Generation of Carbon Monoxide

The concept of in situ liberation of carbon monoxide would be even more attractive if a metal-free material could serve as the carbon monoxide source. In the ideal carbonylation method, the organic solvent itself could be exploited for controlled generation of carbon monoxide. In 2002, Wan et al. addressed this issue and developed a microwave-promoted carbamoylation process based on the commonly used solvent dimethylformamide (DMF) as the carbon monoxide precursor75. Firstly, it was discovered that aryl dimethyl amides were accessible from the corresponding bromides in the presence of a nucleophilic catalyst, imidazole (Scheme 2.34). Secondly, tertiary benzamides other than dimethylamides were synthesised by addition of 3 equiv of an external amine (Scheme 2.34). 

Kaiser, N.F.K., Hallberg, A. and Larhed, M In situ generation of carbon monoxide from solid molybdenum hexacarbonyl a convenient and fast route to palladium-catalysed carbonylation reactions, J. Comb. Chem., 2002, 4, 109-111. 

Chlorine atoms are thus released and are available to attack the environmental ozone. The free radical, [CCIF j] , reacts with dioxygen to release [CIO] and form COF j. Further dissociation of COFj results in the generation of carbon monoxide, and fluorine atoms, which are ultimately precipitated as HF in the troposphere [36b],... 

Generation of carbon monoxide during the microsomal metabolism of methylenedioxyphenyl compounds. Biochem. Pharmacol. 29, 1113-1122. 

Burden materials are relatively easy to reduce in most blast furnaces. This, in conjunction with high blast temperatures, results in coke rates that are marginal with respect to providing sufficient carbon monoxide during combustion to reduce the burdens below 1000°C (1830°F). Consequently, some carbon solution above 1000 C (1830°F) is required to supplement the generation of carbon monoxide by combustion. 

Incomplete combustion of hydrocarbons leads to the generation of carbon monoxide rather than carbon dioxide. As a result, improperly vented furnaces can poison people who live in an affected building because of the toxicity of CO. Calculate the heat of reaction for the incomplete combustion of methane, CH4(g), to yield liquid water and CO(g). 

Lehn JM, Ziessel R (1982) Photochemical generation of carbon-monoxide and hydrogen by reduction of carbon dioxide and water under visible light irradiation. Ptoc Natl Acad Sci USA 79 701-704... 

The thermal decomposition of acetone isfree-radical chain reaction. The initiating process may consist in the generation of carbon monoxide and methyl radicals. 

Baldelli, S., Eppler, A. S., Anderson, E., Shen, Y.-R., and Somorjai, G. A. (2000] Surface enhanced sum frequency generation of carbon monoxide adsorbed on platinum nanoparticle arrays, /. Chem. Phys., 113,5432-5438. 

Scheme 1.33 Generation of carbon monoxide based on )S-hydride elimination. Reprinted (adapted) with permission from J. Am. Chem.Soc. 2011, 133, 6061. Copyright 2011 American Chemical Society...

Because intense heat is generated in these furnaces it is understandable that the arc volatilizes such metals as tin, zinc, lead, cadmium, and the like. In addition, both melting and smelting furnaces may generate large amounts of carbon monoxide. As a result all new furnace installations require pollution... 

Synthesis Gas Chemicals. Hydrocarbons are used to generate synthesis gas, a mixture of carbon monoxide and hydrogen, for conversion to other chemicals. The primary chemical made from synthesis gas is methanol, though acetic acid and acetic anhydride are also made by this route. Carbon monoxide (qv) is produced by partial oxidation of hydrocarbons or by the catalytic steam reforming of natural gas. About 96% of synthesis gas is made by steam reforming, followed by the water gas shift reaction to give the desired H2 /CO ratio. 

Nickel Carbonyl The extremely toxic gas nickel carbonyl can be detected at 0.01 ppb by measuring its chemiluminescent reaction with ozone in the presence of carbon monoxide. The reaction produces excited nickel(II) oxide by a chain process which generates many photons from each pollutant molecule to permit high sensitivity (315). 

