Hexane Subject

No formation of bimetallic complexes is observed on MoO(OPr )4 dissolution in the alcohol solutions of zirconium isopropoxide, due presumably to the high stability of the structure of the latter. A very unusual complex of Zr3Mo,024(OPri)12( PrOH)4 composition precipitates slowly from solutions of isopropoxides in hexane subjected in advance to evacuation to dryness and redissolution repeated three times. The structure of the complex obtained is very close to that of the zirconium methoxide hydrolysis product, Zr O OMe) (Fig. 5.1 c) [901]. The formation of a complex very rich in oxoligands is presumably due to the trend of ZrCOPhV PrOH to form oxocomplexes on desolvation (see Section 12.12). 

Cytochalasin B (from dehydrated mould matter) [14930-96-2] M 479.6. Purified by MeOH extraction, reverse phase Cl8 silica gel batch extraction, selective elution with 1 1 v/v hexane/tetrahydrofuran, crystn, subjected to TLC and recrystallised [Lipski et al. Aruil Biochem 161 332 1987]. 

As the alkaloid was extracted with hexane, acetone, and ethanol, subjected to column chromatography, acidified (AcOH) and then neutralized (NaOH), the cationic form was formulated as a hydroxide salt. However, only two OH groups were detectable on H NMR spectroscopy. Only slight differences were found in the UV spectra taken in methanol [kmax (loge) = 218 (4.68), 302 (4.39), 394 (4.08) nm] and methanol+NaOH [T-max (loge) = 228 (4.66), 310 (4.39) nm]. Three tautomeric forms can be formulated which are shown in Scheme 42. Two of them possess the isoquinolium-7-olate moiety. The H NMR data are presented in Table IV. They indeed unambiguously resemble the cationic species 112. 

Chiral salen chromium and cobalt complexes have been shown by Jacobsen et al. to catalyze an enantioselective cycloaddition reaction of carbonyl compounds with dienes [22]. The cycloaddition reaction of different aldehydes 1 containing aromatic, aliphatic, and conjugated substituents with Danishefsky s diene 2a catalyzed by the chiral salen-chromium(III) complexes 14a,b proceeds in up to 98% yield and with moderate to high ee (Scheme 4.14). It was found that the presence of oven-dried powdered 4 A molecular sieves led to increased yield and enantioselectivity. The lowest ee (62% ee, catalyst 14b) was obtained for hexanal and the highest (93% ee, catalyst 14a) was obtained for cyclohexyl aldehyde. The mechanism of the cycloaddition reaction was investigated in terms of a traditional cycloaddition, or formation of the cycloaddition product via a Mukaiyama aldol-reaction path. In the presence of the chiral salen-chromium(III) catalyst system NMR spectroscopy of the crude reaction mixture of the reaction of benzaldehyde with Danishefsky s diene revealed the exclusive presence of the cycloaddition-pathway product. The Mukaiyama aldol condensation product was prepared independently and subjected to the conditions of the chiral salen-chromium(III)-catalyzed reactions. No detectable cycloaddition product could be observed. These results point towards a [2-i-4]-cydoaddition mechanism. 

Residues containing high levels of heavy metals are not suitable for catalytic cracking units. These feedstocks may be subjected to a demetallization process to reduce their metal contents. For example, the metal content of vacuum residues could be substantially reduced by using a selective organic solvent such as pentane or hexane, which separates the residue into an oil (with a low metal and asphaltene content) and asphalt (with high metal content). Demetallized oils could be processed by direct hydrocatalysis. 

The extinction coefficients of carotenoids have been listed completely bnt solvent effects can shift the absorption patterns. If a colorant molecnle is transferred into a more polar environment, then the absorption will be snbjected to a bathochro-mic (red) shift. If the colorant molecnle is transferred into a more apolar enviromnent, the absorption will be subjected to a hypsochromic (blue) shift. If a carotenoid molecule is transferred from a hexane or ethanol solution into a chloroform solution, the bathochromic shift will be 10 to 20 nm. 

Further members of this class of alkaloids are the araguspongines K (10) and L (11), isolated from the marine sponge Xestospongia exigua collected at Bayadha, on the Saudi Arabian Red Sea coast [16]. After evaporation of the EtOH extract, it was partitioned between hexanes and MeCN. The polar fraction was subjected to a series of chromatographic separations by column chromatography on silica gel. The structures of both alkaloids 10 and... 

A homogenized sample of cereals, vegetables, fruits or potatoes (10-20 g) is extracted with an organic solvent such as acetone and methanol. After filtration, the extract is concentrated to about 20 mL by rotary evaporation below 40 °C. The residue is transferred with 5% sodium chloride (NaCl) aqueous solution and partitioned twice with n-hexane. The n-hexane extracts are dried with anhydrous sodium sulfate and subjected to a Florisil column chromatographic cleanup procedure. The eluate from the Horisil column is concentrated to dryness and the residue is dissolved in an appropriate amount of acetone for analysis by GC/NPD. ... 

The eluate from the Cig cartridge is concentrated by rotary evaporation and the residue is dissolved in n-hexane and then subjected to a cleanup procedure using a Florisil cartridge. The eluate is dried and analyzed by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). 

Plant materials are homogenized with methanol. Hexythiazox residue is extracted with hexane and then transferred to acetonitirile by liquid-liquid partitioning. The acetonitirile is removed by rotary evaporation and the sample is cleaned up using Florisil PR column chromatography. The concentrated eluate is subjected to high-performance liquid chromatography (HPLC) analysis. 

Isoxathion is extracted from plant materials with aqueous acetone. The extracts are concentrated and partitioned with n-hexane after addition of sodium chloride. The n-hexane phase is collected and concentrated after dehydration. The extract is partitioned with n-hexane and acetonitrile. The acetonitrile phase is collected, concentrated, and subjected to Horisil column chromatography. Isoxathion is eluted with diethyl ether-n-hexane after washing the column with the solvent. Isoxathion in the eluate is concentrated and dissolved in acetone and injected into a gas chromatograph for quantitative determination. 

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