Study of the exchange rates of ethanol and water on ferriprotoporphyrin IX by n.m.r. line broadening

1969 ◽  
Vol 47 (17) ◽  
pp. 3217-3224 ◽  
Author(s):  
N. S. Angerman ◽  
B. B. Hasinoff ◽  
H. B. Dunford ◽  
R. B. Jordan
Keyword(s):  
Exchange Rates ◽  
Temperature Jump ◽  
Aqueous Ethanol ◽  
Ion Pair ◽  
Solvent Composition ◽  
Water Proton ◽  
Solvent Exchange ◽  
Line Broadening ◽  
Kcal Mole ◽  
Ethanol Molecule

The nuclear magnetic resonance (n.m.r.) line broadening technique has been used to determine the rate of solvent exchange from the first coordination sphere of ferriprotoporphyrin IX (hemin) in aqueous ethanol. The line broadenings of the methyl and methylene protons of ethanol and the water protons have been studied as a function of solvent composition at 35° and of temperature in 48.8 mole % ethanol.The average values of the kinetic parameters for ethanol molecule exchange, taken from the CH3 and CH2 proton broadening are ΔH≠ = 6.2 ± 1.0 kcal mole−1 and ΔS≠ = −9.1 ± 4.4 cal mole−1 deg−1. Both proton transfer and water molecule exchange contribute to the water proton line broadening with a net value of ΔH≠ = 6.3 ± 0.5 kcal mole−1 and ΔS≠ = −3.8 ± 2.0 cal mole−1 deg−1.From the n.m.r. study at varying solvent composition, it is concluded that monomeric and dimeric hemin undergo solvent exchange at the same rate. The equilibrium constant for formation of the monoethanol solvated hemin from hydroxyhemin is determined as 8.7 at 35° from this study.A comparison of the rate of ethanol exchange (1.8 × 106 s−1 at 25°) and the rate of imidazole binding to hemin (from a separate temperature jump study) indicates that the imidazole substitution occurs through an SN1 ion pair mechanism.

Notizen: Binding and Kinetics of 1-Methylimidazol on Fe(III)-Protoporphyrin(IX)dimethylester and Fe(III)-Tetraphenylporphyrin in Chloroform

1976 ◽  
Vol 31 (2) ◽  
pp. 242-245 ◽  
Author(s):  
Eberhard V. Goldammer ◽  
Herbert Zorn
Keyword(s):  
Spin State ◽  
Chemical Exchange ◽  
Phase 1 ◽  
Protoporphyrin Ix ◽  
Bulk Phase ◽  
Paramagnetic Species ◽  
Solvent Exchange ◽  
Line Broadening ◽  
Axial Ligands ◽  
Kinetics Of

Nuclear magnetic line widths data have been used to determine the rate of solvent exchange between the coordination sphere of Fe(III)-protoporphyrin(IX)dimethylester or Fe(III)-tetraphenylporphyrin and the bulk phase of 1-methylimidazol/chloroform. At temperatures below 322 K both porphyrins are in the low-spin state and separate PMR absorption caused by the methyl protons of two 1-methylimidazol molecules complexed in fifth and sixth position of ferri-porphyrins is detected. At T ≳ 320 K an accelerated exchange of these ligands was observed and the underlying kinetic parameters have been extracted. It was found that this exchange takes place when the paramagnetic species is in its low-spin state. For 240 K ≲ T ≲ 290 K dynamic line broadening of bulk phase 1-methylimidazol indicates occurrence of chemical exchange attributed to 1-methylimidazol interacting with ferri-porphyrin in addition to the strongly bound axial ligands.

scholarly journals Modeling size controlled nanoparticle precipitation with the co-solvency method by spinodal decomposition

Soft Matter ◽  
2016 ◽  
Vol 12 (34) ◽  
pp. 7231-7240 ◽  
Author(s):  
Simon Keßler ◽  
Friederike Schmid ◽  
Klaus Drese
Keyword(s):  
Exchange Rates ◽  
Spinodal Decomposition ◽  
Scaling Relations ◽  
Solvent Exchange ◽  
Nanoparticle Sizes ◽  
Size Controlled

Experimentally observed scaling relations between nanoparticle sizes and solvent exchange rates can be explained by spinodal decomposition.

scholarly journals Microsolvation and sp2-stereoinversion of monomeric α-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR

2014 ◽  
Vol 10 ◽  
pp. 2521-2530 ◽  
Author(s):  
Rudolf Knorr ◽  
Monika Knittl ◽  
Eva C Rossmann
Keyword(s):  
Title Compound ◽  
Low Temperatures ◽  
Ion Pair ◽  
Coupling Constants ◽  
Ionic Mechanism ◽  
Line Broadening ◽  
Aryl Group ◽  
H Nmr ◽  
Nmr Signals ◽  
Butyl Methyl Ether

