Spectra 3-substituted

It is suggested that for 9 e [(-/ , Pf] the dependence U(9) is analogous. The smaller the/, the narrower the calculated absorption loss spectrum. Substituting Eq. (214) into the Hamiltonian for planar rotation, we have29... 

Because deuterium signals are not seen in an NMR spectrum, substituting a deuterium for a hydrogen is a technique used to identify signals and to simplify NMR spectra (Section 14.14). 

In the fully substituted porphins, changing the relative positions of the side chains (with the exception of the C=0 groups) to form different isomers has no effect on the absorption spectrum. Substitution of one... 

By substituting back into the definition of a , we get the solution set for the energy spectrum Ei. In ethylene there are two elements on the diagonal, xu and X22, leading to Ei and 2- In larger conjugated n systems, there will be more. 

Due to the structure of the symmetrical anhydrobase. every time a 2-methylthiazolium undergoes the attack of a base, theoretically it can result in two trimethine thiazolocyanines the mesomethylsubstituted one and the unsubstituted one. For an unexplained reason, it seems that when position 5 of the starting molecule is substituted, only the mesomethyl dye is produced according to the absorption spectrum, 530 nm for the methylmeso and 569 nm for the 4-phenyl substituted derivative (Scheme 29). ... 

Out-of-Plane Vibrations, yCH and yCD. In accordance with all the proposed assignments (201-203), the bands at 797 and 716 cm correspond to yCH vibrators, which is confirmed by the C-type structure observed for these frequencies in the vapor-phase spectrum of thiazoie (Fig. 1-9). On the contrary, the assignments proposed for the third yCH mode are contradictory. According to Chouteau et al. (201), this vibration is located at 723 cm whereas Sbrana et al. (202) prefer the band at S49cm and Davidovics et al. (203) the peak at 877 cm This last assignment is the most compatible with the whole set of spectra for the thiazole derivatives (203) and is confirmed by the normal vibration mode calculations (205) (Table 1-25). The order of decreasing yCH frequencies, established by the study of isotopic and substituted thiazole derivatives, is (203) yC(4)H > 70(2)13 > yC(5)H. Both the 2- and 4-positions, which seem equivalent for the vCH modes, are quite different for the yCH out-of-plane vibrations, a fact related to the influence observed for the... 

Carbon-hydrogen stretching vibrations with frequencies above 3000 cm are also found m arenes such as tert butylbenzene as shown m Figure 13 33 This spectrum also contains two intense bands at 760 and 700 cm which are characteristic of monosub stituted benzene rings Other substitution patterns some of which are listed m Table 13 4 give different combinations of peaks... 

The mass spectrum of 2-pyrone shows an abundant molecular ion and a very prominent ion due to loss of CO and formation of the furan radical cation. Loss of CO from 4-pyrone, on the other hand, is almost negligible, and the retro-Diels-Alder fragmentation pathway dominates. In alkyl-substituted 2-pyrones loss of CO is followed by loss of a hydrogen atom from the alkyl substituent and ring expansion of the resultant cation to the very stable pyrylium cation. Similar trends are observed with the benzo analogues of the pyrones, although in some cases both modes of fragmentation are observed. Thus, coumarins. 

The H NMR spectrum of pyridazine shows two symmetrical quartets of an A2X2 or A2B2 type dependent on the solvent and concentration. The satellites have been used to obtain all coupling constants. Spectra of C-substituted pyridazines, methylthio- and methylsulfonyl-pyridazines, both as neutral molecules and as cations, N-1 and N-2 quater-nized species, pyridazinones, hydroxypyridazinones, A-oxides and 1,2-dioxides have been reviewed (b-73NMR88> and are summarized in Tables 6, 7 and 8. 

A comparison of the relative basicities of pyrrole, furan and thiophene may be made by comparing the pK values of their 2,5-di-t-butyl derivatives, which were found to be -1.01, —10.01 and —10.16, respectively. In each case protonation was shown by NMR to occur at position 2. The base-strengthening effect of alkyl substitution is clearly apparent by comparison of pyrrole and its alkyl derivatives, e.g. A-methylpyrrole has a pKa. for a-protonation of -2.9 and 2,3,4,5-tetramethylpyrrole has a pK of 4-3.7. In general, protonation of a-alkylpyrroles occurs at the a -position whereas /3-alkylpyrroles are protonated at the adjacent a-position. As expected, electron-withdrawing groups are base-weakening thus A-phenylpyrrole is reported to have a p/sTa of -5.8. The IR spectrum of the hydrochloride of 2-formylpyrrole indicates that protonation occurs mainly at the carbonyl oxygen atom and only to a limited extent at C-5. 

H-Azepine derivatives form a diene complex with tricarbonyliron, leaving uncomplexed the third of the double bonds. If the 3-position is substituted, two different such complexes are possible, and are in equilibrium, as seen in the NMR spectrum. An ester group in the 1-position of the complex can be removed by hydrolysis, to give an NH compound which, in contrast to the free 1/f-azepine, is stable. The 1-position can then be derivatized in the manner usual for amines (Scheme 22). The same tricarbonyliron complex can, by virtue of the uncomplexed 2,3-double bond, serve as the dienophile with 1,2,4,5-tetrazines. The uncomplexed N-ethoxycarbonylazepine also adds the tetrazine, but to the 5,6-double... 

Simple aziridines are optically transparent in the UV region of the electromagnetic spectrum (B-69MI50401). In more highly substituted aziridines, such as the 2-aroyl-3-arylaziridines (9), there is an interaction between the carbonyl and aryl ring substituents... 

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