Decoupling proton

Figure 9.1. 395 MHz M NMR spectra of 2-iiorbornyl 50 MHz proton decoupled C NMR spectra cation in SbF5/S02CIF/S02F2 solution of 2-norbornyl cation ( C enriched) in SbF5/S02ClF/S02F2 solution.

Fig. 7. Nmr spectra of quinine [103-95-0] C2QH24N2O2, acquired on a Bruker 300AMX spectrometer using a Bmker broadband CP/MAS probe, (a) Proton-decoupled spectmm of quinine in CDCl (b) the corresponding spectmm of solid quinine under CP/MAS conditions using high power dipolar decoupling (c) soHd-state spectmm using only MAS and dipolar decoupling, but without cross-polarization and (d) soHd quinine mn using the...

Figure 1.10. NMR spectra of 2,4,6-trichloropyrimidine [CeDe, 75% v/v 25 °C, 20 MHz], (a) NMR spectrum without proton decoupling (b) NOE enhanced coupled NMR spectrum (gated decoupling)...

There has been considerable discussion about the extent of hydration of the proton and the hydroxide ion in aqueous solution. There is little doubt that this is variable (as for many other ions) and the hydration number derived depends both on the precise definition adopted for this quantity and on the experimental method used to determine it. H30" has definitely been detected by vibration spectroscopy, and by O nmr spectroscopy on a solution of HF/SbFs/Ha O in SO2 a quartet was observed at —15° which collapsed to a singlet on proton decoupling, 7( 0- H) 106 Hz. In crystalline hydrates there are a growing number of well-characterized hydrates of the series H3O+, H5O2+, H7O3+, H9O4+ and H13O6+, i.e. [H(0H2) ]+ n = 1-4, Thus... 

Figure 2.97 3IP NMR spectrum (ethyl protons decoupled) of IrH5(PEt2Ph)2. (Reprinted from J. Inorg. Nucl. Chem., 1973, 33, 2195. Copyright (1973) with kind permission from Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.)...

Fig. 7. A C-13 relaxation time measurement of solid state wetted cellulose acetate (6% by weight water) using the inversion recovery (IR) method at 50.1 MHz and spinning at 3.2 kHz at the magic angle (54.7 deg) with strong proton decoupling during the aquisition time (136.3 ms), (upper part of the Figure). Tau represents the intervals between the 180 deg (12.2 us) inverting and 90 deg (6.1 us) measuring pulse. 2200 scans were collected and the pulse delay time was 10 s, Cf. Table 3 and Ref.281...

NMR Spectroscopy. All proton-decoupled carbon-13 spectra were obtained on a General Electric GN-500 spectrometer. The vinylldene chloride isobutylene sample was run at 24 degrees centigrade. A 45 degree (3.4us) pulse was used with a Inter-pulse delay of 1.5s (prepulse delay + acquisition time). Over 2400 scans were acquired with 16k complex data points and a sweep width of +/- 5000Hz. Measured spin-lattice relaxation times (Tl) were approximately 4s for the non-protonated carbons, 3s for the methyl groups, and 0.3s for the methylene carbons. 

Fig. 3 shows a portion of the aliphatic region of the proton-decoupled, C-n.m.r. spectra of virgin glycophorin and fully reductively [ C]methy-... 

Fig. 3.—A Portion of the Aliphatic Region of the Proton-decoupled, C-N.m.r. Spectra of Native Glycophorin A (in HjO at 30°) and Fully Reductively [ C]Methylated Glycophorins A, A , and A (in H2O at 30°), at 22.5 MHz. [Taken from Ref. 56. Time-domain data were accumulated in 8192 addresses, with a recycle time of 1 s (except for A, where 2 s was used). A digital broadening of 2.8 Hz was applied (A) 1.9 mM virgin glycophorin A, at pH 6.5, after 50,000 accumulations (B) 1.6 mM fully reductively [ C]methylated glycophorin A , at pH 8.5, after 12,015 accumulations (C) 1.6 mM fully reductively [ C]methylated glycophorin A, at pH 7.3, after 14,208 accumulations (D) 1.5 mM fully reductively [ C]methylated glycophorin A °, at pH 7.2, after 12,815 accumulations.]...

