Methylcyclohexane as solvent

Dyes can also be incorporated into hydrogen-bonded superstructures using the complementarity of the hydrogen bond donors and acceptors. The addition of a perylene bisimide dye to chiral dialkyl melamine derivatives leads to aggregates (Fig. 26) which show induced circular dichroism in the dye part of the assembly in methylcyclohexane as well as the formation of mesoscopic fibres when the solvent is evaporated [227]. The melamine compounds... 

Figure 13.24. Composition profiles and flowsketches of two extractive distillation processes, (a) Separation of methylcyclohexane and toluene with phenol as solvent (data calculated by Smith, 1963). (b) Separation of aqueous ethanol and isopropanol, recovering 98% of the ethanol containing 0.2 mol % isopropanol, employing water as the solvent. Flow rates are in mols/hr (data calculated by Robinson and Gilliland, 1950).

The amination reaction is not limited to aromatic hydrocarbons it is also applicable to r-alkanes. r-Butyl chloride reacts with trichloramine in the presence of aluminum chloride to give f-butylamine in 88% yield.5 Methylcyclohexane is converted into 1-amino-1-methylcyclohexane in yields as high as 67% (based on trichloramine). The most satisfactory conditions use C7H14-A1C13-NC13 in a 2 2 1 ratio with methylene chloride as solvent and a temperature of 0 5°.6 Under the same conditions adamantane gives 1 -aminoadamantane in nearly quantitative yield.7... 

It has recently been shown that Lewis acidic zeolites such as Ti-fi [12] give excellent results in the rearrangement of (5) in both liquid and gas phases [30]. Experiments conducted in the liquid phase with 1,2-dichloioethane as solvent resulted in 81 % selectivity for (6) at 29% conversion after 24 h. Gas-phase tests resulted in further improvements in the catalytic performance of this system. With methylcyclohexane as co-adsorbate 93 % selectivity for (6) at an initial conversion of 100 % was achieved at 90 °C. Although the conversion decreases linearly after 6 h on stream, the catalyst can be completely regenerated up to 100 times by an bum-off in air at 480 °C. 

It is very important to choose the reaction conditions so as to avoid further oxidation of the glycols formed if, for instance, the permanganate is added too rapidly to a neutral solution of olefin, the main product is an acyloin RCH(OH)—COR. 112 Hydroxylation is usually effected in the cold with neutral or alkaline potassium permanganate solution water, acetone, alcohols, methylcyclohexane, and mixtures of alcohol and water can serve as solvent. Magnesium sulfate is often added for reactions in a neutral medium.113... 

A mixture containing 50 wt% methylcyclohexane (MCH) in n-heptane is fed to a countercurrent stage-type extractor at 25°C. Aniline is used as solvent. Reflux is used on both ends of the column. 

The activation enthalpies for these reactions are respectively 10 and 7 kcal/mol greater than the corresponding Mn-L bond strengths in heptane. Assuming that methylcyclohexane and heptane are similar as solvents and that both reactions proceed via dissociative pathways as proposed, this implies that the Mn-heptane interaction is close to 8 or 9 kcal/mol. This is close to the 10 kcal/mol Cr-heptane interaction in (CO)5Cr-heptane (2,4) and the 9.6 kcal/mol W-ethane interaction in (CO)5W-ethane (22). We can also calculate the gas phase Mn-CO bond dissociation energy in CpMn(CO)3 to be close to 55 kcal/mol. Further experiments are necessary to confirm the magnitude of the Mn-heptane interaction. 

The influence of polymer architecture on intermolecular interactions in dilute solutions was investigated by membrane osmometry in toluene (good solvent for polystyrene), cyclohexane (theta or 0 solvent), and methylcyclohexane (poor solvent Striolo et al., 2001). The osmotic second virial coefficient (B22) measured for arborescent polystyrene in toluene was lower than for homologous linear polymers, as expected due to their smaller Rg. In a 0 solvent (cyclohexane), branching lowered the 0 temperature from 34.5 °C (linear homolog) to 32.2 °C (GO polymer). The 0 temperature for the GO polystyrene sample in methylcyclohexane was likewise lowered to 36 °C, as compared to values estimated between 60 and 70 °C for linear polystyrene samples. The experimental osmotic pressure data were successfully fitted with a molecular-thermodynamic equation suitable for colloids, indicating that the behavior of arborescent polystyrene molecules in dilute solution corresponds to a perturbed (weakly interacting or interpenetrable) hard sphere. 

