- 1. INTRODUCTION
- 2. NUCLEAR SPIN PROPERTIES
- 3. CHEMICAL SHIFTS
- 3.1. Background
- 3.2. Recommendations endorsed
- 3.3. Definition and reporting of δ scales
- 3.4. Referencing procedures
- 3.5. A unified scale
- 3.6. Practical application of the unified scale
- 3.7. Alternative reference compounds
- 3.8. Magic‐angle spinning
- 3.9. Solids
- 4. SUMMARY OF RECOMMENDATIONS
- (1) The rates of reaction of 2,4-dinitrofluorobenzene with benzylamine and with N-methylbenzylamine have been measured in benzene solution, with and without the addition of pyridine or 1, 4-diaza-bicyclo[2.2.2]octane (DABCO) as catalyst.
- (2) Both reactions are catalyzed by the reacting amine, by pyridine and by 1, 4-diaza-bicyclo[2.2.2]octane.
- (3) Whereas the dependence on base concentration is linear in the case of N-methyl-benzylamine, the rate constants are curvilinearly related to base concentration in the reaction with benzylamine. Steric effects are shown to be responsible for this different behaviour, which is easily understood in terms of the two-step intermediate mechanism (eq.1) for nucleophilic aromatic substitutions.
- (4) Part of the pyridine catalysis has to be attributed to a medium effect, as can be shown directly in the reaction involving benzylamine.
- (5) The sensitivity of both reactions to base catalysis is much greater than that of the reaction of piperidine with 2, 4-dinitrofluorobenzene, but is found to be considerably smaller than in the reaction of p-anisidine with the same substrate, thus suggesting a correlation between the basicity of the reacting amine and the sensitivity of the reaction to base catalysis.
- The molecular weight is about 159000 (s = 7.81 S, D = 4.55 · 10?7).
- From the frictional ratio f/f0 = 1.236 the axial ratio for an oblong non hydrated ellipsoid of rotation can be calculated as b/a = 4.74.
- The molecular activity is 2700 for FDP and approximately 200 for F-1-P.
- Amino acid analysis shows significant differences between Drosophila aldolase and rabbit muscle and liver aldolases, especially in the contents of histidine, glycine, alanine and cysteine.
- Hybridization with rabbit brain aldolase gives three new hybrids.
- Anti-Drosophila aldolase serum (guinea pig) does not precipitate rabbit muscle aldolase (type A) or rabbit brain aldolase (type C) in the OUCHTERLONY test.
- 1 The kinetics of the competitive reactions of three monochlorotriazine reactive dyes with water and with sorbitol have been investigated.
- 2 The reactions of the monochlorotriazine dyes with sorbitol anions and hydroxyl ions can be divided as follows: (a) With dyes without a NH-group between the triazine nucleus and the other part of the molecule, the reaction follows the simple addition-elimination mechanism (AN2E), in which the addition of the nucleophile is ratelimiting. (b) The reactions of dyes containing a NH-group can be explained by assuming that more than one of the tautomeric isomers are reactive. With one isomer the addition of the nucleophile is the slowest step; with another the base-catalysed decomposition of the addition complex is rate-limiting.
- 3 The first acid dissociation constant of sorbitol is evaluated (pKa = 13.14;60°).
- 1 [M-COCH3]+-Ion.
- 2 Breakdown of one of the two 1,3-diaminopropan moieties: m/e 242, 256, 268. This type of fragmentation is characteristic for all acetylated 1,3-diaminopropan-derivatives e.g. triacetylspermidine.
- 3 Expulsion of a neutral amine: m/e 169.
- 4 SNi-type reactions, by which cyclic ions are formed: m/e 100.
- 1 The anodic synthesis of triarylsulfonium salts,
- 2 The addition of anodically generated N3-radicals to olefins, producing “monomeric” 1,2-diazides and “dimeric” 1,4-diazides,
- 3 The cathodic synthesis of optically active 1-(2-pyridyl)ethanol,
- 4 The synthesis of 1,2- and 1,4-diol ethers by anodic oxidation of vinyl compounds in alcoholic solutions.
- 1. Direct absorption and phosphorescence excitation techniques have been used to locate the 3(n,π*) states, and in each case it has been found to be the second triplet state.
- 2. The lowest excited state in each case is assigned as 3(π,π*) state.
