , f ), have been analyzed and compared with those of methoxytropylium salt 5a . The results concerning ³J (H,H) values and ¹³C-chemical shifts are shown in Figs. 5 and 6. It turns out that all the NMR parameters are strongly influenced by substituents R¹, R², but contrary to planar pentafulvenes, no linear correlations of the NMR parameter vs. Hammett substituent constant σ⁺ are obtained in the series 3l → 3d . ³J coupling constants J(2,3)/J(4,5) and J(3,4) are not much influenced by substituent changes in the series 3l → 3h , but are approaching in the row 3h → 3d . Similarly, signals of the ¹³C-atoms undergo a moderate shift to higher frequencies in the row 3l → 3h , but are strongly influenced by ? M groups, whereby the sensitivity is decreasing in the series C(7) > C(2)/C(5) > C(3)/C(4) > C(1)/C(6). These results are essentially explained by a boat conformation of inversely polarized heptafulvenes of the type 3l and an increasing planarization of the ring on going to polar heptafulvenes of type 3d .     

1H-and 13C-NMR Investigation of Pentafulvenes

¹H- and ¹³C-NMR spectra of a series of 6-(p-X-phenyl)pentafulvenes 1 – 9 as well as of 6-R-substituted and 6,6-R¹,R²-disubstituted pentafulvenes 10 – 23 have been analysed. It turns out that the π-system of pentafulvenes is an attractive probe for the investigation of electronic substituent effects. Changes of vicinal H,H-coupling constants with increasing electron-donating capacity of the substituents X and R are interpreted in terms of an increasing π delocalisation in the 5-membered ring, and linear correlations of Hammett Substituent constants σ or MNDO-calculated C–C bond lengths and ³J values are observed. On the other hand, a systematic high-field shift of ₁₃C chemical shifts of the ring C-atoms is induced by electron-releasing substituents R and X, which decreases in the series C(5) > C(2)/C(3) > C(1)/C(4), and which mainly reflects changes in π-charge density.     

1H- and 13C-NMR Investigation of Nonafulvenes

¹H- and ¹³C-NMR spectra of a series of nonafulvenes 1 have been investigated. Most nonafulvenes are olefinic molecules with alternating bond lengths, their nine-membered ring deviating strongly from planarity. The 10-monosubstituted nonafulvenes contain 2 sterically different ring segments with a nearly planar (E)-diene system consisting of C(7), C(8), C(9), C(10), and R. Substituents R are influencing C(9) > C(7) > C(5). In symmetrically substituted nonafulvenes a fast process equilibrating olefinic conformers is operating so that pairs of ring protons and ring C-atoms are equivalent and only average substituent effects are observed for C(9) > C(7,2). ¹H- and ¹³C-NMR chemical shifts are not significantly influenced by changes of solvent or temperature. On the other hand, new ¹³C- and ¹H-NMR experiments completing previous investigations by Hafner and Tappe confirm that NMR spectra of 10,10-bis (dialkylamino)nonafulvenes are strongly dependent on solvent polarity and temperature. At ambient temperature and in unpolar solvents, nonplanar conformers are predominant, their spectral data fitting into the series of other nonafulvenes. At low temperature and/or in polar solvents, dipolar conformers are favoured which are characterised by charge separation and a planarised (but not necessarily completely planar) nine-membered ring with negative excess charge. The spectroscopic behaviour of nonafulvenes is reasonably explained by a qualitative scheme (Fig. 7) which is based on a model proposed by Boche for nonafulvenolates.     

1H-and 13C-NMR study of the dilithium naphthalene and its TMEDA complex

Dilithium naphthalene ( 2 ) and its TMEDA complex 3 have been prepared, and their ¹H-and ¹³C-NMR spectra were analyzed in terms of chemical shifts and coupling constants. From its Q value, 2 is characterized as delcoalized [4n] π system and the ¹H - as well as the ⁶Li-NMR shifts classify the ion as strongly paratropic. For the quarternary C-atoms, a down-field shift of 30.4 ppm is observed. The conclusions drawn from the NMR parameters are compared with the results of MNDO calculations for naphthalene and biphenylene and their ions.     

1H and 13C-NMR data of hydroxyflavone derivatives

Many hydroxyflavone derivatives have been found in nature and shown to have many biological functions. Because their function is changed by the position and number of hydroxyl group, their structural identification is a fundamental and necessary step for understanding their functions. In the present study, the complete 1H and 13C NMR spectral assignments were presented for 6 hydroxyflavones, and NMR data of additional 14 hydroxyflavone derivatives were compared with those of the 6 hydroxyflavones. In addition, the partially incorrect NMR data of two of the dihydroxyflavones whose NMR data were previously reported were corrected.     

Synthesis, 1H, 13C-NMR and mass spectral study of aryloxyquinuclidinium salts

A series of 3 -aryl -3 -hydroxy-N -(4 ′-aryloxobutyl)quinuclidinium salts have been synthesized. The ¹H nmr, ¹³C nmr and mass spectra of these compounds are described and discussed.     

