Reaction temperature, and reactions

The ratio of the two diastereomeric products 190 and 191 was found to depend on the reaction temperature and reaction time. The addition of acrolein or methyl vinyl ketone proceeded smoothly, but in the case of methylacrylate or acrylonitrile the reaction did not proceed under the same conditions (EtsN THF 30°C). An accompanying AMI calculation of these Q ,/3-unsaturated compounds [LUMOs for acrolein, -0.13877 for methyl vinyl ketone, -0.06805 (s-trans) for methyl acrylate, -0.01413 (s-tmns) for acrylonitrile, 0.04971] suggested the low reactivity of methyl acrylate and acrylonitrile toward the Michael reaction (99H1321). 

The combination of highly exothermic reactions with a sharp increase in viscosity as conversion proceeds controls reactor design and operational conditions in full-scale operations. The art of sulfonation is to maintain the optimal reaction temperature and reaction time, resulting in products with small amounts of byproducts and good color. 

The rate of reaction was found to be strongly dependent on starting molecular weight, reaction temperature and reaction time and to a lesser extend on the particle size and the waterconcentration in the reactor gas. 

Metal-polysulfido complexes have been synthesized by a variety of methods using various reagents as sulfur sources, e.g., Ss, M2S (M=alkali metal), P2S5, H2S, organic polysulfanes, etc. The nature of the resulting polysulfido complexes often depends on the reaction conditions such as the ratio of starting materials, solvents, reaction temperature, and reaction time. In addition, the use of different ligands leads to the different results in most cases. This section shows typical synthetic methods for metal-polysulfido complexes based on recent reports on their syntheses. 

Depending on the reaction temperature and reaction time, tetrahydroisoquinoline 357 afforded different mixtures of 1,2,3,4,11,11 a-hcxahydro-6//-pyrazino[ 1,2-3]isoquinolines 358-361 and tetracyclic compound 362 (Scheme 30) <2005JA16796>. Each of the individual diastereoisomers 358-361 could be transformed into the compound 362. z7r-3//,4a//-3-Phcnylpcrhydropyra/ino[ 1,2-7]isoquinoline-l,4-dione was prepared via automated parallel solid-phase synthesis on Kaiser oxime resin <1998BML2369>. l,2,3,5,6,7-Hexahydropyrido[l,2,3-r/f ]quinoxaline-2,5-dionc was obtained by catalytic hydrogenation of ethyl 3-(2-oxo-l,2,3,4-tetrahydro-5-quinoxalinyl)acrylate in the presence of TsOH over 5% Pd/C catalyst under 40 psi of hydrogen <1996JME4654>. 

Figures 1-3 demonstrate the effect of KOH/precursor ratio, reaction temperature and reaction time, respectively, on porous structure parameters of carbon produced by KOH activation. While the presented relationships concern mostly carbonaceous mesophase, basically they are typical of all coal and pitch-derived materials of the study.

The sustained decomposition of a substance without introduction of any other apparent ignition source besides thermal energy and without air or other oxidants present. Autodecomposition is the result of a thermal self-decomposition reaction for given initial conditions (temperature, pressure, volume) at which the rate of heat evolution exceeds the rate of heat loss from the reacting system, thus resulting in an increasing reaction temperature and reaction rate. 

The three operating variables—reaction pressure, reaction temperature, and reaction time or space velocity. 

In the batch-type reaction system, however, the pressure cannot be controlled during the treatment. Table 1 shows a maximum pressure for various supercritical alcohols at 300 and 350°C. It can be observed that at the same temperature, they gave different maximum pressure and that the pressure tended to be lower as the alkyl chain of the alcohol became longer. Previously, it was found that the reaction pressure is an important reaction parameter in enhancing the reaction rate (11). Therefore, the flow-type reaction system, which can control the reaction pressure up to 50 MPa, was used to study the effect of the reaction pressure on the formation of alkyl esters. Reaction temperature and reaction time were set at 300°C and 20... 

When optimizing the reaction of trichlorosilane with silica gel, the first important factor to consider is the effectiveness. The pretreatment temperature of the silica, the reaction temperature and reaction time must be controlled to yield an effectiveness of... 

