NMR spectra recording

Fig. 12.3. NMR spectra recorded during thermal decomposition of dibenzoyl peroxide. Singlet at high field is due to benzene other signals are due to dibenzoyl peroxide. [From H. Fischer and J. Bargon, Acc. Chem. Res. 2 110 (1969). Reproduced by permission of the American Chemical Society.]...

The structure of telomers Tj - T3 is confirmed by NMR spectra recorded for individual compounds. 

Figure 1.37 The effect of line broadening (LB) multiplication on the appearance of H-NMR spectra. (a IJB = 10) and (b LB = 5) H-NMR spectra recorded after multiplying the FIDs by positive LB values. (c LB = 0). The same H-NMR spectrum recorded without line broadening. (d LB = -2) Sharper signals are obtained when the FID is multiplied by negative LB values. 

Fig. 2.5.2 ]H NMR spectra recorded at 100 MHz showing the ring proton resonances of 3,5-dinitrocyanobenzene (a), and spectral changes during its reaction with methoxide ion...

Figure 5. 7Li NMR spectra recorded during 3 cycles of reversible lithium insertion-deinsertion in the composite carbon electrode. The peak at 0ppm is due to ionic lithium (Li+PF6 and passivation layer). The peak of lithium at 263 ppm is not shown.

Fig. 12.27 200 MHz H-PHIP-NMR spectra recorded duringthe hydrogenation of phenylacetylene using a colloidal Pd catalyst.

In i C NMR spectroscopy the i C signal due to the carbon in CDCI3 appears as a triplet centred at 5 77.3 with peaks intensities in the ratio 1 1 1 (due to spin-spin coupling between i C and H). This resonance serves as a convenient reference for the chemical shifts of i C NMR spectra recorded in this solvent. 

Macchioni and coivorkers [147] have investigated the effect of the counterion on CO/Styrene copolymerization catalyzed by [Pd(ti -Ti -C8Hi20Me)bipy]X, (92, Figure 1.21) where X is the counterion. The bipyridine ligand shows dynamic behavior and a series of NMR spectra recorded between 204 and 302 K (Figure 1.21) pro-... 

Figure 7.7 Selected P H NMR spectra recorded during a CO/ethene copolymerization assisted by [Pd TFA)2(Na2DPPPDS)] in the presence of 20 equiv of TsOH and a 1 1 CO/C2H4 pressure of 600 psi (10 mm sapphire tube, D2O, 20—85°C,...

Figure 2.3 Variable-temperature H NMR spectra recorded in a hexamethyl phosphoric triamide solution of 2,6-dihydroxybenzoic acid at 135, 163, 177, and 240 K. (Reproduced with permission from ref. 26.)...

Calculated by GC using monomer/DMF ratios ° Determined by GPC in DMAc using p(MMA) calibration NMR spectra recorded in CDCI3... 

The NMR spectra [recorded in (CD3)2CO relative to tetra-methylsilane(TMS)] both show broad, ill-defined resonances in the region from 1.6 to 4.3 ppm of the spectrum, with the aromatic protons of the tetraphenylborate anion appearing between 6.8 and 7.6 ppm. 

As an example. Fig. 18 shows CP/MAS NMR spectra recorded during the investigation of surface ethoxy species (7S) formed on acidic zeolite HY ( si/ Ai = 2.7) by a SF protocol. Figure 18a shows the CP/MAS NMR spectrum recorded after a continuous injection of C-1-enriched ethanol, CHI CHzOH, into the MAS NMR rotor reactor containing calcined zeolite HY. The ethanol was injected at room temperature for 10 min. Subsequently, the loaded zeolite was purged with dry nitrogen (200 mL/min) at room temperature for 2h. 

