Yields base effect

In 1968 a new methanol carbonylation process using rhodium promoted with iodide as catalyst was introduced by a modest letter (35). This catalyst possessed remarkable activity and selectivity for conversion to acetic acid. Nearly quantitative yields based on methanol were obtained at atmospheric pressure and a plant was built and operated in 1970 at Texas City, Tex. The effect on the world market has been exceptional (36). 

Table 6 shows the effect of varying coil oudet pressure and steam-to-oil ratio for a typical naphtha feed on the product distribution. Although in these tables, the severity is defined as maximum, in a reaUstic sense they are not maximum. It is theoretically possible that one can further increase the severity and thus increase the ethylene yield. Based on experience, however, increasing the severity above these practical values produces significantly more fuel oil and methane with a severe reduction in propylene yield. The mn length of the heater is also significantly reduced. Therefore, this is an arbitrary maximum, and if economic conditions justify, one can operate the commercial coils above the so-called maximum severity. However, after a certain severity level, the ethylene yield drops further, and it is not advisable to operate near or beyond this point because of extremely severe coking. 

Mesitylene (Coil. Vol. i, 334) Preparation in 43 per cent yield, based on the acetone used, by heating acetone with 5 vol. per cent of concentrated hydrochloric acid at 145 and an initial pressure of 100 atmospheres for twenty-four hours. Ipatiew, Dolgow, and Wolnow, Ber. 63, 3072 (1930). The synthesis can he effected at lower pressures than that first recommended. Sucharda and Kuczyiiski, Roczniki Chem. 14, 1182 (1934) [C. A. 29, 6224 (2935)). 

Peroxide ring closures were effected by stirring the 2,3-dibromocycloalkyl hydroperoxides with silver trifluoroacetate, and the bromo-substituted bicyclic peroxides were isolated by silica chromatography at —25 °C. Yields (based on 2-cycloalkenyl hydroperoxide) of 56 and 38% were achieved respectively for the [3.2.1]- and [4.2.11-compounds, but only 16% of the [2.2.1]- and 13% of the [5.2.1]-peroxide was obtained. The main reason for the low yield of the [2.2.1]-peroxide was that substitution by trifluoroacetate, which competes with the desired dioxabicyclization, is particularly prevalent with the 5-membered ring. 

The R-squared value, which indicates how well the three chosen parameters account for the variability in the yield, was 84.2%. The analysis of variance indicates that only temperature and pressure (both P-value = 0.026) have significant impact at 90% confidence level. The P-value of 0.37 for [NaOH] indicates that, within the parameter space examined, the concentration of NaOH does not significantly affect the cyclohexanone yield. Based on the above equation, one can predict the cyclohexanone yield at any given condition within the parameter space chosen. Since [NaOH] does not have a significant effect on the yield, one can fix its value and plot the yield of cyclohexanone as a function of temperature and pressure (Figure 1). 

Seebach and Brenner have found that titanium enolates of acyl-oxazolidinones are added to aliphatic and aromatic nitroalkenes in high diastereoselectivity and in good yield. The effect of bases on diastereoselectivity is shown in Eq. 4.59. Hydrogenation of the nitro products yields y-lactams, which can be transformed into y-amino acids. The configuration of the products is assigned by comparison with literature data or X-ray crystal-structure analysis. 

H202 in TS-1. On the basis of the observed solvent and acid/base effects on the kinetics and yield in alkene epoxidation in various alcohols, an end-on (7) group with a simultaneously coordinated alcohol group was envisioned as the reactive intermediate. 

The total synthesis of carbazomycin D (263) was completed using the quinone imine cyclization route as described for the total synthesis of carbazomycin A (261) (see Scheme 5.86). Electrophilic substitution of the arylamine 780a by reaction with the complex salt 779 provided the iron complex 800. Using different grades of manganese dioxide, the oxidative cyclization of complex 800 was achieved in a two-step sequence to afford the tricarbonyliron complexes 801 (38%) and 802 (4%). By a subsequent proton-catalyzed isomerization, the 8-methoxy isomer 802 could be quantitatively transformed to the 6-methoxy isomer 801 due to the regio-directing effect of the 2-methoxy substituent of the intermediate cyclohexadienyl cation. Demetalation of complex 801 with trimethylamine N-oxide, followed by O-methylation of the intermediate 3-hydroxycarbazole derivative, provided carbazomycin D (263) (five steps and 23% overall yield based on 779) (611) (Scheme 5.91). 

Overall sampling quality — quantitative analysis. For dynamical trajectories, the "structural decorrelation time" analysis [10] can estimate the slowest timescale affecting significant configuration-space populations and hence yield the effective sample size. For non-dynamical simulations, a variance analysis based on multiple runs is called for [1]. Analyzing the variance in populations of approximate physical states appears to be promising as a benchmark metric. 