The solubility of many steroids in ammonia-tetrahydrofuran-/-butyl alcohol is about 0.06 A/, a higher concentration than has been reported in other solvent systems. Still higher concentrations may be possible in particular cases by suitable variation in the solvent ratios Procedure 3 (section V) describes such a reduction of estradiol 3-methyl ether at a 0.12 M concentration. A few steriods such as the dimethyl and diethyl ketals of estrone methyl ether are poorly soluble in ammonia-tetrahydrofuran-/-buty] alcohol and cannot be reduced successfully at a concentration of 0.06 even with a 6 hour reduction period. The diethyl ketal of estrone methyl ether is reduced successfully at 0.12 M concentration using a two-phase solvent system of ammonia-/-amyl alcohol-methylcyclohexane (Procedure 4, section V). This mixture probably would be useful for any nonpolar steroid that is poorly soluble in polar solvents but is readily soluble in hydrocarbons. 

Solvents influence rate as well as selectivity. The effect on rate can be very great, and a number of factors contribute to it. In closely related solvents, the rate may be directly proportional to the solubility of hydrogen in the solvent, as was shown to be the case for the hydrogenation of cyclohexene over platinum-on-alumina in cyclohexane, methylcyclohexane, and octane 48). Solvents can compete for catalyst sites with the reacting substrates, change viscosity and surface tension (108), and alter hydrogen availability at the catalyst surface. 

Solvents can have a large influence on the extent of double-bond migration (6). The factors involved are complex as shown in the hydrogenation of methylenecyclohexane, 3-methylcyclohexene, and 4-methylcyclohexene to methylcyclohexane in benzene-ethanol, in peniane, and in ethanol over 5% Pd, 5% Pt, and 5% Rh-on-carbon. The amount of isomerized 2-methylcy-clohexene was measured ai 25% completion and, depending on the system,... 

Micelle formation of our block copolymers in fluorinated solvents indicates that these polymers might act as stabilizers or surfactants in a number of stabilization problems with high technological impact, e.g., the surface between standard polymers and media with very low cohesion energy such as short-chain hydrocarbons (isopentane, butane, propane), fluorinated solvents (hexafluoroben-zene, perfluoro(methylcyclohexane), perfluorohexane) and supercritical C02. As... 

Aware of the enhanced reactivity of trivalent [( ArO)3tacn)U] towards non-innocent solvents, such as ethers and chlorinated solvents, the reactivity of this molecule was challenged by exposure to more inert solvents like alkanes. Remarkably, recrystallization of 4 -bu u pentane solutions containing various cycloalkanes, i.e., methylcyclohexane, afforded the coordination of one cycloalkane molecule to the electron-rich U center (Scheme 4) (37). 

Extreme cases were reactions of the least stabilized, most reactive carbene (Y = CF3, X = Br) with the more reactive alkene (CH3)2C=C(CH3)2, and the most stabilized, least reactive carbene (Y = CH3O, X = F) with the less reactive alkene (1-hexene). The rate constants, as measured by LFP, were 1.7 x 10 and 5.0 X lO M s, respectively, spanning an interval of 34,000. In agreement with Houk s ideas,the reactions were entropy dominated (A5 —22 to —29e.u.). The AG barriers were 5.0 kcal/mol for the faster reaction and 11 kcal/ mol for the slower reaction, mainly because of entropic contributions the AH components were only —1.6 and +2.5 kcal/mol, respectively. Despite the dominance of entropy in these reactive carbene addition reactions, a kind of de facto enthalpic control operates. The entropies of activation are all very similar, so that in any comparison of the reactivities of alkene pairs (i.e., ferei)> the rate constant ratios reflect differences in AA//t, which ultimately appear in AAG. Thus, car-benic philicity, which is the pattern created by carbenic reactivity, behaves in accord with our qualitative ideas about structure-reactivity relations, as modulated by substiment effects in both the carbene and alkene partners of the addition reactions. " Finally, volumes of activation were measured for the additions of CgHsCCl to (CH3)2C=C(CH3)2 and frani-pentene in both methylcyclohexane and acetonitrile. The measured absolute rate constants increased with increasing pressure Ayf ranged from —10 to —18 cm /mol and were independent of solvent. These results were consistent with an early, and not very polar transition state for the addition reaction. 

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