From peroxides

Diethyl ether will be abbreviated throughout the book to ether. The ether should be reasonably free from peroxides, see Section 11,47,1. 

Free cydohexene from peroxides by treating it with a saturated solution of sodium bisulphite, separate, dry and distil collect the fraction, b.p. 81-83°. Mix 8 -2 g. of cycZohexene with 55 ml. of the reagent, add a solution of 15 mg. of osmium tetroxide in anhydrous butyl alcohol and cool the mixture to 0°. Allow to stand overnight, by which time the initial orange colouration will have disappeared. Remove the solvent and unused cydohexene by distillation at atmospheric pressure and fractionate the residue under reduced pressure. Collect the fraction of b.p. 120-140°/15 mm. this solidifies almost immediately. Recrystallise from ethyl acetate The yield of pure cis-l 2 cydohexanediol, m.p. 96°, is 5 0 g. 

Apparatus See Fig. 7 size of the flask, 2 1 a gas-tight stirrer should be used the top of the condenser was connected uia a plastic tube to 2 tubes filled with lumps of CaCl2- These tubes in turn were connected to 2 cold traps (-80°C) each of which contained 40 ml THF or CH3OCH2CH2OCH3 (free from peroxides). 

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

A simple test for ether peroxides is to add lOmL of the ether to a stoppered cylinder containing ImL of freshly prepared 10% solution of potassium iodide containing a drop of starch indicator. No colour should develop during one minute if free from peroxides. Alternatively, a 1% solution of ferrous ammonium sulfate, O.IM in sulfuric acid and O.OIM in potassium thiocyanate should not increase appreciably in red colour when shaken with two volumes of the ether. 

Allyl acetate [591-87-7] M 100,1, b 103°, d 0.928, 04 1,40488, np 1.4004, Freed from peroxides by standing with crystalline ferrous ammonium sulfate, then washed with 5% NaHC03 followed by saturated CaCl2 soln. Dried with Na2S04 and fractionally distd in an all-glass apparatus. 

Dibutylcarbitol [di(ethyleneglycol)dibutyl ether] [112-73-2] M 218.3, b 125-130 /0.1mm, d 0.883, n 1.424. Freed from peroxides by slow passage through a column of activated alumina. The eluate was shaken with Na2C03 (to remove any remaining acidic impurities), washed with water, and stored with CaCl2 in a dark bottle [Tuck J Chem Soc 3202 1957]. 

Diethylene glycol monoethyl ether [111-90-0] M 134.2, b 201.9", d 0.999, n 1.4273, n 1.4254. Ethylene glycol can be removed by extracting 250g in 750mL of benzene with 5mL portions of water, allowing for phase separation, until successive aqueous portions show the same volume increase. Dried, and freed from peroxides, as described for diethylene glycol mono-n-butyl ether. 

Dried with CaH2, then passed through a column of silica gel to remove oleFinic impurities and fractionally distd. Freed from peroxides and moisture by refluxing with sodium, then distilling from LiAlH4. Alternatively, peroxides can be removed by treatment with aqueous ferrous sulfate and sodium bisulfate, followed by solid KOH, and fractional distn from sodium. 

The original compound, maleimide (2,5-dioxo-A -pyrroline), is synthesized by the cyclo-condensation of ammonia and maleic acid. Similarly, primary amine is added to maleic anhydride, followed by cyclocondensation, to form N-substituted maleimide (Fig. 2). This reaction is applied to the preparation of bis-maleimides (BMl) [1]. At first, BMI was used as a crosslinking agent for natural rubber (NR). An o-dichlorobenzene solution of NR was crosslinked by BMI at I08-150°C in the presence of peroxides. The radicals generated from peroxides react with the double bonds of both BMI and NR [ 1 ]. 

The production of aryl radicals from peroxides normally provides a cleaner method of arylation than the methods based on the decomposition of azo and diazo compounds, and, in the case of benzenoid compounds, better yields of arylated products are obtained. The... 

Figure 6.5 Proposed structure for the vanadium complex prior to the oxygen transfer from peroxide to the allylic olefin.

The composition of I, and possibly its structure, may be deduced by identifying Q. Certain examples from peroxide chemistry will illustrate the scope of the method. The reactions of ferrous(nitriloacetate) and ferrous(ethylenediamine-N,N -diacetate) with hydrogen peroxide are complicated processes.1 A particular scavenger T did indeed divert the reaction at high concentrations of T. The required levels of T were, however, much higher than those that would have been needed to trap the hydroxyl radical, HO. It is thereby ruled out. With this and with spectroscopic evidence, a reactive hypervalent iron complex was suggested as the intermediate. 

Apart from peroxide types and amount of peroxide incorporated in compounds, the efficiency of cross-linking depends on co-agents. The commercially notably ones are... 

Lithium aluminium hydride Higuchi and co-workers100 introduced it as a titrant, usually in tetrahydrofuran (previously liberated from peroxide), for the titration of alcohols and phenols according to the overall reaction... 

Reductive bleaches are generally less costly than oxidative bleaches but tend to give a greenish white compared with the reddish white tones from peroxide. Combining the two in an oxidation/reduction sequence gives a more neutral white, this being known as a full... 

Ethereal extracts of pulp exploded during or after concentration by evaporation. Although the ether used for the extraction previously had been freed from peroxides by treatment with cerium(III) hydroxide, the ethereal extracts had been stored for 3 weeks before concentration was effected. (During this time the ether and/or extracted terpenes would be expected to again form peroxides, but no attempt seems to have been made to test for, or to remove them before distillation was begun). 

Dopamine, a strong water-soluble antioxidant, was identified in banana fruit (Musa cavendishii) by Kanazawa and Sakakibara (2000). Banana fruit contained high levels in the pulp and peel 2.5-10 mg/100 g and 80-560 mg/100 g, respectively. A banana water extract was reported to suppress the autoxidation of linoleic acid by 65-70% after a 5-day incubation in an emulsion system, as determined from peroxide value and thiobarbituric acid reactivity (Kanazawa and Sakakibara 2000). 

In the absence of an initiator, alcohols are oxidized with self-acceleration [7-9]. As in the oxidation of hydrocarbons, the increase in the reaction rate is due to the formation of peroxides initiating the chains. The kinetics of radical formation from peroxides was studied for the oxidation of isopropyl alcohol [58] and cyclohexanol [59,60]. 

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