Nuclear magnetic resonance 13C NMR spectroscopy

A study on the effectiveness of the E-plastomers as impact modifiers for iPP was carried out in relation to the traditional modifier EPDM. In this study, the flow properties of the E-plastomer-iPP and EPDM-PP blends were also evaluated. The blends were analyzed by solid-state 13C-nuclear magnetic resonance (NMR) spectroscopy, microscopy (SEM), and DSC. The results showed that E-plastomer-PP and EPDM-PP blends present a similar crystallization behavior, which resulted in a similar mechanical performance of the blends. However, the E-plastomer-PP blend presents lower torque values than the EPDM-PP blend, which indicates a better processibility when E-plastomer is used as an impact modifier for iPP. 

Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-VIS) and fluorescence spectroscopy can be integrated with chromatographic techniques especially in the study of ageing and degradation of terpenic materials. They can be used to study the transformation, depletion or formation of specific functional groups in the course of ageing. 

No detailed description of H or 13C nuclear magnetic resonance (NMR) spectroscopy has been reported on this class of compound. A general description of the NMR spectra of compound 25 is given in the synthesis of a pyrrole <1998JOC9131>. 

GC and GC-MS (see Chapter 2), are ideal for the separation and characterization of individual molecular species. Characterization generally relies on the principle of chemotaxonomy, where the presence of a specific compound or distribution of compounds in the ancient sample is matched with its presence in a contemporary authentic substance. The use of such 6molecular markers is not without its problems, since many compounds are widely distributed in a range of materials, and the composition of ancient samples may have been altered significantly during preparation, use and subsequent burial. Other spectroscopic techniques offer valuable complementary information. For example, infrared (IR) spectroscopy and 13C nuclear magnetic resonance (NMR) spectroscopy have also been applied. 

Both of these methods have been used for DOM isolation from major rivers and the surface ocean, and the general characteristics of these fractions of DOM are presented in Table I. The major C functional groups of humic substances and ultrafiltered DOM (UDOM) have been characterized by solid-state, cross-polarization magic angle spinning 13C nuclear magnetic resonance (NMR) spectroscopy. The samples of humic substances that were characterized by NMR spectroscopy were collected from the Amazon River... 

The direct detection of radiation induced crosslinks in polyethylene has been a major goal of radiation chemists for many years. It was recognized as early as 1967 that solution 13c nuclear magnetic resonance (NMR) spectroscopy could be used to detect structures produced in polymers from ionizing radiation. Fischer and Langbein(l) reported the first direct detection of radiation induced crosslinks (H-links) in polyoxymethylene using 13c NMR. Bennett et al.(2) used 13c NMR to detect radiation induced crosslinks in n-alkanes irradiated in vacuum in the molten state. Bovey et al.(3) used this technique to identify both radiation induced H-links and long chain branches (Y-links) in n-alkanes... 

Spectroscopy, 490. See also 13C NMR spectroscopy FT Raman spectroscopy Fourier transform infrared (FTIR) spectrometry H NMR spectroscopy Infrared (IR) spectroscopy Nuclear magnetic resonance (NMR) spectroscopy Positron annihilation lifetime spectroscopy (PALS) Positron annihilation spectroscopy (PAS) Raman spectroscopy Small-angle x-ray spectroscopy (SAXS) Ultraviolet spectroscopy Wide-angle x-ray spectroscopy (WAXS)... 

The bulky, stable silenes of Brook et al. (104,122-124,168) and Wiberg et al. (166,167) have been the only systems capable of being studied by nuclear magnetic resonance (NMR) spectroscopy to date. Table III lists the 13C and 29Si chemical shifts and the relevant coupling constants of these compounds. 

Nuclear magnetic resonance (NMR) spectroscopy, with X-ray analysis, forms the basis for the determination of the structures of most of the compounds discussed in this chapter. H and 13C NMR played a key role in the revision of the structure of the antifungal metabolite strobilurin D 2, which was shown to contain a benzodioxepin moiety rather than epoxide <1999T10101>. 9-Methoxystrobilurin K was also shown to contain a 1,4-benzodioxepin <1997TL7465>. 

Nuclear Magnetic Resonance (NMR) Spectroscopy is by far the most widely used analytical technique in the modern organic chemistry lab. Numerous monographs have been written on this subject. It would be impossible to cover all of the significant points here. The reader who is interested in knowing what the proton ( H) or carbon (13C) spectrum of a particular compound is directed to the Aldrich Library of NMR Spectra or the Sadtler Library. 

Nuclear magnetic resonance (NMR) spectroscopy is also largely used to characterize C02 complexes. The 13C NMR spectrum of C02 dissolved in a nonpolar solvent shows a resonance at 124ppm, which is shifted when C02 is bonded to a metal center. Depending on the mode of bonding, the shift may be up or down field, and may vary from a few ppm up to several hundreds of ppm. A few examples are given below for different types of bonding. 

Nuclear magnetic resonance (NMR) spectroscopy has been used to directly observe varied persistent superelectrophilic species. Although H and 13C NMR have been the most often used techniques, there have also been applications of 15N, 170, and 19F NMR in their structural characterization. Coupled with theoretical computational methods capable of estimating NMR chemical shifts, these studies have been very useful in the study of superelectrophiles. 

