W-Hexane

Figure 12.18 LC-SFC analysis of mono- and di-laurates of poly (ethylene glycol) ( = 10) in a surfactant sample (a) normal phase HPLC trace (b) chromatogram obtained without prior fractionation (c) chromatogram of fraction 1 (FI) (d) chromatogram of fraction 2 (F2). LC conditions column (20 cm X 0.25 cm i.d.) packed with Shimpak diol mobile phase, w-hexane/methylene chloride/ethanol (75/25/1) flow rate, 4 p.L/min UV detection at 220 nm. SFC conditions fused-silica capillary column (15 m X 0.1 mm i.d.) with OV-17 (0.25 p.m film thickness) Pressure-programmed at a rate of 10 atm/min from 80 atm to 150 atm, and then at arate of 5 atm/min FID detection. Reprinted with permission from Ref. (23).

Fig. 7-14. Separation of terfenadine and MDL 16,455 methyl ester on Chiralpak AD , (a) Terfenadine Chiralpak AD 250-4.6, w-hexane/2-propanol (90 10), flowrate 1.0 ml min, UV-detection 224 nm. (b) MDL 16,455 methyl ester Chiralpak AD 250-4.6, w-hexane/2-propanol (90 10), flowrate 1.0 ml min , UV-detec-tion 224 nm. (Reproduced with permission from A. Terhechte, PhD Thesis, University of Munster, Munster, 1993 [24].)...

Engberts [3e, 9] has extensively investigated the Diels Alder reaction in aqueous medium. Recently Engberts and colleagues reported [9c] a kinetic study of a Diels Alder reaction of N-alkyl maleimides with cyclopentadiene, 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene in different solvents. The reaction rates of the cycloadditions with the open-chain diene relative to w-hexane are reported in Table 6.3. The aqueous medium greatly accelerates the Diels Alder reaction and the acceleration increases as the hydrophobic character of the alkyl group of the dienophile increases. These and other kinetic data [3e, 9], along with the observation that the intramolecular Diels-Alder reaction is also accelerated in... 

A compound is most soluble in that solvent to which it is most closely relaM in structure. Thus w-hexane, which is sparingly soluble in water, dissolves in three volumes of methyl alcohol, is more soluble in anhydrous ethyl ilcohol, and is completely miscible with n-butyl and higher alcohols. As the chain length increases the compound tends to resemble the hydrocarbon more and more, and hence the solubility increases. 

Qian et al. [46] determined miconazole nitrate and benzoic acid in paint by a thin-layer chromatographic densitometric method. The drug was spotted on a GF254 silica gel plate, developed with a 42 21 13 5 w-hexane-chloroform-methanol-... 

Alkaline hydrolysis, in some cases carried out with the help of a microwave system, followed by extraction with organic solvents (normally w-hexane and diethyl ether), allows neutral and acidic compounds to be separated into two fractions, and the chromatographic data to be more easily interpreted. 

SnCl2 reacts with triphenylethenyllithium Li(CPh=CPh2) in Et20-w-hexane-THF to yield an alkenyltin(II) derivative which, subsequently treated with butyl bromide, yields a mixed alkyltin halide362 ... 

Dichloromethane, diethyl ether, petroleum ether, ethyl acetate, w-hexane... 

After 2 hours the reaction was quenched. The reaction mixture was transferred into a 100 mL beaker, w-hexane (10 mL) was added and stirred for 10 minutes. 

The (Z)-ethyl cinnamate was obtained by hydrogenation of ethyl phenyl propiolate using Lindlar s catalyst (5% palladium on calcium carbonate, poisoned with lead) in w-hexane under an atmospheric pressure of hydrogen. The mixture, containing 75% of the (Z)-ethyl cinnamate, 22% of the overreduced alkane and 3 % of the (E )-ethyl cinnamate, was used without further purification. 666 mg of this mixture contains 500 mg of (Z)-ethyl cinnamate (2.55 mmol). 

The reaction mixture was transferred into a separating funnel and was extracted with w-hexane (4 x 40 mL). The combined organic layers were washed with brine, dried over sodium sulfate, filtered and concentrated under reduced pressure to give a colourless oil (200 mg). 

The crude material was purified by flash chromatography on silica gel (60 g), buffered with 1 % of triethylamine, using w-hexane-diethyl ether (95 5) to afford (R,R)-( )-stilbene oxide as a colourless oil (123 mg, 0.62 mmol, 62%). 

The resulting residue was chromatographed (eluent //-hexane-ethyl acetate, 95 5) on silica gel pre-deactivated with triethylamine w-hexane (2 98) to afford the (R, R, pS, PS)-1.1 -bisfa-acetoxypropyl)-2.2 -bis(diphenylphosphi-no)ferrocene as an orange solid (1.26 g, 78.0%). 

Cyclohexane or w-hexane can be used in place of carbon tetrachloride. Technical normal hexane may contain substantial amounts of methylcyclopentane and isohexane that lower the yield through formation of C7-acids that are hard to remove. 

Analytical Methods for Determining w-Hexane in Biological Samples... 

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