Methylene chloride design

Miscellaneous Pharmaceutical Processes. Solvent extraction is used for the preparation of many products that ate either isolated from naturally occurring materials or purified during synthesis. Among these are sulfa dmgs, methaqualone [72-44-6] phenobarbital [50-06-6] antihistamines, cortisone [53-06-5] estrogens and other hormones (qv), and reserpine [50-55-5] and alkaloids (qv). Common solvents for these appHcations are chloroform, isoamyl alcohol, diethyl ether, and methylene chloride. Distribution coefficient data for dmg species are important for the design of solvent extraction procedures. These can be determined with a laboratory continuous extraction system (AKUEVE) (244). 

Different MSAs may lead to completely different separation systems designs. The systematic generation procedure given in the separations synthesis algorithm is demonstrated for two potential solvents, hexane and methylene chloride. 

Chemical Designations - Synonyms Methylene Chloride Methylene Dichloride Chemical Formula CH2CI2. 

Table 3 Pre-selected properties for the design of alternatives for Methylene Chloride...

One particular method is designed to characterize Ce to C28+ petroleum hydrocarbons in soil as a series of aliphatic and aromatic carbon range fractions. The extraction methodology differs from other petroleum hydrocarbon methods because it uses n-pentane, not methylene chloride, as the extraction solvent. If methylene chloride is used as the extraction solvent, aliphatic and aromatic compounds cannot be separated. 

The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for methylene chloride is 50ppm (174mg/m ) with an A3-confirmed animal carcinogen with unknown relevance to humans designation. 

The models obtained after extraction of nine sulphonamides in ternary mixtures of methylene chloride, chloroform and methyl tert.-butyl ether from spiked plasma samples have been used to design response surface plots of all the criteria involved. 

Ott. M.G. Skory, L.K.. Holder. B.B.. Bronson, J.M. Williams, P.R. (1983d) Health evaluation of employees occupationally exposed to methylene chloride. General study design and environmental considerations. Scand. J. Work Environ. Health, 9 (Suppl. 1), 1-7... 

The route described by Hoffmann-La Roche scientists in 1995 was designed to make use of the drug substance 5-DFCR (10) to prepare capecitabine in a few steps without multiple protection/deprotection transformations.19 In this process, 5 -deoxy-5-fluorocytodine (10)24 27 was added to three equivalents of -pentyl chloroformate and pyridine in methylene chloride while maintaining an internal temperature below -5 °C, ultimately providing the tris-acylated cytodine adduct 26 in a 92% isolated yield. Removal of the two ester functional groups by selective hydrolysis with aqueous sodium hydroxide in methanol at -10 °C for a short time followed by adjustment to pH5 with concentrated HCI provided the crude carbamate 1 in quantitative yield. Purification of... 

Either steam or air could be used to remove methylene chloride from the wastewater stream. Air will be used in this design. To simplify the problem, assume that the air is saturated with water. If the air is dry, the temperature in the column will vary because water will evaporate into the air, cooling the water. 

To illustrate the procedure for sizing a Karr extractor, we will use a process design described by Drew [69]. The design requires separating a solution of methylene chloride and methanol. The first step in the process is to contract. 

In view of the labile nature of the weak peroxide bond, the cyclization methods must be executed at low temperatures (—30 to + 10°C), but in the case of the thermally more stable derivatives, room temperature (up to -b 30°C) can be tolerated. In the silver ion-catalyzed cyclizations, solvents such as alkanes (pentane, hexane, cyclohexane) and haloalkanes (carbon tetrachloride, methylene chloride, dichlorodifluoromethane) are advantageous. In the base-catalyzed reactions, protic solvents are employed, that is, water and/or methanol and ethanol but heterogeneous solvent systems, for example, aqueous methanol and pentane, are useful. The latter conditions are designed to minimize base-catalyzed destruction of the dioxetane product by extraction into the alkane phase. The preparations of 1,2-dioxetanes via the Kopecky method are collected in Table 1. 

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