| Abstract
| - Tetraethyl orthocarbonate (TEOC), diethyl carbonate (DEC), anddiethoxymethane (DEM) have beendecomposed in single-pulse shock tube experiments. TEOC decomposesto give DEC, ethylene, and ethanolas organic products, while DEC results in only the latter two. Inboth cases the ethylene to ethanol ratio isequal to 1, and the mechanisms appear to involve moleculareliminations. The rate expressions for the initialprocesses are the following: k(TEOC → products) =1013.91±0.14 exp((−27 529± 348)K/T) s-1,T = 1005−1180 K; k(DEC →C2H5OCO2H +C2H4) =1013.03±0.11 exp((−23 290± 26 7 K/T) s-1, T= 955−1095 K.The listed uncertainties are one standard deviation. DEMdecomposes more slowly than the other twocompounds. For each DEM reacted, 1.2 ethylene and 0.5 ethanol areproduced. Methane and ethane arealso observed as products. The mechanism is postulated to involveboth molecular and bond-breaking channels.It is concluded that ethanol arises only through the molecularchannel, and on this basis the following rateexpressions have been derived: k(DEM → products) =1015.93±0.15 exp((−36 179± 403 K/T) s-1, T =1150−1260 K; k(DEM → ethanol + products) =1015.07±0.45 exp((−34 517± 1090 K/T) s-1;k(DEM → ethyl +OCH2OC2H5) =1016.32±0.45 exp((−38 214± 1160 K/T) s-1. Theresults are compared with those dealingwith the stability of analogous ethers, esters, and silicon compounds.For carbon compounds the addition ofethoxy groups to the compound destabilizes the molecule. It isfurther concluded that rate data on the moleculardecompositions of ethoxy carbon compounds cannot be easily extrapolatedto silicon-containing species.
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