Organic cycle

Thus, while water is an indispensable ingredient for the organic cycle (Equations (2) and (3)), a high concentration of water causes the major loss of one of the feedstocks. Water is also made in situ from methanol and acetic acid together with methyl acetate. In addition to water, HI is the cause of by-product formation ... 

The reaction scheme follows that of the Monsanto process except for the "organic" cycle, in which acetic acid replaces water, and methyl acetate replaces methanol (Figure 6.5) ... 

Spectroscopic Studies of the Organic Cycles of Carbonylation Reactions... 

Spectroscopic Studies of the Organic Cycles of Carbonylation Reactions 219 MeOAc + H2O AcOH + MeOH (3)... 

When the salt [BU4NHAUX2] (X = Cl, Br) was reacted with 2 equiv of the dppm-substituted iron silyl metallate K[Fe Si(OMe)3 (CO)3(dppm)], instead of the expected [Fe—Au—Fe]- silyl derivative anion chain, the complex [AuFe Si(OMe)3 (CO)3(/r-dppm)]2 CH2Cl2 (30) was obtained with a Au—Au and two Au—Fe bonds. It is interesting to point out that complex 30 forms a 10-membered-ring structure in which the Au—Au interaction is reminiscent of the transannular interactions that occur in organic cycles of middle size (8-12). The similar reaction with HgCl2 yielded the expected Fe—Hg—Fe complex (31)96. 

Besides their biochemistry and toxicology, the environmental chemistry of OCs has been extensively studied (44, 43). The photochemistry of the cyclodienes, for example, offers a feast for the chemist (44), though perhaps a headache for the residue analyst and toxicologist. The breakdown of terminal residues to simple molecules capable of entering the natural organic cycles depends ultimately on microbial activity and anaerobic dechlorination seems an essential preliminary for OC destruction. 

Figure 4.3 BASF process The catalytic cycle for the conversion of CH3I plus CO to CH3COI. The organic cycle is not shown and is the same as in Figs. 4.1 and 4.2.

Figure 4.9 Carbonylation of methyl acetate to acetic anhydride. The right-hand-side cycle is the same as in 4.1 and 4.2. The big cycle on the left is similar to the organic cycle of 4.2, where acetic acid and methyl acetate substitute for water and methanol. The small inner cycle on the left is the dominant product-forming pathway.

Pohlman, J. W., Diffe, T. M., and Cifuentes, L. A. (1997). A stable isotope study of organic cycling and the ecology of an anchiahne cave ecosystem. Marine Ecology-Progress Series 155, 17—27. 

The build-up of the original, photosynthetically-generated oxygenated atmosphere resulted from an evolutionary lag between the event of photosynthesis and that of the oxidative respiration that followed. Its maintenance, however, throughout the latter eons was essential to keep the organic cycle operative. Because the residence time of O2 in the present atmosphere is relatively short in the geological sense (6000 y Holland,... 

The traditional parameter for monitoring CO2 flux through the organic cycle in open community studies is oxygen (Sargent and Austin, 1954 Odum and Odum, 1955 Kohn and Helfrich, 1957 Gordon and Kelly, 1962 Kinsey, 1972). 

An alternative method is to determine changes in total CO2 content of the sea water by monitoring pH, chlorinity, temperature and alkalinity (Park, 1969 Smith and Key, 1975 Smith and Kinsey, 1978) and to derive values for the flux of CO2 through the organic cycle, by subtracting from the total flux that component attributable to the inorganic carbonate flux as determined by alkalinity measurements. These estimates are relatively free from errors caused by diffusion, as CO2 exchange with the atmosphere is much slower than that of O2. However, the absolute precision of the measurement... 

Even fewer investigations have been made on the quantitative fluxes of carbonates in coral reefs than have been made on the turnover of carbon through the organic cycles. Most of the data on carbonate fluxes are summarized in Smith and Kinsey (1976) and are repeated in modified form in Tables 2.5.6 and 2.5.7. These data are quoted only as net cedcification, because independent estimates of production and dissolution are not possible. 

The much faster land-based organic cycle is sustained by application of this rock phosphate to soils as fertiliser, as well as contributions from natural weathering. 

When using low water concentrations, the reduction of Rh(iii) back to Rh(i) is slower, but so is the formation of [Rhl4(CO)2] due to the lower HI content available for reactions (3) and (4). The promotional effect of Li salts is attributed to the coordination of either acetate or iodide to 58 forming a highly nucleophilic intermediate dianion, [Rh(GO)2l2X] (X = I or OAc) and also to the kinetic and thermodynamic parameters of this new organic cycle, in which water has been replaced by LiOAc. ... 

Figure 4.3 Iridium-catalyzed carbonylation of methanol. Hydrolysis of 4.14 and 4.15 is not shown and the organic cycle is on the left.

Compounds with Small Organic Cycles Incorporated into the Macrocyclic Backbone... 

The subjects of this part are compounds with small organic cycles which are incorporated into the P-based macrocyclic backbone and determine the structure and specific properties of the macrocycles to an essential extent. 

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