2613-44-7Relevant articles and documents
Main-group compounds selectively oxidize mixtures of methane, ethane, and propane to alcohol esters
Hashiguchi, Brian G.,Konnick, Michael M.,Bischof, Steven M.,Gustafson, Samantha J.,Devarajan, Deepa,Gunsalus, Niles,Ess, Daniel H.,Periana, Roy A.
, p. 1232 - 1237 (2014)
Much of the recent research on homogeneous alkane oxidation has focused on the use of transition metal catalysts. Here, we report that the electrophilic main-group cations thallium(III) and lead(IV) stoichiometrically oxidize methane, ethane, and propane, separately or as a one-pot mixture, to corresponding alcohol esters in trifluoroacetic acid solvent. Esters of methanol, ethanol, ethylene glycol, isopropanol, and propylene glycol are obtained with greater than 95% selectivity in concentrations up to 1.48 molar within 3 hours at 180°C. Experiment and theory support a mechanism involving electrophilic carbon-hydrogen bond activation to generate metal alkyl intermediates. We posit that the comparatively high reactivity of these d 10 main-group cations relative to transition metals stems from facile alkane coordination at vacant sites, enabled by the overall lability of the ligand sphere and the absence of ligand field stabilization energies in systems with filled d-orbitals.
Mechanism of Hydrocarbon Functionalization by an Iodate/Chloride System: The Role of Ester Protection
Schwartz, Nichole A.,Boaz, Nicholas C.,Kalman, Steven E.,Zhuang, Thompson,Goldberg, Jonathan M.,Fu, Ross,Nielsen, Robert J.,Goddard, William A.,Groves, John T.,Gunnoe, T. Brent
, p. 3138 - 3149 (2018/04/14)
Mixtures of chloride and iodate salts for light alkane oxidation achieve >20% yield of methyl trifluoroacetate (TFA) from methane with >85% selectivity. The mechanism of this C-H oxygenation has been probed by examining adamantane as a model substrate. These recent results lend support to the involvement of free radicals. Comparative studies between radical chlorination and iodate/chloride functionalization of adamantane afford statistically identical 3°:2° selectivities (～5.2:1) and kinetic isotope effects for C-H/C-D functionalization (kH/kD = 1.6(3), 1.52(3)). Alkane functionalization by iodate/chloride in HTFA is proposed to occur through H-atom abstraction by free radical species including Cl? to give alkyl radicals. Iodine, which forms by in situ reduction of iodate, traps alkyl radicals as alkyl iodides that are subsequently converted to alkyl esters in HTFA solvent. Importantly, the alkyl ester products (RTFA) are quite stable to further oxidation under the oxidizing conditions due to the protecting nature of the ester moiety.
OXIDATION OF ALKANES TO ALCOHOLS
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Page/Page column 12; 13; 14, (2014/09/03)
The invention provides processes and materials for the efficient and cost- effective functionalization of alkanes, such as methane from natural gas, to provide esters, alcohols, and other compounds. The method can be used to produce liquid fuels such as methanol from a natural gas methane-containing feedstock. The soft oxidizing electrophile, a compound of a main group, post- transitional element such as Tl, Pb, Bi, and I, that reacts to activate the alkane C- H bond can be regenerated using inexpensive regenerants such as hydrogen peroxide, oxygen, halogens, nitric acid, etc. Main group compounds useful for carrying out this reaction includes haloacetate salts of metals having a pair of available oxidation states, such as Tl, Pb, Bi, and I. The inventors herein believe that a unifying feature of many of the MXn electrophiles useful in carrying out this reaction, such as Tl, Pb, and Bi species, is their isoelectronic configuration in the alkane -reactive oxidation state; the electrons having the configuation [Xe]4f145d10, with an empty 6s orbital. However, the iodine reagents have a different electronic configuration.
