Diethyl Dimethyl Pyrocarbonate

Diethyl pyrocarbonate (DEPC or diethyl dicarbonate) is a colorless liquid of fruit-like or ester odor. Its antimicrobial activity covers yeasts (10-100 ppm), bacteria (Lactobacilli 100-170 ppm) and molds (300-800 ppm). The levels of the compound required for a clear inhibition are given in brackets. Diethyl pyrocarbonate readily hydrolyzes to yield carbon dioxide and ethanol  

In the presence of ammonium salts, DEPC can form ethyl urethane in a pH-dependent reaction  

Since diethyl carbonate may be a teratogenic agent and ethyl urethane is a carcinogen, the use of diethyl pyrocarbonate is discussed under toxicological aspects. The compound should be replaced by dimethyl pyrocarbonate, since methyl urethane, unlike ethyl urethane, is not carcinogenic. 

Both compounds are used in cold pasteurization of fruit juices, wine and beer at a concentration of 120-300 ppm. 

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The protocol described also can be used for the acylation of ketone enolates with carbonic acid derivatives (Figure 13.62). Especially good acylating agents are cyanocarbonic acid methyl ester (Mander s reagent, Figure 13.62, top) and dialkyl pyrocarbonates (bottom). Usually it is not possible to use dimethyl carbonate for the acylation of ketone enolates because dimethyl carbonate is a weaker electrophile than cyanocarbonic acid methyl ester or diethyl pyrocarbonates. 

Cobalt chloride (ous) Diethyl pyrocarbonate Lithium citrate BHT substitute, polyolefins Octadecyl 3,5-di-t-butyM-hydroxyhydrocinnamate Bi detection Dimethyl glyoxime biaryl formation Trifluoromethane sulfonic acid bilirubin testing, urine 5-Sulfosalicylic acid 5-Sulfosalicylic acid dihydrate binder... 

Diethyl dicarbonate (diethyl pyrocarbonate) was used in the past as a preservative for soft drinks and some alcohohc beverages (including wine). In aqueous solution, however, diethyl dicarbonate is rapidly hydrolysed to ethanol and carbon dioxide, and in alcoholic beverages it is transformed into diethyl carbonate by reaction with ethanol. In the presence of ammonium salts toxic ethyl carbamate then results, which is also known as urethane (Figure 11.2). For these reasons, diethyl dicarbonate is not approved in the EU, but the approved compound is dimethyl dicarbonate (E242), which can be used for the preservation of soft drinks, teas, herbal teas and in some countries to stabilise wine. The methyl carbamate produced from dimethtyl dicarbonate is a non-toxic substance. In treated wines it occurs in amounts up to 10 xg/l. 

FIGURE 1.8 Some chemical reactions of bases and nucleotides, (a) Hydrolysis of a dinucleotide by alkali. Bases are denoted by B1 and B2. R denotes ribose or deoxyribose. (b to k) Chemical reactions (b) bisulfite, (c) chloroacetaldehyde, (d) diethyl pyrocarbonate, (e) dimethyl sulfate, (f) formaldehyde, (g) glyoxal, (h) hydrazine, (i) nitric acid, (j) nitrous acid, and (k) osmium tetroxide. Partly from R. L. P. Adams, J. P. Knowler, and D. P. Leader (1986). In The Biochemistry of the Nucleic Acids, 10th ed., pp. 5—34. Chapman Hall, with permission. 

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