Solids removal theory filtration

Surprisingly, we found that the reaction of an alcohol with 1-chloroethyl-N,N-dialkylcarbamates can proceed through B mechanism to give alkylation rather than acylation (Ref. 195). This result appears to be a violation of the HSAB theory. In a typical example, N-(1-chloroethyloxy-carbonyl) piperidine was added to a stirred mixture of sodium hydrocarbonate and methanol at 25°C. The reaction was instantaneous. Solids were removed by filtration, excess alcohol was then distilled off and the resulting product was isolated by flash chromatography in 96% yield [Scheme 139]. 

This was heated on the steam bath for an hour, added to 1 L H20, and acidified with HCI, producing a heavy crystalline mass. This was removed by filtration, air dried, and distilled at up to 170 deg C at 0.2 mm/Hg. There was thus obtained 21.4 g of 4-methoxy-5,6,7,8-tetrahydronaphthol as an off-white solid with a mp of 107-114 deg C. An analytical sample was obtained by recrystallization from 70% EtOH, and melted at 119-120 deg C. Hexane is also an excellent recrystallization solvent. Anal. (Cl 1H1402) C,H. As an alternate method, the oxidation of the naphthaldehyde to the naphthol can be achieved through heating the aldehyde in acetic acid solution containing hydrogen peroxide. The yields using this route are consistently less than 40% of theory. 

Purification is accomplished by crystallization from a solution prepared from the crude product and 100 mL of water at a maximum temperature of 50°. (The time at this temperature should be kept minimal.) Filtration of the nearly saturated solution through coarse fiber-glass paper (Whatman GF/A) removes impurities of low solubility. At 0° the solid product crystallizes slowly 12 hours are required for complete deposition. The orange solid is collected on a filter and dried under atmospheric conditions (not vacuum). Yield 17.0 g, 66% of theory. Water of hydration is lost under low humidity conditions or under vacuum. Anal. Calcd. for Na6V10O2g 18H2O V, 35.89 H20, 22.84. Found V, 35.51 H20, 22.65%. 

The crude 3-(p-nitrobenzenesulfonyl)-3-azabicyclo[3.2.2]nonane (44.0 g, 0.14 mole), 5.0 g alcohol wet Raney nickel, and 400 ml methyl alcohol were charged to an autoclave and reduced at 70°C at 1000 p.s.i. hydrogen pressure until absorption of hydrogen had stopped. The crude reduced product was filtered hot to remove the Raney nickel catalyst. The filtrate was cooled to 20°C and the solid 3-(p-ammobenzenesulfonyl)-3-azabicyclo[3.2.2]nonane was collected by filtration (38.9 g 98% theory), melting point 149°-151°C. 

The reaction mixture is transferred to a 2-L, round-bottomed flask with ethanol washing and the ethanol is removed by rotatory evaporation. Diethyl ether (1 L) is added to precipitate the electrolyte salt, which is collected by filtration and washed with ether. The crude electrolyte is obtained as a white solid (32-32.5 g, theory 34.1 g). The filtrate and washings were combined and evaporated to give a viscous brown oil, which was vacuum distilled through a short Vigreux column (15 x 2.5 cm). After a forerun of 70 mL of material boiling below 150°C (0.15 mm) the product (92-96 g, 53-56%), bp 150-155°C (0.1 mm), is collected (Notes 8 and 9). The forerun contained diethyl maleate, diethyl fumarate, diethyl succinate, and diethyl ethoxy succinate. The product is a mixture of diastereomers on standing some meso isomer, mp 74-75°C, crystallizes. 

The dynamic filtration theory of Outmans (127) requires experimental terms such as particle-particle stresses, particle friction factors, and thickness of a shear zone within the filter cake that would be difficult to determine. However, the qualitative picture of dynamic filtration presented by Outmans, namely, irreversible adhesion of solid particles up to a certain thickness that is determined by the shear stress (or shear rate) at the surface of the cake, accords with the experiments of Fordham and co-workers (129,135). Once a filter cake has formed under dynamic conditions, it is difficult to remove it by subsequent changes in yc or vm. Figure 44 shows the effect of changes in the flow rate on cumulative filtrate volume. The limiting filtration rate obtained when the initial flow rate of the drilling fluid was 1.8 m3/h remained unaltered when the flow rate of the drilling fluid was increased to 7.0 m3/h in a step-... 

To a well-chilled solution of 122.5 gm (4 moles) of methylamine in 500 ml of dry benzene is added a solution of 176 gm (1.94 moles) of freshy distilled acrylyl chloride in 100 ml of benzene over a 2.75-hr period while a reaction temperature below 5°C is maintained. The solid which forms is filtered off. The filtrate is preserved. The solid is dissolved in water. The aqueous solution is extracted with two portions of benzene. The benzene extracts are combined with the filtrate. The benzene, excess amine, and water are removed from the product solution by distillation. The high-boiling residue is then fractionally distilled. The fraction boiling between 92° and 97°C (4-5 mm) is collected and redistilled at 79°C (0.7 mm). The yield is 107 gm (66% of theory), 1.4730. The product may be stored after inhibition with 0.1% of p-methoxyphenol. By-products are believed to be the addition products of hydrogen chloride or of methylamine to the double bond. 

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