Partial 13C-NMR spectra

Figure 3. Partial 13C NMR spectra of (A) the steam explosion lignin and (B) its phenolated product.

Figure 2. Partial 13C-NMR spectra (in DMSO-de) of the acetylated materials (a) EXWL (b) EXBWL (c) TomL (d) Reichold PF resin and (e) Bakelite PF resin.

Figure 58 Partial 13C NMR spectra for (R,R)-trans-1,2- diaminocyclohexane-( )-irani-l, 2-cyclopentanediol and (R)-l,l -bi-2-naphthol adducts. Left (a) (R,R)-trans-1, 2-diaminocy-clohexane (b) inms-( )cyclopentanediol (c) 1 1 adduct between (R,R)-trans-1, 2-diamino-cyclohexane and tranx-( )-cyclopentanediol (d) 0.5 1 adduct between (R,R)-trans-1, 2-diaminocyclohexane and Znms-(+/-)-cyclopentanediol. Right (a) (R,R)-trans-1, 2-diami-nocyclohexane (b) 1 1 adduct between (i )-l,l -bi-2-naphthol and trans-( )-1, 2-diaminocyclohexane (c) 1 1 adduct between R,R)-trans-1, 2-diaminocyclohexane and (2 )-1,1 -bi-2-naphthol (e.e. 35%) showing molecular recognition and chiral discrimination of the diastereomeric supraminols (d) 1 1 adduct between (R)-l,l -bi-2-naphthol and (R,R)-trans-1, 2-diaminocyclohexane [60],...

The 50.31 MHz 13C NMR spectra of the chlorinated alkanes were recorded on a Varian XL-200 NMR spectrometer. The temperature for all measurements was 50 ° C. It was necessary to record 10 scans at each sampling point as the reduction proceeded. A delay of 30 s was employed between each scan. In order to verify the quantitative nature of the NMR data, carbon-13 Tj data were recorded for all materials using the standard 1800 - r -90 ° inversion-recovery sequence. Relaxation data were obtained on (n-Bu)3SnH, (n-Bu)3SnCl, DCP, TCH, pentane, and heptane under the same solvent and temperature conditions used in the reduction experiments. In addition, relaxation measurements were carried out on partially reduced (70%) samples of DCP and TCH in order to obtain T data on 2-chloropentane, 2,4-dichloroheptane, 2,6-dichloroheptane, 4-chloroheptane, and 2-chloroheptane. The results of these measurements are presented in Table II. In the NMR analysis of the chloroalkane reductions, we measured the intensity of carbon nuclei with T values such that a delay time of 30 s represents at least 3 Tj. The only exception to this is heptane where the shortest T[ is 12.3 s (delay = 2.5 ). However, the error generated would be less than 10%, and, in addition, heptane concentration can also be obtained by product difference measurements in the TCH reduction. Measurements of the nuclear Overhauser enhancement (NOE) for carbon nuclei in the model compounds indicate uniform and full enhancements for those nuclei used in the quantitative measurements. Table II also contains the chemical... 

C NMR of linear cross-linked PS. The proton decoupled 13C NMR spectra of linear and 1% cross-linked PS at 75 MHz in chloroform are illustrated in Figure 3. These spectra are similar to those for linear and cross-linked chloromethylated PS previously reported at lower field (14), although we have been able to resolve more structure in tHe" aliphatic and aromatic regions here. The quarternary and methylene carbon resonances at about 146 ppm and between 40 and 50 ppm respectively, are the most strongly affected by stereochemistry (20). The ortho and meta resonances at 128.4 ppm show partially resolved structure in the linear PS, as does the para carbon at 126.1 ppm. The methine resonance at... 

Hirota and coworkers41 reported a planar structure of new polyene macrolide antibiotic YS-822A (65), which they isolated. XH and 13C NMR spectra of 65 showed a number of broad and overlapping signals, but the 1H-1H and 13C- H COSY spectra implied the existence of a mycosamine moiety and several other partial structures. The connectivity of these partial structures was established by extensive 2D NMR experiments, including homonuclear Hartmann-Hahn and heteronuclear multiple-bond connectivity measurements, which led to the determination of the gross planar structure of 65. 

