Pyrocarbonate

Pyrocarbonates or dicarbonates (anhydrides of carbonic acids) have been prepared as follows (29) ... 

Diethyl pyrocarbonate (DEP) [1609-47-8] M 162.1, b 38-40°/12mm, 160-163 /atm, d 1.119, Op 1.398. Dissolve in Et20, wash with dilute HCl, H2O, dry over Na2S04. filter, evaporate and distil the residue first in vacuo then at atmospheric pressure. It is soluble in alcohols, esters, ketones and hydrocarbon solvents. A 50% w/w soln is usually prepared for general use. Treat with great CAUTION as DEP irritates the eyes, mucous membranes and skin. [Boehm and Mehta Chem Ber 71 1797 1938 Thoma and Rinke Justus Liebigs Ann Chem 624 30 1959.]... 

Hydrocarbon pyrocarbons, carbon blacks, vapour grown carbon ... 

The chloro atom of 2-[4-(6-chloronicotinoyl)benzyloxy]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one, its 6-methyl derivative and 2-[4-(6-chlo-ronicotinoyl)benzylthio]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one was replaced by a 4-piperidinopiperidino and 4-phenylpiperazino group with 4-piperidinopiperidine and 4-phenylpiperazine (96EUP733633). The carboxyl group of 2-[4-(4-carboxybenzoyl)benzyloxy]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one, prepared by hydrolysis of methyl ester in DMF with 1 N NaOH, was reacted first with diethyl pyrocarbonate in DMF at room temperature and then with 4-phenylpiperazine and 4-piperidinopiperidine to give the appropriate amide derivatives (96EUP733633). 

W. Golkiewicz, C. E. Werkhoven-Goewie, U. A. Th Brinkman, R. W. Erei, H. Colin and G. Guiochon, Use of pyrocarbon sorbents for rtace enrichment of polar compounds from aqueous samples with on-line HPEC analysis , /. Chromatogr. Sci. 21 27-33 (1981). 

Highly oriented pyrolitic graphite Glassy carbon -Pyrocarbon Graphite monocrystal Doped graphite (C,6 AsF5 )... 

The A-( 1 -alkoxyalkyl)carbamates are more simply obtained by a one-step synthesis on heating of the imine and diethyl pyrocarbonate in ethanol 57 58. In the case of a secondary alkyl substituent toluene appears to be the preferred solvent59. 

Reaction of Imines with Diethyl Pyrocarbonate General Procedure59" ... 

A solution of 0.9 mmol of the imine and l.2mmol of diethyl pyrocarbonate in 1.5 mL of dry ethanol (distilled from magnesium ethoxide) is stirred under nitrogen at 60 C for 24 h. Then the solvent is removed in vacuo and the residue flash chromatographed (silica gel, ethyl acetate/hexane 1 5) to give the product as an oil. 

By reducing an elementary reaction model taken fi om the database, a comprehensive gas-phase reaction model of propane pyrolysis was derived objectively. The reaction rate constants that were not accurate under the conditions of interest were found and refined by fitting with the experimental results. The obtained reaction model well represented the effects of the gas residence time and temperature on the product gas composition observed in experiments under pyrocarbon CVD conditions. 

The deoxygenation of peroxycarbonates (53) with phosphines and phosphites has been examined. Reaction with phosphites favours pyrocarbonate formation (Path A) whilst phosphines favour carbonate formation (Path B). Secondary phosphine oxides are oxidized to phosphinic acids by perbenzoic acid. The kinetics of the deoxygenation of hydroperoxides by triphenylphosphine have been examined and the reaction shown to be catalysed by strong acids. ... 

Cobalt(II) alkoxides are known and monomeric forms are part of a wider review.413 The interest in these compounds pertains to a potential role in catalysis. For example, a discrete cobalt(II) alkoxide is believed to form in situ from a chloro precursor during reaction and performs the catalytic role in the decomposition of dialkyl pyrocarbonates to dialkyl carbonates and carbon dioxide.414 A number of mononuclear alkoxide complexes of cobalt(II) have been characterized by crystal structures, as exemplified by [CoCl(OC(t-Bu)3)2 Li(THF)].415 The Co ion in this structure and close relatives has a rare distorted trigonal-planar coordination geometry due to the extreme steric crowding around the metal. 

Figure 3 c. HRTEM image of a cross-section of a carbon fiber after propylene pyrolysis the black line represents the boarder between the lamellar pyrocarbon (at the top) and the microporous fiber (at the bottom). 

The histogram of Figure 5 shows that the layers of both kinds of carbon are short, especially in the case of the fiber where about 75 % of the layers are smaller or equal to 0.75 nm, i.e. to 3 cycles. By contrast, this proportion is only about 55 % for the pyrocarbon. 

Based on these HRTEM data, a sketch of the multiscale organisation of the composite is proposed13 in Figure 6. Even if this representation is very schematic, it illustrates the two types of carbon short and very disordered layers mainly in the fiber, and a developed preferential orientation of longer and better stacked layers in the pyrocarbon coating. 

Figure 6. Sketch of the cross-section of a carbon fiber coated by pyrocarbon, taking into account the HRTEM image analysis data.

In conclusion, the composite formed by a carbon fiber cloth coated with pyrocarbon is a very promising material for the negative electrode of lithium batteries, since it couples a high reversible capacity due to the disordered fiber (1.5 time the graphite value) with a small irreversible... 

Diethyl pyrocarbonate (DEPC)-treated water. Prepare as a 0.1% (v/v) solution and incubate at 37° for 18 hrs. Autoclave for 15 min to destroy excess DEPC. 

From Sigma 3-aminoethylcarbazole (AEC) acrylamide/bis-acrylamide (30%) 37.5 1 amino acids alumina bentonite benzamidine bovine fiver tRNA bovine serum albumin (BSA) creatine phosphate (CP) diethyl pyrocarbonate (DEPC) dithiothreitol (DTT) Escherichia coli MRE600 tRNA pyrophosphatase (Ppase) Ca++ salt of folinic acid, (5-formyl THF) IIHPHS K salt of phospho-enol pyruvic acid, (PEP) creatine phospho kinase (CPK) protease inhibitor cocktail for fungal and yeast extracts phenylmethylsulfonyl fluoride (PMSF) spermidine trihydrochloride Tween 20. 

---