Aromatic absorptivities

The infrared spectrum of the l-methoxy-l,4-cyclohexadiene shows the absence of strong aromatic absorption at 1600 cm.the ultraviolet spectrum shows absence of absorption at 270 nm., indicating absence of the conjugated isomer. 

If the solution contains an appreciable concentration of unhydrated carbonyl compound, the variation of carbonyl u.v. absorption with pH can be used to obtain (Bunnett et al., 1961 Hiiie et al., 1965). Similarly, in the weakly dissociated compounds X.CoH4.C(OH)2.CF3 the variation of the aromatic absorption with pH provides a means of determining Kx or (Stewart and Van der Linden, 1960). 

The absorption band that frequently appears in the spectra of substituted benzenes near 600-420 cm-1 is attributed to out-of-plane ring bending. Some spectra showing typical aromatic absorption appear in Appendix B benzene (No. 4), indene (No. 8), diethylphthalate (No. 21), and m-xylene (No. 6). 

The long wave absorption band is overlapped by a strong aromatic absorption near 240 nm. 

During the solid-state polymerization the maleimide disappears as the substituted succinimide forms as shown in Fig. 7. An aromatic absorption at 1515 cm-1 similar for both the maleimide and crosslinked succinimide network was used as an internal standard. The disappearance of the absorption band located at 1150 cm-1 (v C-N-C) plotted as a function of the increase of the corre-... 

Signals around 6 7 to 6 8 suggest the presence of an aromatic ring. If some of the aromatic absorptions are farther downfield than 87.2, an electron-withdrawing substituent may be... 

Liquid crystalline solutions of KB LG (or of RBDG) and films prepared from such srdutions also ow significant CD in the wavelength range of the aromatic absorption bands 46,47) the CD for PBDG in methylene chloride is positive (46). CD bands are also induced when dye mdecules are introduced in liquid crystal films of polypeptide (PMDG). These induced CD bands are interpreted as arising from the dissymmetric field of the cholesteric structure 48). 

The steam distillation residue contains heavy oils and asphaltenes. These were separated by solubility differentiation. Both of these materials were sufficiently soluble in CCl, to permit examination by both IR and NMR. Principal featuris of the IR and NMR spectra are shown in Table VI. The possibility of colloidal dispersion of the asphaltenes instead of true solubility may have caused some loss of fine structure for the aromatic absorption regions. 

The partial IR spectrum of base Subfraction 1 shows N-H absorption at 3460 cm S amide absorption at 1690 cm S and aromatic absorption at 1600 cm. Base Subfraction 2 shows increased amounts of aromatic absorption at 1600 cm and an additional band at 1720 cm S which is thought to be an amide carbonyl absorption. Subfraction 3 shows N-H absorption at 3460 cm S amide absorption at 1685 cm S and large amounts of aromatic absorption at 1600 cm that shows asymmetry typical of pyridine benzologs. Strong bases such as pyridine benzologs appear to be the predominant basic compound type in Subfraction 3. 

The absorption below 210 nm Is attributed to the sensitizer aromatic absorption and/or the absorption by additives and structural Imperfections present In the host polymer. 

The determination of the position of the phenolic hydroxyl in X-methylcassyfiline, and hence in cassyfiline itself, follows from the application of Barton s deuteration method as applied to apocrotonosine. X-Methyldeuterocassyfiline (XVI) was prepared from X-methyl-cassyfiline (XVIIa) by treatment with NaOD in D2O, and the NMR-spectra of the two bases compared. From the disappearance of the singlet at 3.20 T it was clear that it was the C-8 position that had been deuterated, so that the phenolic group was placed at C-9. If the phenolic group had been present at C-3, no aromatic deuteration would have occurred while if it had been situated at C-10, it is the downfield aromatic absorption that would have disappeared upon deuteration. Cassyfiline is thus correctly represented by expression XVIIb. 

As seen in the peak table presented, the shifts in the aromatic absorption region of the polystyrene specimen exposed to hydrochloric acid appear to be toward lower frequencies versus the expected higher frequency shift seen in poly (4-chlorostyrene). The absorptions at approximately 706 and 764 cm" appear at approximately 690-698 cm and 748-756 cm l whereas poly(4-chlorostyrene) exhibits absorptions at approximately 730 and 750 cm"l. The absorptions at 907 cm, 1022 cm-1, 1067 cm l, 1290 cm" , 1322 cm l, 1370 cm" , 1464... 

Aliphatic absorption is strongest at higher frequencies and is almost missing below 900 cm" aromatic absorption is strong at lower frequencies between 650 cm and 900 cm". We can also determine the number and position of substituent groups on the benzene ring from the IR spectrum. 

From the mother liquors of crude herbaceine a second alkaloid, herbaine, C22H28N2O4 (mp 126°-127°) could be isolated [24, 24a). Its UV-spectrum was typical of a 6-methoxyindole and its IR-spectrum was very similar to that of herbaceine, except for the differences in the aromatic absorption. NMR- and mass-spectral evidence 24a) showed... 

The average aromatic absorptivity for model compounds (a (ar) 768) are higher than those derived for bituminous coals and products C(ar) 686) and for lignite and subbituminous coals and products (a (ar) 541) The comparison is similar for the... 

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