Cyclohexane results

It was found that the first step was rate determining. When, moreover, the reaction was run with the same reaction-temperature profiles under both conventional (oil) and microwave (monomode cavity) conditions, different distributions of the intermediate (1) and final (2) products were obtained (Tab. 5.10). Indeed, the product distribution was strongly affected by microwaves when the reaction was run at 85 °C rather than 110 °C, and addition of a small amount of a polar or nonpolar solvent also affected the product distribution. In this work two solvents capable of extensive coupling (i.e. ethanol) and not coupling (i.e. cyclohexane) with microwaves were used. Addition of ethanol strongly shifted the product distribution towards the final product (2), whereas addition of cyclohexane resulted in much lower yield of 2 [34]. 

Very fast reactions of R02 and ROOH with tin(II) and the fast reaction of RO with cyclohexane result in the formation of cyclohexanol as the main oxidation product. 

Another example of the dynamic equilibrium is that owing to ring inversion in cyclohexane resulting in two isomers of the monosubstituted six-membered ring... 

The discovery of 1 -aryl-1 -dimethylamino-cyclohexanes resulted from a surrey of compounds in which aromatic and basic features, both critical structural requirements of opioid analgesics, but usually separated by two or three carbon atoms, are linked to the same quaternary carbon. The synthesis of these compounds yielded a series of highly potent opioids (e.g. 1-Benzyl-4-(4-bromo-phenyl)-4-dimethylamino-cyclohexanol), however none of them are in clinical use (Lednicer et al., 1981). 

THF, ethyl acetate, and methanol. In contrast, use of other chlorinated solvents, e.g. CCI4, and cyclohexane resulted in higher enantioselectivity, comparable with that for chloroform. The range of dienophile substrates was also studied. Replacing N-methylmaleimide by N-phenylmaleimide, in the presence of quinidine as a catalyst, also led to a good yield, although enantioselectivity was lower (20% ee compared with 61% ee). Much slower reaction rates were observed when methyl acrylate and methyl fumarate were used and enantioselectivity was low (0% ee for methyl acrylate and 30% ee for methyl fumarate). With methyl maleate as a dienophile no reaction was observed. Mechanistic studies were also conducted by Kagan et al. results were in accordance with a concerted [4+2]-cycloaddition process. 

In the most recent study by Dong et al. the impact of solvents was determined for the ternary catalyst system Nd(() Pr)3/[ I INMe2Ph]+[B(C6F5)4] / TIBA (1/1/30) [233]. In heptane and cyclohexane polymer yields are particularly high. Polymerization in heptane provided a polymer with a relatively narrow MMD whereas the use of cyclohexane resulted in a bimodal MMD. Czs-1,4 contents are slightly higher in cyclohexane (91.3%) than in heptane (90.4%). Polymerization in dichloromethane results in a very low polymer yield and an increased cis- 1,4-content (93.4%). In toluene no polymer is obtained, at all. 

The increased energy content, compared with the open chain, for the C—C bond even in the strain-free cyclohexane, results from the same cause as the higher energy content of the normal alkanes, compared with the branched alkanes with more CH3 groups which are completely missing in cyclohexane. 

Conformational inversion of monosubstituted cyclohexanes results in equilibration of the substituent between axial and equatorial positions. The bulkier a substituent, the more it prefers the equatorial position. The 1.1-dimethylethyl group occupies the equatorial position exclusively,... 

In another example, irradiation of 2-benzoylbicyclo[2.2.2]octane (286) in cyclohexane results primarily in the formation of the Norrish type II (Section 6.3.4) photoelimination product 287 (Scheme 6.124).965 In contrast, 2-benzoyl-2-methylbicyclo[2.2.2] octane (288) undergoes complete and stereoselective conversion to the tricyclo [3.3.1.02,7]nonane 289.965 The eclipsing interactions between the methyl and phenyl groups in the cxo-2-methyl-substituted derivative slow the hydrogen abstraction step by two orders of magnitude and presumably the same interactions enhance the probability of cyclization. 