Protons attached to the C atoms of the 1,2,4-trioxolane moiety of FOZs have chemical shifts at distinctly lower field than alcohols, ethers or esters. For example, the chemical shifts of the ozonide product in equation 100 (Section VIII.C.6.a) are <5 (CDCI3) 5.7 ppm for the H atoms of the trioxolane partial structure, and 4.1 ppm for the protons at the heads of the other ether bridge639. Measurement of the rate of disappearance of these signals can be applied in kinetic studies of modifications in the ozonide structure. The course of ozonization of the methyl esters of the fatty acids of sunflower oil can be followed by observing in H and 13C NMR spectra the gradual disappearance of the olefinic peaks and the appearance of the 3,5-dialkyl-1,2,4-trioxolane peaks. Formation of a small amount of aldehyde, which at the end of the process turns into carboxylic acid, is also observed636. 

The carbide atom in 1 is located in the center of the square face such that it is partially exposed whereas the carbide atom in 2 is completely encapsulated by the six ruthenium atoms. From a spectroscopic viewpoint, carbide atoms are very distinctive and the earlier reviews have dealt with these aspects in detail.7 8 The IR spectrum of 1 contains peaks at 701 (s) and 670(m) cm 1, and 2 contains peaks at 717(sh), 703(s), 680(m), and 669(m) cm-1.22 I3C-NMR spectra of 1 and 2 do not appear to have been reported. This is probably due to the low yields in which these compounds were initially obtained at a time when, 3C-NMR was still not in widespread use in cluster chemistry. In general, the 13C-NMR resonance of carbide atoms ranges from 8 250 to 500. The high frequency resonances exhibited in 13C-NMR spectra reflect the different diamagnetic and paramagnetic effects experienced by a nucleus in such an unusual chemical environment.23... 

Fig. 5.4. 13C NMR spectra of franganine at 100.576/400.133 MHz(l3C/ H), in deuteriochlorofonn (30 mg/0.4 mL) at 30 C (a) two-dimensional CH correlation of sp3 (top) and sp2 carbon nuclei (bottom) intense correlation signals due to one-bond CH couplings weak correlations due to two-and three-bond CH couplings obtained in an additional experiment (b) DEPT-subspectrum of sp3 CH carbon nuclei (c) DEPT-subspectrum of CII and C1I3 carbons (positive) and of CH2 carbons (negative amplitude) (d, e) partial spectra of sp2 carbon nuclei, proton broadband-dccouplcd.

Peptide aldehydes are fairly reactive and usually exist in solution partially as hydrates Xaa[CH(OH)2] (e.g., 3), which are identified using 13C NMR spectroscopy. 3 3" With amino acids containing nucleophilic side chains, cyclized forms predominate (Scheme 2). Argininal analogues such as Z-Leu-Phe-Arg-H have been shown to exist primarily as the carbinol amine 4 with no spectroscopic evidence for an iminium structure. Lysinal derivatives such as Z-Leu-Phe-Lys-H exist both as a cyclic carbinol amine 5 and as an iminium ion 6 as shown by 3H and 13C NMR spectra. The C-terminal ornithinal analogue Z-Leu-Phe-Orn-H exists primarily as the carbinol amine form 7 and the cyclic iminium form 8 as characterized by the 13C NMR spectra. 3,21 In general, the existence of carbinol and iminium cyclized forms does not preclude the existence of the free or hydrated aldehydes under aqueous conditions. 

The structures of regioisomers, represented by the partial formulas 77 and 78 and formed by addition of organic azides to Bredt olefins, can be assigned unambiguously by lH- and 13C-NMR spectra. In structure 77 the proton a to the N=N double bond appears at lower field than the proton a to the /V-Ph group with approximately AS = 0.8 ppm. In the13C-NMR spectra a chemical... 

