Positive peroxide test

If sodium hydroxide is omitted in this preparation and the reaction mixture is refluxed until it no longer gives a positive peroxide test with iodide ion (Note 3) (about 2 hours), the product is the methyl ester of diphenaldehydic acid in 91-98% yield (m.p. 50-51°).2... 

Compound IV gave a positive peroxide test with potassium iodide in methanol and analyzed reasonably well for the structure shown. However, it was difficult to purify and decomposed upon standing, and we believed that mass spectral evidence was necessary for its final structure proof. We experienced some difficulty in obtaining pure dideutero IV but were able to obtain a satisfactory monodeutero compound by exchange of the enolic pattern with methanol-d. Table II compares the mass spectrum of IV with that of the monodeutero derivative. 

Chaturvedula et al. identified other derivatives of nemorosone named ochrocarpinones A-C (85-87) which constitute the first PBDs isolated from genus Ochrocarpus [14]. The structures of ochrocarpinones B-C showed NMR data very similar to those observed in hyperibones A-G. The presence of a 2,2-dimethyl-3-hydroperoxy-2-H-dihydropyran ring in ochrocarpinone A was indicate by a positive peroxide test with FeSCN. Ochrocarpinone A was a derivative of plukenetione G, but, the l3C chemical shifts were most similar to scrobiculatone A (C-7 epimer of plukenetione G) a derivative of nemorosone isolated from floral resins of Clusia sp. Ochrocarpinone C (87) seems to have the same structure of hyperibones A or B, two epimers isolated from H. scabrum, stereochemistry of ochrocarpinones was not reported. 

Antioxidant capacities of common individual curcuminoids were determined in vitro by phosphomolybdenum and linoleic acid peroxidation methods. Antioxidant capacities expressed as ascorbic acid equivalents (pmol/g) were 3099 for curcumin, 2833 for demethoxycurcumin, and 2677 for bisdemethoxycurcumin at concentrations of 50 ppm. The same order of antioxidant activity (curcumin > demethoxycurcumin > bisdemethoxycurcumin) was observed when compared with BHT (buty-lated hydroxyl toluene) in linoleic peroxidation tests. The antioxidant activity of curcumin in the presence of ethyl linoleate was demonstrated and six reaction products were identified and structurally characterized. The mechanism proposed for this activity consisted of an oxidative coupling reaction at the 3 position of the curcumin with the lipid and a subsequent intramolecular Diels-Alder reaction. ... 

A sample of the readily peroxidisable allyl ether, tested with a peroxide test strip gave a negative test result, so was charged into a distillation apparatus, but there was a detonation during distillation. It was recommended that an additional test (potassium iodide-acetic acid) should be used unless it is certain that the test strips will give a positive result with a particular peroxide-containing liquid. 

Tetrahydrofuran freshly distilled from lithium aluminum hydride should be used. A commercial product with a peroxide content giving a positive iodine test must be treated with about 0.3% of cuprous chloride (boiling for 30 minutes and distillation) before the addition of the hydride. 

The very sensitive ether peroxide test strips (Merckoquant, Art. No. 10011), available from E. Merck, Darmstadt, are used. If the test is still positive at this point, an additional 0.2 ml. of N-methyl morpholine is added. Stirring and heating at 75° are continued for another 5 hours. Remaining peroxide renders the work-up and drying of the product potentially hazardous. N-Methylmorpholine N-oxide (1) and hydrogen peroxide form a strong 1 1 complex. In the reaction with osmium tetroxide, this complex produces conditions similar to those of the Milas reaction,7 and some ketol formation may result. 

If the test is still positive, thiosulfate solution should be added until a negative test is attained. The checkers found EM Quant Peroxide Test Strips obtained from EM Science to be more sensitive than conventional Kl-Starch test paper. 