Spectroscopic methods provide rapid, nondestructive ways to determine molecular structures. One of the most powerful of these methods is nuclear magnetic resonance (NMR) spectroscopy, which involves the excitation of nuclei from lower to higher energy spin states while they are placed between the poles of a powerful magnet. In organic chemistry, the most important nuclei measured are 1H and 13C. 

GAs of previously unknown structure have been fully characterized and their structure determined by a combination of chemical and spectroscopic methods. Proton Nuclear Magnetic Resonance (NMR) spectroscopy provides a great deal of structural information (1+). 13c NMR promises to be a very powerful technique for both structure determination and metabolism studies of GAs ( UO,Ul). Yamaguchi et al. ( Ug) used a combination of proton and 13c NMR to determine the structure of GA o (2 -hydroxy GAg), a minor metabolite of G. fujlkurol. 

Key references prior to 1993 on 111 and 13C nuclear magnetic resonance (NMR) shifts for oxetanes are found in CHEC(1984) <1984CHEC(7)363>. Further references on 13C NMR coupling constants and chemical shifts, and 170 NMR data on oxetanones are in CHEC-II(1996) <1996CFIEC-II(1)721>. Since 1995, several NMR spectroscopy studies of oxetanes have been used for the structural identification of novel natural products (see Sections 2.05.11 and 2.05.12). 

An important objective in materials science is the establishment of relationships between the microscopic structure or molecular dynamics and the resulting macroscopic properties. Once established, this knowledge then allows the design of improved materials. Thus, the availability of powerful analytical tools such as nuclear magnetic resonance (NMR) spectroscopy [1-6] is one of the key issues in polymer science. Its unique chemical selectivity and high flexibility allows one to study structure, chain conformation and molecular dynamics in much detail and depth. NMR in its different variants provides information from the molecular to the macroscopic length scale and on molecular motions from the 1 Hz to 1010 Hz. It can be applied to crystalline as well as to amorphous samples which is of particular importance for the study of polymers. Moreover, NMR can be conveniently applied to polymers since they contain predominantly nuclei that are NMR sensitive such as H and 13C. 

Nuclear magnetic resonance (NMR) spectroscopy is a powerful and theoretically complex analytical tool that can be used to characterize organic matter. Proton (1H) and 13C-NMR have been the most common NMR tools for the nondestructive determination of functional groups in complex biopolymers in plants, soils/sediments, and DOM in aquatic ecosystems. 

Nuclear magnetic resonance (NMR) spectroscopy is routinely applied to small carbohydrate molecules. NMR spectroscopy is based on the principle that radiofrequencies are absorbed by hydrogen and carbon atoms ( H and 13C) spinning in one of two directions (spin quantum number +1 /2) in a magnetic field. In liquids, absorption is recorded as sharp peaks. The frequency displacement (chemical shift) is a function of the H and 1SC surroundings. +A is proportional to the number of photons absorbed between these two quantum states, correlating well with anomeric and... 

Nuclear magnetic resonance (NMR) spectroscopy (Section 14.1) A type of spectroscopy that uses transitions between the energy states of certain nuclei when they are in a magnetic field to supply information about the hydrocarbon part of a compound. There are two NMR techniques that are of most use to organic chemists proton magnetic resonance (lH-NMR) spectroscopy, which provides information about the hydrogens in a compound, and carbon-13 magnetic resonance spectroscopy (13C-NMR), which provides information about the carbons in a compound. 

Nuclear magnetic resonance (NMR) spectroscopy — Nuclear magnetic resonance (NMR) spectroscopy of atoms having a nonzero spin (like, e.g., H, 13C) is an extremely powerful tool in structural investigations in organic and inorganic chemistry. Beyond structural studies atoms observable with NMR can also be used as probes of their environment. Thus NMR may be employed for in situ spectroelectrochemical studies [i]. Cell designs for in situ NMR spectroscopy with electrochemical cells are scant. Because of the low sensi-... 

Several physical methods have been employed to ascertain the existence and nature of ICs infrared (IR) absorption spectroscopy nuclear magnetic resonance (NMR) spectroscopy,14 including JH nuclear Overhauser effect (NOE) difference spectroscopy, H 2-D rotating-frame Overhauser effect spectroscopy (2-D ROESY),15 and solid-state 13C cross-polarization/magic angle spinning (CP/MAS) spectroscopy 16 induced circular dichroism (ICD) absorption spectroscopy 17 powder and singlecrystal X-ray diffraction 18 and fast atom bombardment mass spectrometry (FAB MS). 

Azo dyes of the common formula X—N=N—Y represent a very important class of dyestuffs,1 with more than 50% of commercial dyestuffs based on this type of compound. Nuclear magnetic resonance (NMR) spectroscopy, especially in its multinuclear form, is a powerful technique for the characterization of such compounds and also for the description of azo-hydrazone tautomerism, a property which is indivisibly linked with this group of dyes. This chapter reports on high-resolution lH, 13C, 14N, 15N, nO, 19F and 31P NMR spectra of azo dyestuffs measured in solutions. 

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