- 3. The diffuseness in the phosphorescence emission from the 3(π,π*) states is attributed to a large change in the molecular geometry upon excitation (probably to a non-planar configuration).
- 4. The diffuseness in the S→ Tn,π* absorption is correspondingly attributed to interaction between the 3(n,π*) and 3(π,π*) states. A summary of the energy levels for these compounds is given in Fig. 4.
- 1 The kinetics of the hydrolysis of a dichlorotriazine reactive dye have been determined in aqueous buffer solutions at pH values between 8.50 and 13.47, at 24.0° and ionic strength I = 0.625.
- 2 The reaction order with respect to the concentration of the dye and the hydroxyl ions is a complex function of the reaction conditions.
- 3 Only in very dilute solutions the kinetics follow the mechanism postulated by Ackermann and Dussy [4].
- 4 Several types of base catalysis can be detected, depending on conditions (pH, concentrations).
- 1 The measured τp vary regularly with the sample immersion time in liquid N2, reaching a constant value after a few hours. This effect is related to the glass matrix relaxation. The rate constant Kisc (S, 1→T1) is also found to vary during relaxation of the solvent.
- 2 In the expression giving the nonradiative rate constant Knr (T1→S0), the bimolecular quenching term appears negligible for high viscosity matrices i.e. for η= 109 poises for benzene and for TMPD. Knr is found to vary linearly with log η, as well as the intersystem crossing S1→T1 rate constant Kisc.
- 3 Both Knr (T1→S0) and Kisc (S1→T1), increase with decreasing polarity of the solvent.
- 4 From our own observations and literature data[6] for C6H6 it appears that solvent viscosity does not contribute appreciably to the observed temperature effect on the solute τp when only a monomolecular triplet deactivation is operative.
- k(2‐chloropropane) = 10(13.98±0.08) exp(?26, 225 ± 130) K/T) s?1; 590–1020 K; 1–3 bar
- k(chlorocylopentane) = 10(13.65 ± 0.10) exp(?24,570 ± 160) K/T) s?1; 590–1020 K; 1–3 bar
- k(chlorocylohexane) = 10(14.33 ± 0.10) exp(?25,950 ± 180) K/T) s?1; 590–1020 K; 1–3 bar
- k∞ (2‐chloropropane) = 5.74 × 109T1.37 exp(?25,680/T) s?1; 600–1600 K
- k∞ (chlorocylopentane) = 7.65 × 107T1.75 exp(?23,320/T) s?1; 600–1600 K
- k∞ (chlorocylohexane) = 8.25 × 109T1.34 exp(?25,010/T) s?1; 600–1600 K
- (i) The line area variations are associated with the overall progression of crystallization in the sample, which is shown to obey on Avrami law. The time exponent n and rate constant k were determined for each isotherm; their temperature dependence reflects the nucleation and crystal growth mechanisms and provides an estimate of relevant thermodynamic parameters.
- (ii) The line-width is assumed to be closely related to a statistical network with the average mesh size determined by a random distribution of crystallites. Finally, concomitant spin-lattice relaxation time (T1) measurements show an increase of this parameter which parallels the development of the crystalline fraction.
- 1 Loss of the N-substituent (R) from the molecular ion, leading to the [M+—R]-ions.
- 2 Loss of NH3, primary or secondary amines from the [M+—R]-ion in the case of monodi-, tri- and tetra-substituted diamino compounds respectively.
- 3 α-Cleavage to the non charged nitrogen atom by forming the ions
- 4 SNi-type fragmentation.
- 相似文献
- 1 The kinetics of the hydrolysis of three monochlorotriazine reactive dyes have been determined in alkaline buffer solutions at 60°, 80° and 98° (ionic strength I = 0.0625).
- 2 The kinetic results as well as diffusion measurements in aqueous solution indicated that these dyes form aggregates at dye concentrations at 6 · 10?4, but practically not at 6·10?6 moles/l.
- 3 The reaction order with respect to hydroxyl ions has been determined. The influence of general base concentration was negligible.
