For peroxide formation

A powerful explosion which occurred dining distillation of a 10-year-old sample of the alcohol was attributed to presence of peroxy compounds formed by autoxidation, possibly involving 2-butanone as an effective photochemical sensitiser [1], After a later explosion, it was found that the sample being distilled contained 12% of peroxide [2], A further incident involved a 12-year old sample which exploded at the end of distillation, and which also contained a high level of peroxide. Several other stock alcohols were found to contain much lower levels of peroxide than the 2-butanol, and recommendations on clean-up or disposal, depending on the level of peroxide, are made [3], A further report of an explosion at the end of laboratory distillation confirms the potential for peroxide formation on prolonged storage of 2-butanol [4],... 

The dialkyl denomination also includes cyclic peroxides (endoperoxides). The most significant route for peroxide formation is probably that of autoxidation of organic materials, leading to their gradual degradation. Although hydroperoxides are the main products of this process, also peroxyesters are formed, as is the case, for example, of isoprostane bicyclic endoperoxides (25) mentioned in Section II.A.2.C. 

The commercial grade of this solvent is obtainable in greater than 99.5 per cent purity, in which water and peroxides are the major impurities an inhibitor for peroxide formation may have been added by the manufacturers. Peroxide, if present, must be removed by passage through a column of alumina (see 1. Light petroleum for footnote on the disposal of used alumina), or by shaking with iron(n) sulphate solution as described under diethyl ether before drying and further purification is attempted. If the latter method is employed the solvent should then be dried initially over calcium sulphate or solid potassium... 

The mobile phases used in normal-phase chromatography are based on nonpolar hydrocarbons, such as hexane, heptane, or octane, to which is added a small amount of a more polar solvent, such as 2-propanol.5 Solvent selectivity is controlled by the nature of the added solvent. Additives with large dipole moments, such as methylene chloride and 1,2-dichlor-oethane, interact preferentially with solutes that have large dipole moments, such as nitro- compounds, nitriles, amines, and sulfoxides. Good proton donors such as chloroform, m-cresol, and water interact preferentially with basic solutes such as amines and sulfoxides, whereas good proton acceptors such as alcohols, ethers, and amines tend to interact best with hydroxylated molecules such as acids and phenols. A variety of solvents used as mobile phases in normal-phase chromatography are listed in Table 2.2, some of which may need to be stabilized by addition of an antioxidant, such as 3-5% ethanol, because of the propensity for peroxide formation. 

Many common laboratory chemicals can form peroxides in the presence of atmospheric oxygen. A single opening of a container to remove contents can introduce enough air for peroxide formation to occur. Some compounds form peroxides that are violently explosive in a concentrated solution or as solids. Accordingly, peroxide-containing liquids should never be evaporated to dryness. Peroxide formation also can occur in many polymerizable unsaturated compounds, and these... 

Flammable liquid. A very dangerous fire hazard when exposed to heat, flame, or oxidizers. Moderately explosive when exposed to heat or flame. Reacts with air to form dangerous peroxides. The presence of 2-butanone increases the reaction rate for peroxide formation. Hydrogen peroxide sharply reduces the autoignition temperature. Violent explosive reaction when heated with aluminum isopropoxide + crotonaldehyde + heat. Forms explosive mixtures with trinitromethane, hydrogen... 

Occurs primarily in etheric solvents slower in ketones, amides, and secondary alcohols. Solvents with a tendency for peroxide formation should be monitored routinely.6... 

Detection of peroxides by sodium iodide Sodium iodide (0.1 g) is dissolved in glacial acetic acid (1 ml), and this reagent is mixed with the solvent (10 ml) to be tested for peroxide. Formation of iodine indicates the presence of peroxide. 

Because of its extreme flammability and tendency for peroxide formation, diethyl ether should be available for laboratory use only in metal containers. Carbon disulfide is almost as hazardous. 

Spectral similarities between P-450 and chloroperoxidase originally led to suggestions that both enzymes had thiolate ligation [20, 22, 42]. However, the two systems displayed clear differences in their catalytic activities. Furthermore, at the time when EXAFS studies of chloroperoxidase were initiated, it was not clear whether the enzyme had a free (non-disulfide linked) cysteine available to coordinate to the heme iron [100]. Also, the unusually low pH optimum of the chloroperoxidase halogenation reaction, pH 3.0 for peroxidative formation of a carbon-halogen bond [42], raised questions concerning possible protonation of the axial heme ligand(s). 

The most important fact that needs to be conveyed about ether compounds has been raised numerous times already they form peroxides, which, at a high enough concentration, can detonate. A typical reaction scheme for peroxide formation is shown below for ethyl ether [799] ... 

Fats and oils have double bonds (—CH=CH—CH2—CH=CH—) that are separated by two single bonds. The mechanism for their oxidation by O2 is shown next. Notice the similarity of this mechanism to that shown for peroxide formation in Section 13.6. 

In this mechanism. Reaction (12.1) is the chemical reaction to form the adduct, which has a reaction rate constant of 1.0 x 10 cms, as determined by the RDE measurements in this work. Reaction (12.11) is the ORR RDS on the Ti407 electrode surface, whose rate constants are given in Table 12.1. Reaction (12.III) represents the reactions for peroxide formation. After HO2 formation, HO2 can react in one of two ways further 2-electron reduction to OH through Reaction (12.1V), or chemical desorption through Reaction (12.V) to form a free peroxide ion, which then enters into the bulk solution and can be detected by the ring electrode of the RRDE. The ORR on the Ti407 electrode has a mixed 2- and 4-electron transfer pathway and gives an overall electron transfer number of <4. The relative portion of Reaction (12.IV) can be expressed as x, and the portion of Reaction (12.V) can be expressed as (1-x). When x= 1, the mechanism will follow a totally 4-electron transfer pathway, and when x = 0, the mechanism will be a totally 2-electron pathway. If the x value is >0 and < 1, the ORR will have a mixed 2- and 4-electron transfer pathway. Note that this ORR mechanism is only hypothetical, to facilitate further discussion. More evidence is needed to validate the mechanism. 

Following reactor shutdown, peroxide formation and decomposition will result from the delayed neutrons and from the /3 and 7 radiation of the fission products. The yield for peroxide formation will be essentially that for 7-rays, G = 0.46. The yield for radiation-induced decomposition [37] may be as high as 4.5, but will depend in a complicated way on the amount of oxygen, hydrogen, and other solutes such as fission products, corrosion products, etc., present. 

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