We can confirm the reports of Sullivan et al. that the reaction between dicyclopentadiene and sulfur is exothermic. If the temperature rises above 150 °C, the extreme viscosity increase causes the mixture to become almost solid and the reaction difficult to control. Diehl (5) and Bordoloi and Pearce (6,7) have reported quantitative studies of these viscosity changes. They show that there are large viscosity increases as the amount of dicyclopentadiene added, reaction temperature, and reaction time are increased. Our results show that these increases in viscosity are caused by the formation of high-molecular-weight polysulfides. 

The reaction enthalpies at 298 °K are those calculated from the corrected activation energies. Reaction entropies at mean reaction temperatures and reaction heat capacities (not shown) were estimated from group additivities and should be... 

The material to be mixed or ground is optionally compressed and, depending upon the required reaction temperature and reaction atmosphere, reacted in one of the following furnace types ... 

Calixarenes are cyclic oligomers obtained by condensation reactions between para-t-butyl phenol and formaldehyde. By judicious choice of base, reaction temperature, and reaction time, calixarenes having different ring sizes can be prepared in good yield. Calixarenes are like crowns in that they are preorganized complexants, yet, unlike crowns, they can be readily synthesized in large quantities. Unlike porphyrins, calixarenes are not fully conjugated, and the three-dimensional structure leads to cavities. 

In general, there are two main methods to control the mesostructures (1) change various reactant concentrations, reaction temperature, and reaction-mixture composition ... 

The angular isomer 254 which was obtained previously (Volume VII, pp. 235, 237) was a minor product (5%) of the cyclization of aldehyde 247. Heating dictamnine with PPA at 180° resulted in partial conversion (20%) to the angular 2-quinoline, indicating that to obtain maximum yields of furoquinoline alkaloids in the aldehyde cyclization reaction temperature and reaction time must be carefully controlled. The mechanism of the dictamnine rearrangement may involve initial cleavage of the protonated vinyl ether 253 followed by formation of aldehyde 255 and cyclization to the more stable angular derivative (Scheme 20) (196). 

For semibatch operation, there is little chance of a runaway reaction if the added reactant is always present at low concentrations in the reactor. This is the case when the added reactant is a slightly soluble gas, such as oxygen or hydrogen. The reaction temperature and reaction rate can be controlled by the feed rate of the reactant. However, if the added reactant is a liquid or a very soluble gas, it might accumulate in the reactor, and this could lead to a stability problem if the difference between reactor and jacket temperature becomes large. 

Treatment of Lu(0Ac)3-nH20 with phthalonitrile in the presence of 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU) in 1-hexanol gives the sandwich compound Lu(Pc)2 and the half-sandwich complex Lu(Pc)(0Ac)(H20)2 (De Cian et al. 1985). Both compounds were structurally characterized and the latter was believed to be an intermediate in the formation of the former complex. A solid-state reaction of Lu(OAc)3 and phthalonitrile may also lead to the formation of Lu(Pc)(OAc) and Lu(Pc)2, along with the metal-free phthalocyanine H2(Pc). The ratio of these products depends on the reaction temperature and reaction time (Clarisse andRiou 1987). The 1,2-naphthalocyanine analog Lu(l,2-Nc)(OAc) has recently been prepared in 56% yield by treating Lu(OAc)3 with Li2(l,2-Nc) in 1,2,4-trichlorobenzene (Guyon et al. 1998). 

Optimization of reactor operation policy is of paramount importance if improvement of product quality and increase of business profits are sought. In very specific terms, optimization of the reactor operation conditions is equivalent to producing the maximum amount of polymer product, presenting the best possible set of end-use properties, with minimum cost under safe and environmentally friendly conditions. This optimum solution is almost always a compromise. Increase of polymer productivity is usually obtained with the increase of the operational costs (increase of reactor volumes, reaction temperatures and reaction times, for instance). Besides, the simultaneous improvement of different end-use properties is often not possible (the improvement of mechanical performance is usually obtained through increase of molecular-weight averages, which causes the simultaneous increase of the melt viscosity and decrease of product processibihty). Therefore, the optimization can only be performed in terms of a relative balance among the many objectives that are pursued. 

The autoclave was sealed and maintained at 200 °C for 24 h after which the NiS/CdS heterostructured particles were washed and dried. A detailed study of the effect of reaction time, reaction temperature, and reaction solvent was also carried out. Figure 14 shows the electron microscopy... 

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