Cyclohexane water removal

Prepare one 100-mL volumetric flask and five 25-mL volumetric flasks. These flasks should be clean and dry. They may be prepared by washing with soapy water and a brush, rinsing with water, removing the water with several rinses with acetone, and removing the acetone with several rinses with the alkane solvent to be used (e.g., hexane, heptane, or cyclohexane). 

The composite materials have been used to form selective membranes for the separation of liquid mixtures [181]. The membranes should consist of a polymer which is soluble in the liquid components) to be separated, as the dispersed phase-derived polymer, and a continuous phase-derived polymer which is insoluble in all components of the liquid mixture. Thus, membranes consisting of polystyrene in polyacrylamide will separate toluene from cyclohexane, and those comprising polyacrylamide in crosslinked polystyrene can be used for water removal from ethanol. Due to the very thin films of polymer which separate the polyhedral dispersed phase cells, the permeation rates, which are measured by pervaporation, are relatively high. 

A solution of ethyl cyanoacetate (20 mmol), /i-dodecane (0.3 g) and the carbonyl compound (20 mmol) in cyclohexane or toluene (25 cm ) containing AMP-silica (0.5 g, ca. 2 mol% amino groups) was heated to reflux and the water removed using a Dean and Stark trap. The reaction was monitored by GC and the product isolated by filtration of the catalyst followed by normal workup. 

Cleavage of cinnamyl esters. Cinnamyl esters can be cleaved by mercuration in CH3OH catalyzed with nitric acid after neutralization and removal of solvent, demercuration is effected with excess potassium thiocyanate in cyclohexane-water overall yields are about 907o. ... 

The photoresist-patterned Si substrates were placed in a sample holder inside an appropriate reaction vessel (approx. 500 mL, home-built) and 2 g HMDS was added to the bottom of the glass vessel. The reaction took 30 min at room temperature. After silanization the substrates were immersed in a remover solution (5 min, Microposit 1165), washed with methylene chloride/acetone (1 1 v/v), then wiped with ethanol-soaked tissue (KimWipe), rinsed with water, and sonified in cyclohexane (sonification repeated three times, replacing the cyclohexane). Water contact angle 84775765° (advancing/static/receding). 

In this section, you will prepare N-cinnamyl-m-nitroaniline (9) by a sequence beginning with the condensation of cinnamaldehyde (5) with nx-nitroaniline (6), followed by reduction of the intermediate imine 7 with sodium borohydride, as shown in Equations 17.12-17.14. The formation of the imine is reversible, but the reaction is driven to completion by azeotropic distillation. Because cyclohexane and water form a minimum-boiling azeotrope (Sec. 4.4), the water generated by the condensation of 5 and 6 is continuously removed by distilling the cyclohexane-water azeotrope throughout the course of the reaction. 

Another example is the use of cyclohexane to separate isopropyl alcohol (IPA)and water inwhichcrudelPAispumpedtothe first tower or dryer and cyclohexane and water leaves the top of the tower, is condensed, and separates into two layers. Cyclohexane in the top layer is sent as reflux to the tower and the lower wateraqueous IPA layer pumped to another tower for part water removal. The amount of cyclohexane in the system is regulated by the level in the reflux drum. 

A solution of 2,3-dimethylindole (145 g, 1 mol) in dry dioxan containing hydroquinone (100 mg) was treated with JV,JV,JV-trimethylbenzylammonium ethoxide (5 ml of a 40% solution in MeOH) and warmed to 35 C. Freshly distilled acrylonitrile (150 ml, 2.5 mol) was added at a rate such that the temperature did not rise above 40°C. The solution was then stirred overnight and diluted with 10% aq. acetic acid (11). The solution was extracted with CH Clj and the extract was washed with water and dried (MgS04). extract was then mixed with silica gel (800 g) and the solvent removed in vacuo. The silica was placed in a Soxhlet extractor and extracted with cyclohexane. The extract deposited the product as colourless needles (125 g, 63% yield). 

The reaction rate is increased by using an entraining agent such as hexane, benzene, toluene, or cyclohexane, depending on the reactant alcohol, to remove the water formed. The concentration of water in the reaction medium can be measured, either by means of the Kad-Eischer reagent, or automatically by specific conductance and used as a control of the rate. The specific electrical conductance of acetic acid containing small amounts of water is given in Table 6. 

