Structural Analysis Of Organic Compounds Research Articles

Complementary studies of NMR spin diffusion and atomic force microscopy – Structural characterization of diblock copolymers

Abstract Due to their unique microphase structure copolymer systems have become important potential candidates for nanolitographic purposes. In order to properly design copolymeric templates a complete characterization of the phase separated system is required. Due to the fact that structural analysis of organic compounds remains demanding, especially when it comes to nanometer scale features such as interfacial spaces, there are very often at least two complementary experimental techniques employed to fully characterize observed morphologies. In this work diblock copolymers of poly (styrene)-b-poly (ethylene oxide) (PS-PEO) with three different molecular weights were investigated. Two different experimental methods were used: nuclear magnetic resonance spectroscopy (NMR) and atomic force microscopy (AFM). AFM topographic images of self-assembled polymer films enabled estimation of average interdomain distances, whereas the NMR spin diffusion experiment provided structural parameters related to stiff PS domains and interfacial space thickness. An application of two complementary methods enabled complete description of the studied morphologies and revealed substantial differences in polymer chain mobility between two distinct phases.

Nuclear magnetic resonance detection and spectroscopy of single proteins using quantum logic.

Nuclear magnetic resonance spectroscopy is a powerful tool for the structural analysis of organic compounds and biomolecules but typically requires macroscopic sample quantities. We use a sensor, which consists of two quantum bits corresponding to an electronic spin and an ancillary nuclear spin, to demonstrate room temperature magnetic resonance detection and spectroscopy of multiple nuclear species within individual ubiquitin proteins attached to the diamond surface. Using quantum logic to improve readout fidelity and a surface-treatment technique to extend the spin coherence time of shallow nitrogen-vacancy centers, we demonstrate magnetic field sensitivity sufficient to detect individual proton spins within 1 second of integration. This gain in sensitivity enables high-confidence detection of individual proteins and allows us to observe spectral features that reveal information about their chemical composition.

An experimental and theoretical study on fragmentation of protonated N‐(2‐pyridinylmethyl)indole in electrospray ionization mass spectrometry

The dissociation reactions of protonated molecules are the base of structural analysis in electrospray ionization tandem mass spectrometry (ESI-MS(n)). However, general rules for elucidating the numerous fragmentation reactions in ESI-MS(n) are still rather lacking. Therefore, it is very important at all times to carry out mechanistic investigations for fragmentation reactions in the gas phase. The fragmentation reactions of protonated N-(2-pyridinylmethyl)indoles were studied by both of ESI ion trap tandem mass spectrometry and ESI Fourier transform ion cyclotron resonance tandem mass spectrometry in positive-ion mode. In ESI-MS/MS, the ionizing proton is first bound to the most thermodynamically favored site, the pyridine nitrogen; then it transfers to the dissociative protonation sites and triggers the fragmentation. In the fragmentation of the target compounds, some interesting reactions, such as rearrangement, proton transfer and electron transfer reactions, take place via ion/neutral complexes. The proposed mechanisms are supported by both theoretical calculations and isotopic labeling experiments. This study is a case for better understanding the dissociative protonation sites and enriching the knowledge about the role of ion/neutral complexes in ESI-MS. It also provides useful information for the structural analysis of organic compounds, especially drug analysis in pharmaceutical chemistry.

Application of electronic circular dichroism in configurational and conformational analysis of organic compounds

This tutorial review is addressed to readers with a background in basic organic chemistry and spectroscopy, but without a specific knowledge of electronic circular dichroism. It describes the fundamental principles, instrumentation, data analysis, and different approaches for interpretation of ECD. The discussion focuses on the application of ECD, also in combination with other methods, in structural analysis of organic compounds, including host-guest complexes, and will emphasize the importance of the interplay between configurational and conformational factors. The tutorial also covers modern supramolecular aspects of ECD and recent developments in computational methods.

Computer-assisted structural analysis of organic compounds from 13C-NMR spectra.

Computer-assisted structural analysis of organic compounds from 13C-NMR spectra.

A theoretical study of x-ray photoelectron spectra of model molecules for polymethylmethacrylate

We explore the usefulness of the delta self-consistent-field (ΔSCF) approximation in connection with high-resolution x-ray photoelectron spectra for component and structural analysis of organic compounds. Results for core electron binding energy shifts for model molecules of the polymethylmethacrylate polymer are presented. A previously devised method for proper self-consistent-field solutions for core hole states in molecules is evaluated. The results indicate that chemical shifts can be obtained within a few tenths of an eV. A discussion is presented on the inherent errors in the ΔSCF approximation, the proper corrections for zero-point vibrational energies, and the role of relaxation of core orbitals.