The β-unsubstituted title compound dissolves in THF as a uniformly trisolvated monomer, whereas it forms exclusively disolvated monomers in tert-butyl methyl ether, Et2O, TMEDA, or toluene with TMEDA (1.4 equiv). This was established at low temperatures through the observation of separated NMR signals for free and lithium-coordinated ligands and/or through the patterns and magnitudes of 13C,6Li NMR coupling constants. An aggregated form was observed only with Et2O (2 equiv) in toluene as the solvent. The olefinic geminal interproton coupling constants of the H2C= part can be used as a secondary criterion to differentiate between these differently solvated ground-states (3, 2, or <2 coordinated ligands per Li). Due to a kinetic trisolvation privilege of THF, the cis/trans sp2-stereoinversion rates could be measured through analyses of 1H NMR line broadening and coalescence only in THF as the solvent: The pseudomonomolecular (because THF-catalyzed), ionic mechanism is initialized by a C–Li bond heterolysis with the transient immobilization of one additional THF ligand, followed by stereoinversion of the quasi-sp2-hybridized carbanionic center in cooperation with a “conducted tour” migration of Li+(THF)4 along the α-aryl group within the solvent-separated ion pair.

The Disorder-Order Transformation in Ni4Mo

1971 ◽  
Vol 15 ◽  
pp. 319-329 ◽  
Author(s):  
Fu-Wen Ling ◽  
E. A. Starke
Keyword(s):  
Order Parameter ◽  
Domain Size ◽  
Antiphase Domain ◽  
Domain Growth ◽  
Range Order Parameter ◽  
Line Broadening ◽  
Kcal Mole ◽  
X Ray ◽  
Isothermal Ageing ◽  
Internal Strains

The progressive ordering of a single crystal of Ni4Mo by isothermal ageing at 650°C (transformation temperature = 868°C) has been studied by x-ray line broadening techniques using the Warren- Averbach method employing computer techniques. The long-range-order parameter, antiphase domain size, and internal strains were measured as a function of ordering time and compared with those previously obtained at 700°C. The activation energies for domain growth and ordering were found to be 91 kcal/mole and 44.5 kcal/mole respectively. The rms strain developed during ordering was found to be dependent on the degree of tetragonality of the structure.

A Carbon-13 Nuclear Magnetic Resonance Study of Cation Solvation in Alcohols

1974 ◽  
Vol 52 (5) ◽  
pp. 744-748 ◽  
Author(s):  
Gerald W. Stockton ◽  
John S. Martin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Exchange Rates ◽  
Low Temperatures ◽  
Solvation Shell ◽  
Nuclear Magnetic Resonance Study ◽  
Solvent Exchange ◽  
Magnetic Resonance Study ◽  
Sign Reversal ◽  
Solvation Complex

Natural abundance 13C spectra of solvent coordinated to the cation have been observed in solutions of Mg(II) and Al(III) salts in alcohols. Carbon shielding changes induced by cations resemble those induced by electronegative substituents; a sign reversal between the β and γ positions is found in both instances. Solvent exchange rates correspond to those found by 1H n.m.r.; this confirms that whole molecule exchange is dominant. Selective relaxation of the solvation shell signals at low temperatures reflects differences in conformational mobility within the solvation complex.

Rearrangement studies with 14C. XLII. The solvolysis of triphenylvinyl-2-14C bromide in aqueous acetic acid and in 2,2,2-trifluoroethanol

1978 ◽  
Vol 56 (18) ◽  
pp. 2459-2466
Author(s):  
Choi Chuck Lee ◽  
Eric C. F. Ko
Keyword(s):  
Acetic Acid ◽  
Reaction Time ◽  
Ion Pair ◽  
Solvent Composition ◽  
Aqueous Acetic Acid ◽  
Mean Values ◽  
Mechanistic Explanations ◽  
The Mean ◽  
Return Process

Solvolytic studies with triphenylvinyl-2-14C bromide (l-Br-2-14C) in HOAc–H2O and in 2,2,2-trifluoroethanol (TFE) containing 2,6-lutidine were carried out under a variety of conditions. Scramblings of the label from C-2 to C-l in the reaction product and in the unconsumed reactant were determined. For solvolyses in HOAc–H2O, scrambling was observed in the product, but not in the recovered reactant. The extent of scrambling was higher when the proportion of H2O in the solvent was lower. With a given solvent composition, the amount of scrambling did not change with reaction time, the average extents of scrambling being 9.6,12.7, 15.3, 16.7, and 18.4%, respectively, for solvolysis in 50, 60, 70, 80, and 90% HOAc. With 70% HOAc, the presence of about 3 equiv. of NaOAc or NaBr did not influence the extent of scrambling. For the reactions in TFE, there was scrambling in both the reaction product and the recovered reactant, indicating the occurrence of a return process, The presence of added Et4NBr did not affect the extent of scrambling, suggesting that the 1,2-phenyl shift occurred in the ion-pair stage and the return is, therefore, an ion-pair return. The amount of scrambling in the product and in the recovered reactant increased with increasing reaction time, but for a given reaction time, the extents of scrambling in the product and in the recovered reactant were the same. The mean values for the scrambling of the label from C-2 to C-l in the product and the recovered reactant, after a reaction time of 1, 2, 4, and 20 days at 150 °C, were 20.1, 30.0,40.0, and 44.1%, respectively. Mechanistic explanations for both reactions in HOAc-H2O and in TFE are discussed.

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