Solution state *H NMR

Table 2. Selected solution-state H-NMR (CDC13) parameters for nefopam methiodide (19) ...

Figure 1. A comparison of the static solid-state and solution-state H NMR spectra of a typical organic compound.

As mentioned above, Tl can also stabilize G-quadruplex structures. The ability for Tl" ions to compete with Na" ions for coordination within the G-quadruplex [d(G4T4G4)]2 has been verified by solution-state H NMR. The results from these experiments were similar to the K -Na titration experiments discussed above for the same G-quadruplex. A recent solution-state NMR structure of [d(G4T4G4)]2 folded in the presence of Tl" " ions has also confirmed that the Tl form of this quadruplex is similar to that of the K form. The excellent NMR properties of " Tl, spin 1/2 with a high natural abundance of 70% and relative sensitivity to protons of 0.13, also make ° T1 a... 

In the opening chapter, An Introduction to Solution, Solid-State, and Imaging NMR Spectroscopy Leslie Butler (Louisiana State University) introduces the fundamental structure parameters in the NMR experiment through a discussion on solution state H NMR. The shielding of nuclei by core and valence electrons, gives rise to those structure-pregnant numbers called chemical shifts, d, that have been accrued and correlated since the earliest days of NMR. Scalar coupling,... 

In this short introduction to NMR spectroscopy, a discussion of important NMR parameters will be presented through experiments that cover solution-state H NMR, solid-state NMR and magnetic resonance imaging. 

Figure 7.1 Solution-state H NMR spectrum 3.33 ms per complex data point) and (simulated) of l-chloroethene for So = 2.3488 X 212 complex data points. At this resolution, v F = (1-5 X 10" ) X 100 MHz, T2 = 1 s, 11 distinct peaks are observed, spectral width = 300 Hz (digitization rate =...

The solution-state H NMR spectrum of 1-chloroethene (Fig. 7.1) is easily described by time-independent quantum mechanics using an uncoupled basis set of spin functions. The total Hamiltonian is... 

Fig. 7.5 Solution-state H NMR spectrum of is the simple, coupled H NMR spectrum 1-chloroethene and 1-fluoroethene. The results (or the double negative F undecoupled") of of selective homonuclear decoupling are shown 1-fluoroethene, which has twice as many H in (b) and (c). The results of heteronuclear de- transitions as shown in (d) and (e) (each line is coupling are shown in (d) and (e). Not shown then a doublet from /( H— F), n = 2, 3).

The isoelectronic CH2/O analogs 6 and 8 were studied by solution-state H-NMR experiments in the temperature range of 27-128°C (6) and 27-124°C (8) (solvent [D6]DMSO). In accordance with the chiral nature of the A, 5/-silicate framework of these compounds, diastereotopism for the two... 

NMR spectroscopy enables the direct analysis of crude extracts in solution or, using the magic angle spinning (MAS) technique, of intact tissues. Potentially NMR spectroscopy can detect any molecule containing one or more atoms with a non-zero nuclear magnetic moment such as H, C, N, TSf or P. The technique is non-destractive and non-invasive and allows the analysis of in vivo samples. In routine profiling only one-dimensional (ID) solution state H NMR spectra of extracts are acquired. In addition some two-dimensional (2D) NMR spectra are acquired ( H- H COSY, H- H TOCSY, H- C HSQC, HMBC are the most common experiments) from a few representative samples in order to determine H and chemical shifts of constituents in the extracts. These can then be compared with data from chemical shift libraries of pure compounds for identification. 

Multidimensional spectroscopy plays an essential role in solution state H NMR, by providing correlations through bonds (COSY, TOCSY), through... 

Dioxathiolane 2,2-dioxide (21) adopts a puckered conformation in the solid state, as shown by x-ray diffraction (Section 4.15.3.1). In solution, the H NMR spectrum of (21) indicates that the compound undergoes a rapid pseudorotation between twist-envelope forms (Section 4.15.3.3.1) the O NMR spectra of simple derivatives also indicate a rapid conformational equilibrium by pscudorotation, although substitution may act as a barrier to complete ring inversion (Section 4.15.3.3.3). The solution-phase dipole moment of 1,3,2-dioxathiolane 2,2-dioxide is consistent with a nonplanar conformation (Section 4.15.3.8). 

By means of solid-state H-NMR spectroscopy, the open-chain structure of 2-(2-iV-methylaminoethyl)-3-nitrobenzaldoxime (73A) was corroborated (84CB702). In (CD3)2SO solution, the equilibrium 73A 73B was detected (Kt = 0.54, H-NMR). 

The heteropolyanion stabilizes protonated intermediates by coordination in solution and the pseudoliquid phase as well as on the surface, thus lowering the activation energy and accelerating reactions. Several protonated intermediates including the protonated ethanol dimer and monomer [18], the protonated pyridine dimer [12, 19], and protonated methanol [20] have been detected in the pseudoliquid phase directly by use of X-ray diffraction (XRD), IR or solid-state NMR. In solid-state H NMR, the chemical shift for the protonated ethanol dimer, (C2HsOH)2H+ is 9.5 ppm down-field from tetramethylsilane, which lies in the range of supcracids reported by Olah et al. [18]. This fact also supports the strong acidity of heteropolyacids. 

The purity (97%) of PFES was determined by solution state H (400 MHz) NMR spectra of its solution in dimethylsulfoxide-d6 using a Varian VXR-400 spectrometer. 

Tropolone is known to undergo a tautomeric hydrogen shift shown below. In solution state H and 13C NMR spectra, averaged signals due to interconversion between the two tautomeric forms are observed. 

Table 7. Selected solution-state H- and 13C-NMR (CDC13) spectral parameters for 4-methyl-6-phenyl-3,4-dihydro-2//,6//-l,5,4-benzodioxazocine (28)a...

Table 13. Selected solution-state H- and 13C-NMR (CD2C12), and solid-state cp/mas 13C-NMR spectral parameters for (IRS,35R)-A-desmethyl-3-methyl-2,6-homonefopam hydrobromide (37) ...

Compound (+)-27 was synthesized according to Scheme 7 by reaction of Si(OMe)4 with one mole equivalent each of (i ,) )-tartaric acid and 2-(dimethylamino)ethanol in boiling dimethylformamide and isolated in 79 % yield as a crystalline solid [10]. Its identity was established by elemental analyses, solution-state ( H, C, Si) and solid-state ( Si CP/MAS) NMR studies, and FAB-MS investigations. By analogy to (+)-25, compound (+)-27 is optically active. 

---