Hydrogenation aliphatic

Where there is symmetrical disubstitution of an aliphatic hydrogen then, as might be expected, the is usually raised, as seen from the data in Figure 25.18. 

Only a limited number of coal-denved pitches were examined by H NMR because of their low solubility in solvents commonly used m conventional proton magnetic resonance. Table 12 reports the distribution of hydrogen for three of the pitches. Unlike coal-tar pitches, which typically have over 85% of the hydrogen bonded to aromatic carbon, the matenals listed in Table 12 are characterized by a high content of aliphatic hydrogen. 

The earliest attempts to prepare deuterated steroids were carried out by exchange reactions of aliphatic hydrogens with deuterium in the presence of a surface catalyst. Cholesterol, for example, has been treated with platinum in a mixture of deuterium oxide and acetic acid-OD, and was found to yield... 

The aliphatic hydrogens of a-picoline (1) are relatively acidic, so that treatment with phenyl lithium... 

Working co-operatively with others, we have found some indication that certain alilphatic linkages between aromatic nucleii are involved in the rapid dissolution of coal. The absolute aliphatic hydrogen content as determined by P. Solomon using FTIR (22) shows a very good linear relationship with conversion of coal in 3 minutes to pyridine soluble materials (Figure 14a). 

Figure 14a. Response of coal conversion to aliphatic hydrogen content...

Figure 14b. Relationship between SRC yield and reactive aliphatic hydrogen...

Figure 14. A stereoview of a typical "snapshot" from a molecular dynamics simulation of a-D-glucopyranose in aqueous solution, showing selected water molecules close to the 01 and 02 hydroxyl groups. The hydrophobic hydration requirements of the aliphatic hydrogen atoms on Cl and C2 impose additional structuring restrictions of the orientations of the water molecules hydrogen bonding to the 02 hydroxyl group. (Reproduced from Ref. 32. Copyright 1989 American Chemical Society.)...

For each coal, at the maximum in hydrogen content, or H/C atomic ratio, the aliphatic hydrogen content (determined by H NMR analysis) accounted for over 90% of the total hydrogen. The aliphatic hydrogen contents were 10.5% for the subbituminous coal,PSOC-1403, and 6.9% for the bituminous coal, PSOC-1266. The high aliphatic hydrogen content was associated with the presence of polymethylene chains. The early release of paraffinic material, as n-alkanes and as long chain substituents to aromatic structures, under conditions of mild pyrolysis has been observed in other research (13-15. ... 

Figure 3. Activation energy for conversion to THF solubles vs. aliphatic hydrogen for Argonne Premium Coal sample bank bituminous coals. Data on proton distribution from Dr. Charles Bronnimann, Colorado State University.

HC 1401-350 residue may not show the effect of bond breaking because of its low aliphatic hydrogen which must be available for free radical stabilization. 

When the NMR spectrum of a 30% (w./v.) solution of peroxide in toluene was recorded at 34°C., absorption was observed between 8 2.74 and 5.46. There were seven main resonances, all multiplets, which were interpreted in terms of aliphatic hydrogen shifted by oxygen. Resonance from ethylenic hydrogen amounted to only a fraction of a proton. However, the sample darkened while in the instrument and probably decomposed extensively. When the spectrum of a solution of peroxide prepared by oxidation to 10.4 mole % was recorded using a cold probe at —35°C. a different picture was obtained. There was complex absorption from both ethylenic and saturated hydrogen which was interpreted as arising from a mixture of 1,2 and 1,4 oxygen copolymers in an approximate jatio of 1 to 2. In this sample the residual chloroprene amounted to 0.15% of the monomer units in the peroxide and dimers of chloroprene to 0.6% of the peroxide. 

An interesting comparison can be made on the basis of the hydrogen distribution of the three macerals. The aromatic hydrogen content (%H.r) has been calculated from the total area of the infrared absorption between 11 and 14 n (aromatic HCC rocking vibrations) (6). The aliphatic hydrogen content (% H.i) has been derived from the absorption of the aliphatic H-C stretching vibration between 3.3 and 3.6 m (7). The values found for the three macerals under investigation are reported in Table II, columns 3 and 4. 

Table III. Aliphatic Hydrogen Distribution Derived from PSR Measurements and H.i/H for an Exinite, Vitrinite, and Micrinite...

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