Solvent hexane—ether

Samples extracted into strong organic solvents (hexane, ether, pet ether, ethyl acetate, etc.) must be transferred into a solvent miscible with the mobile phase. A small volume (e.g., 1 ml) of the organic extract should be evaporated under N2 gas and dissolved in reagent alcohol. Further dilutions with alcohol may be necessary to obtain 5 to 10 mg/liter concentration before HPLC injection. 

Primary, secondary, and tertiary alkyl halides also can be reduced with dissolving metals. The primary reduction product is an organometallic compound. Whether the latter is formed quantitatively or whether it is converted into the corresponding hydrocarbon by protonation depends on the solvent. The organometallic compound is stable in aprotic solvents (hexane, ether, THF), while it is protonated in protic solvents (HOAc, alcohols). 

The 2,3-dihydro-l,4-thiazepine (1) has been synthesized (Scheme 1) and its photochemistry studied, Irradiation in aprotic solvents (hexane, ether ... 

Lipids differ from the other classes of naturally occurring biomolecules (carbohy drates proteins and nucleic acids) in that they are more soluble m nonpolar to weakly polar solvents (diethyl ether hexane dichloromethane) than they are m water They include a variety of structural types a collection of which is introduced m this chapter... 

In contrast to the hydrolysis of prochiral esters performed in aqueous solutions, the enzymatic acylation of prochiral diols is usually carried out in an inert organic solvent such as hexane, ether, toluene, or ethyl acetate. In order to increase the reaction rate and the degree of conversion, activated esters such as vinyl carboxylates are often used as acylating agents. The vinyl alcohol formed as a result of transesterification tautomerizes to acetaldehyde, making the reaction practically irreversible. The presence of a bulky substituent in the 2-position helps the enzyme to discriminate between enantiotopic faces as a result the enzymatic acylation of prochiral 2-benzoxy-l,3-propanediol (34) proceeds with excellent selectivity (ee > 96%) (49). In the case of the 2-methyl substituted diol (33) the selectivity is only moderate (50). 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

The isolation of product is usually possible after evaporation of the solvent and extraction with hexane, ether, or toluene. Supported versions, for example on polystyrene grafted with PPh2 groups, have proved unsatisfactory because the rate of deactivation is greatly enhanced under these conditions [37]. Asymmetric versions exist, but the ee-values tend to be lower than in the Rh series [38]. With acid to neutralize the basic N lone pair, imine reduction is fast. Should it be necessary to remove the catalyst from solutions in order to isolate a strictly metal-free product, a resin containing a thiol group should prove satisfactory. A thiol group in the substrate deactivates the catalyst, however. 

Dissolve your product in a low boiling point solvent. Maybe ether or hexane or the like. Now dry this whole solution, and gravity filter. Remove the solvent carefully. Hoo-ha Dried product. 

Use a hydrocarbon solvent (hexane, ligroin, petroleum ether—and no flames ) to dissolve the oil that s left. 

The purity of the ligand depends largely on the purity of the dibenzyl ester. Flash chromatography was carried out with silica gel purchased from Merck (Kieseigel 60, Art. 9385). For TLC analysis, Merck silica gel F-254 TLC plates were used, with, 3 1 5 hexane-ether-dichloromethane as eluent. Mono(2,6-dimethoxybenzoyl)tartrate has an Rf of ca. 0.35 in this solvent system. 

Solvent ethyl acetate/hexane. b Solvent diethyl ether/pentane. 

Using h NMR spectroscopy the complex-formation equihbria between halothane (2-bromo-2-chloro-l,l,l-trifluoroethane) and methyl tert-butyl ether or tetrahydrofu-ran in various inert solvents (hexane, heptane, decane, cyclohexane) were measured as a function of temperature (Tkadlecova et al., 1995). 

A 10 gram sample was placed in a 200 ml round bottom flask and 100 ml of distilled water added. A Dean-Stark trap and condenser were used and the mixture was brought to a boil. The steam distilled oil was measured after four hours versus control mixtures. In order to measure surface oil on the spray-dried powders, the powder was first washed with a solvent (ethyl ether or hexane) then oil retentions were run by the steam distillation method illustrated above. Differences in oil volume for solvent washed versus non-washed were attributed to surface oil on the spray-dried powders. 

In old contaminated soil sites, CPs are less accessible to biodegradation than CPs in more recently contaminated sites (Salkinoja-Salonen et al., 1989) inaccessibility correlates with unavailability of CPs to extraction by nonpolar solvents (diethyl ether, hexane). Remediation studies with artificially contaminated soil are likely to give lower residual CP concentrations than obtained in actual remediation. Decreased CP concentrations due to analytical limitations should not be interpreted as biodegradation. 

Extraction is the transfer of a solute from one phase to another. Common reasons to carry out an extraction in analytical chemistry are to isolate or concentrate the desired analyte or to separate it from species that would interfere in the analysis. The most common case is the extraction of an aqueous solution with an organic solvent. Diethyl ether, toluene, and hexane are common solvents that are immiscible with and less dense than water. They form a separate phase that floats on top of the aqueous phase, as shown in Color Plate 25. Chloroform, dichloromethane, and carbon tetrachloride are common solvents that are denser than water. In the two-phase mixture, one phase is predominantly water and the other phase is predominantly organic. 

Amino Alcohol Catalyzed Alkylation. (—)-3-exo-(Dimethylamino)-isobomeol [( —)-DAIB] is a sterically restrained jS-dialkylamino alcohol that has proven to be an extremely efficient catalyst 13). For instance, in the presence of 2 mol % of (—)-DAIB, the reaction of benzaldehyde and diethylzinc proceeds smoothly to give, after aqueous workup, (5)-1 -phenyl-1 -propanol in 98% ee and in 97% yield along with a small amount of benzyl alcohol (Scheme 9). Nonpolar solvents such as toluene, hexane, ether, or their mixtures produce satisfactory results. The optical yield in toluene is affected by temperature and decreases from 98% at —20°C to less than 95% at 50°C. The catalytic enantioselective reaction has been extended to a range of alkylating agents and aldehyde substrates, which are summarized in Scheme 10 (75). p-Substituted ben-... 

The protonation of [Ru3(CO)10(NO)] shows a dependence on the acid.131 Whilst CF S03H leads to the O-protonated product, CF3C02H gives the species HRu3(CO)10(NO) in which H+ addition has occurred at the metal unit. The two isomeric forms do not interconvert in inert solvents such as hexane, ether and CH2C12, However, addition of a catalytic amount of [CF3C02]- causes the rapid O—H to M—H rearrangement. 

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