Ethane + methanol

Additional experiments were done in mixtures of alcohol alkane [16,17]. The spectra and kinetics were measured in mixtures of 1-propanol n-hexane. Some experiments were done in cyclohexane, where the behavior was qualitatively similar however, the exact concentration where spectra and kinetics changed depended on the alkane [16]. Additional experiments observed the shift of the final spectrum of the solvated electron in supercritical ethane-methanol mixtures. These experiments were done using standard pulse radiolysis techniques and thus we were unable to observe the kinetics [19]. 

The electron will be solvated in a region where the solvent molecules are appropriately arranged. There must be a cluster of electrons of a size of 4-5 to support the formation of the solvated electron from the results of Gangwer et al., [23], Baxendale [24,25], and Kenney-Wallace and Jonah [16]. This behavior does not depend on the specific alcohol or alkane and even occurs in supercritical solutions, as has been shown in experiments done using mixtures of supercritical ethane-methanol mixtures [19]. Experiments have also shown that the thermodynamically lowest state might not be reached. For example, the experiments of Baxendale that measured the conductivity of the solvated electron in alcohol-alkane mixtures showed that when there was a sufficient concentration of alcohols to form dimers, there was a sharp decrease in the mobility of the electron [24,25]. This result showed that the electron was at least partially solvated. However, the conductivity was not as low as one would expect for the fully solvated electron, and the fully solvated electron was never formed on their time scale (many microseconds), a time scale that was sufficiently long for the electron-alcohol entity to encounter sufficient alcohols to fully solvate the electron. Similarly, the experiments of Weinstein and Firestone, in mixed polar solvents, showed that the electron that was observed depended on the initial mixture and would not relax to form the most fully solvated electron [26]. 

In addition, little amounts of intermediate, oxygen-containing compounds, such as ethanal, methanol and ethanol, were produced, which was not unexpected since alkanes are oxidized under these conditions (vide supra). The maximum quantum yield was about 0.1. Much higher conversions were obtained in the presence of O2. In this case, the Pt deposit seemed to play a minor role, whereas it was more important for deoxygenated solutions. 

Methane, ethane, methanol, benzene, acetate, methylammonium, H2O (SPC/E),H20 (POL3) nonbonded parameters Meng 1996b... 

Figure 8.20 Critical mixture curves for methanol with methane, ethane, ethylene, xenon, and carbon dioxide (Robinson, Peng, and Chung, 1985 Brunner, 1985 Francesconi, Lentz, and Franck, 1981). The P-T traces for the ethane, ethylene, xenon, and carbon dioxide systems are virtually indistinguishable in the region shown in the graph. But near —50°C the ethane-methanol critical mixture curve turns up abruptly. Not shown in this figure are the three phase lines exhibited by the ethylene-methanol and the ethane-methanol systems at conditions close to their respective critical points.

Ethane, 21, 77, 100, 102,109, 115,282 critical temperature, 9 Ethane-butanol system, 37 Ethane-ethanol system, 37 Ethane-hydrocarbon mixtures, 36, 37 Ethane-methanol system, 183 Ethane-octane system, 114, 115 Ethanol, 17,20, 81,82 and water separation, 170 Ethanol-water-carbon dioxide system, 73 Ethanol-water-ethylene system, 73 Ethanol-water-ethane system, 73 Ethylene, 11-13, 20, 22, 51, 68, 81,100, 107, 215, 318... 

Type 2c resembles type 2b but the branch of the critical curve starting from CP II does not end at the critical end point B but runs through an additional pressure minimum. This types was found by Kuenen for ethane + methanol. Being a transition to other types of phase behaviour it will be of great importance in the discussion of Section 3 where other examples will also be given e.g. CH H- methylcyclopentane). - For all systems belonging to types 2b and 2c the branch of the critical curve starting from CP I ends at the critical end point C on the three-phase line LLG. 

Let s compare four other fuels (hydrogen, ethane, methanol, and ethanol) by writing out the complete balanced equations for combustion and doing the simple mathematics using the bond energies in Table 12.1. 

The height of the potential energy barrier, as would be expected, decreases with increasing bond distance (see ethane-methyl silane-disilane in Table 4-3). The potential barrier also decreases in going from trivalent CH3— groups to monovalent OH— groups (see ethane-methanol). 

M. Pecul, T. Helgaker, The spin-spin coupling constants in ethane, methanol and methylamine a comparison of DPT, MCSCF and CCSD resrJts, Int. J. Mol. Sci. 4 (2003) 143. 

The bottom line is that SPT methods are very successful. The ethane/ methanol relative solvation energy is obtained with essentially experimental accuracy. Once the concept is established, much more than just relative solvation energies can be obtained, as indicated in the following Going Deeper highlight. The method is computationally intensive—the study described above would require 21 full MC or MD runs—but the results are often worth it. 

We know AG i by measurement. We want to know AG2, where I2 is a molecule that is proposed, but perhaps not even synthesized yet. It is easy to see that AG, - AG2 = AG3 - AG4. Note that AG3 and AG4 are easily obtained by SPT. AG3 is just the relative solvation energy of the two inhibitors, as in the ethane/ methanol example in the text (the protein, P, does not even figure into the calculation of AG3.) Similarly, AG4 can be readily obtained from SPT by jermuting 1, as it is bound to the protein to I2 in its molecular mechanics calculated geometry for binding to the protein. Thus, from two SPT runs that might be expected to be quite reliable, we can get AG, - AG2 and, because we know AG], we obtain AG2. In principle, this could be done for many compounds, and the information could be used to decide which new inhibitors are worth the effort of synthesis and testing. 

Class B1 systems show closed loop vapour/liquid pressure/composition diagrams in the vapour liquid region at all temperatures between the solvent critical temperature and the critical temperature of the heavy component. The system ethane/methanol shows this behaviour. Carbon dioxide/w-hexadecane is probably also of this type (Figure 1.10 and 1.11). 

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