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1.
Angelo C. Pinto Susan K. Do Prado Raimundo Braz Filho William E. Hull Andras Neszmelyi Gabor Lukacs 《Tetrahedron letters》1982,23(50):5267-5270
With the help of Natural Abundance 13C - 13C Coupling Constants, observed via double quantum coherence, the structural determination of VELLOZIOLONE (1), a new diterpene, has been carried out. 相似文献
2.
Hans. R. Kricheldorf William E. Hull 《Journal of polymer science. Part A, Polymer chemistry》1978,16(3):583-595
The tripeptides Phe-Gly-Gly, β-Ala-Gly-Gly, and ?-Aca-Gly-Gly as well as the peptide derivatives δ-isothiocyanatovaleroyl-Gly-Gly and ?-isothiocyanatocaproyl-Gly-Gly were synthesized by using known methods so that the peptide nitrogen between the two glycyl residues was isotopically enriched in 15N to a level of 0.8–0.9%. These monomer units were then used to produce the sequence polymers (Phe-Gly-Gly)n, (β-Ala-Gly-Gly)n, (δ-Ava-Gly-Gly)n, and (?-Aca-Gly-Gly)n. The 18.24 MHz 15N-NMR spectra of the oligo- and polypeptides were obtained by using trifluoroacetic acid as solvent, since the solutions have relatively low viscosity and exhibit a strong negative nuclear Overhauser enhancement of the 15N signals. For comparison, 15N-NMR spectra of the homopolymers (Gly)n, (β-Ala)n, (γ-Abu)n, (δ-Ava)n, and (?-Aca)n were also recorded. The 15N signals from the ω-aminoacyl residues in the sequence polymers appear up to 11 ppm upfield of the signals observed for the homopolyamides. The 15N signals from the two glycyl residues are separated by 3–7 ppm. Comparison with the 13C-NMR spectra of the same polymers indicates that 15N-NMR is better suited for the characterization and sequence analysis of these types of polymers. 相似文献
3.
The 400 MHz 1H NMR spectra of two deuterated derivatives of 4-t-butylcycloheptanone ( and ) provided 2JHH values for the α-methylene protons on each side of the carbonyl group. The interpretation of their magnitude shows clearly that the carbonyl group is located at position 1 of the twist-chair conformation while the t-butyl group is located at position 4e. 相似文献
4.
The reaction of sodium hydride or potassium t-butoxide with methyl epoxycitronellate (1) in dimethylformamide affords a mixture of cis,cis-puleganolide (2) and cis,trans-puleganolide (3) in high yield. When the cyclization is conducted at 110°, the isomeric 2-isopropenyl-5-methylcyclopentanecarboxylic acids (8a–d) become the major products. It is demonstrated that γ-lactones undergo alkoxide-induced elimination to afford γ,δ-unsaturated acids. 相似文献
5.
MM. J. Duflos D. Letouz G. Queguiner P. Pastour 《Journal of heterocyclic chemistry》1973,10(6):1083-1084
This communication describes the synthesis of l-methyl-2,3-diformylpyrrole. This new compound is used to prepare a new heterocycle, l-methylcyclohepta[b]pyrrol-6-one and thus allows a new synthesis of l-methylpyrrolo[2,3-d]pyridazine. 相似文献
6.
Useful procedures for preparing a novel tetraazacyclotetradecadiene and a pentaazacyclotetradecatriene are reported. J. Heterocyclic Chem., 14, 1097 (1977) 相似文献
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8.
Fire gas toxicity is an essential component of any fire hazard analysis. However, fire toxicity, like flammability, is both scenario and material dependent. A number of different methods exist to assess the fire toxicity, but many of them fail to relate this to a particular fire scenario. Sample thickness alone, in a closed box test such as the NBS Smoke Chamber, is shown to change the fire scenario from well-ventilated to under-ventilated. Data from two flow-through tests, the static tube furnace (NF X 70-100) and the steady state tube furnace (the Purser furnace, BS 7990 and ISO TS 19700) show that there are different patterns of behaviour for different polymers (LDPE, polystyrene, rigid PVC and Nylon 6.6). The predicted toxicities show variation of up to two orders of magnitude with change in fire scenario. They also show change of at least one order of magnitude for different materials in the same fire scenario. Finally, they show that in many cases CO, which is often assumed to be the most, or even the only toxicologically significant fire gas, is of less importance than either HCl, or HCN, when present, and in some cases less important than organo-irritants. Nylon 6.6 shows the highest predicted toxicity, the greatest scenario dependence, and the least sensitivity to different apparatuses, while polystyrene shows the highest sensitivity to the different apparatuses, but the lowest to different fire scenarios. PVC shows high toxicity, mostly due to HCl in the fire effluent, under all fire conditions, and LDPE shows a more progressive increase in toxicity from well-ventilated flaming to both smouldering and under-ventilated flaming. 相似文献
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