Spectra of Compounds

On emitting phases it is not possible to determine directly (in situ) the fluorescence and absorption spectra of compounds that absorb in the excitation range of luminescence indicators without distorting the measurement signal. 

Compound A and compound B are isomers having the molecular formula C10H12O. The mass spectrum of each compound contains an abundant peak at nih 105. The C NMR spectra of compound A (Figure 17.23) and compound B (Figure 17.24) are shown. Identify these two isomers. 

The enamine formed by dehydrogenation of indollzidine was considered to be a mixture of Zl (54) and Zl (55) isomers because of infrared spectra (126). According to the NM R spectrum, the A isomer Isthe majorconstituent. This is demonstrated by comparison of this spectrum with the spectra of compounds 56 and 57 containing fixed double bonds. 

Rapid exchange of positions was observed for acyl and amidoyl groups in the NMR spectra of compounds 36 in 1-chloronaphthalene solution at high temperatures (170-215°C) (Scheme 18). [72JCS(CC)709]. Crossover experiments clearly indicated the intermolecular exchange. The value of the free-energy barrier was determined as AG = 100 kJ mol at the coales-... 

A detailed study of spectra of compounds 1, 2, and 3 has been published as part of a general study of azolopyridines (84OMR209). The shifts are shown in Table III. The N shifts have been used to determine the structure of 7-amino-triazolopyridines 128 and 129 (89T7041). The shifts recorded were 56.8, 56.2 (Nl), 245.4, 246.3 (N2), 320.6, 316.8 (N7a), all from nitromethane as standard at 380 ppm the absorption for the amine was at 345.5, 350 ppm in accordance with the amino structure shown, rather than the imino forms 128a and 129a. 

The ultraviolet spectra of compounds which may exist as either 1-substituted pyrazol-3-oncs (70, R — H) or 1-substituted 3-hydroxypy-razoles (71, R = H) do not allow distinction between the two possible forms, because their spectra and those of fixed derivatives of both types (70, R = Me and 71, R = Me) are too similar. The solid state infrared spectra of these compounds have been interpreted to support both the NH form (see reference 79a for a similar conclusion regarding indazoI-3-one) and the OH form. Basicity data have also been considered to indicate the predominance of the OH form. ... 

Reduction of epoxide 21 with lithium aluminium hydride gave a crystalline branched-chain methyl heptoside derivative 24. The NMR spectra of compounds 21 and 24 were very similar. In the spectrum of compound 24 the disappearance of the two sharp doublets at r 6.80 and 7.45 (2 protons) and the appearance of a singlet at r 8.65 (3 protons) is consistent with the reductive cleavage of epoxide 21 to give a substance 24 with a methyl substituent. The multiplet at r 7.40-8.50 ( 5 protons ) was assigned to the four protons of the two methylene groups and the hydroxylic proton. 

Compound 10 was also prepared using acetone-d6 Peak shifts between the mass spectra of compounds 10 and 10a will be used to interpret the fragmentation of compound 10. 

The and 13C NMR spectra of compound A, C8H9Br, are shown. Propose a structure for A, and assign peaks in the spectra to your structure. 

Such differences of the thermal IR emission spectra of compounds that consist of oxygen-containing ions and halide ions are related to the relationships between the compounds optical parameters. 

Mass spectra of compounds 11 are characterized by the presence of fission products of the molecule tricyclic moiety (m/e of fragments depending on alkaloid type) and ergolene moiety with m/e 448 and after SO2 elimination m/e 384 = 448 -SO2. The characteristic IH-NMR is the absence of signal for C - 2 proton and a new multiplet at region 7-7.5 ppm for aromatic protons from saccharin moiety. 

Irradiation of cyclo-S% dissolved in CS2 by a high-pressure mercury lamp at 20 °C produces the homocycles S7, S, S12, S9, Sio, and probably S5 in concentrations decreasing in this order. Irradiation of Se in CS2 gives mainly Ss and S7 while irradiation of S7 generates Ss and S. Similarly, photolysis of S12 in CS2 yields Ss, S7, and Se [51]. For these reasons UV-Vis spectra of compounds containing S-S bonds must be recorded with caution not to trigger decomposition reactions. 

