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1.
The 1R and 13C NMR spectra of the title compound (1) reveal through-space couplings between the fluorine and the C-4 methylene group 1H and 13C), as well as coupling between the fluorine and the C-3 methine carbon and the C-2 methylene carbon.  相似文献   

2.
The 13C-(1H) NMR spectra of poly(vinyl chloride sulfone)s with macroscopic compositions corresponding to the ratio vinyl chloride (V):SO2(S) = n from ca. 1 to 4 have been analyzed in terms of comonomer sequences and configurational placements. In the copolymer with n ? 1, methylene and methine carbons in SVS sequences were resolved and were sensitive to “across SO2” tacticity. No SVS sequences were observed in the copolymer with n = 2.0, confirming that it had a regular SVVS structure, which also showed a high “internal” stereosequence regularity. It was not possible to discriminate the methylene or methine carbon atoms in S(V)n S sequences with n ≥ 2.  相似文献   

3.
The 1H NMR spectra of methyl 3‐bromo‐2‐methylpropionate (1a) and the corresponding chloro compound (2a) show no long‐range coupling between the methyl and methylene protons. In contrast, in the analogous dihalocompounds, methyl 2,3‐dibromo‐2‐methylpropionate (1b) and methyl 2,3‐dichloro‐2‐methylpropionate (2b), one of the methylene protons exhibits a large 4JHH coupling (0.8 Hz) to the methyl group, but the other proton shows no observable splitting. This can be explained quantitatively by calculations of the conformational preferences in these compounds combined with the known orientation dependence of the 4JHHcouplings. One conformer predominates in the dihalo compounds 1b and 2b, and this is responsible for the 4JHH coupling. In 1a and 2a all three conformers are populated and the 4JHH couplings average to zero. The technique is a potentially general method of unambiguously assigning diastereotopic methylene protons. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

4.
The synthesis and characterization of a 2,10-bis(alkoxycarbonyl)-substituted 6-oxo-12H-dibenzo[d,g][1,3,2]-dioxaphosphocin, 6 , is described. The lack of an observable 5JHP coupling of phosphorus to the downfield C-12 methylene proton and the observation of a 2JHCH geminal coupling constant of 14 Hz suggest that the conformation of 6 in solution is not solely a boat-chair conformation, but may involve a rapid equilibrium of the boat-chair with either a boat or twist-boat conformation.  相似文献   

5.
Detailed 1H NMR studies of ms tetraphenylchlorins (H2TPC), new amino- and hydroxypyrroline substituted ms tetraphenylchlorins and ms tetraphenylisobacteriochlorins (H2TPisoB) are presented and discussed. The results obtained are consistent with the general aspects of the ring current models as applied to the parent porphyrins. According to proton chemical shifts a gradual reduction in the magnitude of the ring current is observed in the order ms tetraphenylporphyrin (H2TPP) > H2TPC> ms tetraphenylbacteriochlorin (H2TPB) > H2TPisoB. The 1H NMR spectra show chemical non-equivalence of the pyrroline ring protons due to adjacent substituents, and effects of steric constraints on the aminoalkyl substituents due to the close vicinity to the meso phenyl rings. The non-equivalence of the methylene protons of the pyrroline ring produces geminal coupling between the two methylene protons and vicinal coupling with the adjacent pyrroline proton, more pronounced in H2TPC? OH and in . Restricted configuration of the methylene groups in the ethyl groups of H2TPC? C(H)(CH3)N(CH2CH3)2 produces observable geminal coupling between the methylene protons. 1H NMR reveals the difference between two types of meso phenyls in the chlorins, and three types of meso phenyls in isobacteriochlorins, as reflected in the chemical shifts of the o-phenyl protons.  相似文献   

6.
The synthesis of phosphonite and thiophosphite derivatives of the 12H-dibenzo[d,g][1,3,2]dioxaphosphocin ring system is described. The 'H nmr shows evidence for long-range coupling of the C-12 methine proton to phosphorus. The 1H nmr of the 12H-dibenzo[d,g][1,3,2]dioxaborocin ring system is compared to that of the phosphorus analog. The nmr spectral data suggest that the phosphorus and boron containing ring systems have similar ring conformations.  相似文献   