The reaction is mn for several hours at temperatures typically below 100°C under a pressure of carbon monoxide to minimise formamide decomposition (73). Conversions of a-hydroxyisobutyramide are near 65% with selectivities to methyl a-hydroxyisobutyrate and formamide in excess of 99%. It is this step that is responsible for the elimination of the acid sludge stream characteristic of the conventional H2SO4—ACH processes. Because methyl formate, and not methanol, is used as the methylating agent, formamide is the co-product instead of ammonium sulfate. Formamide can be dehydrated to recover HCN for recycle to ACH generation. 

The characterization of PIC (products of incomplete combustion) from the combustion of wood treated with pentachlorophenol (penta) is more widely documented in the open literature than creosote alone. However, both products are similar in chemical composition and likely result in comparable forms and concentrations of PIC. Literature reported studies on the combustion of these chemicals and wood treated by them, and the PIC generated are based upon optimal conditions. Optimal conditions are defined as those in which the fuel burns at the designed heat release rate with nominally 160% excess air and a low level (< 100 ppm) of carbon monoxide (CO) emissions in combustion (flue) gases. 

In order to achieve high yields, the reaction usually is conducted by application of high pressure. For laboratory use, the need for high-pressure equipment, together with the toxicity of carbon monoxide, makes that reaction less practicable. The scope of that reaction is limited to benzene, alkyl substituted and certain other electron-rich aromatic compounds. With mono-substituted benzenes, thepara-for-mylated product is formed preferentially. Super-acidic catalysts have been developed, for example generated from trifluoromethanesulfonic acid, hydrogen fluoride and boron trifluoride the application of elevated pressure is then not necessary. 

Future legislation will stimulate burner development in the areas of carbon monoxide, NOx and particulate generation. Techniques will include flue-gas recirculation, staged combustion, and additives to reduce the NOx and more sophisticated controls. Controls over the sulfur generated do not affect burner design greatly since the sulfur dioxide is a natural product of combustion and can only be reduced by lower fuel sulfur contents or sulfur removal from the exhaust gases. 

Figure 7. Total internal reflection sum frequency generation (TIR-SFG) vibrational spectroscopy of high-pressure room temperature adsorption of carbon monoxide on PVP-protected Pt cube monolayers and calcined (373 K, 3h) monolayers [27], The infrared spectra demonstrate CO is adsorbed at atop sites, but is considerably red-shifted on the PVP-protected Pt cubes. After calcination, the atop frequency blueshifts to 2085 cm in good agreement with CO adsorption on Pt(l 0 0) at high coverages [28], (Reprinted from Ref [27], 2006, with permission from American Chemical Society.)...

Akemann W, Friedrich KA, Linke U, Stimming U. 1998. The catal)4ic oxidation of carbon monoxide at the platinum/electrolyte interface investigated by optical second harmonic generation (SHG) Comparison of Pt(l 11) and Pt(997) electrode surfaces. Surf Sci 404 571-575. 

Chou KC, Kim J, Baldelli S, Somorjai GA. 2003a. Vibrational spectroscopy of carbon monoxide, acetonitrile, and phenylalanine adsorbed on liquid vertical bar electrode interfaces by sum frequency generation. J Electroanal Chem 554 253-263. 

The elimination of carbon monoxide can occur by a concerted process in some cyclic ketones. The elimination of carbon monoxide from bicyclo[2.2.1]heptadien-7-ones is very facile. In fact, generation of bicyclo[2.2.1]heptadien-7-ones is usually accompanied by spontaneous decarbonylation. 

When benzyne is generated in the absence of another reactive molecule it dimerizes to biphenylene.132 In the presence of dienes, benzyne is a very reactive dienophile and [4+2] cycloaddition products are formed. The adducts with furans can be converted to polycyclic aromatic compounds by elimination of water. Similarly, cyclopentadienones can give a new aromatic ring by loss of carbon monoxide. Pyrones give adducts that can aromatize by loss of C02, as illustrated by Entry 7 in Scheme 11.9. 

A number of carbonates and lactones have been shown to give rise to quinone methide intermediates on irradiation.90-92 For example, Padwa and coworkers92 demonstrated that 3-phenylisocoumaranone (146) will extrude a molecule of carbon monoxide when irradiated in methanol to generate ort/zo-quinone methide (24) with moderate efficiency ( = 0.058, Eq. 1.39). This intermediate is subsequently trapped by the methanol solvent to give 147. 

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