Cyclohexane literature reporting

Table 7.3 S ummaty of literature reporting on the heterogeneous oxidation of cyclohexane with various oxidants. 

The literature reports failure in experimental observation of the coil-globule transition as well. Kg. Hauer and Ullman (1980) measured R// of polystyrene macromolccules in cyclohexane (iVf =510. .. 4.4 lO with a narrow MWD, within a concentration range 0.150... 0.001%) by means of photon correlation spectroscopy (dynamic light scattering). When T < 9. Ru linearly diminishes with lowering temperature, and no coil-globule transition was detected. 

The next question is, what physicochemical parameters may influence the adsorption-desorption equilibrium We suspected that the difference with different solvents may be due to the fact that the solubilities of cinchonidine in different solvents are different, so we tested the solubilities of cinchonidine in 54 solvents, and found that if the initially established adsorption-desorption equilibrium is perturbed, that is beeause the solubility of einehonidine in that flushing solvent is relatively big (e.g., 12 g/L in diehloromethane). On the other hand, the adsorption-desorption equilibrium is not perturbed by cyclohexane, because the solubility of cinchonidine in cyclohexane is quite small (0.46 g/L). By plotting the measured cinchonidine solubility versus solvent polarity reported in the literature, nice volcano-like correlations ean be identified (Figure 18) [66]. This example shows that some empirical observations in enantioselective hydrogenation may be traeed baek to basie physieoehemieal properties sueh as the solubility of cinchonidine and the polarity of the solvent. 

The yield determined in a certain type of experiment usually strongly depends on the assumptions made about the formation mechanism. In the older literature, the excited molecules were often assumed to be produced solely in neutral excitations [127,139-143] and energy-transfer experiments with Stern-Volmer-type extrapolation (linear concentration dependence) were used to derive G(5 i). For instance, by sensitization of benzene fiuorescence, Baxendale and Mayer established G(5 i) = 0.3 for cyclohexane [141]. Later Busi [140] corrected this value to G(5 i) = 0.51 on the basis that in the transfer, in addition to the fiuorescing benzene state S, the S2 and S3 states also form and the 82- 81 and 83 81 conversion efficiencies are smaller than 1. Johnson and Lipsky [144] reported an efficiency factor of 0.26 0.02 per encounter for sensitization of benzene fluorescence via energy transfer from cyclohexane. Using this efficiency factor the corrected yield is G(5 i) = 1.15. Based on energy-transfer measurements Beck and Thomas estimated G(5 i) = 1 for cyclohexane [145]. Relatively small G(5 i) values were determined in energy-transfer experiments for some other alkanes as well -hexane 1.4, -heptane 1.1 [140], cyclopentane 0.07 [142] and 0.12 [140], cyclooctane 0.07 [142] and 1.46 [140], methylcyclohexane 0.95, cifi-decalin 0.26 [140], and cis/trans-decalin mixture 0.15 [142]. 

It should be pointed out, however, that the details of the vibronic structure of the Lb band are significantly different in some of the spectra which have appeared in the literature and which have been mentioned above. For example, while Jones et al. [44] and Dick et al. [46] have reported only one relatively strong peak in the range 600-625 nm, Mikami et al. [45] observed two peaks. There are also differences in the relative intensities of the Lb transition and the transition to the gerade state around 450 nm. In [44,45], the spectra were obtained in the same solvent (cyclohexane) and for similar concentrations (0.05 M in one case, 0.1 M in the other), while in [46] the solvent used was ethanol. In all three cases the experiments utilized linearly polarized light and detected the 2P-induced fluorescence. The observed differences are probably ascribable to some other experimental condition or a source of error that was not accounted for. This is another example of the repro-... 

Hydrocarbon Oxidation. The oxidation of hydrocarbons (qv) and hydrocarbon derivatives can be significantly altered by boron compounds. Several large-scale commercial processes, such as the oxidation of cyclohexane to a cydohexanol—cyclohexanone mixture in nylon manufacture, are based on boron compounds (see Cylcohexanol and cyclohexanone Fibers, polyamide). A number of patents have been issued on the use of borate esters and boroxines in hydrocarbon oxidation reactions, but commercial processes apparently use boric acid as the preferred boron source. The literature in this field has been covered through 1967 (47). Since that time the literature consists of foreign patents, but no significant applications have been reported for borate esters. 

The solvatochromic probe molecule chosen for this work was 2-nitroanisole (Aldrich Chemical Co.). The s value reported in the literature for 2-nitroanisole is -2.428 + 0.195 ( 1 ). A known s value for the solute allows one to calculate the change in the supercritical fluid solvents it value as temperature or pressure changes. The reference absorption maxima for 2-nitroanisole is 32.56 x 10J cm"1 (vQ) in cyclohexane (1). 

