PMR-spectra

Goto, T., Takase, S., and Kondo, T., PMR spectra of natural acylated anthocyanins determination of stereostructure of awobanin, shisonin and violanin (Commelina communis, Viola tricolor, Perilla orimoides). Tetrahedron Lett, 27, 2413, 1978. Agrawal, P.K., NMR spectroscopy in the structural elucidation of ohgosaccharides and glycosides, Phytochemistry, 31, 3307, 1992. 

There are two other interesting features of the PMR spectra of B12 derivatives which should be mentioned. In the spectrum of coenzyme-B12 where the cobalt bound alkyl group is 5 -deoxyadenosyl, two high field peaks, each with the intensity of one proton, are observed (130). These correspond to the two 5 -methylenic protons. 

The PMR spectra of hexathiaadamantane derivatives are not particularly informative.208 The UV spectra reflect the same three-dimensional network... 

PMR spectrometry is an extremely useful technique for the identification and structural analysis of organic compounds in solution, especially when used in conjunction with infrared, ultraviolet, visible and mass spectrometry. Interpretation of PMR spectra is accomplished by comparison with reference spectra and reference to chemical shift tables. In contrast to infrared spectra, it is usually possible to identify all the peaks in a PMR spectrum, although the complete identification of an unknown compound is often not possible without other data. Some examples of PMR spectra are discussed below. 

In the 1960s, after Kennedy and Thomas [25] had established the isomerisation polymerisation of 3-methylbutene-l, this became a popular subject. From Krentsel s group in the USSR and Aso s in Japan there came several claims to have obtained polymers of unconventional structure from various substituted styrenes by CP. They all had in common that an alleged hydride ion shift in the carbenium ion produced a propagating ion different from that which would result from the cationation of the C C of the monomer and therefore a polymer of unconventional structure the full references are in our papers. The monomers concerned are the 2-methyl-, 2-isopropyl-, 4-methyl-, 4-isopropyl-styrenes. The alleged evidence consisted of IR and proton magnetic resonance (PMR) spectra, and the hypothetical reaction scheme which the spectra were claimed to support can be exemplified thus ... 

Natural oils like olive, peanut, sunflower seed contain mostly the triglycerides, which usually give rise to four characteristic sets of signals in their corresponding PMR-spectra due to the resonance of alkenyl protons, namely ... 

Fiq. 5. PMR-spectra (60 c/s) of mesitylene and of its proton addition complex in HF + BFs at various temperatures according to MaoLean and Mackor (1962). See text. 

PMR studies have been performed on a number of other ribosomal proteins isolated by the acetic acid/urea method (Morrison etal., 1977a). The results of these studies have shown that acedc acid/urea-extracted proteins contain little tertiary structure. However, some structure was seen in protein S4 and especially in protein S16 as indicated by the appearance of ring-current shifted resonances in the apolar region of the spectrum (Morrison et al., 1977b). These are due to the interaction of apolar methyl groups with aromatic amino acids in the tertiary structure of the protein. The PMR spectra were recorded either in water or in dilute phosphate buffer at pH 7.0—conditions under which the proteins were soluble. 

Goto T, Takase S, Kondo T (1978) PMR spectra of natural acylated anthocyanins. Determination of the stereo structure of awobanin, shisonin and violanin. Tetrahedron Lett 27 2413-2416... 

The pyrrolyl ligand is interesting in that it can function as both a u-bonded amido group or a yr-bonded multihapto ligand. The pyrrolyl group appears to be a weaker electron donor than the cyclopentadienide anion 90). In the tetrakis-(2,5-dimethylp3u rolyl)uranium(IV) complex a preliminary structure has been revised with a tris(monohapto) (pentahapto) structure now assigned from variable temperature PMR spectra 90). 

While the preponderance of data thus indicates ionic bonding, there has been some suggestion of covalent interaction. An ABX pattern for the pmr spectrum of the five-membered ring portion of Sm(C9H7)3 THF was interpreted as evidence of covalent bonding, since such a pattern is also found for covalently-bound transition metal indenide complexes 66). However, it has been pointed out in some detail that no conclusions of this type should be drawn from the simple pmr spectra 127). 

Tetraallyluranium [143, 144) and tetra(2-methylallyl)-uranium(IV) [145) are prepared by the reaction of the Grignard reagents with uranium tetrachloride in diethyl ether. The PMR spectra of these temperature-sensitive compounds are listed in Table 7. The AMgXa [146) pattern exhibited by tetraallyluranium is typical of the symmetrical jr-allyl structure in Fig. 14. The spectrum of tetra-... 

The Structure and Bonding of 4/ and 5/ Series Organometallic Compounds Table 7. PMR spectra of actinide allyls... 

