Deuterium decoupling

A convenient way to understand the modern 2D NMR experiment is in terms of magnetization vectors. Figure 3.2 presents a pulse sequence and the corresponding vector diagram of a 2D NMR experiment of a single-line C spectrum (e.g., the deuterium decoupled C-NMR spectrum of CDCl,). 

Figure 4. Deuterium decoupled 270 MHz H NMR spectram of isotactic polypropylene 2,3,3,3,3, d4- From ref, (129) Copyright Pacini Editore, S.R.I., Pisa.

Deuterium-decoupled deuterated amino adds bound to crosslinked polystyrene with sulfonic acid groups show line widths 3 to 4 times narrower than those from... 

Figure 5.2. H NMR spectra recorded at different reaction times for the 13CH4-12CH3D Deuterium-decoupled mixture (1 1 molar ratio) at — 20°C.

This equation is valid only for a (non-coupled) single site-exchanging nucleus, for example the proton in cyclohexane-rfi t (observed with deuterium decoupling). In the case of geminal exchanging nuclei, as in 1,1-difluorocyclohexane (proton-decoupled), the equation... 

E3.1 Explain why the deuterium-decoupled spectrum of cyclohexane- n contains only a sharp singlet at room temperature but two singlets at 170K. 

Deuterium labelling combined with deuterium decoupling is well known as a method in spectral analysis and in stereochemical and conformational studies. The deuterium-decoupled proton spectra of XCHD.CHDY compounds produced during mechanistic studies are useful for determining the stereochemical course of reactions such as the methoxymercuration of ethylene, (478) the conversion of tyramine into tyrosol, (479) the non-catalytic addition of deuterium molecules to cyclopentadiene, (480) and alkyl transfer and olefin elimination in 2-phenyl-l,2-dideuterioethyl transition metal compounds. (481) The proton spectra of [ H ]- and [ Hg]-t-butylcyclohexanes were... 

Most convincing evidence for the equatorial orientation of H-4 was provided by the hydrogen deuterium-decoupled spectrum of... 

Proton NMR spectra were obtained on a Varian XL-200, XL-100, or EM-360 spectrometer, as noted. Chemical shifts are reported in ppm (6) relative to tetramethylsilane. Experiments for which deuterium decoupling was required were run on the Varian XL-200, using the broadband transmitter and coil as the deuterium decoupler, and observing % through the normal decoupler coil. The instrument was operated unlocked for these experiments. 

Hydrozirconation occurs by cis addition of Zr and hydrogen to terminal alkenes . Both the (E) and (Z) diastereomers of l-deuterio-3,3-dimethylbutene react with ( -Cp)2ZrHCl to give primary alkylzirconiums characterized by deuterium-decoupled NMR ... 

Boum describe their use of the line shape method in the temperature range —24° to — 82°C (deuterium decoupling was used so that only the unperturbed single proton resonance was observed) and of a double-resonance method in the temperature range —97° to — 116°C. This involved the observation of recovery of magnetization of one of the two lines in the spectrum after a saturating r.f. field applied to the other line was removed. Consistent rates of inversion were found from both methods as evidenced by linearity of the Arrhenius plot. The results do not agree with the spin-echo results of Allerhand et al In this type of work, while fairly consistent results of rate constants may be obtained, there is dispute as to how the thermodynamic parameters should be derived, even in the relatively simple case of cyclohexane. ... 

Accurate n.m.r. parameters have been obtained for a series of specifically deuteriated methyl- and t-butyl-substituted cyclohexanes with the aid of deuterium decoupling and computer simulation and iteration of the spectra. In [3,3,5,5- H J-methylcyclohexane (40) no change in the value of — 3 6 Hz was noted with... 

The C-satellite spectra have been obtained from the deuterium-decoupled n.m.r. spectra of [1,1,2,2,3,3- Hgjcyclopentane and [2,2,5,5- Hjcyclopentanone. From computer program-derived spectral parameters, an R value of 1.00 was determined, and with the assumption of a projection angle [c/ (463)] of 120° a ring torsion angle of 45° was determined (cf. ref. 130) and a half-chair conformation proposed. In cyclopentane the vicinal coupling constants are in accord with an unrestricted pseudo-rotational model. 

The NMR spectrum of the sample we prepared, run at 100 MHz in o-dichloro-benzene at 135 °C under deuterium decoupling conditions (HMDS as internal reference), is shown in Fig. 1. 

NMR analyses were performed at 100 MHz in o-dichlorobenzene at 135 °C, in the presence of HMDS as internal standard, under deuterium decoupling conditions. Investigations were made on polymers of cis 1,2,3,3,3 propylene. The catalyst system used to obtain samples 1, 2, 3 were respectively VCI3-A1(C2H5)2C1 VCI4-A1(C2H5)3 YCU-A (C2lls)2Cl... 

One solution is the partial deuteration of the molecules. A recent example of this approach is a study on different partially deuterated phenyl-benzoate molecules [68]. The deuterium NMR spectra of partially deuterated molecules are easy to analyze because of the single-particle character of the quadrupole interaction. Also, proton dipolar spectra of partially deuterated molecules, measured under conditions of deuterium decoupling, are less difficult to ana-... 

---