Peroxides in ether solvents. This is one of the commonest causes of explosions in organic chemistry laboratories. Simple dialkyl ethers such as diethyl ether and di-isopropyl ether, and cyclic ethers such as 1,4-dioxane and tetrahydrofuran, form less volatile peroxides on exposure to air and light. If therefore one of these solvents is purified by distillation, the peroxide content in the residue is progressively increased and eventually a violent explosion may occur. In view of this (i) such solvents should not be stored for long periods or in half empty bottles containers should be of dark glass (ii) before the solvents are distilled a peroxide test should be carried out, and, if positive, the peroxide must be removed (Section 4.1.11, p. 402 and Section 4.1.75, p. 404) and (iii) since purified ethers in contact with air rapidly peroxidise again (10 minutes in the case of tetrahydrofuran) they should be retested for peroxides and purified if necessary immediately before use. 

Benzoyl peroxide is used mainly in acne treatment and is an irritant. Allergic contact dermatitis to this compound is not infrequent. Eaglstiein (1968) reported two cases. The sensitization rate has been estimated to be 1 %-2.5%. In a human maximization test, 76% became sensitized (Leyden and Kligman 1977). Crossreactions to benzoic acid and related compounds were not found. The drug has been advocated for treatment of chronic leg ulcers. Eight of 16 patients showed positive patch tests to 2% benzoyl peroxide after 6 weeks of leg ulcer treatment with 10% benzoyl peroxide (Jensen et al. 1980). Patients sensitized to benzoyl peroxide may be at risk in certain occupations (e.g., baking and the plastics industry). 

Aguirre A, Zabala R, Sanz de Galdeano C, Landa N, Diaz-Perez JL (1994) Positive patch tests to hydrogen peroxide in 2 cases. Contact Dermatitis 30 113... 

Benzoyl peroxide has also been used to bleach flour. Fisher (1989) reported two bakers with contact sensitivity to benzoyl peroxide, one of whom had a positive patch test to 1% benzoyl peroxide in petrolatum. 

If a negative peroxide test is obtained, then a gram stain should be performed on the second slide to determine whether the bacteria are gram-positive cocci. Growth in the BHI broth tube is transferred to (a) bile esculin agar (BEA), (b) another fresh tube of... 

Di-n-butyl ether. Technical n-butyl ether does not usually contain appreciable quantities of peroxides, unless it has been stored for a prolonged period. It should, however, be tested for peroxides, and, if the test is positive, the ether should be shaken with an acidified solution of a ferrous salt or with a solution of sodium sulphite (see under Diethyl ether). The ether is dried with anhydrous calcium chloride, and distilled through a fractionating column the portion, b.p. 140-141°, is collected. If a fraction of low boiling point is obtained, the presence of n-butyl... 

Recovery of the wopropyl alcohol. It is not usually economical to recover the isopropyl alcohol because of its lo v cost. However, if the alcohol is to be recovered, great care must be exercised particularly if it has been allowed to stand for several days peroxides are readily formed in the impure acetone - isopropyl alcohol mixtures. Test first for peroxides by adding 0-6 ml. of the isopropyl alcohol to 1 ml. of 10 per cent, potassium iodide solution acidified with 0-6 ml. of dilute (1 5) hydrochloric acid and mixed with a few drops of starch solution if a blue (or blue-black) coloration appears in one minute, the test is positive. One convenient method of removing the peroxides is to reflux each one litre of recovered isopropyl alcohol with 10-15 g. of solid stannous chloride for half an hour. Test for peroxides with a portion of the cooled solution if iodine is liberated, add further 5 g. portions of stannous chloride followed by refluxing for half-hour periods until the test is negative. Then add about 200 g. of quicklime, reflux for 4 hours, and distil (Fig. II, 47, 2) discard the first portion of the distillate until the test for acetone is negative (Crotyl Alcohol, Note 1). Peroxides generally redevelop in tliis purified isopropyl alcohol in several days. 

The checkers used 3-methyl-2-butanone purchased from Eastman Organic Chemicals. One sample that gave a positive test for peroxides was purified by passage through a column of alumina before distillation. The material was distilled routinely before use. 

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