THF/water system

The minimum operating temperatures for various solvent mixtures used in the reversed phase HPLC are shown in Table 9.4. Values for acetonitrile were experimentally determined based on the temperature at which the system could no longer pump the mobile phase [56]. These values are approximate and will vary somewhat with pressure. Values are not shown for THF-water systems. While THF freezes at -65°C, work in our laboratory [56] has shown that water-THF mixtnres separate and the water component freezes at the freezing point of water, making these mixtnres nnnsable below 0°C [96]. No data is available for ternary mixtures, though the addition of another solvent may eliminate the separation of THF and water. 

Water in THF is the second most important problem as it makes polymerization impossible. The vapor/liquid equilibrium diagram of the THF/water system at atmospheric pressure is shown in Figure 95. 

Figure 95. The Vapor/Liquid Equilibrium Diagram of the THF/Water System at 1 ATM.

The redox-active natural product (+)-methanophenazine (MP) is the first phenazine to be isolated from archea. This compound is able to mediate the electron transport between membrane-bound enzymes and was characterized as the first phenazine derivative involved in the electron transport of biological systems. The research team of U. Beifuss prepared this natural product by using the Williamson ether synthesis in the last step of the synthetic sequence. The etherification was conducted under phase-transfer conditions in a THF/water system in the presence of methyltrioctyl-ammonium chloride and using potassium hydroxide as a base. 

We will postpone a detailed discussion of the THF-water system until Chapter 6 where quantitative comparison of the steady-state designs and dynamic controllability of heat-integrated and nonheat-integrated systems are presented. 

THF-WATER SYSTEM STEADY-STATE DESIGN WITH HEAT INTEGRATION... 

We begin with the THF-water system. A comparison of systems with no heat integration, with partial heat integration and with complete heat integration will be presented. The phase equilibria for this system and a nonheat-integrated system have been discussed in Chapter 5. 

THF-WATER SYSTEM DYNAMICS AND CONTROL 183 Ratio feed comp 6.5/5.5THF... 

The energy requirement in the low-pressure column is 14.79 MW, so the auxiliary reboiler must provide 14.79-5.86 = 8.93 MW (32GJ/h, as shown in the TCI faceplate in Fig. 6.30). Flowsheet equations similar to those described in the THF-water system are needed in this system. The pressure-compensated temperature measurement uses the temperature (411.5 K) and pressure (10.354 atm) on Stage 53. 

Although the MBH reaction can be accelerated in the presence of water, the product yield appears to be dependant on the water/co-solvent ratio. For instance, the MBH reaction between methyl vinyl ketone 12 and p-nitrobenzaldehyde 30 in the presence of the co-eatalyst system imidazole/proline in DMF/water was optimized when the DMF water ratio was 9 1. However, in a THF/water system, a 19 1 ratio was optimal. 

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