Polarographic investigation have been carried out on titanium(III)chloride, titanium(IV)oxoperchlorate, vanadium(III)chloride, vanadium(IV)oxoperchlorate, chromium(III)chloride and chromium(III)perchlorate in 1,2-propanediol-carbonate; the nature of the limiting currents, the diffusion current constants, the diffusion coefficients, the reversibility or irreversibility of the electrode process and the half-wave potentials vs. aqueous saturated calomel electrode have been determined in 0,1M solutions of tetraethylammonium perchlorate at 25°. Reduction waves were found corresponding to Ti(IV)–Ti(III), V(III)–V(II), V(IV)–V(II), Cr(III)–Cr(II) and Cr(II)–Cr(0)
Mit 2 Abbildungen
1. Mitt.:V. Gutmann, M. Kogelnig undM. Michlmayr, Mh. Chem.99, 693 (1968).
2. Mitt.:V. Gutmann, M. Kogelnig undM. Michlmayr, Mh. Chem.99, 699 (1968). 相似文献
- (1) Extraction from 7 N HCl was found to be most suitable.
- (2) Degree of the dilution of TBP with diluent was studied and TBP concentration at about 10% was found to be most effective.
- (3) With various kinds of the solvent as diluent, the following order of the extraction was found: o-xylene>carbon tetrachloride>benzene>amy1 alcohol>chloroform.
- 1 (a) the electrode potential for oxidative dimerisation of L,
- 1 (b) the interatomic distances C-Hg in CH3HgL,
- 1 (c) the interatomic distances Hg-Hg in L-Hg-Hg-L,
- 1 (d) the energy of dissociation of CH3HgL into CH3 and HgL,
- 1 (e) the logarithms of the stability constants of CH3HgL,
- 1 (f) the logarithms of the relative nucleophilic reactivites of L in SN2 reactions at a saturated carbon atom
- 1 (g) the proton-bascicity of L (in series of structurally similar ligands, possessing the same ligating atom, as for example carboxylate anions).
The contents of zinc, copper, lead and cadmium were measured in the dominant species (plants:Scripus triquetor andPhrgrmites australis, macrobenthos:Ilyoplax deschampsin, Helice tridens tientsinensis, Bullacta exarata and Corbicula fluminea, and migrating waders: Calidris ruficollis and C. alpina) of the ecosystem of Yangtze Estuary, China, from 1995–1998. Results show that:
-
(1)
Since the heavy metals stored in plants during growth seasons will be released into the environment in winter, plants are temporary stocks for metals. For the aboveground parts of reeds, about 156.6 kg·ha-1·a-1 of zinc, 369.9 kg·ha-1·a-10 of copper, 32.9 kg·ha-·a-1 of lead and 6.5 kg·ha-1·a-1 of cadmium were released.
-
(2)
The mollusca, especially C.fluminea, are the key species storing and transporting heavy metals on the food chain.
-
(3)
The temporal change in the highest trophic level was studied and found that it was significantly related with metabolic rates. The contents of heavy metals in Dunlin reach the peaks in January and October, which are wintering season and migratory season, respectively, of the bird.
-
(4)
Organisms often show regulation/accumulation mechanisms to different elements of heavy metals. The elements that are widely required, such as zinc and copper, are accumulated at the metabolically active parts. It is quite another thing for the other two elements. Lead was regulated well and scarcely accumulated in the bodies of macrobenthos, but cadmium was absolutely accumulated in the animals.
-
(5)
Heavy metals were found accumulated in some parts of the bodies of these organisms, such as shells and skeletons of macrobenthos and lives and muscles of waders.
-
(6)
All these four elements were accumulated higher in the bodies of waders than in the plants and macrobenthos, which showed a bio-magnification function of the food chain. Overall, besides the physical and chemical processes, biological processes of heavy metal elements in Yangtze Estuarine ecosystem play a very important role in self-purification function of the ecosystem. Measurement of heavy metal contents in plants and animals in the estuarine ecosystem is an efficient technology for monitoring the environmental quality of the estuary.
Polarographic investigations on the anhydrous chlorides of niobium(V), tantalum(V), molybdenum(V) and tungsten(VI) have been carried out in dimethylsulfoxide and N,N-dimethylformamide. The half-wave potentials (vs. aqueous saturated calomel electrode), the nature of the limiting currents, the reversibility or irreversibility of the electrode processes and the influence of water have been determined in 0,1M-solutions of tetraethylammonium perchlorate at 25,0°. For all compounds investigated irreversible reductions to the oxidation state III have been found.
Mit 4 Abbildungen
3. Mitt.:M. Michlmayr undV. Gutmann, Inorg. Chim. Acta, im Druck. 相似文献