NMR integration

It is evident from the figure that impurities can complicate the use of NMR integrals for quantitation. Further complications arise if the relevant spins are not at Boltzmaim equilibrium before the FID is acquired. This may occur either because the pulses are repeated too rapidly, or because some other energy input is present, such as decoupling. Both of these problems can be eliminated by careful timing of the energy inputs, if strictly accurate integrals are required. 

The checkers observed small MMR peaks assigned to mineral oil at 6 0.9 and 1.28 and peaks assigned to 2-methyl-l-trimethylsi1oxy-3-trimethy1sily1-2-propene at 6 1.87 and 4.1. When the reaction was carried out at half scale the quantity of the latter Impurity was not measurable from the NMR integral however, a run at full scale gave about 10% of the Impurity as estimated from the MMR integral. The product from the run at half scale had bp 56-57 C (2 nm), submitters bp 65 0 (5.5 am). 

Proton NMR integrations of methylene and aromatic regions can be used to calculate the number-average molecular weights of novolac resins29 ... 

NMR spectroscopy, 93. See also Proton NMR integrations Hoechst continuous process, 548 Homo-coupling reactions, aryl halide, 486-487 Homopolymers, 7 Hot-cast prepolymer method, 211 Hot phosgenation, 222 Houvink-Sakurada equation, 286 HTMAB. See Hexadecyltrimethylammonium bromide (HTMAB)... 

Propylene glycol, glycolysis of polyurethanes with, 572 Propylene oxide (PO), glycolysis of polyurethanes with, 572-573 Propylene oxide (PO) polyols, 211, 223 Proton exchange membrane fuel cells (PEMFCs), 272-273 Proton NMR integrations, 386. See also H NMR spectroscopy Protonic acids, reactions catalyzed by, 67-68... 

The diastereomeric ratio was determined by the NMR integral ratio of the methine protons adjacent to the hydroxyl group (3.33 ppm for the (//-isomer 3.44 ppm for the waw-isomer). 

If mixtures of two or more potential guest molecules are offered, the host lattice of 1 allows the selective accommodation of solvent molecules 2). In many cases, a pra-tically 100% discrimination of one guest species (>95% by NMR integration) is achieved by a single crystallization process using /, e.g. from an equimolar two-component solvent mixture. Table 2 summarizes important results (Entries 1-15). 

Solvents printed in italics refer to those preferentially enclathrated. b Determined by NMR integration of the isolated crystals after a drying period of 12 h at 0.5 torr. 

Determined by NMR integration as specified in Table 1. b No clear stoichiometry. 

Determined by NMR integration as specified in Table 1. b Numerical data in parentheses give the largest extension (A) of guest molecules (based on van der Waals radii from space Ailing models, taking into consideration in most probable conformations, Ref. 65). Unstoichiometric or low stability of the compound at atmospheric conditions. d Traces of solvent included. 

H NMR and 2H NMR spectra of fractionated coal products from El0 and El9 were recorded and analyzed to determine and 2H composition for each structural position. In our study, y y and 2Hx,v are defined as the fraction of the JH and 2H determined from the integrals of the NMR spectra of a given soluble fraction where y equals HS, BS or BMS and x = y-alkyl, 0-alkyl, a-alkyl or aromatic structural positions. The spectral range of the NMR integrations are given in Table V. 

Figure 6. Top The two enantiomeric forms of the "american football" monomer 40 and views of the tetrameric capsule formed from four identical monomers along the mutually perpendicular C2-axes. Bottom Chiral guests 41 -46 and the corresponding de values obtained from 1H-NMR integrations.

Loadings of substrates on resins were determined by cleavage of the resin samples with a known quantity of hexamethyl-disiloxane (HMDS) in 50 50 TFA/CDCI3 and comparison of the H NMR integrals of the HMDS standard and the cleaved... 

Deuterium nmr spectroscopy has been utilized for the last decade to determine large (primary deuterium) KIEs in reactions with isotopes present at the natural abundance level (Pascal et al., 1984,1986 Zhang, 1988). A great advantage of this approach is that labelled materials do not have to be synthesized. Neither is there any need for selective degradation procedures, which are often necessary to produce the molecules of low mass, e.g. C02, acceptable for isotope ratio mass spectrometry. Moreover, the KIEs for several positions can be determined from one sample. However, until quite recently the relatively low precision of the nmr integrations that are used for the quantitative assessment of the amount of deuterium at specific molecular sites has limited the applicability of this technique for determining small (secondary deuterium) KIEs. 

Samples of about 50 mg are weighed and dissolved in 0.5 mL of (methyl sulfoxide)-d6 (DMSO-d6) and 10 pL of dichloromethane is added. A small portion of this solution is then withdrawn and diluted in an NMR tube with DMSO-d6- 1H NMR integration parameters are as follows 32K data points, recycle delay of 5 s, 30° pulse angle. Measurement is against the hydroxyl proton doublet (2 H) at 8 4.63. If the hydroxyl doublet is not satisfactorily resolved, additional dilution is performed. 

Figure 21. Distribution of water-soluble ruthenium(II)-hydrides as a function of pH, based on the avarage of H and P NMR integrated intensities, [HRuCI(TPPMS)3], [HiRu(TPPMS)4], [HRuCI TPPMS)2]2. [Ru]=2,4 x 10 M, [TPPMS]=7.2 X 10 M. 0.2 M KCl, 50 C, Hj, P oiai=l bar. Reprinted with permission from Angew. Chem. Ini. Ed. 1998, 37, 969. Copyright (1998) Wiley-VCH Verlag GmbH.

J. C. Edwards and P. J. Giammatteo, Detailed hydrocarbon analysis of naphtha by on-line NMR integration of real-time NMR Feed analysis with advanced process control and optimization, Presented at Eastern Analytical Symposium, Somerset, NJ, November 18-21, 2002. 

Lit.5 mp 160-162° (dec.). TLC shows a weak spot for ditosylate, and 1H NMR integration (aromatic region) shows this impurity to be 8-9%. The physical... 

Despite its ionic structure 12 is almost insoluble in water. The affinity toward amino acids was studied by extraction experiments, where the enantiomers of Phe, Val, and Trp were extracted into CD2C12 from aqueous solutions. The amounts of amino acids extracted were determined by NMR integration . As expected, the aromatic amino acids were preferred (40% extraction efficiency for L-Phe and L-Trp). In the organic phase, no valine was detected. Moreover, almost no D-enantiomers were extracted by (S,S)-12 (D-Trp<0.5%,D-Phe<2%). 

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