Methine, aliphatic

By comparing a number of aliphatic hydrocarbons of different structure, Mare and RoCek ° compute relative rates of oxidation of methyl, methylene and methine groups to be 1 114 7000-18,000. 

Moreover it has been shown that PV0CC1 prepared by free-radical polymerization of vinyl chloroformate (V0CC1) is an atactic polymer having a Bernouillian statistical distribution as expected (J[9). In order to extend our studies on the chemical modification of PV0CC1, the stereoselective character of the nucleophilic substitution of the chloroformate units with phenol has been examined by the study of the 13c-NMR spectra of partly modified polymers in the region of the aliphatic methine carbon atoms. The results obtained in this field are presented here. 

In the case of partly modified polymers the spectra B, C and D show more complicated structures which can be presumably due to significant neighbouring-groups effects between phenyl carbonate groups and modified or unmodified groups linked to the next aliphatic methine carbon atoms. 

Polyene and polymethine dyes are two structurally related groups of dyes which contain as their essential structural feature one or more methine (-CH=) groups. Polyene dyes contain a series of conjugated double bonds, usually terminating in aliphatic or alicyclic groups. They owe their colour therefore simply to the presence of the conjugated system. In polymethine dyes, electron-donor and electron-acceptor groups terminate either end of the polymethine chain, so that they may be considered as typical donor-acceptor dyes. 

The rule in carbon-13 NMR is that sp2-hybridized carbons (carbonyl, aromatic, olefinic) absorb at lowest field, followed by sp-hybridized (acetylenic, nitrile) and sp3 (aliphatic). A first glance leads us to believe we have seven signals, but we must remember that the methine carbon is directly bonded to phosphorus, so that we shall expect a relatively large C-P coupling. The other C-P couplings will probably be very much smaller. 

Figure 21 Expansion of the aliphatic region of the HSQC-1,1-ADEQUATE spectrum of the CDK-2 inhibitor dinaciclib (48). The connectivity network is traced out for the 2-(P-hydroxyethyljpiperidine moiety contained in the structure. Methylene resonances are inverted and plotted in grey methine and methyl resonances have positive intensity and are plotted in black.

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... 

First, peak heights are measured at five points in the NMR spectra (Figure 2). All NMR spectra of fulvic acids described in this study were determined as the sodium salt in D20 at pH 8 (21). Peak heights were used rather than peak areas to minimize overlapping spectral contributions from various proton structures. From structural-model considerations, peak 1 appears to be a combination of methylene and methine protons in aliphatic alicyclic rings and branched methyl groups located beta to carbonyl groups of a carboxylic acid, ester, or ketone. The structural model rules out meth-... 

The Effect of Dipolar Interaction on Cross Polarization and Carbon-Proton Dephasing, J. Am. Chem. Soc., in press. The dipolar dephasing data on an Illinois No. 6 coal has allowed the semi-quantitative separation of methyl, CH2 plus aliphatic methine, and protonated and nonprotonated aromatic carbons, L. B. Alemany, D. M. Grant, R. J. Pugmire, and L. M. Stock, Solid State Magnetic Resonance Spectra of Illinois No. 6 Coal and Some Reductive Alkylation Products, Fuel, (in press). 

The influence of the alcohol on the reaction was evaluated (Scheme 26). The results of a competition experiment between the alcohols are shown in Table 7. Both alcohols were treated with mono-alkoxysilane le using 10 % Pd/C as the catalyst. The silyl ketals of both alcohols were isolated as a mixture and the area under the methine protons, from the (+)-ethyl lactate moiety of both silyl ketals, was compared by NMR analysis. The difference in reactivity of primary, versus secondary, versus tertiary alcohol was small. The differences in reactivity range from 1.5 1 for 1° vs 2°, to 3 1 for 1° vs 3°. The reactivity of a benzyl alcohol is slower than the aliphatic alcohol as shown in entries 4 to 6. Entries 4 and 5 show an increase in the ratio of 1° 2° alcohol and a decrease in ratio for the 2° 3° for the secondary benzyl alcohol. Entries 6 and 7 confirm that benzyl alcohols are less reactive than aliphatic alcohols. The inductive electron withdrawing effect of the aryl group in the benzyl alcohol renders it less nucleophillic and this may affect the rate of reaction with the silane. Although the difference in reactivity is small, this trend may be informative. The influence of the alcohol s nucleophilicity on the reaction mechanism will be addressed in a later section. 

DIB in combination with sodium azide and diphenyl disulphide or diphenyl diselenide can replace the methinic hydrogen of aliphatic, aromatic and heteroaromatic aldehydes by the phenylthio or phenylseleno group. The corresponding esters were obtained in moderate (for unsaturated aldehydes) to very good yields [109] ... 

If infrared and ultraviolet spectra are available, they should be inspected for preliminary clues about the functional groups and conjugation that might be present. A fairly superficial survey of the JH and 13C spectra should enable you to assess such factors as the degree and kind of symmetry in the molecule the ratio of aromatic to aliphatic carbons the number of methyl, methylene, methine and quaternary carbons and the number of exchangeable protons. The next stage is a detailed study of the one-dimensional or COSY spectrum ... 

Hydrogen nuclei attached to carbon are divided among the following groups aliphatic (methyl, methylene, methine), vinyl (olefinic), acetylenic, aromatic, and formyl. 

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