沙棘果JS1多糖结构研究中GC—MS及^13C—NMR分析

近年来由于新技术的发展和应用,糖类结构的测定和生物活性的研究取得了空前的进展,大量研究表明多糖具有多方面的生物活性,如增强机体的免疫能力、抗肿瘤和抗感染等,而且多数无毒副作用。     

2,4,6-三甲氧基苯-1-O-D葡萄糖苷的核磁共振谱的理论研究

The 1H and 13C-NMR of 2,4,6-trimethoxyphenol-1-O-D-glucopyranoside(Compound 1) isolated from Celastrus angulatus (Celastraceae) was calculated theoretically at the both levels HF/6-311+G(2d,p)//B3LYP/6-31G(d) and HF/6-311+G(2d,p)//B3LYP/6-31G(d,p) using the GIAO (gauge-independent atomic orbital) method. Statistical error analysis for theoretically predicted δH and δC values versus those experimentally observed for compound 1 was discussed. The results show that the theoretically predicted δH and δC values of β conformer of compound 1 are more close to the experimentally observed values than α conformer, and the β conformer of compound 1 is more stable than α conformer according to molecular energy theoretically calculated. So compound 1 is assigned to be 2,4,6-trimethoxyphenol-1-O-β-D-glucopyranoside, which is in good consistence with the conclusion deduced by the anomeric proton signal (δH=4.80, J=7.3 Hz) experimentally observed.     

A solid state 13C-NMR study of diamonds and graphites

The ¹³C-NMR spectra of gem quality and industrial diamonds show two resonances with the more intense resonance at high field. Two resonances are also shown in ¹³C-NMR spectra of various graphites; however, the low field resonance is of greater intensity than the high field resonance in the graphites. The resonances are very broad and they are assigned to graphite type (sp²) carbon and diamond type (sp³) carbon.     

2-丁基-四氢噻吩亚砜13C-NMR的理论研究

在RHF/6-31G和B3LYP/6-31G水平上对顺式(Cis-)与反式(Trans-)2-丁基-四氢噻吩亚砜(BTHTO)进行几何优化,应用规范不变原子轨道法(GIAO)在6-31G、6-31+G、6-31++G和6-31+G(2d,p)水平上计算了Cis-和Trans-BTHTO的13C-NMR,对13C-NMR谱进行了归属。结果表明,BTHTO噻吩五元环的稳定构象呈半椅式,Cis-和Trans-BTHTO中与硫原子直接碳原子13C-NMR的显著差异主要是由于空间构型不同引起分子的静电势场对相应碳原子的屏蔽作用不同所致。     

1H- und 13C-NMR.-Spektroskopie der Nonadride

¹H- and ¹³C-NMR. Spectroscopy of the Nonadrides The ¹H- and ¹³C-NMR. spectra of the nonadrides glaucanic acid ( 1 ), glauconic acid ( 2 ), heveadride ( 3 ), byssochlamic acid ( 4 ), scytalidin ( 5 ), rubratoxin A ( 6 ), and rubratoxin B ( 7 ) have been measured. Partial decoupling experiments permitted assignment of the majority of the signals.     

13C-NMR of substituted tetrazoles

Inductive and resonance effects of phenyl substituted tetrazoles from¹³C NMR studies are calculated.¹³C NMR shifts of a series of these compounds is reported and the aminotetrazole—iminotetrazoline tautomerism of the compounds studied is discussed.     

Use of 13C-NMR in the study of reactions on crosslinked resins

Crosslinked poly(3,4-pyrrolidinediylethylene)s with functional side chains that contain acid and ester groups were synthesized by a number of different methods and the structures of the various resins were compared by ¹³C-NMR studies. The advantages and problems of this technique for structural determination of crosslinked polymers are compared with those methods normally used; for example, infrared (IR) and elemental analysis. Preliminary selective metal chelating abilities of the resins were determined.     

13C-NMR study of cellulose derivatives in the solid state

The application of NMR for natural organic compounds has been carried out from the early history of NMR. But they reported on the liquid state NMR and the samples were limited to the materials which dissolved in proper solvents. It has been possible to measure the samples in the solid state in 1970s and is widely used as a familiar analytical method in 1980s. Whereas some of the data is inadequate, concerning cellulose derivatives, in particular, only nitrate and acetate were reported by Patterson¹ and Doyle,² respectively. In this paper, the ¹³C CP/MAS solid state NMR spectra of several cellulose derivatives are shown and the relationship between the structure and spectrum is discussed.     

13C-NMR spectra of cis-polymyrcene and cis-polyfarnesene

Homopolymers of myrcene and farnesene were prepared anionically in pure cyclohexane. The microstructure, determined from an analysis of the ¹³C-NMR spectrum and spin-lattice relaxation times, indicates the polymers are at least 85% cis-1,4, 10% cis-3,4, and under 3% trans-1,4.     

CP-MAS 13C-NMR study of the degradation of polyacetylene in air

High resolution ¹³C-NMR spectra of solid polyacetylenes were observed by the CP-MAS technique after oxidation in air. On the basis of the analysis of the observed spectra one can conclude that networks were formed during the oxidation by cross-linking between saturated carbon atoms in the polyacetylene molecules. Formation of carbonyl groups in the polyacetylene started in the early stages of the oxidation but was not the predominant reaction throughout the oxidation process. These conclusions were supported by the results of elemental analysis, infra-red and optical spectroscopies.     

13C-NMR study of chlorinated ethylene–vinyl acetate copolymers

¹³C-NMR has been used to analyze the microstructures of a series of experimental chlorinated ethylene–vinyl acetate copolymers (15–56% CI). Previously established line assignments for EVA copolymers and substituent effect parameters for chlorine have enabled us to tentatively assign partial structures up to five carbon atoms in length. The ¹³C-NMR analyses of a commercial vinyl chloride–vinyl acetate copolymer, a commercial vinyl chloride–vinyl acetate–ethylene terpolymer, and a commercial chlorinated polyethylene support the structural assignments. Data obtained for the experimental resins indicate that the acetate groups influence the way in which chlorine is added to the polymer chain. furthermore, the data indicate the acetate groups undergo little, if any, chlorination.