A-Hexane

When pure needle-like crystals of -aminobenzoyl chloride are polymerized in a high temperature, nonsolvent process, or alow temperature, slurry process, polymer is obtained which maintains the needle-like appearance of monomer. PBA of inherent viscosity, 4.1 dL/g, has been obtained in a hexane slurry with pyridine as the acid acceptor. Therefore PBA of fiber-forming molecular weight can be prepared in the soHd state. 

Butenhoff et al. diseovered the near-infrared (NIR)-indueed tautomerism of H2P embedded in a hexane Shpol skii matrix [90SA(A)519] and gave a detailed deseription of its vibrational photoehemistry (90JPC7847). 

Figure 12.14 IR spectra of (a) hexane, (b) Vhexene, and (c) 1-hexyne. Spectra like these are easily obtained on milligram amounts of material in a few minutes using commercially available instruments.

Note that the longest chain in 2-ethyl-4-methylpentanal is a hexane, but this chain does not include the -CHO group and thus is not considered the parent. 

These ideas might be used to explain the interesting results obtained recently by Williams et al.53 These workers observed formation of crystalline polystyrene when the reaction was initiated by triphenyl methyl potassium (or some other potassium metallo-organic compounds) in a hexane solution, but an amorphous polymer was formed in benzene. They point out that the catalyst is soluble in benzene but insoluble in hexane, and suggest that the heterogeneity of the catalyst is responsible for the results. Although this might be the case, an alternative explanation could be advanced.42 1... 

The precursors dissolved in a hexane/ethyl acetate mixture (90 10, v/v) are adsorbed on a silica gel column that has been packed with hexane. The precursors were eluted with hexane/ethyl acetate mixtures, 80 20, 70 30, and 60 40 (v/v), in that order. 

Benzhydryl trichloromethanesulfenate rearranged to the corresponding sulfoxide after 10 min of reflux of a hexane solution, while the benzyl ester remained practically unchanged even after heating for 24 h at 120°C in benzene. Isomerization of optically active ( — )-a-phenylethyl trichloromethanesulfenate, [a]D20 = — 20.5° on heating in... 

A hexane solution of n-butyllithium was purchased from the Aldrich Chemical Company Inc. and was titrated prior to use. 

Analysis of methyl parathion in sediments, soils, foods, and plant and animal tissues poses problems with extraction from the sample matrix, cleanup of samples, and selective detection. Sediments and soils have been analyzed primarily by GC/ECD or GC/FPD. Food, plant, and animal tissues have been analyzed primarily by GC/thermionic detector or GC/FPD, the recommended methods of the Association of Official Analytical Chemists (AOAC). Various extraction and cleanup methods (AOAC 1984 Belisle and Swineford 1988 Capriel et al. 1986 Kadoum 1968) and separation and detection techniques (Alak and Vo-Dinh 1987 Betowski and Jones 1988 Clark et al. 1985 Gillespie and Walters 1986 Koen and Huber 1970 Stan 1989 Stan and Mrowetz 1983 Udaya and Nanda 1981) have been used in an attempt to simplify sample preparation and improve sensitivity, reliability, and selectivity. A detection limit in the low-ppb range and recoveries of 100% were achieved in soil and plant and animal tissue by Kadoum (1968). GC/ECD analysis following extraction, cleanup, and partitioning with a hexane-acetonitrile system was used. 

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. 

We investigated lipase-catalyzed acylation of 1-phenylethanol in the presence of various additives, in particular an E. additive using diisopropyl ether as solvent. Enhanced enantioselectivity was obtained when a BEG-hased novel IE, i.e., imidazolium polyoxyethylene(lO) cetyl sulfate, was added at 3-10 mol% vs. substrate in the Burkholderia cepacia lipase (hpase PS-C) catalyzed transesterification using vinyl acetate in diisopropyl ether or a hexane solvent system. ... 

Residues are extracted with acetone. The extract is rotary evaporated to remove acetone, the concentrated residue is diluted with 5% aqueous sodium chloride, and residues are partitioned into dichloromethane. The extract is then concentrated and purified on a silica gel column. Residues of pyriproxyfen are quantitated by gas chromatography with nitrogen-phosphorus detection (GC/NPD). For citrus, a hexane-acetonitrile solvent partition step is required for oil removal prior to the dichloromethane partition step. 

For enolates with additional functional groups, chelation may influence stereoselectivity. Chelation-controlled alkylation has been examined in the context of the synthesis of a polyol lactone (-)-discodermolide. The lithium enolate 4 reacts with the allylic iodide 5 in a hexane THF solvent mixture to give a 6 1 ratio favoring the desired stereoisomer. Use of the sodium enolate gives the opposite stereoselectivity, presumably because of the loss of chelation.61 The solvent seems to be quite important in promoting chelation control. 

Procedure. A hexane solution of Compound 118 is diluted or concentrated so as to bring the 118 content within a range of 15 to 150 micrograms per ml. In cases where the hexane solution requires concentration, the evaporation is carried out in a beaker on a steam bath with a gentle stream of air passing over the surface. The concentrated or diluted solution of 118 is washed with hexane into a volumetric flask and made up to volume with the hexane washings. One milliliter of the adjusted Compound 118 solution is precisely measured into a spectrophotometer cell, 2 drops of phenyl azide are added, and the dihydrotriazole is quantitatively formed and then treated with diazotized dinitroaniline to produce the red color as in the preparation of the standard curve. A blank, starting with 1.0 ml. of hexane and 2 drops of azide, is run at the same time. 

Irradiation of a hexane solution of the polymer 1 with a 15-W low-pressure mercury lamp under a nitrogen atmosphere, produced the insoluble crosslinked polymer whose IR spectrum shows a weak absorption at 2150 cm- attributed to the stretching vibration of an Si-H bond. 

A 500-ml. three-necked flask is fitted with a reflux condenser and a thermometer, the bulb of which reaches far enough into the flask to be covered by the liquid. A solution of 46.0 g. (0.205 mole) of a-phenylcinnamic acid (p. 70) (Note 1) in 280 ml. (307 g., 2.38 moles) of quinoline (Note 2) is added to the flask along with 4.0 g. of copper chromite.2 The reaction flask is heated by means of a mantle or an oil bath until the temperature of the reaction mixture reaches 210-220°. The mixture is kept within this temperature range for 1.25 hours. The solution is then cooled immediately and added to 960 ml. of 10% hydrochloric acid in order to dissolve the quinoline (Note 3). The product is extracted from this mixture with two 200-ml. portions of ether followed by a 100-ml. portion. The combined ether extracts are filtered to remove particles of catalyst, washed with 200 ml. of 10% sodium carbonate, and dried over anhydrous sodium sulfate. The dry solution is removed from the drying agent by filtration and heated on a steam bath to distil the ether. The residue is dissolved in a hexane fraction, b.p. 60-72° (Skellysolve B) the solution is cooled to 0° and filtered to remove /raws-stilbene, if any. The hydrocarbon solvent is removed by distillation, and the czs-stilbene is distilled. The yield is 23-24 g. (62-65%), b.p. 133-136°/10 nun., 95-97°/l mm. tig 1.6183-1.6193, 1.6212-... 

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