7.
The 13C chemical shifts and the carbon–proton coupling constants have been determined for some chlorinated isobutane and isobutene compounds. The one-bond coupling constants in isobutane derivatives showed a regular increase with an increasing number of γ-chlorine substituents. The three-bond coupling constant of the methyl carbon decreased from 4.2 to 2.0 Hz as the number of chlorine substituents in the γ-position increased. In the isobutene compounds, the vicinal coupling of C-1 was larger to protons in a group that is trans with respect to a chlorine substituent on C-1 than to those in the corresponding group cis to the chlorine. The vicinal coupling constants between atoms in geminal groups (on C-2) seem to be affected by the orientation of the chlorine substituent on C-1.  相似文献   

8.
Carbon-13 NMR data for 15 substituted 1,2,4-triazol-3-ones are presented and discussed with regard to enolization in the neutral molecules. The coupling constant and chemical shift data show that the proton at N-2 is not exchanging rapidly in the DMSO-d6 solvent. Using D2O? OD? as a solvent, it is found that the C-3 and C-5 resonances are shifted downfield by nearly the same amount, suggesting that the proton at N-4 is being removed. Enolization in the neutral molecules does not occur to any significant extent.  相似文献   

9.
The internal and overall motions of 1,3- and 1,4-diethylpyridinium bromides have been studied by 13C relaxation. The enthalpies of activation for the rotation of the ethyl groups in positions 1 and 3 are deduced from the temperature dependence of the T1 values of the methylene and methine carbons. The 14N quadrupolar relaxation time, Tq, together with 13C relaxation data provide an estimate of the 14N quadrupolar coupling constants.  相似文献   

10.
The NMR. spectra of droso- and isodrosopterin ( 1 ) in DMSO-d6, 1% DCl/D2O solution, CF3CO2D, and conc. sulfuric acid are discussed in detail. Missing of methine and methyl groups and proof for the presence of three isolated methylene functions of which two show a geminal coupling are consistent with the proposed structure of atropisomeric di(7,8-dihydropterinyl)- methane dye stuffs.  相似文献   

11.
Improved pulse sequences for measuring long‐range C‐H coupling constants (nJC‐H), named selective COSY‐J‐resolved HMBC‐1 and ?2, have been developed. In the spin systems, such as ‐CHC‐CHA(CH3)‐CHB‐, a methine proton HA splits into a multiplet owing to several vicinal couplings with protons, resulting in attenuation of its cross‐peak intensity. Therefore, the measurements of nJC‐H with HA are generally difficult in the J‐resolved HMBC or selective J‐resolved HMBC spectrum. With the aim of accurate measurements of nJC‐H in such a spin system, we have developed new pulse sequences, which transfer the magnetization of a methyl group to its adjacent methine proton. The proposed pulse sequences successfully enable to enhance the sensitivity of HA cross peak in comparison with the selective J‐resolved HMBC pulse sequence. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

12.
The 1H and 19F NMR spectra of the α- and β-pyranose anomers of 4-deoxy-4-fluoro-D -glucose (4FG) and 6-deoxy-6-fluoro-D -galactose (6FGA) in methanol-d4, DMSO-d6, acetone-d6 and D2O solution are reported. Computer analysis of the ABMX spectra of the CH CH2F fragments gives accurate vicinal HH and HF coupling constants. An iterative computational analysis of the observed vicinal couplings in this fragment for 6FG, 6FGA and other molecules allows the determination of both the individual rotamer couplings and the rotamer populations. Consideration of the derived rotamer couplings strongly suggests that the correct assignment for the prochiral C-6 methylene protons in 6FG is that with the 6S proton having the larger coupling to H-5. This is the reverse of the assignment of these protons in D -glucose. In contrast, the assignment of these protons in 6FGA follows that given previously for D -galactose. The relative energies for the conformations about the C-5 C-6 bond for 4FG, 6FG and 6FGA are given from the derived rotamer populations. For 6FGA the rotamer in which the fluorine is antiperiplanar to C-4 is particularly favoured. For 4FG the rotamer with OH anti-periplanar to the ring O is highly unfavoured, but the other two rotamers are of almost equal energy. Consideration of the effect of replacing hydroxyl by fluorine in these molecules indicates that any hydrogen bonding involving the C-4 or C-6 hydroxyls plays little part in determining the conformer energies of glucose or galactose in polar solutions.  相似文献   

13.
The long-range coupling through the sulphur atom observed in a number of 2-aryl-3-(2-pyridyl)-4-thiazolidinones suggests that the C2 proton and one of methylene protons are in a cis 1,3 diequatorial relationship. Some additional information concerning the preferred orientations of the substituents in this system are given from Eu(fod)3, [tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionato)]europium, induced shift data.  相似文献   

