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Author: Subject: Analysis of Peroxides
BromicAcid
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[*] posted on 29-10-2005 at 20:59
Analysis of Peroxides


Considering the size of the DPPP thread (although this is now somewhat irrelevant to it) and the variety of novel organic peroxides yet to be explored that can be used as energetic materials I thought it would be relevant to post this thread, all the information here is from Organic Peroxides by Stern Volume III by Wiley Interscience, don’t know if it is up on the FTP or anything but I don’t think it is. Anyway, here is some of the information from the text on the analysis of organic peroxides, some of it specifically relating to cyclic peroxides.
Quote:
1)Physical Properties
The melting and/or boiling points of a number of peroxides are listed in the Appendix. Melting above 100C is usually accompanied by decomposition, and melting points may vary with the rate of heating. Equally unreliable are boiling points for most, since distillation without decomposition requires such low pressures that gauge readings are inaccurate.

…….

Spectra
1. Infrared
The infrared spectra of alkyl peroxides are chiefly useful for detecting the presence or absence of impurities, such as the structurally related alcohols, hydroperoxides, aldehydes, or ketones. The presence of a weak to moderately strong absorption in the 820-860 /cm region (C-O-O-) coupled with the absence of O-H or C=O absorption may be confirmatory evidence of dialkyl peroxide structure but does not constitute strong proof. Monitoring the disappearance of this band has been used for kinetic studies, however.
2. Ultraviolet
Like other peroxides, dialkyl peroxides exhibit weak absorption starting at 300-320 nm and gradually increasing at lower wavelengths. Published spectra of ethyl, t-butyl, and cumyl peroxide are typical, the latter showing aromatic absorption imposed on that from O-O.

…….

Determination of Active Oxygen
A mixture of 10 ml concentrated hydrochloric acid and 10 ml of chloroform is boiled for 10 min. The peroxide is then added in a solution of 10 ml chloroform and 10 ml isopropanol. Approximately 1 millimole peroxide is used. Then a solution of 1 g potassium iodide in 2 ml of water is added, and the mixture boiled for 10 min. After heating, 100 ml of water is added, and the cooled solution is titrated with 0.1N thiosulfate solution. A 1-ml volume of titrant solution corresponds to 1/40 millimole of dimeric ketone peroxide or 1/60 millimole of trimeric ketone peroxide. Blanks are required.

The reduction of the peroxide bond by iodine in glacial acetic acid proceeds slowly; dimeric ketone peroxides are reduced faster then the trimeric ones. With sodium iodide in glacial acetic acid at 20C, 50% of dimeric acetone peroxide is reduced in 50 min. Trimeric acetone peroxide and trimeric cyclohexanone peroxide, in contrast, yield hardly any iodine under the same reaction conditions. A similar difference is found in catalytic hydrogenation with palladium black in glacial acetic acid. The following decreasing order of hydrogentation rate points to the importance of steric effects (blocking of the O-O groups) : dimeric dipropyl ketone peroxide > dimeric benzyl methyl ketone peroxide > dimeric methyl propyl ketone peroxide > dimeric methyl t-butyl ketone peroxide > dimeric diethyl ketone peroxide > dimeric dimethyl ketone peroxide > dimeric methyl ethyl ketone peroxide > dimeric bromoacetone peroxide >> Trimeric dimethyl ketone peroxide > Trimeric methyl isobutyl ketone peroxide = Trimeric methyl isopropyl ketone peroxide > Trimeric diethyl ketone peroxide.
Though the spectroscopic methods are not attainable by the home lab, the determination of active oxygen is a relatively simple affair and can help point to the identity of an unknown peroxide.



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[*] posted on 30-10-2005 at 07:02


Where are you going with this? Have you thought about purposefully using ethers to make explosive peroxides? If so tell me about it....
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[*] posted on 30-10-2005 at 10:17


Humm... you missed my point? :o This has nothing to do with methods of synthesis, just that one can determine the active oxygen of a peroxide species relatively easily and this can help differentiate and compare peroxides to one another, I mentioned the DPPP thread because comparing the active oxygen of the theoretical DPPP molecule with TCAP would have given different noteable results without the effort of using instrumental analysis, this thread was just so that people at home had some method to compare the active oxygen content of one peroxide to another. The other information was just interesting.



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