HNMR Spectra

The NMR speetra of the parent heteroeyeles cf. Table 7) eaeh eonsist of two multiplets, 

Structure of Five-membered Rings with One Heteroatom 

In the ease of pyrrole the ring protons are also eoupled to the N—H with = = 

Annelation of a benzene ring on to the [Z ] faee of the heteroeyelie ring does not have any pronouneed effeet upon the ehemieal shifts of the heteroeyelie protons (cf. Table 8). The rather unexpeeted heteroatom sequenee for shifts to progressively lower field for both H-2 and H-3 remains NH S 0 Se Te, as for the parent heteroeyeles. The ehemieal shift of the indolie N—H is also very solvent dependent and as in pyrrole it is also eoupled to the ring protons with Ji,2 = 2.4Hz and Ji,3 = 2.1 Hz. The assignment of the benzenoid protons H-5 and H-6 has eaused some eonfusion in the literature as they have almost 

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In the HNMR spectra of 1,2,4-triazine 2-oxides the signals of the H(3) andH(6) were found to be shifted upheld by about 0.8 ppm in comparison with the parent... 

HNMR spectra of the deuterated complex obtained in CH2CI2 and in [EMIM]C1/A1C13 (1 1.2) are displayed in Figure 5.2-3. 

Table 2. HNMR Spectra of (Bcnzo)Thiepins (Chemical Shifts in ppm)...

The first known synthesis of a benzothiepin, 3-benzothiepin-2,4-dicarboxylic acid, was in 1953.3 3 Many claimed syntheses of monocyclic thiepins were later proven erroneous. The determination of who had synthesized the first monocyclic thiepin can be based on the criterion of the observation of the decay in low temperature HNMR spectra,78 or of isolation.18... 

The H and 13CNMR spectra of various cyclopentazepines have been recorded (Tables 1 and 2), as has the HNMR spectrum of 7V,7V-dimethylcyclopent[e]azepin-l-amine.68 A detailed analysis of geminal and long-range 13C-H coupling constants for cyclopent[c]azepine is also available.87 The HNMR spectra of 9//-pyrrolo[l,2-a]azepin-9-one (8b) and its fully delocalized cation have been recorded in various solvents.7... 

Isomer ratios of mixtures of 5//-dibenz[c,e]azepines have been determined by integration of the C7 methylene resonance signal in their HNMR spectra.48... 

The isolated iron hydride complexes introduced in this chapter are listed in Table 12, where the hydride chemical shifts in the HNMR spectra and the Fe-H bond distances are summarized. 

Analytical Methods. A Schimadzu Liquid Chromatograph was used to monitor the reaction conversion and to assign chemical and chiral purity to the final product. Structures were verified by HNMR spectra obtained on a Bruker (Model UltraShield 400 spectrometer). Optical rotations were measured on a Perkin Elmer Model 341 Polarimeter. 

An interesting effect of pH was found by Ogo et al. when studying the hydrogenation of olefins and carbonyl compounds with [Cp Ir(H20)3] (Cp = ri -CsMej) [89]. This complex is active only in strongly acidic solutions. From the pH-dependence ofthe HNMR spectra it was concluded that at pH 2.8 the initial mononuclear compound was reversibly converted to the known dinuclear complex [(Cp Ir)2(p-OH)3] which is inactive for hydrogenation. In the strongly acidic solutions (e.g. 1 M HCIO4) protonation of the substrate olefins and carbonyl compounds is also likely to influence the rate ofthe reactions. 

Fig. 10. ID HNMR spectra of the h3rperfine-shifteddownfield region of (a) 4 mMNPl and (b) 6 mM NP2 in D2O at pH 7 (50 mM phosphate buffer) and 37°C, in the absence of added ligand. Note the well-resolved peaks of NP2, but the broad peaks observed for NPl. The NMR spectrum of NP4 is similar to that of NPl, and that of NP3 is similar to that of NP2. It is concluded that NPl and NP4 do not have His59 bound to the heme at neutral pH in solution in the absence of a strong field distal-side ligand.