14.
An assignment of the out-of-plane vibrations of the trans-buta-1,3-diene molecule was performed by analysis of the isotopic shifts of wavenumbers in the methylene moieties =CHX, where X = H, D or T. A suggestion for the mutual reassignment of the wavenumbers belonging to the twisting vibration of the methylene moiety =CH2 and the out-of-plane vibration of the methine moiety =CH— was shown to be incorrect.  相似文献   

15.
Avery Rosegay  David Taub 《合成通讯》2013,43(7-8):1137-1145
Treatment of (R) methionine sulfoxide with NaOD led to exchange of the C-4 methylene and C-5 methyl protons; exchange of the chiral C-2 proton did not occur. Reducation with mercaptoacetic acid gave (R)-[4-2H2, 5-2H3] methionine. The latter was converted into its carbobenzyloxy methyl ester sulfoxide, pyrolysis of which followed by deprotection yielded (R)-[4-2H2] vinylglcine as the hydrochloride.  相似文献   

16.
NAMFIS (NMR Analysis of Molecular Flexibility In Solution) was applied to 1‐[2‐(benzyloxy)phenyl]ethanone using quantitative 1H‐1H NOE distances and 3J proton‐carbon coupling constant (CC) restraints for averaged methylene proton 3JHCOC and 3JHCCC pathways H23J‐X imposed by density functional theory‐generated Karplus relationships. Comparison of the NOE‐only versus the NOE + CC conformational selections illustrates that the experimentally measured average 3J coupling constants of methylene protons can be used for solution conformational analysis, potentially valuable in the study of small‐molecule drugs and natural products which lack the typically studied H13J‐X Karplus relationships. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

17.
Six of the eight possible diastereoisomeric 5-methylperhydropyrido[3,2,1-i,j][3,1]benzoxazines have been synthesized, and the utility of the C-3 methylene proton NMR parameters [J(3ax3eq) and Δ3ax3eq] in the assignment of configurations has been demonstrated.  相似文献   

18.
Polymerization of linear methyl ω-epoxyalkanoates of C-3 to C-10 carboxylic acids (0 to 7 methylene groups between oxirane ring and carbomethoxy group) was accomplished with a triethylaluminum/water/acetylacetone (1.0/0.5/1.0) initiator system to yield polymers of high molecular weight, apparently via a coordinative anionic mechanism. The rate of polymerization increased as the number of methylene groups between the oxirane ring and the carbomethoxy group increased, up to three methylene groups. When more than three methylene groups separate the polymerizable oxirane group and the carbomethoxy group, the rate of polymerization becomes essentially constant. The polymers were characterized by their infrared and 13C-NMR spectra, DSC, GPC, and inherent viscosity. The lower members of the series (ω-epoxyalkanoates of n < 3) gave polymers of lower molecular weight and wider-molecular-weight distribution (M w/M n > 2), while the higher members had molecular weight distributions between 1.5 and 2. The glass transition temperatures of the polymers also decreased from ?26°C for n = 1 to around ?50 to ?55°C for n ≥ 3.  相似文献   

19.
The acrylonitrile/methyl methacrylate copolymers of different monomer concentration were prepared by photo polymerization using uranyl ion as initiator. The carbon 13 and proton spectra of these copolymers are overlapping and complex. The complete spectral assignment of the 13C- and 1H-NMR spectra were done with the help of Distortionless Enhancement by Polarization Transfer (DEPT) and two dimensional 13C–1H Heteronuclear Single Quantum Correlation (HSQC) experiments. The methylene, methine and the methyl carbon resonances show both stereochemical (triad level) and compositional (dyad, triad, tetrad, pentad and hexad level) sensitivity. 2D Double Quantum Filtered Correlated Spectroscopy (DQFCOSY) experiment was used to ascertain the various geminal couplings between the methylene protons. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1081–1092, 1998  相似文献   

20.
Spin-lattice relaxation times (T1) for methyl, methylene, and methine carbons in an amorphous polypropylene have been measured as a function of temperature from 46 to 138°C. The carbons from isotactic sequences characteristically exhibited the longest T1's of those observed. The T1 differences increased with temperature with the largest difference occuring for methine carbons where a 32% difference was observed. Activation energies were determined for the motional processes affecting T1's for isotactic and syndiotactic sequences with essentially no dependence upon configuration noted.  相似文献   

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