The concept of reactivity scales is based on ranking organics in terms of their potential for ozone production. A number of different parameters have been used to rank organics by their reactivity, including observed rates of reaction, product yields, and effects observed from irradiated VOC-NO. mixtures. For example, the rates of 03 or N02 formation or the hydrocarbon loss have been used to develop reactivity scales, as have the yields or dosages of products such as 03 and PAN in... 

The diazotization stage plays the most important part in yielding fluoroarenes effectively. It is greatly influenced by the composition of the hydrogen fluoride solution and is enhanced by employing appropriate amounts of base such as pyridine under carefully controlled conditions. The fluorodediazoniation stage was effectively accelerated photochemically to afford fluoroarenes with polar substituents (hydroxy, nitro, etc.).329... 

As is normally the case with esterification reactions, an equilibrium situation exists in this particular series, and Reaction 2, with respect to its degree of completion is dependent upon the concentration of the olefin in the reaction medium. We studied the effect of the olefin excess in the reaction on yield of ester and found that at levels less than 50%, the yields based on the acid-ester components were considerably less. With olefin excesses larger than 50%, the rate of the primary reaction, that is formation of the diester, was decreased. We therefore determined that an olefin excess of about 50% favored the primary reaction (number 2) as opposed to the secondary reaction in which the olefin can undergo polymerization in the acid media. 

The result of our effort to develop the best possible detector for MES is as follows. Our detector has a resolution of approximately 2 KeV (fwhm) at 15 KeV as shown in Figure 6. There is virtually no deterioration in performance over a period of several months. The overall efficiency of the detector when used for MES with 14-KeV y-radiation is such that a 0.001-inch thick sample of stainless steel type 302 (natural isotopic abundance) gives a spectrum with the peak height some 400% of the base line, Figure 7. (For comparison, when we started we were quite content with 50%.) With our 10-mc Co-57 source, the data acquisition rate in the peak is approximately 500 counts/min. This means that in a matter of a minute or less one obtains a recognizable spectrum. As a bonus, the observance of 6-KeV x-rays yields an effect of approximately 50% of the baseline. To accomplish this, we interpose a plastic filter between the source and the sample to absorb most of the 6-KeV radiation from the source (which does not contribute to the effect but is elastically... 

Deoxygenation of esters. Esters can be reduced to hydrocarbons by (QH5)3SiH in the presence of a radical generator, di-f-butyl peroxide, at 140°. Highest yields are obtained with acetates yields based on the alcohol decrease in the order secondary > primary > tertiary. Other silanes are much less effective than triphenylsilane, which is required in excess for high yields. Radical initiators such as AIBN or benzoyl peroxide are not useful.1... 

Chromium activation allows a strategy for aryl ether synthesis in four stages (i) electrophilic chlorination (ii) chromium coordination (iii) alkoxide substitution for chloride and (iv) oxidative decomplexa-tion.33 The process is effective for the synthesis of 6-methoxytetrahydroquinolines and 5-methoxydihydroindole derivatives, for example. Chlorination of iV-acetyltetrahydroquinoline with SO2CI2 followed by deacetylation provides 6-chlorotetrahydroisoquinoline in 77% yield (equation 11).33 Complexation with [Cr(CO)6] in diglyme-cyclohexane at 125 °C for 53 h using the Strohmeier apparatus gave the chromium complex (13) in 85% yield, based on 40% recovery of starting material. The unre-... 

Silver acetate has a small catalytic effect on the alkene substitution reaction but 5 equiv. of the salt only give 140% of stilbene in the styrene phenylation, based upon palladium.15 The same reaction carried out at 80 C under 300 lbf in-2 (1 lbf in-2 = 6.89 kPa) of oxygen gives stilbene in 248% yield, based upon palladium.16 The best reoxidation reagent is f-butyl perbenzoate, which yields 10-14 turnovers of the palladium in the vinyl substitution of cinnamaldehyde and similar alkenes with benzene.17... 

The reaction was carried out in dioxane, HMPA, and sulfolane as well as in mixtures of dioxane-DMSO (5 1 by volume) and water-DMSO (1 2) at 100-140°C with alkali metal (Li, Na, K, Rb, Cs) hydroxides, tetrabu-tylammonium hydroxide, and rubidium chloride examined as catalysts. All tests were run in an autoclave (1 L) at an initial acetylenic pressure of 12 atm. The most significant effect on the yield of 1-ethynylcyclo-hexanol (110) is that of the catalyst and the solvent. According to their diminishing efficiency, the catalysts examined are arranged as follows KOH RbOH > (Bu4)NOH > LiOH RbCl failed to catalyze the reaction and in the presence of CsOH, resinification was observed. The alcohol 110 is formed most readily in aqueous DMSO, dioxane being next in efficiency (with account for the yield based on the oxime consumed). Addition of DMSO to dioxane does not improve the yield of 110, and only trace amounts of this compound were obtained in HMPA and sulfolane. 

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