Figure 4, PMR spectra (90 MHz) observed during the irradiation of chloranil (0.02 M) in acetonitrile-d3 solutions containing 0.02 M trans- (top) or c/s-diphenylcyclo-propane (bottom), respectively. ...

The PMR spectra of thiophene and selenophene have been thoroughly studied. The close similarity of the spin-sirin coupling... 

Figure 4. PMR spectra with integrations for CH, PMMA and POM absorptions for 85 15 P(M-OM) copolymer and 65 25 10 P(M-OM-CN) terpolymer. Data obtained from CDCls solutions (50 mg/0.4 mL) on a Varian T-60 NMR spectrometer.

Figure 19. PMR spectra at 185°K for magnesium perchlorate in acetone-water mixtures at low water content (6) showing mixed solvate species.

PMR spectra have frequently been used to solve structural problems including azide-tetrazole tautomerism (Section IV,B,l),185b, 186<1,187b,c> 307b, 308,382,383.435 the sjte 0f C-protonation (Section IV,C,l,a)281,393, 395 and TV-protonation (Section IV,C,l,b),268b,36z and the conformation of C-phenyl substituents.146,451 The low-field displacement of chemical shifts by the introduction of a COR group into the molecule has frequently been noted,1860, 195, 203, 364,365 and use has been made of this effect to study the site of N-acylation (Section IV,C,3). 

The PMR spectra of substituted derivatives, however, provide additional evidence for the structure of bridged [12]annulenes. A comparison of 92a and 92b reveals a normal control of the cyano group over the chemical shift of the neighboring protons (A = 1.0 ppm), the influence on the remote pyrrolic protons being small (A = 0.11-0.39 ppm). Hence diazapyracylenes should be composed of loosely connected closed-shell moieties (formula 97a) the influence of the substituents on the chemical shift being limited to the substituted part of the molecule.112... 

The diatropism of diazapyraceheptylenes (106), which follows from a comparison of the PMR spectra with that of 105a (Table VI), may be due to the effect of the cyano groups on the electronic configuration of the 7r-system. The chemical shift difference between the inside and outside protons clearly reveals the expected diamagnetic ring current in the annulene derivatives (110). The coupling constants of the seven-membered rings of 110 show that this part of the molecule is planar and delocalized. 

Proton Magnetic Resonance (PMR) Spectra of IOMOc-Diazapyraceheptylenes and Bisimino[14]annulenes... 

High resolution proton magnetic resonance (PMR) spectra were recorded on a Perkin-Elmer R-10, 60-megacycle per second spectrometer fitted with a decoupling unit, a temperature probe, and a computer averaging attachment. Unless specified otherwise, spectra were obtained at 33.5°C. Chemical shifts in the high resolution NMR spectra are expressed as usual in parts per million relative to the protons of tetra-methylsilane at 10 p.p.m. (t scale). 

As in the case of cytosine, several NMR and NQR studies were performed in search of the predominating tautomeric structures of uracil and thymine and their nucleotides and nucleosides. Investigation of PMR spectra of these compounds in nonaqueous solvents, such as dimethyl sulfoxide, localized the mobile protons in a number of 5- and 6-substituted uracils.59,61,328 These and similar studies63,85,329,330 indicated that dilactam structure 32 predominates in uracil compounds in aqueous and nonaqueous solutions as well as in the solid state. Proton and N-15 magnetic resonance spectra of several pyrimidines85 confirmed the diketo structure usually ascribed to uracil. 

A review of the PMR spectra of phytoxanthones contains an extensive list of spectral data for oxygenated xanthones (79H(l2)42l). 

Early work on the PMR spectra of flavonoids was hindered by their lack of solubility in CDCI3 and CCU. Progress was made following the introduction of DMSO-cf6 (64AJC428), but the most significant advance arose from the conversion of flavonoids into their more soluble trimethylsilyl ethers (64TL513,65P177). 

The temperature-dependent PMR spectra of the M(R2Dtc)3 complexes [M = Ga(III), In(III)] show them to be stereochemically nonrigid. Kinetic parameters for the intramolecular metal-centered rearrangement (by a trigonal... 

The synthesis of the Cl2 Sn(R2 Dtc)2 and (Me)2Sn(R2Dtc)2 complexes has been described (589). Line-shape analysis of the variable-temperature PMR spectra of the X2 Sn(/-Pr2 Dtc)2 complexes in CHC13 was carried out to obtain the activation parameters of the hindered rotation around the S2C-N bond. Barriers to rotation of 18.3 kcal mole-1 for X = Cl and 16.4 kcal mole-1 for X = Me were reported. 

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