Alkyl Perchlorate Esters

 
Perchlorate esters are very unstable and dangerously sensitive to detonation. Even extremely small quantities are extremely brissant. When the perchlorate group is not in anionic form and does not have an extra electron resonating around the oxygen atoms, it loses much stability.  As such, extreme caution and safety measures should be used.
 
A container of organic perchlorate ester, should never be turned to its side. This can wet the area around the lid so that when the lid is forcefully removed, there is a danger of friction that can cause detonation.

If working with perchlorate esters, use only small ammounts at any one time, preferably use a test tube holder with rubber gripping to securely hold the tube. It would be a good idea use plastic containers and test tubes to handle the the compound right after it is made. Of course, during the actual synthesis a glass beaker might be required to resist the concentrated perchloric acid, but if possible, teflon be used to avoid scrapnel in case of an accident. There do exist plastic test tube holders. In the event that the compound was accidently detonated, this would prevent shredded bits of the metal tongs from being imparted into your body, but most likely if there was an accident it would be because the test tube fell out from the tongs, and so using a plastic test tube holder may be somewhat unnecessary. The test tube holder puts distance between the compound and your hands. Even a small ammount of distance offers much protection in case of accidental detonation. Make sure you have textured rubber gripping (you could superglue a piece of rubber onto the tongs); having a holder without good grip greatly increases the chance that it could slip out and fall to the floor, causing detonation. While the chance of accidental detonation may be greater than just using unprotected hands, it is much preferable to have an increased risk of detonation, rather than risk direct injury to a hand in the event of an accident. You should put a plush carpet mat or rug around the floor, in case of accidental dropping of the tube, provided it does not create a possibility of slipping on the mat. Always wear protective goggles around dangerously sensitive compounds, preferably thick plastic. If it goes off, it could launch fast moving bits of whatever container it was in toward your eyes. While all this may seem like a lot of unnecessary trouble, it should be mentioned that perchlorate esters are far more sensitive than nitroglycerin, and may go off with little provocation, or seemingly no reason at all. Experienced researchers have suffered irreversible injury, despite taking extreme safety measures and using what they thought was the utmost caution. An accident could cause severe personal injury, and all the trouble is worth mitigating the risk of potential injuries.
 
It is advised not to store perchlorate esters, especially for a prolonged length of time, as they can undergo spontaneous detonation. If they are stored, however, the compound should be highly diluted into a solvent, such as acetone or nitromethane. No more than 1g of ethyl perchlorate should be stored in any one tube, and if multiple tubes are present, they should be separated by at least 20cm with plastic separation between the tubes. It is advisable to store test tubes surrounded by foam to protect it from the possibility of accidental impact. The outside packaging should be clearly marked with the danger, in case a person unfamiliar with the compound happens to find it. Refrigeration could potentially help with stability, but the danger of freezing, and the subsequent thawing, is almost assuredly a guarantee of detonation. If a situation arises that the perchlorate ester has been stored of over sixty days, full safety precautions should be taken when removing it, and it should be assumed that it could detonate from the slightest movement at any time. The packaging should not be opened, and the whole thing should be remotely detonated in an appropriate area. Perchlorate esters become significantly more sensitive after time, far more so than even the extreme sensitivity they display when first prepared. Never open by hand  or remove the stopper from a container or tube of perchlorate ester, even if diluted in solvent, that has been stored for more than two days.
 
While Ethyl Perchlorate is extremely sensitive, Methyl Perchlorate is virtually touch-sensitive, and as such unstorable in the pure or highly concentrated form. Trying to separate Methyl Perchlorate from its protective solvent is all but guaranteed to result in explosion. Perchlorate Esters slowly hydrolyze with water. Whereas ethyl perchlorate is stable under distilled water for 1-2 days, methyl perchlorate reacts within under an hour.
 
Another dangerous aspect of alkyl ether perchlorates, not commonly known of, and overshadowed by the sensitive explosive nature of the compounds, is extreme toxicity. Methyl perchlorate is an alkylating agent, the vapors should be assumed to be deadly. Exposures that can lead to death can potentially occur prior to development of any warning signs. Symptoms would appear within 4 to 6 hours after exposure, but could take up to 20 hours to become apparent. If the oil comes in contact with skin, assuming spontaneous detonation does not occur, severe blisters will quickly develop, with delayed secondary toxicity that may be fatal. However, a few amateur researchers have actually tasted drop sized quantities without ill effect (it is highly recommended that this not be attempted), likely owing to the fast hydrolysis of the ester with saliva. The ester has a very pleasant odour and a sweet taste that changes to a burning taste analogous to cinnamon.
 
There are at least five different routes to prepare Alkyl Perchlorates.
 
"Iodine(I) perchlorate can be made by reaction of I with silver perchlorate in a benzene solution:
I2 + AgClO4 -->  IClO4 + AgI; Iodine(III) perchlorate is obtained by reaction of the same substances in ether at -85C;
2I2 + 3AgClO4 --> I(ClO4)3 + 3AgI." Iodine (I) compounds can be stabilized by Lewis bases, such as pyridine, which forms
[I Py2][ClO4]. "Concise encyclopedia chemistry" by Mary Eagleson. If the IClO4 is prepared in the solvent with an alkane present, such as dissolved propane, alkane perchlorates will be formed, the intermediate IClO4 attacking the hydrocarbon.
 
"The procedure involves addition of a secondary alcool or unbranched olefin to a well-stirred emulsion of perchlorate acid, sulfuric acid, and an inert hydrocarbon or halocarbon. The acid reagent can be prepared by combining 70% perchloric acid, 96% sulfuric acid, and oleum, or by dissolving lithium perchlorate in 96% sulfuric acid. The formation of...alkyl perchlorates is...rapid and virtually quantitative. The ester products are found in the organic layer... the use of nonreactive organic <solvent> in combination with the <acids>...give either alkyl hydogen sulfate or alkyl perchlorate. The alkyl perchlorate, being covalent in nature, moves quickly to the organic layer, where it is largely protected from further decomposition. The alkyl hydrogen sulfate remains in the acid layer until futher reaction produces alkyl perchlorate. However, prolonged <standing> of the emulsion leads to slow decomposition of the perchlorate, giving <undesired> products <typical of the reaction between> alcohols or olefins to sulfuric acid" The Preparation of sec-Alkyl Perchlorates in Strong Acid, J. Org. Chem. Vol. 36, #12, 1971, David M. Hoffman.
 
When ether perchlorates are being neutralized from their concentrated acid solution, explosion will result from straight addition of water. First, the solution must be diluted with 85% perchloric acid, and then successively diluted with ever more less concentrated solutions of perchloric acid (usually in four separate stages), until finally the solution is able to be mixed with a solution of bicarbonate.
 
Perhaps the most certain way for the researcher to meet with a swift demise would be the reaction of dissolved diazomethane with concentrated perchloric acid. http://www.cdodgyd.heliohost.org/perchloric/ms5.jpg
Comments