ChemInform Abstract: Thermochemical Methods in the Structural Analysis of Organic Compounds

ChemInformVolume 19, Issue 27 Reviews ChemInform Abstract: Thermochemical Methods in the Structural Analysis of Organic Compounds K. PIHLAJA, K. PIHLAJA Univ. Turku, Turku, Finl.Search for more papers by this author K. PIHLAJA, K. PIHLAJA Univ. Turku, Turku, Finl.Search for more papers by this author First published: July 5, 1988 https://doi.org/10.1002/chin.198827354Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue27July 5, 1988 RelatedInformation

Structural Analysis of Organic Compounds by Laser Microprobe Mass Spectrometry (LAMMA)

AbstractThe possibilities of the laser microprobe mass analyser (LAMMA) for the mass spectrometric (MS) characterisation of organic compounds have been explored systematically.Specific methods of procedure are proposed to overcome the drawbacks of the actual instrumentation for organic applications. Energy selective ionisation and transmission can be used to discriminate inorganic clusters from organic ions.In general, the microprobe mass spectra are complex and an approach, allowing to extract and rationalise the structurally relevant information, has been developed. The issued model for interpretation and different aspects of laser microbeam induced desorption and ionisation mechanisms are discussed.A variety of polyfunctional molecules has been investigated. Examples are selected to illustrate the potential and limitations of LAMMA in organic mass spectrometry.

Computer-aided structural analysis of organic compounds by an artificial intelligence system

The computer program SEAC is designed to elucidate the structure of organic compounds comprising C (up to 40 C atoms in a molecule), H, N, O, S, Cl, Br and/or I atoms. Artificial intelligence techniques are exploited for empirical interpretation of spectralstructural correlations obtained directly from i.r., 1H-n.m.r. and u.v. spectra. SEAC works on five levels depending on the entropy of the information input on tested molecules. The computer prints out a set of alternative substructures (levels I–IV) or a set of complete structures which are consonant with the input data.

The ories for Mass Spectra and Problems Relating to Structural Analysis of Organic Compounds

The ories for Mass Spectra and Problems Relating to Structural Analysis of Organic Compounds

Prediction of Retention Data in Gas-Liquid Chromatography from Molecular Formulæ

As a result of the introduction of the R x9 method1–3 of presenting gas–liquid chromatographic retention ratios, it has been possible to derive a simple method of predicting retention data from a knowledge of molecular weight and structure. Preliminary investigations have indicated its value in the structural analysis of organic compounds.

Terpenic compounds with medium-sized rings

The study of all aspects of living matter is a constant source of information and stimulation of the greatest theoretical and practical importance. The very origins of organic chemistry are rooted in a desire for knowledge of the composition of living bodies and the products of their metabolism, and, ever since the birth of our science, the study of natural products has always remained one of its important concerns. The investigation of plant constituents has been of particular significance for the development of organic chemistry; it should be borne in mind that the plant kingdom accounts for much the greatest part of living matter on our earth-more than 99·9 per cent, in fact lMoreover, plants not only produce all the types of compounds found in the animal kingdom but also a number of special groups of organic substances, especially terpenoids, alkaloids, and glycosides. The varied chemical structure of the numerous, genetically related compounds of these groups, and the biological activity and practical importance of many of them have ever invited their closer investigation, and it may be said fairly that the systematic researches in these fields have contributed greatly to the finest traditions of organic chemistry, and to the present extent and variety of this science. In my opinion, it is the work on terpenes and steroids which was of the greatest importance in the development and shaping of organic chemistry. On the one hand, there is the classical unity of each of these groups, given by their simple composition, limited to the three basic organogenic elements, and by the uniformity of rules governing their structure; on the other hand, we have the great structural diversity and ubiquity of occurrence-it is these features which have made the terpene and steroid field an arena in which many minds active in our science have tried their strength. It was in research on substances of these two groups that the principal methods of structural analysis of organic compounds were devised and put to the test, especially the methods of controlled degradation; at the same time, it provided a powerful stimulus to the development of synthetic methods. Studies on the alicyclic terpenes, and on the whole steroid group, have been the source of our present ideas on the spatial structure of organic compounds. The whole of chemistry has profited from the valuable techniques developed in these fields for the isolation of individual substances from complex mixtures, their characterization and identification by physical constants. Let me recall particularly the determination of relations between chemical structure and physical properties, especially spectroscopic properties, which form such an essential part of organic chemistry today.