To study NMR spectra of compounds, apparatus is required that consists of three sets of components. These are a radio-frequency transmitter, a homogeneous magnetic field and a radio-frequency receiver. In addition to these, the apparatus includes a unit to sweep the magnetic field over a small range, a mere few parts per million. 

The H-NMR spectra of compound 71a in DMSO-de showed the presence of a signal at 12.5 ppm corresponding to the exchangeable NH proton, the ethylenic proton as a singlet at S 5.6 ppm, and the aromatic protons appear between 7.27 and 7.80 ppm. The elemental and spectral analysis was in agreement with the structures of these compounds. 

Markey, S.P. Urban, W.G. Levine, S.P. (eds.). "Mass Spectra of Compounds of Biological Interest" Technical Information Division, U.S. Atomic Energy Commission (26553 P1-P3), 1975,... 

Estimated precision in the chemical shifts is 0.05 p.p.m. The chemical shifts are given relative to external 1,4-dioxane, which was introduced into some samples only to obtain chemical shifts. Spectra obtained at 258 for — 10% solutions. Spectra of compounds were obtained at 22.5 MHz see Ref. 20. Spectra of compounds were obtained at 22.5 MHz see Ref. 24.J Spectrum obtained at 100.6 MHz see Ref. 24. Data taken from Ref. 61. Chemical shifts for GalNAc only are given. The data given in the parentheses for compounds 51 and 32 refer to the carbon count. 

The He(I) photoelectron spectra of compounds 9,10,11,12, 2, 2-H2, 23,23-H2, and 5059) and of 26-29 60> have been recorded. The spectra of peroxides 9, 2, and 23 have been measured independently by another group and the results are in good agreement with ours data for compounds 6,2a, and 20 were also reported 28). 

Fig. 9 Spectra of compound 1 obtained from an inversion-recovery experiment. Pulse sequence fixed delay - 180° pulse - variable delay x - 90° pulse - acquisition of FID...

Fig. 15a,b Carbon-13 spectra of compound 1. a Protons broad-band decoupled b carbon-proton coupling present (gated decoupling)... 

Figure 15 shows the normal broad-band decoupled and gated decoupled spectra of compound 1 in the latter we can see the multiplets arising from C-H coupling (across one or more bonds) and C-P coupling. The rules for the number of lines in a multiplet and their intensities are the same as for protons, since 13C and 31P are both spin-Vi nuclei. 

Fig. 16a,b Carbon-13 spectra of compound 1 recorded at 50 MHz. a Standard spectrum with integral values (measurement time 1.5 hours) b inverse gated decoupled spectrum with integral values (measurement time 28 hours )... 

Fig. 19a-c Carbon-13 spectra of compound 1. a Standard spectrum (broad band decoupling) b APT spectrum c DEPT-135 spectrum... 

Since the phosphorus spectra of compounds 1 to 5 are rather boring (only one phosphorus resonance), we shall also use compound 6, which contains three non-equivalent phosphorus nuclei, to demonstrate the results of the experiments we describe. 

We shall use compound 3 to demonstrate the results obtained from a 2D NOESY experiment, and for comparison we shall use the COSY spectrum obtained from the same compound. Figure 25 shows the COSY (a) and 2D NOESY (b) spectra of compound 3. 

Fig. 25 2D spectra of compound 3. Top COSY (200 MHz, CDC13, measurement time 15 min) below NOESY spectrum (200 MHz, CDC13, measurement time 40 min)... 

Fig. 51 A—C Phosphorus-31 MAS spectra of compounds A-C. Signals marked with an asterisk are due to spinning sidebands...

NMR Spectra of Compounds Containing the CF3 Group—General Considerations / 137... 

A comment about the carbon NMR spectrum of t-butyl fluoride is appropriate. Because of the signal weakness of carbons such as the tertiary carbon of r-butyl fluoride, which bear fluorine but no hydrogens, many published tabulations of 13C spectra of compounds that contain such structural features fail to report these crucial signals. They can easily be missed, especially if you do not know what you are looking... 

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