A second difficulty of fully decoupled 13C NMR spectra is that die connectivity in the molecule is difficult to establish (except by chemical shift correlation) because coupling patterns are absent. This dilemma is partially resolved by die use of a technique called off-resonance decoupling. In off-resonance decoupled 13C spectra, the carbons are coupled only to diose protons directly attached to diem and die coupling is first order. Thus quaternary carbons are singlets, methine carbons are doublets, methylene carbons are triplets, and methyl carbons are quartets. It is possible to use diis information to establish proton-carbon connectivity,... 

FIGURE 4.31 Score plot of PCA performed on partial reduced molar fractions fi/Fi of sites 1 and 5-8 of vanillin calculated from 13C NMR spectra (125 MHz) acquired with D = 21 s. The 21 samples are represented in the plane of the two main axes, and the relative weights are indicated in parentheses. (From Tenailleau ef ai, 2004.)... 

C NMR spectra of partially modified dextran with a-naphthylacetate moieties show that the reactivity of the individual hydroxyl groups decreases in the order C2 > C4 > C3. A mechanism for the reaction is suggested, which includes formation of an acylium complex as observed for the reaction with acid chlorides (Fig. 23). 

Figure 2.9. 13C NMR spectra of 3,4-dimcthoxy-p methyl (3-nitrostyrene (9) [CDCb, 25 C, 20 MHz], (a, b) 1H broadband decoupled, (a) complete spectrum with CH3 quartets at 8C = 14.1 and 56.0 (b, c) decoupled and coupled partial spectrum of benzenoid and alkene carbon atoms, (c) obtained by gated decoupling...

Conditions (CD3)2CO, 25 °C, 400 MHz ( //), 100 MHz (13C), 40.55 MHz (15N). (a) SH NMR spectrum with expanded partial spectra and integrals (b, c) 13C NMR spectra, in each case sho-wing proton broadband decoupled spectrum below and gated decoupled spectrum above, (b) aliphatic resonances and (c) heteroaromatic resonances (d) l5N NMR spectrum, coupled, with expanded sections and integrals. 

Reuben J (1984) Isotopic multiplets in the carbon-13 NMR spectra of polyols with partially deuterated hydroxyls. Fingerprints of molecular structure and hydrogen bonding effects in the 13C NMR spectra of monosaccharides with partially deuterated hydroxyls. J Am Chem Soc 106 6180-6186... 

FIGURE 8.8 (<2) Partially relaxed 13C NMR spectra from an inversion-recovery pulse sequence. (b) Values of Tj (seconds) for 13C nuclei in n-decanol. (c) Values of Tr for 13C nuclei in phenol. 

The thienylethylamines 29 and 30 were synthesised according to Scheme 2.3. The secondary amine 47 was acylated with 2- or 3-thienyl acetyl chloride. As a result of the rotation around a binding with a partial double bond character the aliphatic protons and the aliphatic carbon atoms of 48 and 49 were according to the 1H- and 13C-NMR spectra chemically nonequivalent. The resulting amides were reduced with BH3.Me2S complex. 

In the IR spectra, the partially saturated heterocyclic /S-enamino nitriles do not exhibit the normal group frequencies that the corresponding esters display. The comparison of the 13C-NMR spectra of nitriles 299,300,302, and 305 with those of the esters 8,71, and 72 reveal for the nitriles a greater high-field shift of 27 ppm (Table III). As a consequence, it is concluded that in the enamino nitriles the double bond is more polarized than that of the corresponding esters several canonical forms can be discussed (Scheme 85). This difference in polarization (8, 71, and 72 versus 299, 300, 302, and 305) leads to several significant differences in the chemical behavior, which are briefly discussed in the following sections. 

Our previous reports concerned 20 MHz 13C-NMR spectra of partially epimerized polystyrenes. The aromatic C-l carbon resonances were recorded at room temperature and were poorly defined when the extent of epimerization was high. A need for remeasuring these resonances at higher temperature, using higher field spectrometers was clearly evident. This paper is therefore concerned with the 75 MHz 13C-NMR specrra of partially epimerized isotactic polystyrenes. 

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