Iodine in hexane

J. Zimmerman and R. M. Noyes, The primary quantum yield of dissociation of iodine in hexane solution. J. Chem. Phys. 18(5), 658-666 (1950). 

Frozen solutions of molecular iodine can give information about the solvent-solute interaction [81]. The spectra of iodine in hexane, CCI4, and solid argon are very similar and differ from solid iodine in showing no asymmetry parameter. It therefore seems likely that the species observed is a free iodine molecule. These values were used to derive the currently accepted calibration of the 1 chemical isomer shift. The spectrum in benzene is considerably different because of charge transfer from the benzene to the iodine. 

One isomerization reaction whose kinetics were studied occurs when allyl iodide-is treated with iodine in hexane solution in the dark, viz-... 

Figure A3.6.13. Density dependence of die photolytic cage effect of iodine in compressed liquid n-pentane (circles), n-hexane (triangles), and n-heptane (squares) [38], The solid curves represent calculations using the diffusion model [37], the dotted and dashed curves are from static caging models using Camahan-Starling packing fractions and calculated radial distribution fiinctions, respectively [38],...

Fractions may be monitored by thin-layer chromatography on silica gel, developing with 10% v/v ethyl acetate in hexane and visualizing with iodine vapor. The following Rf values were observed famesol, 0.07 farnesyl acetate, 0.35 bromohydrin acetate, 0.20. 

Because Me3SiI (TIS) 17 is relatively expensive and very sensitive to light, air, and humidity, it is usually prepared in situ from TCS 14 and Nal in acetonitrile [1-6], although other solvents such as CH2CI2, DMF, benzene, or hexane have also been used [5, 6] (Scheme 12.1). It is assumed that TIS 17 forms, in situ, with MeCN, a (T-complex 1733 [2, 3-6], yet Me3SiI 17 can also be prepared by treatment of hex-amethyldisilane 857 with iodine in organic solvents [4-6]. The chemistry of TIS 17 has been reviewed [4—6]. 

Elimination Procedures. Chemical redox-induced elimination was performed on precursor thin films by exposure to bromine or iodine vapor or by immersion of films in hexane solutions of these halides. 

The iodine-catalyzed photoisomerization of all-trans- a- and (3-carotenes in hexane solutions produced by illumination with 20 W fluorescence light (2000 lux) and monitored by HPLC with diode-array detection yielded a different isomer distribution (Chen et al. 1994). Four cis isomers of [3-carotene (9-cis, 13-cis, 15-cis, and 13,15-cli-r/.v) and three cis isomers of a-carotene (9-cis, 13-cis, and 15-ri.v) were separated and detected. The kinetic data fit into a reversible first-order model. The major isomers formed during the photosensitized reaction of each carotenoid were 13,15-di-d.v- 3-carotene and 13-ds-a-carotene (Chen et al. 1994). 

Iodine dissolved in water gives the water a brown color. Iodine dissolved in hexane gives the hexane a pink color. Hexane and water are immiscible. How can these facts be used to demonstrate a liquid-liquid extraction ... 

Olivetol. 3,5-Dimethoxybenzyl alcohol. (This can be made by reducing 3,5-dimethoxybenzoic acid, or it can be purchased.) (10 g) in 100 ml of methylene chloride is cooled to 0° and 15 g of PBrs is added. Warm to room temp and stir for 1 hour, then add a little ice water followed by more methylene chloride. Add petroleum ether to precipitate the benzyl bromide, which is separated off. 9.3 g of the benzyl bromide is put in a flask with 800 ml of dry ether and then add 15 g of copper iodine at 0°. Add butyl lithium (16% in hexane) and stir for four hours at 0°. Add saturated NH4CI and extract with ether. The ether is removed by evaporating in vacuo to give the olivetol dimethyl ether which must be demethylated by one of the methods given in the above formulas. Yield A little over 4 g. Taken from HCA, 52, 1132. 

Develop the plate in hexane-diethyl ether-acetic acid (80 20 1) by plac mg the TLC plate in a chamber containing the solvent system, making sun. the edge with the applied samples is down. The solvent level in the cham ber must not be above the application spots on the plate. (Why ) Leave the chromatogram in the chromatography jar until the solvent front rises to about 1 cm from the top of the plate (45 to 60 min). Remove the plate and make a small scratch at the solvent level. Allow the chromatogram to dry (Hood ) and then place it in an iodine chamber for several minutes. Remove the plate and lightly trace, with a pencil or other sharp object, around each red-brown spot. This should be done promptly, as the colors will fade with time. Calculate the mobility of each standard and unknown lipid relative to the solvent front (R() ... 

Next step of this synthesis consisted in the conversion of alcohol (17) to pisiferic acid (1) and this has been described in Fig. (3). The alcohol (17) in hexane was treated with Pb(OAc)4 in presence of iodine at room temperature to obtain the epoxy triene (19) (51%) whose structure was confirmed by spectroscopy. Treatment of (19) with acetyl p-toluene-sulfonic in dichloromethane yielded an olefinic acetate (20) and this was hydrogenated to obtain (21). The compound (22) could be isolated from (21) on subjection to reduction, oxidation and esterification respectively. The conversion of (22) to (23) was accomplished in three steps (reduction with sodium borohydride, immediate dehydration in dichloromethane and catalytic hydrogenation). Demethylation of (23) with anhydrous aluminium bromide and ethanethiol at room temperature produced pisiferic acid (1). Similar treatment of (23) with aluminium chloride and ethanethiol in dichloromethane yielded methylpisiferate (3). 

The salt is insoluble in water and in solvents such as hexane or toluene and may, therefore, be separated from dicobalt octacarbonyl which is readily soluble in hydrocarbon solvents. Thus, two analyses and the requisite simple calculations permit the estimation of both [Co(CO)4]2 and Co(CO)4-. A convenient apparatus for the determination has been described (Orchin and Wender, 41). Alternately, the concentration of dicobalt octacarbonyl may be measured by adding pyridine to the solution containing the carbonyls. All the dimer is converted to the anion with the evolution of carbon monoxide according to Equation (2). After gas evolution has ceased, a solution of iodine in pyridine may be added. This reagent is similar to aqueous iodine and liberates all the carbon monoxide in the anion originally present as well as that formed from the dimer by reaction with pyridine. 

Indicate whether dilute solutions of iodine in the following liquids will be violet, red, brown, or colorless (a) hexane, (b) benzene, (c) trimethylamine, (CH3)3N, (d) acetic acid, (e) ethyl alcohol, (f) liquid ammonia, (g) liquid hydrogen fluoride. 

Polymer. The polymer used in laboratory ozonation studies was from a masterbatch of a copolymer of small amounts (2-4% ) of piperyl-ene and isobutylene. The polymer was dissolved in hexane, shaken with silica gel to remove any impurities, and precipitated with acetone. The precipitated polymer was washed several times with methanol and then dried in a vacuum oven at 50°C./— 10 mm. Hg for 2 days. The resulting material was colorless and had an iodine number of 20.7. 

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