Reactions with ethylene temperature effects

Unsubstituted 20-ketones undergo exchange dioxolanation nearly with the same ease as saturated 3-ketones although preferential ketalization at C-3 can be achieved under these conditions. " 20,20-Cycloethylenedioxy derivatives are readily prepared by acid-catalyzed reaction with ethylene glycol. The presence of a 12-ketone inhibits formation of 20-ketals. Selective removal of 20-ketals in the presence of a 3-ketal is effected with boron trifluoride at room temperature. Hemithioketals and thioketals " are obtained by conventional procedures. However, the 20-thioketal does not form under mild conditions (dilution technique). ... 

Interaction of chlorine with methane is explosive at ambient temperature over yellow mercury oxide [1], and mixtures containing above 20 vol% of chlorine are explosive [2], Mixtures of acetylene and chlorine may explode on initiation by sunlight, other UV source, or high temperatures, sometimes very violently [3], Mixtures with ethylene explode on initiation by sunlight, etc., or over mercury, mercury oxide or silver oxide at ambient temperature, or over lead oxide at 100°C [1,4], Interaction with ethane over activated carbon at 350°C has caused explosions, but added carbon dioxide reduces the risk [5], Accidental introduction of gasoline into a cylinder of liquid chlorine caused a slow exothermic reaction which accelerated to detonation. This effect was verified [6], Injection of liquid chlorine into a naphtha-sodium hydroxide mixture (to generate hypochlorite in situ) caused a violent explosion. Several other incidents involving violent reactions of saturated hydrocarbons with chlorine were noted [7],... 

These catalysts require temperatures above 100° and usually 150-200° for reasonable rates. Alkylsodium compounds at their decomposition temperatures (50-90°) have also been used by Pines and Haag (9). Lithium reacted with ethylene diamine has also been reported by Reggel et al. (4) as a catalyst for this reaction. The homogeneous system thus formed seems to lower the temperature requirement to 100° (4), whereas the use of potassium amide in liquid ammonia requires 120° (S). Sodium reacted with ethylene diamine has been reported to be an ineffective catalyst (4)- The most active catalyst systems reported so far are high-surface alkali metals and activated-alumina supports. They are very effective at or near room temperature (10-12). 

It is necessary, however, to maximize the intermediate olefin product at the expense of the aromatic/paraffin product which makes up the gasoline ( ). The olefin yield increases with increasing temperature and decreasing pressure and contact time. Judicious selection of process conditions result in high olefin selectivity and complete methanol conversion. The detailed effect of temperature, pressure, space velocity and catalyst silica/alumina ratio on conversion and selectivity has been reported earlier ( ). The distribution of products from a typical MTO experiment is compared to MTG in Figure 4. Propylene is the most abundant species produced at MTO conditions and greatly exceeds its equilibrium value as seen in the table below for 482 C. It is apparently the product of autocatalytic reaction (7) between ethylene and methanol (8). 

Tphe excellent catalytic activity of lanthanum exchanged faujasite zeo-A lites in reactions involving carbonium ions has been reported previously (1—10). Studies deal with isomerization (o-xylene (1), 1-methy 1-2-ethylbenzene (2)), alkylation (ethylene-benzene (3) propylene-benzene (4), propylene-toluene (5)), and cracking reactions (n-butane (5), n-hexane, n-heptane, ethylbenzene (6), cumene (7, 8, 10)). The catalytic activity of LaY zeolites is equivalent to that of HY zeolites (5 7). The stability of activity for LaY was studied after thermal treatment up to 750° C. However, discrepancies arise in the determination of the optimal temperatures of pretreatment. For the same kind of reaction (alkylation), the activity increases (4), remains constant (5), or decreases (3) with increasing temperatures. These results may be attributed to experimental conditions (5) and to differences in the nature of the active sites involved. Other factors, such as the introduction of cations (11) and rehydration treatments (6), may influence the catalytic activity. Water vapor effects are easily... 

Two years later Thompson and Hinshelwood (40) after studying the kinetics of the oxidation of ethylene in silica vessels at temperatures between 400° and 500° and finding that the rate is affected by the total pressure approximately in a reaction of the third order, the effects depending very much more on the partial pressure of the ethvlenes than on that of oxygen, suggested as a via media that while there is no doubt that Bone s interpretation of the course of the oxidation as a process of successive hydroxylations is essentially correct... the first stage in the reaction is the formation of an unstable peroxide if this reacts with more oxygen the chain ends but if it reacts with ethylene, unstable hydroxylated molecules are formed which continues the chain. It should be noted, however, that they adduced no experimental proof of the actual initial formation of the assumed peroxide. 

A detailed study of the effect of temperature on the reaction kinetics of etr with a set of acceptors over a broad time interval of 10 5-l s in the region of ultralow temperatures (4.2-100 K) was performed in ref. 79. For the acceptors CrO, Fe(CN)jF, and N02, the decay curves for electrons et stabilized in deep traps of a water-alkaline (8M NaOH) matrix were found to vary only slightly with variation of temperature. The same result was obtained for the reactions of these acceptors with e stabilized in deep traps of vitrified mixtures of water with ethylene glycol [105]. Thus, at temperatures of 4-100 K, the main contribution of the reaction of et with the above acceptors in both matrices is made by a temperature-independent channel of electron tunneling. 

Another method for the arylation of ethylene involves its reaction with arenediazonium salts (equation 177). [Pd(DBA)2] (105) was used as catalyst for the reaction.627 These reactions can be carried out at room temperature, unlike the reactions of aryl bromides above. At ethylene pressures of 0.6-0.8 MPa, styrene derivatives were obtained in good yields. [Pd(PPh3)4] (103) and [Pd(DBA)2] (105) plus diphos were also used as catalysts, but were less effective than complex (105) alone. The mechanism proposed is similar to that for arylation with aryl bromides and is given in Scheme 66.628... 

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