Medium Boiling Esters. Esterificatioa of ethyl and propyl alcohols, ethylene glycol, and glycerol with various acids, eg, chloro- or bromoacetic, or pymvic, by the use of a third component such as bensene, toluene, hexane, cyclohexane, or carbon tetrachloride to remove the water produced is quite common. Bensene has been used as a co-solvent ia the preparatioa of methyl pymvate from pymvic acid (101). The preparatioa of ethyl lactate is described as an example of the general procedure (102). A mixture of 1 mol 80% lactic acid and 2.3 mol 95% ethyl alcohol is added to a volume of benzene equal to half that of the alcohol (ca 43 mL), and the resulting mixture is refluxed for several hours. When distilled, the overhead condensate separates iato layers. The lower layer is extracted to recover the benzene and alcohol, and the water is discarded. The upper layer is returned to the column for reflux. After all the water is removed from the reaction mixture, the excess of alcohol and benzene is removed by distillation, and the ester is fractionated to isolate the pure ester. 

Impurities can sometimes be removed by conversion to derivatives under conditions where the major component does not react or reacts much more slowly. For example, normal (straight-chain) paraffins can be freed from unsaturated and branched-chain components by taking advantage of the greater reactivity of the latter with chlorosulfonic acid or bromine. Similarly, the preferential nitration of aromatic hydrocarbons can be used to remove e.g. benzene or toluene from cyclohexane by shaking for several hours with a mixture of concentrated nitric acid (25%), sulfuric acid (58%), and water (17%). 

Cyclohexane-l,2-diaminetetraacetic acid (H2O CDTA) []329]-6]-7] M 364.4, pK 1.34, pK2 3.20, PK3 5.75 (6.12), PK4 9.26 (12.35). Dissolved in aq NaOH as its disodium salt, then pptd by adding HCl. The free acid was filtered off and boiled with distd water to remove traces of HCI [Bond and Jones Trans Faraday Soc 55 1310 7959]. Recrystd from water and dried under vacuum. 

Tri-n-octylphosphine oxide [78-50-2] M 386.7, m 59.5-60°, pK jt <0. Mason, McCarty and Peppard [J Inorg Nuclear Chem 24 967 7962] stirred an O.IM solution in benzene with an equal volume of 6M HCl at 40° in a sealed flask for 48h, then washed the benzene solution successively with water (twice), 5% aq Na2C03 (three times) and water (six times). The benzene and water were then evaporated under reduced pressure at room temperature. Zingaro and White [J Inorg Nucl Chem 12 315 7960] treated a pet ether solution with aqueous KMn04 (to oxidise any phosphinous acids to phosphinic acids), then with sodium oxalate, H2SO4 and HCl (to remove any manganese compounds). The pet ether solution was slurried with activated alumina (to remove phosphinic acids) and recrystd from pet ether or cyclohexane at -20°. It can also be crystd from EtOH. 

To 10 g of cyclohexane-1,4-oxide is added 40 ml of 12 N hydrochloric acid solution. The solution is mixed thoroughly and allowed to stand at room temperature for 8 days. Water (50 ml) is added to the mixture, the phases are separated, the aqueous phase is extracted with 25 ml of ether, and the ether extract is combined with the organic phase. The ether solution is washed with bicarbonate solution and water and dried over anhydrous sodium sulfate. Ether and unreacted oxide are removed on a rotary evaporator, and the product is recrystallized from petroleum ether, mp 82-83 (yield, 8 g). 

A co-solvent that is poorly miscible with ionic liquids but highly miscible with the products can be added in the separation step (after the reaction) to facilitate the product separation. The Pd-mediated FFeck coupling of aryl halides or benzoic anhydride with alkenes, for example, can be performed in [BMIM][PFg], the products being extracted with cyclohexane. In this case, water can also be used as an extraction solvent, to remove the salt by-products formed in the reaction [18]. From a practical point of view, the addition of a co-solvent can result in cross-contamination, and it has to be separated from the products in a supplementary step (distillation). More interestingly, unreacted organic reactants themselves (if they have nonpolar character) can be recycled to the separation step and can be used as the extractant co-solvent. 

To a stirred solution of 1 g (3.48 mmol) of (3R,4R)-4-acetoxy-3-[(R)-l-(( Tt-butyldimethylsilyloxy)ethyl]-2-azetidinone in 20 mL of CH2C12 are added 1.46 g (5.17 mmol) of tetrakis(2-propeny])tin and 49.5 mg (0.348 mmol) of BF3 0(C2H5)2 under a nitrogen atmosphere. After stirring for 15 h at 20 °C, CH2C12 is added and the mixture is washed three times with water and then dried over MgS04. The solvent is removed in vacuo and the residue is purified by flash chromatography (cyclohexane/ethyl acetate 2 1) yield 800 mg (85%) nip 70-77 °C. 

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