Ethane reaction with oxygen

The reaction with oxygen has been used to measure the rate of dissociation of the ethane.7... 

Another category of compounds that play the role in diminution of oxidation rate are 3,5-di-t-butyl-4-hydroxy derivatives of ethane and ethene [02J1, 02J2]. Their efficiency in the scavenging of radicals in the competition with the reaction with oxygen occurs with a rate comparable with the rate of good commercial antioxidants like Cyanox 2246 or lonol. 

Using values of AGf from the Data Book, calculate AG for the reaction of (a) methane, CH4, and (b) ethane, C2H6, with oxygen to give CO2 and H2O. Calculate AG, values for the analogous reactions of (c) monosilane, SiH4, and (d) disilane, Si2H6. 

A typical oxidation is conducted at 700°C (113). Methyl radicals generated on the surface are effectively injected into the vapor space before further reaction occurs (114). Under these conditions, methyl radicals are not very reactive with oxygen and tend to dimerize. Ethane and its oxidation product ethylene can be produced in good efficiencies but maximum yield is limited to ca 20%. This limitation is imposed by the susceptibiUty of the intermediates to further oxidation (see Figs. 2 and 3). A conservative estimate of the lower limit of the oxidation rate constant ratio for ethane and ethylene with respect to methane is one, and the ratio for methanol may be at least 20 (115). 

Thioketals are readily formed by acid-catalyzed reaction with ethane-dithiol. Selective thioketal formation is achieved at C-3 in the presence of a 6-ketone by carrying out the boron trifluoride catalyzed reaction in diluted medium. Selective protection of the 3-carbonyl group as a thioketal has been effected in high yield with A" -3,17-diketones, A" -3,20-diketones and A" -3,l 1,17-triones in acetic acid at room temperature in the presence of p-toluenesulfonic acid. In the case of thioketals the double bond remains in the 4,5-position. This result is attributed to the greater nucleophilicity of sulfur as compared to oxygen, which promotes closure of intermediate (66) to the protonated cyclic mercaptal (67) rather than elimination to the 3,5-diene [cf. ketal (70) via intermediates (68) and (69)]." " ... 

Also to be mentioned are the reactions of oxygen atom radical anions with organic substrates. These reactions were reviewed by Gronert (2001). For the reactivity of the atomic oxygen anion-radical, see Section 1.7.2. The atomic oxygen anion-radical reacts with benzene, tetramethylene ethane, or cyclopentadienylidene trimethylenemethane. The reactions consist in abstraction of H2 with the formation of H2O and the corresponding distonic anion-radicals as products. 

Fig. 4. The rates of formaldehyde and COt accumulation as a function of the ethane flow rate in reactions of oxygen atoms with etiiane.

It follows from the data obtained that the primary reaction between oxygen atoms and ethane should be that yielding CH20 and some other particle (but not an aliphatic radical). This particle reacts with the 02 molecule to form CO. 

Thus, CH20 and CO are obtained in equal amounts. Other reactions of a lower probability are the formation of alcohol by reaction 0 + C2H6 - C2H6OH, possibly depending on pressure, and the formation of acetaldehyde 0 + C2H6 - C2H 0 + H2. It will be noted that the formation of alcohol was observed by Murad and Noyes63 in the course of oxygen atom reactions with ethane. 

It may be seen from Table III that in reactions of oxygen atoms with ethylene, formaldehyde and CO are obtained practically in equal amounts, as in the reaction involving ethane. It will be taken into account that the amount of formaldehyde obtained is practically equal to that of oxygen atoms (Table II). This is indication that CH20 is formed by a nonchain mechanism. On the basis of these facts it should be considered that the main reaction between oxygen atoms and ethylene is... 

If hydroxyl were to react by H atom abstraction in the case of ethane, and by addition with ethylene, an inverse dependence would be observed for the activation energy, namely, a decrease from ethane to ethylene, as is the case for hydrogen atom reactions. The activation energies for reactions of oxygen atoms with ethane and ethylene decrease from ethane... 

Methane reacts only slowly with oxygen below 400° C. Ethane oxidation was observed by Bone and Hill (S) at 290° to 323° C. Formaldehyde, a reaction product, was found to increase, reach a maximum, and then decrease. Addition in amounts of 1% to a 3 to 1 ethane-oxygen mixture at 316° C. and 720 mm. eliminated the induction period, but other additives such as nitregen dioxide, acetaldehyde, ethyl alcohol, or water, were also more or less effective. 

A series of halogenated ethanes 1 containing the trifluoromethyl group has been oxidized under various conditions.5-7 When water is present in the reaction mixture, the acid 3 is usually formed during the reaction when water is absent, the acid halide 2 formed can be hydrolyzed in a trap with water. Trifluoroacetaldehyde hydrate 4 is formed6 as a minor product in addition to the acid when 2-chloro-l,l,l-trifluoroethane is treated with oxygen and chlorine under UV irradiation with subsequent reflux of the mixture with hydrogen peroxide. 

A wave in which the reaction runs more slowly turns out to be more powerful and has a greater supply of energy, in accord with the fact that it is harder to generate. These arguments are evidently confirmed by the data of Rivin and Sokolik [35] according to which a mixture of carbon with oxygen (with a small addition of fire-damp) is no less able to cause detonation, if not more able, than the fire-damp and a mixture of ethane with oxygen. 

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