Unless otherwise indicated, data taken from <1971PMH(3)67>, which contains references to the original literature. A dash indicates that a substituent cannot be in that position a blank means that the value has not been reported. Asterisk ( ) indicates, exceptionally, acidified or basified solvent for details, see references quoted in <1971PMH(3)67>. a<1964JCS446>. bCf.. cln cyclohexane <1966T2119>. d<1964HCA942>. 

Pentacarbonyl(methoxymethylcarbene)chroniiuin(0) is a dull-yellow, crystalline solid mp 34°. It slowly decomposes in the solid state at room temperature in air, but may be stored at 5° for a few days before appreciable decomposition is observed. It is soluble in aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and other common laboratory solvents such as benzene, 1,4-dioxane, tetrahydrofuran, chloroform, dichloromethane, and methanol, and is slightly soluble in ethanol. The infrared spectrum (cyclohexane solution) has v(CO) bands at 2065, 1985, 1965, and 1950 cm-1. The H nmr spectrum in chloroform-d shows the methoxy proton resonance at t6.15 and the methyl proton resonance at t7.70. Other physical properties are reported in the literature.6,7... 

The H-bonded sheets create distorted super-cyclohexane boats (and not chairs ) that are neither zincblende-nor wurtzite-like super-structures. A careful revision of the literature reveals other interesting examples of super-structures formed by alcohols and amines. For example, during their studies dealing with the preparation of a stable form of hydrazine, Toda and co-workers [41] reported the formation of the supramolecular 1 1 amine-alcohol complex 1 3 between hydrazine (1) and hydroquinone (3) (Scheme 3). 

Nanoparticles of PS (M =1.0xl0 -3.0xl0 mol ) microlatexes (10-30 nm) have also been successfully prepared from their respective commercial PS for the first time [75]. The dilute PS solutions (cyclohexane, toluene/methanol or cyclohexane/toluene) were induced to form polymer particles at their respective theta temperatures. The cationic CTAB was used to stabihze th microlatexes. The characteristics of these as-formed PS latex particles were quite similar to those obtained from the microemulsion polymerization of styrene as reported in literature. These microlatexes could also be grown to about 50 nm by seeding the polymerization of styrene with a monodisperse size distribution of D /Djj=1.08. This new physical method for preparing polymer nano-sized latexes from commercial polymers may have some potential applications, and therefore warrants further study. 

There is one report of a concentration dependence of the 313 nm photo-stationary state of azobenzene and 4-methoxyazobenzene in cyclohexane— not in benzene or CCI2F-CCIF2—in the literature.A bimolecular excimer intermediate was postulated. Further work is needed to elucidate whether the absorption coefficients or the quantum yields are concentration-dependent, for instance by ground or excited-state association (cf. Equation 1.3). 

Ti-p and Ox-Ti-P samples exhibited very low activity in the oxidation of alkanes (Table 3). Literature data indicate that as compared to TS-1, Ti-P has very low catalytic conversions in the oxidation of alkanes [10]. For example conversions of about 0.5 and 0.8 % have been reported in the oxidation of n-hexane and cyclohexane at 333 K and H202/alkane = 0.082. In addition, we found that the conversion does not improve when the ratio of hydrogen peroxide to substrate is increased to 0.5. As for Ox-Ti-P samples, they had higher n-hexane conversions, however the selectivity towards oxygenated products was low. Most of the by-products formed over Ox-Ti-P are likely due to the presence of aluminum (Table 1). 

The best result reported in the open literature is of 73% conversion with 73% selectivity to AA, obtained at normal O2 pressure, in acetic acid with 1 mol% Mn (acac)2, the by-products being glutaric acid (9%), succinic acid (6%), cyclohexyl acetate (2%) and cyclohexanol (1%) [30bj. The generation of the PINO from NHPI (Scheme 7.7) with oxygen is assisted by the Co(II) species therefore, the addition of a small amount of Co (O Ac) 2 enhances the oxidation process. In contrast, if the reaction is performed in an acetonitrile solvent, with a Co(OAc)2 catalyst at 75 °C, the main product is cyclohexanone (78% selectivity at 13% cyclohexane conversion). 

We have not found in the open literature experimental data on the heat of mixing for the two binary systems examined in this work. However, the parameters reported in Table 2.9 should, in principle, be valid for all mixtures of alkoxyethanols with inert hydrocarbons. Figure 2.17 compares the calculated heats of mixing with the experimental ones for the system of 2-ethoxyethanol with n-octane at 25°C. A similar picture is obtained for the mixture of 2-ethoxyethanol with cyclohexane. A number of comments regarding the above experimental data and the calculations are in order. 

A standard method used to separate single polyamine components from these fractions involves neutralization of the amines with a mineral acid and subsequent fractional crystallization of the salt adducts. Some purified polyethylene polyamines have been obtained from DETA (8), TETA (9), and TEPA (10), as well as from technical grade 1,2-diamino-cyclohexane, DACH (11), using this procedure. Fractional crystallization of certain polyamine hydrates has also been reported (12). The difficulties associated with these methods—poor yields and low separation selectivi-ties—appear in the literature, however (13, 14). 

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