Fig. 8. HNMR spectra of N3P3CI [NHCH2CH2NH] (a) and NjPjiNMe ) [NHCHjCHjNH] (b) (from Ref. 82)...

The HNMR spectra of the diaqua and aqua (hydroxo) hemin complexes encapsulated in micelles have been reported [20] (Fig. 5). The heme methyl resonances in the diaqua species lie in the same region as those of the high-spin bis(dimethyl sulphoxide) iron (III) porphyrin complex [37-39], while those of the aqua (hydroxo) complex appear in a more upheld region. The positions and linewidths of the heme methyl resonances in these complexes are similar to those observed in the aqua and hydroxo hemoproteins [19,40]. The broadness of the ring methyl resonances of both the diaqua and aqua (hydroxo) species in micelles has been ascribed to arise from the hindered rotational tumbling motion of the heme inside the micelles. The spread and linewidth of these resonances are much larger than those of similar high-spin model heme complexes in simple solution [3]. 

The HNMR spectra of the Fe(II) porphyrins in aqueous micelles are however characterized by two important differences from those in benzene [12,13]. The porphyrin proton resonances are much broader in aqueous micelles than in the benzene solution, and the spread of the heme methyl resonances is also larger (see Table 2). These will be discussed in detail in the next sections. 

The micelle-encapsulated six coordinated bis(pyridinato) iron(II) complexes of protoporphyrin and OEP have been reported by addition of pyridine to the four coordinate ferrous complex in aqueous micellar solution. The optical spectrum of [Fe(II)(PP)(Py)2] in micelle (Fig. 10) is identical to S = 0 six-coordinate bis(pyridinato) iron(II) porphyrin complex [3]. The magnetic moment measurements in solution confirm their diamagnetic nature. The HNMR spectra are also characteristic low-spin iron(II) resonances (S = 0) with shifts lying in the diamagnetic region (Table 2). 

HNMR spectra in suitable solvents (see procedures) under an N2 atmosphere provides the best method of checking their purity. 

The structures of vanicosides A (1) and B (2) and hydropiperoside (3) were established primarily by one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy techniques and fast atom bombardment (FAB) mass spectrometry (MS).22 The presence of two different types of phenylpropanoid esters in 1 and 2 was established first through the proton (4H) NMR spectra which showed resonances for two different aromatic substitution patterns in the spectrum of each compound. Integration of the aromatic region defined these as three symmetrically substituted phenyl rings, due to three p-coumaryl moieties, and one 1,3,4-trisubstituted phenyl ring, due to a feruloyl ester. The presence of a sucrose backbone was established by two series of coupled protons between 3.2 and 5.7 ppm in the HNMR spectra, particularly the characteristic C-l (anomeric) and C-3 proton doublets... 

VC13 treated with Bu NC produces mer-[VCl3(CNBu,)3]. The structure was determined by X-ray diffraction.182 The HNMR spectra in CDC13 showed that the free ligand exchanges more rapidly with the isocyanide tram to chloride than with the trans isocyanide groups. Therefore, the kinetic trans effect of chloride ion is larger than that of isocyanide. 

In other substituted phosphorinanes the HNMR spectra are too complicated for a clear-cut conformational (and configurational) analysis. Even in 1-methylphosphorinane the H atoms of the 1-Me group appear as two multiplets due to coupling with the (a) and (e) H atoms of C-2 and C-6. However, the (a,a), (a,e) and (e,e)4/H-h coupling constants are too similar to allow conformational analysis by H NMR. We shall see later that 13C NMR is an excellent method for solving these problems. 

Wanless and Kennedy (S) pyrolyzed polymers synthesized using 4-methyl-1-pentene and 4-d-4-methyl-1 -pentene. The mass, infrared, and HNMR spectra of the pyrolyzates, as well as those of a polymer produced by Ziegler-Natta initiator indicated that the cationically produced polymer contained about 70% 13 and 1,4 units, with 1,4 units predominating, and that the 1,4 structure most probably resulted from two consecutive hydride shifts rather than a single hydride jump". 

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