Doublets, crystalline

A recent publication by Clements et al. [36] describes the effect of applied tensile stress on the proton spectra of polyvinylidene fluoride. The spectra consist of a narrow singlet superimposed on a broad doublet, which are assigned to amorphous and crystalline material, respectively. When stress is applied, the proportions of these components change, the fractional crystallinity increasing when the stress is parallel to the draw direction and decreasing when perpendicular. These measurements were all carried out with the draw direction parallel to the magnetic field direction because the crystalline doublet was most apparent in this case. The authors offer this crystallinity change as a partial cause of the piezoelectric response of the material. 

Reduction of epoxide 21 with lithium aluminium hydride gave a crystalline branched-chain methyl heptoside derivative 24. The NMR spectra of compounds 21 and 24 were very similar. In the spectrum of compound 24 the disappearance of the two sharp doublets at r 6.80 and 7.45 (2 protons) and the appearance of a singlet at r 8.65 (3 protons) is consistent with the reductive cleavage of epoxide 21 to give a substance 24 with a methyl substituent. The multiplet at r 7.40-8.50 ( 5 protons ) was assigned to the four protons of the two methylene groups and the hydroxylic proton. 

Epiervafolidine (C4oH46N405) was a crystalline compound (MP >256°C, [a]D +52°) and could be analyzed by X-ray crystallography, resulting in formula 243. The only significant difference between it and ervafolidine was the down-field shift of H-3 in the H-NMR spectrum at 4.14 ppm as a doublet (J = 5Hz) attributable to the coupling with the hydroxy proton. This is a characteristic feature of alkaloids of this series with a (35) configuration. 

The in situ spectra obtained at -1.0 V, shown in curve B, Fig 2, yielded a doublet with values of S and A in excellent agreement with those of crystalline Fe(0H)2 (Table I). This provides rather definite evidence that the redox process associated with the voltammetric peaks is given by ... 

The IR spectrum for d-FeOOH shows an OH stretch at 3130 cm", OH bending bands at 1124, 890 and 810 cm" and Fe-O stretch bands at 580 and 480 cm" (Oka-moto, 1968). In its poorly crystalline form as feroxyhyte, 5 -FeOOH, this material shows similar, but less well expressed features. High pressure FeOOH shows a broad band at 2800 cm due to the bulk OH stretch, a doublet at 1150 and bands at 970 and 685 cm corresponding to OH bending vibrations and an Fe-O stretch, respectively (Pemet et ak, 1973). 

On warming to — 30°C., the spectrum of the crystalline samples changed to a sextet with a doublet substructure. By analogy with poly( 1-butene) this spectrum was interpreted as arising from allylic radicals (XXII), but this assignment needs further justification. 

The checkers obtained the cyclobutane 1 as a colorless crystalline solid, m.p. 45-47° (a mixture of major and minor isomers), that is relatively free of l,2-dichloro-l,2-dicyanocyclobutane. The product had the following spectral properties proton magnetic resonance (chloroform-d) 8 (multiplicity) 2.35-3.15 (multiplet), 3.40-4.20 (multiplet) l3C magnetic resonance (chloroform-d) 8 major isomer 21.58 (triplet), 38.41 (doublet), 37.24 (triplet), minor isomer 22.48 (triplet), 36.72 (doublet), 36.91 (triplet). 

In strong crystalline fields or highly distorted fields a doublet S= state becomes lowest in energy. In this situation there are generally no nearby states, so that g factors are close to 2.0023 and the ESR is observed at higher temperatures. The ESR results can be fitted to Eq. (171) and observed values for the spin Hamiltonian parameters are given in Table XVI. 

A melting point of 82°-83°C and [ ]D20 —85° - —100° were reported for 2,3-di-O-methyl-D-arabinose by Verheijden and Stoffyn (20). These authors preparation must have been largely or wholly an a-anomer, whereas ours is preponderantly ft. In view of the rarity of crystalline furanoses, it is presumed to be the / -pyranose, and in the PMR spectrum run at 0°C on a sample freshly dissolved in DoO the anomeric proton gave a signal, with the appearance of an unresolved doublet, at t 4.50. This chemical shift and a small value of Jit2, would be expected for H-l of a / -arabinopyranose in the 1C conformation. 

In an attempt to investigate the phase structure of this sample, the line shape analysis of the CH2 resonance line in the DD/MAS spectrum at 87 °C that is shown in Fig. 25 was examined. The result is shown in Fig. 26-(a). The elementary line shape of the crystalline phase was obtained as the line shape of the longest Tic component by Torchia s pulse sequence [53]. It was a doublet and was represented approximately by two down- and upheld Lorentzians with an intensity ration of 2 1 (Spectrum A shown by dotted line in Fig. 26). Since all methylene carbons in the a-crystalline form of this polymer are equivalent in the intramolecular helical conformation, the origin of the doublet could be attrib-... 

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