Since the molecular formula afforded 19 carbon atoms, the resonances of only eight carbon nuclei in the 13C NMR spectrum substantiated symmetrical dimeric nature of 2 with two p-substituted benzene rings
. Thus the combination of the above spectroscopic data with HMBC (Figure 2) information, compound 2 was finally characterized as bis[di-p-phenylmethane]ethyl carbamate, which is also a new natural carbamate derivative.
In summary, the effect of changing the electron withdrawing effects of the functional group works, in two opposing ways, by varying the electron density at both the imidazole ring and the substituted benzene ring
. This ability to reduce the electron density at the substituted benzene ring
by adding a less electron-accepting functional group, such as Br, limits the contribution across the imidazole bridge.
The [sup.1]H NMR of GB-19 has a H signal on the median of the benzene ring
including 5H 6.38 (1H, d, J = 1.6) and 5h 6.17 (1H, d, J = 1.6), which indicating that all the compounds have A and C rings that are substituted by typical flavonoids C-2,3,5,7.
By comparison with the solution P concentrations, sorption of the phenolic acids was highly dependent upon the number (and position) of hydroxyl groups attached to the benzene ring
, rather than the distance of the carboxyl group from the benzene ring
As another basic structure characteristic for a product with benzene ring
, the UV-Vis absorption spectra of PANI prepared in four kinds of inorganic acids are shown in Fig.
was promoted by substituting the electron-donating substituent on the benzene ring
of phenylhydrazone (the opposite is also true).
The secret to the molecules' capability to turn heat into power lies in their structure-like water reaching a fork in a river, the flow of electrons along the molecule is split in two once it encounters a benzene ring
, with one flow of electrons following along each arm of the ring.
PREG is particularly pronounced when the polar groups are attached to a benzene ring
and other larger aromatic systems.
Functional group test, decrease in iodine number, increase in acid number and IR spectra confirms the sulfonation on the benzene ring
(probably at ortho and para positions).
The following FTIR spectral data could be observed: 3660~3150 [cm.sup.-1] (OH stretch), 3066 [cm.sup.-1] (stretch of unsaturated C-H in benzene ring
), 1642 [cm.sup.-1] (C=O stretch), 1598 [cm.sup.-1] and 1452 cm- 1 (Benzene ring
skeleton), 1226 [cm.sup.-1] (CO stretch), 750 [cm.sup.-1] and 697 [cm.sup.-1] (extemal plane bending of C-H in benzene ring
) (Zhang and Li 2007).
The observed wave number 1610 cm-1 corresponds to the aromatic ring vibration; 1451 [cm.sup.-1] indicates benzene ring
obscured by -CH2- methylene bridge; 1058 corresponds to single bond C-O stretching vibrations of CH2OH group and 976 [cm.sup.-1] to 1,2,4-substituted benzene ring
The electron density on the alkyl carbon in the [alpha] position with respect to the benzene ring
was discovered to be considerably higher in the case of the cyclized form than on the other carbons and, especially, on hydrogen atoms of the methyl group in an alkyl chain.