13C NMR Spectra of organic peroxides

A study has been made of the13C NMR spectra of hydroperoxides, peroxides, peroxy esters, and diacyl peroxides. The signal of the carbon atoms of a hydrocarbon radical present in the α-position relative to the peroxide group is shifted downfield in comparison with the nonperoxide analog. The replacement of -O- by an -OO-group at a carbonyl carbon produces an upfield shift of the signal from this atom. © 1982 Plenum Publishing Corporation

Shibusawa Eiichi\u27s View of Japan\u27s Foreign Affairs: Focusing on His Influences on the Meiji Government

From the mid-nineteenth century, Asia, including China and Japan, has been involved in the trend of modernization that was triggered by the activities of European and American powers in this area. In a time of drastic changes, Shibusawa Eiichi (1840-1931) assumed several roles successively: he served as retainer during the bakumatsu period, as official in the Meiji government, and afterwards as businessman, philanthropist, and non-official diplomat. During his service in the Meiji government from 1869 to 1873 and as an entrepreneur from 1873 to 1909, Shibusawa played a key role in devising economic and diplomatic policies for the Meiji government. He is even considered a major designer of modem Japanese economic systems and society. This paper examines Shibusawa Eiichi\u27s view of Japan\u27s foreign affairs and focuses on the way he influenced the Meiji government

Calculations of intermolecular interactions and their influences on structure and 13C, 1H magnetic shielding constants of solute molecules

On the basis of an improved method of molecular mechanics the spatial structures of molecular clusters modelling the solvate shell of methane in acetone and benzene, 2,9,10-trimethyl-1,3-dithia-5,6-benzocycloheptene in carbon disulfide have been calculated. The nuclear magnetic shielding constants for these structures are calculated by quantum chemical methods in the approach of the density functional theory of the B3LYP/6-31(d,p) level with the usage of gauge-invariant atomic orbitals. It is shown that the increase of the number of the solvent molecules results in better agreement of the calculated and experimental values of 1H and 13C chemical shifts. © Springer-Verlag 2005

Structure of molecules in crystalline lattice obtained by a modified method of molecular mechanics: Calculations of 13C chemical shifts

A program for the calculation of the geometric structure of molecular crystals on the basis of the methods of molecular mechanics (MM) has been developed. A standard MM method has been modified by including force fields taking into account the specific (H-bond and van der Waals) interactions and the periodicity of the crystal lattice of an arbitrary form and symmetry. The geometric parameters of the molecule in a crystal calculated by this method are in agreement with the experimental X-ray data within reasonable accuracy. The nuclear magnetic resonance 13C chemical shifts have been calculated for the molecular geometry obtained by the quantum chemical UB3LYP/6-31G(d, p) method. The results of the calculations have been used to explain some unusual NMR spectral data

Dynamic 1H, 13C, 31P NMR spectroscopy of the crown containing N-(thio)phosphoryl(thio)urea

The variable temperature and concentration 1H, 13C, 31P NMR spectroscopy of the N,N′-bis[diisopropoxy(thio)phosphorylamido-(thio)carbonyl]-1,10-diaza-18- crown-6 containing the reaction pentade C(X)NHP(Y) and stereononrigid macrocycle in solutions (CD2CL2, CD3CN, (CD3)2CO as solvent) was studied. The complex chemical exchange is described in terms of tautomeric processes, hindered rotation around C-N bond and macrocycle ring inversion. NMR spectral parameters (chemical shifts and spin-spin coupling constants) of the observed exchange partners as well as thermodynamic parameters of the equilibrium and transition between tautomeric and conformational forms are given. © Springer-Verlag 1998 Printed in Austria

Calculation of the structure and nuclear magnetic shielding constants of some H-bonded carbon acid complexes

Electronic and spatial structure of some H-bonded complexes ((HCOOH)(n) (n = 1-4), formic, acrylic acids and their complexes with water and dimethylsulfoxide) were studied by ab initio methods using MP2/RHF//6-31G*, RHF/6-31G* basis sets, and also by using density functional theory (DFT)within the B3LYP approximation. The possibility of formation of chain and cyclic complexes of formic and acrylic acids with dimethylsulfoxide is shown. In a cyclic complex two hydrogen bonds are formed. One is as usually with the O-H bond (S=O···H-O), the other is between the acid carbonyl group and one hydrogen atom of DMSO methyl groups (C-H···O=C). The calculations of nuclear magnetic shielding were carried out within a framework of the coupled Hartree-Fock method using gauge invariant atomic orbitals. Analysis of the results for various basis sets and comparison of the calculated and experimentally obtained chemical shifts show that the calculations predict a significant downfield shift for 1H and 13C nuclei for H-bonded systems. The results of calculations of 17O magnetic shielding constants strongly depend on the used basis set and theoretical approach. (C) 2000 Elsevier Science B. V

Nonempirical calculations of the effect of molecular fragments on proton chemical shifts in heterocycles

We have calculated the relative changes in the proton chemical shifts for a number of six-membered heterocycles (1,3-dioxan, 1,3-oxazine, 1,3-dithiane, trimethylene sulfite, and also their derivatives). A procedure is proposed for estimating the chemical shifts due to the effect of model molecular fragments. In calculating the chemical shifts expected allowance is made for the way in which the given molecule differs in structure from a similar molecule for which the chemical shift is known. The chemical shifts were calculated in the approximation of gradient-invariant atomic orbitals in a Gaussian basis. The calculations reproduce correctly the effect of alkyl substituents and the trends in the chemical shifts as a function of the orientation of the substituents and of the heterocyclic component of the molecule. © 1990, Plenum Publishing Corporation. All rights reserved

Electronic and Steric Structure of Tricarbonyl(5-phenyl-1,3-dioxane)chromium

According to the results of quantum-chemical calculations, the conformation of 5-phenyl-1,3-dioxane changes upon complex formation with tricarbonylchromium. The most favorable conformation in the complex is chair with the axial phenyl group oriented along the symmetry plane of the dioxane ring. The tricarbonylchromium fragment is located above the benzene ring plane. The calculated spin-spin coupling constants suggest presence in solution of a mixture of conformers, that with the axial substituent prevailing

New aspects of the application of nuclear magnetic resonance to the study of chemical exchange processes

The application of the analysis of the total line shape (ATLS) in dynamic NMR to the investigation of complex chemical exchange is examined. Theoretical aspects of this problem, illustrated in relation to the available experimental data, are described. The methodological problems of dynamic NMR are discussed: the sources of error and the role of the medium, the interpretation of the activation parameters ΔH≠, ΔG≠, and ΔS≠, and also the new varieties of the method and their applications. © 1985 IOP Publishing Ltd

Indirect detection of spectroscopically unobservable components of chemical exchange by NOESY 2D NMR

A new method for detection of intermediates in chemical exchange is suggested. It is found that the effective exchange rate constant determined from NOESY 2D NMR spectrum depends on the mixing time in the NOESY pulse sequence. The true exchange rates and relative population of the intermediates can be appreciated from this dependence. As follows from estimations, this method is applicable to detect intermediates with relative population up to 0.1% and is also useful to detect the components of exchange hidden in overlapping spectra. © 1993 Springer