Dried material layer solvent transfer

A. l-Phenyl-2,2,2-lrichloroethanol. In a 1-1. round-bottomed-flask fitted with a mechanical stirrer, a thermometer, and a powder funnel is placed a solution of 212 g. (2.00 moles) of freshly distilled benzaldehyde in 400 g. (270 ml., 3.35 moles) of chloroform. The mixture is cooled in an ice bath, and 123 g. of commercial powdered potassium hydroxide is added with stirring at such a rate that the temperature of the solution does not exceed 45° (1-1.5 hours). The reaction mixture is stirred and kept at 40-50° for an additional hour and then poured into a solution of 60 ml. of sulfuric acid in 3 1. of water. The resulting two-phase mixture is transferred to a separatory funnel and extracted with three 250-ml. portions of chloroform (a small amount of insoluble, black resinous material is discarded). The combined organic layers are washed with three 100-ml. portions of aqueous 10% sodium carbonate, dried over anhydrous magnesium sulfate, and filtered into a 1-1. flask. The solvent is removed under reduced pressure on a hot water bath. The residue is transferred to a 250-ml. flask and distilled under reduced pressure to give l-phenyl-2,2,2-trichloroethanol, b.p. 155-165° (26 mm.), 90-100° (0.5 mm.) (Notes 1 and 2). The yield is 170-180 g. (38-40%). 

Evaporation and redissolving. The solvent of the combined upper layer is evaporated under nitrogen flow or low-temperature vacuum distillation. An oily material appears after it is dried. A precisely measured aliquot of mobile phase is normally used to redissolve theextract. These procedures are intended to not only increase the concentration of tocopherols and tocotrienols to the measurable level of the detector, but also to avoid uncertain volume change of organic layer during extraction, which results in inaccurate results. The redissolved sample is transferred to a vial for HPLC analysis. 

After the addition of the reactants is complete, the reaction is allowed to stir for an additional 30 min while the solution warms to room temperature. The reaction mixture is then transferred to a separatory funnel. The viscous organic bottom layer is separated from the aqueous layer and is dissolved in 200 mL of ether. The reaction vessel is washed with 100 mL of ether, and this ether portion is used to extract further the aqueous layer. The ether layers are combined, dried over magnesium sulfate, and filtered, and the solvent is removed under reduced pressure. The viscous oil is allowed to crystallize in an ice bath (0°C). The crystals are collected on a Buchner funnel, washed with 500 mL of water, and dried in a vacuum desiccator at 0.5 mm for 48 hr. 80.8 g (93%) of white crystalline bis(2,2,2-trichloroethyl) hydrazodicarboxylate (mp 85-89°C) is obtained. This material is sufficiently pure for the next preparation. However, further purification can be achieved using an Abderhalden drying apparatus (refluxing 95% EtOH for 12 hr at 0.05 mm MgS04 desiccant). Material purified in this way melted at 96.5-97.5°C (Notes 4 and 5). 

Trilevel Schemes. Trilevel processing (6, 7) requires planarization of device topography with a thick layer of an organic polymer, such as polyimide or a positive photoresist that has been baked at elevated temperatures ( hard baked ) or otherwise treated to render it insoluble in most organic solvents. An intermediate RIE barrier, such as a silicon dioxide, is deposited, and finally, this structure is coated with the desired resist material. A pattern is delineated in the top resist layer and subsequently transferred to the substrate by dry-etching techniques (Figure 3). 

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