Harly extractions of pertechnetate, dissolved in 1 N H2SO4, with a 0.1 M solution of tri-/(-octylamine (TOA) in cyclohexane resulted in distribution coefficients of Dic= 110 at 25 °C jl 11]. Recently, Dy was determined as a function of the nitric acid concentration using 0.01 and 0.1 M solutions of tri- -octylamine in benzene. The distribution coefficients increased with increasing acidity until a maximum was reached near 0.1 M 11N03. At higher concentrations of nitric acid, D y. fell rapidly because of competition from the simultaneously extracted nitric acid, which reduces the concentration of free tri-n-octylamine available to extract TcO (Fig. 7.8.A). llic extraction is considerably affected by the temperature. A linear relation is obtained between D y. and the concentration of TOA. The slope of 1.0 indicates an extractant Tc ratio of 1 1. The extraction of pertechnetate from aqueous HKO3 solution may be represented by the equation [ 117] ... 

Irradiation of a solution of 5-phenyl-l,2,4-thiadiazole in acetonitrile for 150 min was accompanied by the consumption of 53% of the reactant and the formation of 2-phenyl-l,3,5-triazine, 2,4-diphenyl-l,3,5-triazine, and other (gas-liquid chromatography) (GLC)-volatile products. Diphenyl-1,2,4-thiadiazole was observed also to undergo photofragmentation and triazine formation. Thus, irradiation of a solution of diphenyl-1,2,4-thiadiazole in cyclohexane resulted in the formation of benzonitrile and triphenyl-l,3,5-triazine in yields of 26% and 52%, respectively <2003JOC4855>. 

As expected, the solubility of hydrogen increases with increasing pressure. The solubility shows maxima with temperature at the various pressures. The highest solubility is observed at 475 K and 50 bar. Finally, the presence of cyclohexane results in an increased hydrogen solubility in aU cases. 

Figure 12.35 The Perlin effect, where smaller 7ch values are observed experimentally for axial protons in cyclohexane, results from is from ref 55.)...

Photosubstitution.—The primary process in the photosubstitution of [Cr(CO)s] and of [W(CO)8] by pyridine has been studied, in particular to account for the quantum deficit (for example, d>A=0.66 0.05 for [py] = 2.4x 10 M and [Cr(CO)6l = 3.5 X 10- M 292 nm irradiation in cyclohexane). Results in viscous solvents eliminated cage recombination as a possibility, and excited singlet to excited triplet intersystem crossing was shown to occur with unit efficiency so that the triplet state must dissociate and the deficit is due to a radiationless decay which competes with dissociation. 

From benzene to toluene, the molecule "thickness" t increases by ca.0.06 nm. A further growth of t from phenol to cyclohexane results in lower adsorbabilities of the CFC s. Note that a reverse sequence is observed with the same aromatic molecules adsorbed on the GCB and AC. 

The court of enquiry concluded that the discharge of a vapour cloud of cyclohexane resulted in an explosion which was equivalent to the detonation of 15 5 tonnes of TNT, (Health and Safety Executive, 1975). While the mechanism by which the deflagration accelerated to become a detonation has not been made clear, it seems reasonable to expect that if the cyclohexane inventory had been reduced by (say) two orders of magnitude, a discharge would only have involved a deflagration. 

The ability to vary the nature of the liquid phase in LAG allows control over the polymorphic behaviour of mechanochemically obtained co-crystals. This was demonstrated by Trask et al. in mechanochemical co-crystallisation of caffeine with glutaric acid. Co-crystallisation of the two components in chloroform solution provided the co-crystal (caffeine)-(glutaric acid) as two concomitant polymorphs. However, LAG with either chloroform or cyclohexane resulted in the selective formation of each form separately (Figure 8.6(a)).This control of polymorphic behaviour was also observed in LAG screening for co-crystals of piroxicam." The application of LAG to the control of polymorphism is not limited to co-crystals, however and has also been shown to be applicable to single-components systems, for example anthranilic acid (Figure 8.6(b)). ... 

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