Search results for " database"

Symmetry: Friend or foe?

1999

While symmetry in molecules or supramolecular complexes is desirable from the design point of view and affords simpler NMR spectra, the study of symmetrical species by NMR is often subject to ambiguities resulting from signal degeneracy. In this paper we shall discuss different ways of breaking symmetry in order to obtain additional structural information by NMR.

The combined effects of two chlorine substituents and the non-additivities of chemical shifts in aliphatic dichloro esters

1982

Carbon-13 NMR spectra were measured for 25 methyl esters of aliphatic dichlorocarboxylic acids for substituted propanoic to hexanoic acids. Observed 13C shifts are compared with calculated shift values obtained from the shifts of the corresponding monochloro esters by applying a simple sum method. The greatest failures from additivity are observed for αβ and αα substituted carbons. The combined effects of two chlorine substituents were determined, and compared with those obtained from chlorine substituent effects in monochloro esters by assuming additivity. The trends displayed by the combined effects, and also by the non-additivity effects, are discussed.

NMR Spectra of Anilines

2009

1 Introduction 2 Ring and N-Substituted Anilines 3 Multinuclear NMR Studies of p-F-Aniline Derivatives 4 Dynamic NMR of Aniline Derivatives 5 Anilines with Other (Fused) Aromatic Rings 6 NMR Relaxation Studies of Aniline Derivatives 7 Solid State NMR Studies 8 Theoretical Calculations of Aniline NMR Parameters Keywords: aniline NMR spectra; aniline (aminobenzene, phenylamine); ring and N-substituted anilines; dual-substituent-parameter (DSP) analysis; cyclic amine structures; dynamic NMR of aniline derivatives; H NMR spectroscopy as measure of donor strengths; aniline derivative NMR relaxation studies

ChemInform Abstract: 4-Fluoroanilines: Synthesis and Decomposition.

2010

Abstract Fourteen N- and/or 2-substituted 4-fluoroanilines were prepared (the series includes N–C2-bridged compounds). Some of them were found to be thermally unstable when dissolved in chloroform. Both 19 F NMR spectra and comparison of GIAO-DFT calculated and experimental 13 C chemical shifts were used to suggest decomposition products of 4-fluoroanilines.

1971

The polymerisation of ethylene was carried out in the presence of (C5H5)2TiCl2/(C2H5)2AlCl in benzene (I) and of TiCl4/(C2H5)AlCl2 in chlorobenzene (II). In the initial state of the polymerisation with I oligomers with a narrow molecular weight distribution are formed. According to their IR and NMR spectra they were identified as predominantly saturated linear hydrocarbons. The effect of a substitution of the cyclopentadienyl rings by R = CH3 and C2H5 was studied as well as the influence of aging particularly on the molecular weight distribution. The catalytic system II yields predominantly unsaturated branched oligomers with broad molecular weight distribution. The ligand effect on the str…

1H and 13C NMR Measurements of Dimethylchloroformiminium Chloride and Dimethylformamide Hydrochloride

1979

Dual proton and carbon-13 NMR spectra of dimethylchloroformiminium chloride 1 and dimethylformamide hydrochloride 2 in CDCl3 at different temperatures have been measured and the results compared to proton NMR data of dimethyl formamide 3. The energy barriers of internal rotation about C-N bond in 1 and 2 were considerably lower than that of 3. The values of E were 39.3 for 1, 55.9 for 2 and (lit. value) 89.3 for 3 (in kJ/mole).

Solvent effects of pyridine on the NMR spectra of carboxylic acids. I—study of the acrylic,trans-crotonic and 3-butenoic acids

1975

Proton magnetic resonance spectral parameters of acrylic, trans-crotonic and 3-butenoic acids, their methyl esters and the corresponding alcohols (COOH substituted by CH2OH) have been measured for 5% (w/v) solutions in carbon tetrachloride and in pyridine-d5 at 33·5 °C. The total solvent effect of pyridine on the shifts of the skeleton protons of the acid was found to consist of three different effects independently measured from the reference samples.

Analysis of manganese deposits from the Alps

2011

Deposits with unusually high Mn contents sampled at Monte Mangart in the Julian Alps include organic-rich marlstone and black shale with interbedded manganoan and siliceous limestone, which were deposited during the early Toarcian Oceanic Anoxic Event. Mn enrichment during that period has been related to global sea-level change coincident with increasing subsidence rate. The formation of Fe-Mn nodules, marking a hardground at the base of the Monte Mangart section, seems to be triggered by release of Mn from remote hydrothermal vents into a region of relatively elevated submarine topography where oxidizing conditions prevailed. However, very high Mn contents in carbonate phases above the har…

BIOGEOGRAPHY OF TERTIARY PRIMATES: DISCUSSION OF AN UPDATED DATABASE

2009

Biogeography of Tertiary Primates: Discussion over an updated Data Base

2009

A preliminary taxonomic evaluation of the Tertiary Primate fossil record of the Old World is presented. The dataset has been compiled using the information and the structure presented by the NOW database (Neogene Mammalian of the Old World; Academy of Finland, 2007), strongly updated with the additional information derived from different literature sources. A quantitative methodology for compilation and analysis of the data has been applied following the methodology described in Petruso et al. (2008). The adopted numerical treatment of data is particularly effective in synthesizing and analyzing the large amount of information contained in the data set. This analysis gives a synthetic pictu…