Aromatic regions

Conditions CDCI3, 25°C, 400 MHz H), 100 MHz ( C). (a,b) //NMR spectra, aromatic region (a), aliphatic region (b) (c) HH COSY plot of aliphatic shift range (d) CH COSY plot with DEPT subspectra to distinguish CH and CHy,... 

All the peaks are somewhat upfield of the aromatic region, suggesting polyene character. This stmcture would also be consistent with the observed reactivity since the polyene has a. quinodimethane structure (see Section 11.3). The implication of a nonaromatic stmcture is that the combination of ring strain and the antiaromaticity associated with the four--nembered ring results in a localized system. ... 

The 9ai7-quinolizine structure (82) for the labile adduct from 3,5-dimethylpyridine was clearly established by the nuclear magnetic resonance studies of Richards and Higham, and subsequent work showed the labile adduct from 3-methylpyridine was analogous. As the labile adducts from all the pyridines and benzopyridines so far examined have very similar infrared absorption spectra in the 5-7 yn. (carbonyl and aromatic) region and within quite close limits very similar ultraviolet absorption spectra, it can be concluded that all are derivatives of 9aH-quinolizine,... 

All IR spectra have many absorptions, but those useful for identifying specific functional groups are usually found in the region from 1500 cm-1 to 3300 cm-1. Pay particular attention to the carbonyl region (1670-1780 cm-1), the aromatic region... 

In Fig. 11 spectra of resorcinol resins 36) are given. In comparison with prepolymers, it shows that the completely hardned resin is more susceptible than that of uncured resin to the conditions of prepolymer synthesis. Because of only moderate resolution in the aromatic region the spectral pattern is fairly similar for the two resins. 

Proton NMR integrations of methylene and aromatic regions can be used to calculate the number-average molecular weights of novolac resins29 ... 

Fig. 15. Aromatic region of the H NMR spectrum for Zn(C104)2 and ethylenediamine-N,5-ethyladeninc hydrochloride, A-Et-enHf,Cl , in D20, illustrating the broadening of the H2 resonance of the adenine moiety. Reproduced with permission from Ref. (58). Copyright 2000, Wiley-VCH.

Fig. 4.7.3 H NMR spectra of (a) apple juice and (b) grape juice samples. Vertical expansions are shown for aliphatic and aromatic regions and some assignments are indicated. (Permission granted to reprint this figure from Ref. [12].)...

Hexylene glycol has been proposed as a non-flammable substitute for acetonitrile in preparative chromatography.34 It has low viscosity, does not absorb in the aromatic region of the UV, and is powerfully eluotropic. Native... 

Figure 2. Spin-echo -NMR spectra from a diffusion experiment with a cubic phase of dDAVP (10%), MO (60%) and 2H20 (40%). Temperature 40 C, t=20 ms, A=24 ms, g=l 19 gauss/cm and 8=1.0,2.0..., 9.0 ms. The inset shows the aromatic region originating from dDAV P at a higher amplification. Also shown is the pulse sequence used in the NMR-diffusion method (see text for details).

The H-NMR spectrum of 2 in CDCI3 (Figure 1) exhibits broad unresolved resonances in the aromatic region similar to those found in the monomer. Broad signals with lack of resolution are consistent with magnetic non-equivalence of the methyl group protons resulting from a mixture of triad tacticities. 

H spectra (aromatic region) upper spectrum 200 MHz, lower spectrum 600 MHz. 

The near-UV CD spectrum of carbonic anhydrase (Fig. 39) is rather strong and displays substantial fine structure at pH 7 (Wong and Hamlin, 1974). In the molten globule and the acid-denatured forms, the near-UV CD spectrum is nearly abolished, although the authors report weak residual positive CD through the aromatic region. 

Now let us consider Structure 6.21 and Spectrum 6.18 and see how the Karplus curve can be used to aid assignment of the spectrum. (This compound will be referred to from now on as the morpholine compound as we will use it to demonstrate several different techniques) Note that the aromatic region has been omitted as it contains little of interest and we wish to concentrate on the carbocyclic region of the spectrum. It was acquired in CDCI3. 

Q9. Check out the aromatic region. Are you happy with the splitting pattern Now do the same with the alkene. 

C NMR of linear cross-linked PS. The proton decoupled 13C NMR spectra of linear and 1% cross-linked PS at 75 MHz in chloroform are illustrated in Figure 3. These spectra are similar to those for linear and cross-linked chloromethylated PS previously reported at lower field (14), although we have been able to resolve more structure in tHe" aliphatic and aromatic regions here. The quarternary and methylene carbon resonances at about 146 ppm and between 40 and 50 ppm respectively, are the most strongly affected by stereochemistry (20). The ortho and meta resonances at 128.4 ppm show partially resolved structure in the linear PS, as does the para carbon at 126.1 ppm. The methine resonance at... 

The aromatic region provides the only PS related line that is readily measurable, although it can only provide an approximation for the reasons mentioned above. The width of this combination is somewhat greater than found in the resin above, which is consistent with the proton results. 

The similarity of results for peptide resins in both solvents fits nicely with the estimate that this resin sample with about 50 weight % peptide should have similar swelling characteristics in the two solvents (3). In these samples we have measured the integrals of the aromatic region relative to an unenriched peptide peak, and the results are consistent with the observation of all the carbon nuclei, and hence the results are typical of all portions of the cross-linked matrix. 

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