Fisher reaction

Pyridine was used in the beginning of the development of the method. The reaction was slow and the endpoint unstable because of weak basicity of pyridine. The pyridine system buffers at about pH 4. A stronger base, imidazole, has been used to replace pyridine since it gives a faster response and has the advantages of lower toxicity and decreased odor. The optimal pH range for the SO2 imidazole buffer is at pH 6. It is important that the pH of the Karl Fisher reaction be maintained within the range 5 to 7. Outside this recommended pH range, the endpoint may not be reached. 

In contrast to the previous reaction, in this case a single molecule of water reacts with two atoms of iodide. Methylhydrogen sulphite is oxidised to hydrogenosulphate, which is converted in the presence of a base of type RN into an ammonium salt. The Karl Fisher reaction can thus be reformulated as follows ... 

Oh S H, Fisher G B, Carpenter J E and Goodman D W 1986 Comparative kinetic studies of CO-O2 and CO-NO reactions over singie crystai and supported rhodium cataiysts J. Catal. 100 360... 

Fisher J J and McMahon T B 1990 Determination of rate constants for low pressure association reactions by Fourier transform-ion cyclotron resonance Int. J. Mass Spectrom. Ion. Proc 100 707-17... 

The mixture of carbon monoxide and hydrogen is enriched with hydrogen from the water gas catalytic (Bosch) process, ie, water gas shift reaction, and passed over a cobalt—thoria catalyst to form straight-chain, ie, linear, paraffins, olefins, and alcohols in what is known as the Fisher-Tropsch synthesis. 

Reaction of Fisher s base and its quaternary salt with the trisacetal leads to the only synthesized [3.3.3] decamethine dye (33). Higher methinylogous trinuclear dyes have not been obtained. 

HTS catalyst consists mainly of magnetite crystals stabilized using chromium oxide. Phosphoms, arsenic, and sulfur are poisons to the catalyst. Low reformer steam to carbon ratios give rise to conditions favoring the formation of iron carbides which catalyze the synthesis of hydrocarbons by the Fisher-Tropsch reaction. Modified iron and iron-free HTS catalysts have been developed to avoid these problems (49,50) and allow operation at steam to carbon ratios as low as 2.7. Kinetic and equiUbrium data for the water gas shift reaction are available in reference 51. 

G. Fisher and co-workers, "Mechanism of the Nitric Oxide—Carbon Monoxide—Oxygen Reaction Over a Single Crystal Rhodium Catalyst," in M. 

Runaway reaction Interlock manway with vessel pressure with manway, Design system for closed manual operation open—foam out (can be acid based), operator contacted by process materials. CCPS G-22 CCPS G-23 CCPS G-29 Fisher 1990 ISAS84.01... 

Tuma, L. and C. Bagner 1998. Assurance of Safe Pilot Plant Scale-Up of Chemical Processes, in (G. A. Melhem and H. G. Fisher, eds.). International Symposium on Runaway Reactions, Pressure Relief Design, and Effluent Handling, American Institute of Chemical Engineers, New York. 

Leung, J. C., Fauske, H. K and Fisher, H. G., Thermal Runaway Reactions In A Low Thermal Inertia Apparatus, Ther-mochimica Acta, 104, 13-29, 1986. 

Temperature control is important, especially for depolymerization, which is directly proportional to reaction temperature and water content. Figure 12-10 shows the Inventa-Fisher process. ... 

The reaction mixture can also be processed by chromatography. The crude reaction mixture is poured on a 90-cm. x 4.5-cm. column of alumina (e.g, Fisher adsorption grade ) and eluted with about 2 1. of technical-grade pentane. This yields a pale-yellow solution that is free of diethyl phosphorochloridate. Evaporation of the pentane gives 240-255 g. (90-96%) of l,2,3,4,5-pentachloro-5-ethylcyclopentadiene. 

Roberts M. Fisher M Anaphylactoid reaction to iopamiro (after pretreatment). Australas Radiol 1992 36 144-146. 

Hydrotreating was carried out at 3.1 MPa (450 psig) and 613 K (340 °C) in a three-phase upflow fixed-bed reactor (Figure 1). The feed liquid was prepared by combining different quantities of 1.0 wt% tetralin (Aldrich, 99%), 0.02 wt% N as quinoline (Aldrich, 99%), 0.05 wt% S as 4,6-dimethyldibenzothiophene (4,6-DMDBT, Fisher, 95%), 0.3 wt% S as dimethyldisulfide (DMDS, Aldrich, 99%), n-octane (Aldrich, 99%), and balance n-tridecane (Alfa Aesar, 99%). Liquid product compositions were determined with a Hewlett-Packard 5890A chromatograph equipped with a 50 m dimethylsiloxane colunm (Chrompack, CPSil 5B) of 0.32 mm i.d. Reaction products were identified by matching retention times with commercially available standards. 

The iji vitro experiments, using the S-9 fraction from livers of uninduced Fisher 344 rats, was complicated by the fact that it became apparent that formaldehyde production was a poor measure of the extent of metabolism. The reason for that was that the S-9 fraction apparently catalyzed the oxidation of formaldehyde to formate. Consequently, determination of formaldehyde in an S-9 catalyzed reaction consistently gave low values of nitrosamine metabolism. Many workers use semicarbazide to suppress formaldehyde loss. We found, however, that semicarbazide is not a neutral bystander. 

These results indicate that in the in vitro reaction, the a-hydroxylation pathway accounts for about 34% of the metabolism of DMN and about 19% of the metabolism of NMA, when uninduced Fisher 344 rat liver S-9 is used Thus, our data for DMN fall roughly in-between the two previously published... 

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