Fig. 5.—Proton-decoupled, C-N.m.r. Spectra (at 22.5 MHz) of the Partial-reductive, [ C]Methylation Studies of —1.5 mM Glycophorin in H2O at 30°. [Spectra of methylated...

Fig. 12 shows a portion of the aliphatic region (30-50 p.p.m.) of the proton-decoupled, C-n.m.r. spectra of fully reductively [ C]methylated glycophorin A" " and glycophorin B. Glycophorin B was isolated from heterozygous, red-blood cells, and was then separated from glycophorin A by gel-filtration chromatography on Ammonyx-Lo. Clearly, the... 

Nonselective polarization transfer, as implied by the term, represents a process that allows simultaneous polarization transfer from all protons to a//X nuclei. In sefectmepolarization transfer, however, the population of just one nucleus is inverted at any one time. The selective polarization transfer sequence therefore cannot be used to generate a proton-decoupled C-spectrum containing all sensitivity-enhanced C resonances. 

The basic INEPT spectrum cannot be recorded with broad-band proton decoupling, since the components of multiplets have antiphase disposition. With an appropriate increase in delay time, the antiphase components of the multiplets appear in phase. In the refocussed INEPT experiment, a suitable refocusing delay is therefore introduced that allows the C spin multiplet components to get back into phase. The pulse sequences and the resulting spectra of podophyllotoxin (Problem 2.21) from the two experiments are given below ... 

Figure 4.7 Pulse schemes representing separation of decoupling effects from the nOe during X nucleus acquisition. The decoupler is programmed to produce noise-modulated irradiation or composite pulse decoupling at two power levels. Suitable setting of the decoupler may produce either (a) nOe only, (b) proton decoupling only, or (c) both nOe and proton decoupling.

NMR spectroscopy was performed with a Bruker AC-300 spectrometer at 75 MHz in the Fourier-transform mode, with proton decoupling at 30 C, using 5 mm tubes and D2O as solvent. The spectral width was 200 ppm. Chemical shifts are expressed in ppm relative to the resonance of external DSS (sodiiun 4,4-dimethyl-4-silapentane-1 -sulfonate). 

Fic. 1.—Proton-decoupled, Natural-abundance, 13C-N.m.r. Spectra of Native and Denatured A. niger Glucoamylase at 67.9 MHz. [Spectra required 16,384 scans, with a recycle time of 2 s. (A) Native glycoprotein (1.1 mM) in 50 mM phosphate buffer, pH 5.1 (B) denatured glycoprotein (0.6 mM) in 25 mM phosphate buffer, 7.8 M urea, pH 6.2. Spectra were taken from Refs. 25 and 60 reproduced by courtesy of Marcel Dekker, Inc., New York.]... 

Fig. 2.—A Portion of the Proton-decoupled, Natural-abundance, 13C-N.m.r. Spectra of Model Compound 6 and Bovine Ribonuclease B at 67.9 MHz. [(A) Compound 8 in HzO (25 mM, pH 6.5) after 8192 scans (2-s recycle-time) (B) spectrum of ribonuclease B after digital subtraction of the spectrum of ribonuclease A. (This enzyme has the same amino acid composition as ribonuclease B, but contains no carbohydrate.) Spectra were taken from Ref. 27.1...

The proton decoupled carbon 13 NMR spectra for three poly( cyclohexylmethyl-co-isopropylmethyl) copolymers are shown in Figure 4. The backbone methyl group is observed as occurring between -4 and -1 ppm and consists of multiple resonances which are due to polymer microstructure. Multiple resonances are also observed for the methyl and tertiary carbon of the isopropyl group and for the methine carbon of the cyclohexyl group. Microstruc-tural assignments for these resonances remain to be made. It has also been found that increasing the bulky character of the substituent yielded broader resonance peaks in the carbon-13 NMR spectra. 

Figure 5. 67 MHz Carbon-13 NMR Spectra for Poly(n-propyl-methylsilane). (a) Proton Decoupled (b) Proton Coupled.

Fig. 36. Proton-decoupled natural-abundance carbon-13 NMR spectra of some corrinoids at 15.08 MHz, obtained by the Fourier transform method, (a) 0.67 M aqueous dicyano-cobinamide. (b) 0.024 M aqueous cyanocobalamin. (c) 0.038 M 5 -deoxyadenosylcobalamin (compliments of A. Allerhand)...

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