Figure 19 shows the C CP/MAS NMR spectra recorded lOmin to 53 h after adsorption of [ C-l]-l-octene on zeolite HZSM-5. The spectra indicate that the C-labeled terminal olefinic =Cll2 groups evident in the spectra at ca. 113 ppm are transformed into terminal C-labeled paraffinic CH3 groups, evident at 14.3 ppm. Furthermore, the selective label penetrates into internal -CH2- groups of the octene hydrocarbon skeleton, characterized by resonances occurring at 33.0 ppm. 

Fig. 21. C MAS NMR spectra recorded during the photocatalytic oxidation of TCE (48pmol) on 170 mg of TiO2 in the presence of gaseous oxygen (60pinol). The UV irradiation time is indicated in minutes (right). Reproduced with permission from (190). Copyright 1997 American Chemical Society.

Figure 23 shows H and Al CF MAS NMR spectra recorded during the hydration of calcined H-SAPO-34. The H MAS NMR spectrum of the calcined material recorded before the start of the hydration is dominated by a signal of... 

Fig. 24. MAS NMR spectra recorded in the steady state of the synthesis of MTBE by isobutylene and methanol on calcined zeolite H-Beta (nsi/tiAi = 16) (a—c) and after purging of the catalyst with dry nitrogen (d). Reproduced with permission from (230). Copyright 2000 Elsevier Science.

Fig. 28. CF MAS NMR spectra recorded during the conversion of pure CHsOH (left) and an aniline/ CHsOH mixture (right) on calcined zeolite ( sOH Cs.XaY (W/F = 40 gh/mol, molar ani-line/ CH3OH ratio of 1 4) at reaction temperatures of 473 K (a), 498 K (b), and 523 K (c) and at 523 K after stopping the reactant flow (d). Reproduced with permission from (242). Copyright 2001 The Royal Society of Chemistry.

Recently, a novel reaction mechanism was proposed for the alkylation of aniline with methanol on acidic zeolite HY (243). By SF MAS NMR spectroscopy, the formation and decomposition of N, AA-trimethylanilinium ions on the working catalyst were observed. Figure 29 shows the MAS NMR spectra recorded under CF conditions during methylation of aniline by methanol at reaction temperatures of 473-523 K. In these experiments, a mixture of aniline and C-enrichcd methanol (WjF — 40gh/mol) in a molar ratio of 1 2 was injected into the MAS NMR rotor... 

Fig. 29. C MAS NMR spectra recorded during the methylation of aniline by C-enriched methanol on zeolite HY ( si/ Ai = 2.7) under CF reaction conditions (WjF = 40gh/mol, molar aniline/ CHsOH ratio of 1 2) at temperatures of 473 K for 10 min (a), 473 K for 90 min (h), 498 K for 90 min (c), and 523 K for 90 min (d). Reproduced with permission from [243. Copyright 2002 American Chemical Society.

Fig. 32. CF MAS NMR spectra recorded during the conversion of C-enriched methanol ((U/ F = 100 gh/mol) on calcined zeolite HY (nsi/ Ai = 2.7) at reaction temperatures of 393 K (a), 433 K (b), and 473 K (c). The spectra on the left-hand side were obtained with MAS NMR and proton decoupling (HPDEC), and the spectra on the right-hand side were recorded with the CP technique. Asterisks denote spinning sidebands. Reproduced with permission from (74). Copyright 2001 American Chemical Society.

Fig. 36. C and H CF MAS NMR spectra recorded during the alternating conversion of C-enriched and non-enriched methanol (IV/F= 25gh/mol) on calcined zeolite HZSM-5 (nsi/wAi = 22) at reaction temperatures of 548 and 573 K. The relative intensities given below the spectra were determined by integration in the absolute intensity mode by using the spectra obtained during the conversion of C-enriched methanol as intensity standard. Reproduced with permission from (300). Copyright 2003 Kluwer Academic.

The NMR spectra recorded in liquid ammonia are attributed to the products of addition of ammonia across the C-5-N-4 bond (covalent addition) rather than to the products of attachment at C-5 (anionic a-adducts). Actually the present data do not seem to be able to distinguish between the two species. 

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