Aldehydes to hydrocarbons

These reactions represent a gentle method for conversion of aldehydes to hydrocarbons in yields of 40-95% and are frequently used, especially in saccharide chemistry [795, 797, 798. ... 

Reed J. R., Quilici D. R., Blomquist G. J. and Reitz R. C. (1995) Proposed mechanism for the cytochrome P450 catalyzed conversion of aldehyde to hydrocarbon in the house fly, Musca domestica. Biochemistry 34, 16221-16227. 

Seleetive reduction of aliphatic ketones and aldehydes to hydrocarbons Aliphatic... 

Selective reduction of aliphatic ketones and aldehydes to hydrocarbons,6 Aliphatic ketones and aldehydes can be reduced selectively in high yields to hydrocarbons with sodium cyanoborohydride and p-toluenesulfonylhydrazine in DMF-sulfolane containing p-toluenesulfonic acid at 100-105°. The prior preparation of tosylhydrazones is not necessary because carbonyl groups are reduced slowly by sodium cyanoborohydride. Maximum yields are obtained with a fourfold molar excess of NaBH3CN. Yields are in the range 62-98%. Ester groups, if present, are not affected. Aromatic ketones are not reduced. 

Reduction of ketones or aldehydes to hydrocarbons by means ot zinc amalgam and acid... 

Deoxygenation of carbonyl compounds. This system, which has been shown to reduce alcohols to hydrocarbons, also reduces aliphatic and aromatic ketones and aromatic aldehydes to hydrocarbons. Yields are higher when the BF3 is scrubbed by HF before use. The reaction proceeds stepwise, since intermediate alcohols can be isolated. A large excess of the silane is required. 

Wilkinson s catalyst is useful for effecting intramolecular decarbonylation of aldehydes to hydrocarbons with retention of configuration (Walborsky and Allen, 1971). Decarbonylation of disubstituted cyclopropenones by iron, nickel, or cobalt carbonyls results in the formation of alkynes (Bird and Hudec, 1959). Tetraphenylethylene was obtained in 68% yield by reaction of diphenylketene with cobalt carbonyl (Hong et ai, 1968). 

It will also reduce acid chlorides, acid anhydrides and aldehydes to primary alcohols, ketones to secondary alcohols, and amides to the corresponding amines R-CONHi -> R CHiNH. Nitro-hydrocarbons if aromatic are... 

Table 17 2 summarizes the reactions of aldehydes and ketones that you ve seen m ear her chapters All are valuable tools to the synthetic chemist Carbonyl groups provide access to hydrocarbons by Clemmensen or Wolff-Kishner reduction (Section 12 8) to alcohols by reduction (Section 15 2) or by reaction with Grignard or organolithmm reagents (Sections 14 6 and 14 7)... 

Reduction of Aldehydes and Ketones to Hydrocarbons. Deep hydrogenation of aldehydes and ketones removes the oxygen functionahty and produces the parent hydrocarbons. 

Other synthetic methods have been investigated but have not become commercial. These include, for example, the hydration of ethylene in the presence of dilute acids (weak sulfuric acid process) the conversion of acetylene to acetaldehyde, followed by hydrogenation of the aldehyde to ethyl alcohol and the Fischer-Tropsch hydrocarbon synthesis. Synthetic fuels research has resulted in a whole new look at processes to make lower molecular weight alcohols from synthesis gas. 

In the Fischer-Tropsch process, carbon monoxide reacts with hydrogen in the presence of a solid catalyst, with the formation of a mixture of hydrocarbons. The composition of the product varies considerably with the catalyst and the operating conditions. The mixture may include (in addition to hydrocarbons) alcohols, aldehydes, ketones, and acids. 

Most resolution is done on carboxylic acids and often, when a molecule does not contain a carboxyl group, it is converted to a carboxylic acid before resolution is attempted. However, the principle of conversion to diastereomers is not confined to carboxylic acids, and other groupsmay serve as handles to be coupled to an optically active reagent. Racemic bases can be converted to diastereomeric salts with active acids. Alcohols can be converted to diastereomeric esters, aldehydes to diastereomeric hydrazones, and so on. Even hydrocarbons can be converted to diastereomeric inclusion... 

At high pressures the presence of the H02 radical also contributes via HCO + H02 — H202 + CO, but H02 is the least effective of OH, O, and H, as the rate constants in Appendix C will confirm. The formyl radical reacts very rapidly with the OH, O, and H radicals. However, radical concentrations are much lower than those of stable reactants and intermediates, and thus formyl reactions with these radicals are considered insignificant relative to the other formyl reactions. As will be seen when the oxidation of large hydrocarbon molecules is discussed (Section H), R is most likely a methyl radical, and the highest-order aldehydes to arise in high-temperature combustion are acetaldehyde and propionaldehyde. The acetaldehyde is the dominant form. Essentially, then, the sequence above was developed with the consideration that R was a methyl group. 

Combustion of gas takes place in two ways, depending upon when gas and air are mixed. When gas and air are mixed before ignition, as in a Bunsen burner, burning proceeds by hydroxylation. The hydrocarbons and oxygen form hydroxylated compounds that become aldehydes the addition of heat and additional oxygen breaks down the aldehydes to H2, CO, CO2, and H2O. Inasmuch as carbon is converted to aldehydes in the initial stages of mixing, no soot can be developed even if the flame is quenched. 

Reduction of unsaturated aromatic aldehydes to unsaturated hydrocarbons poses a serious problem, especially if the double bond is conjugated with the benzene ring or the carbonyl or both. In Clemmensen reduction the a,)8-unsaturated double bond is usually reduced [160], and in Wolff-Kizhner reduction a cyclopropane derivative may be formed as a result of decomposition of pyrazolines formed by intramolecular addition of the intermediate hydrazones across the double bonds [280]. The only way of converting unsaturated aromatic aldehydes to unsaturated hydrocarbons is the reaction of... 

Conversion of unsaturated aromatic aldehydes to saturated hydrocarbons can be realized by Clemmensen reduction [160]. 

Metallic nickel is known to catalyze the reduchon of NO in its reachons with aldehydes or hydrocarbon gases, and the primary reachon in the dark zone of a double-base propellant is the reduction of NO to N2. Small amounts of fine Ni particles or organic nickel compounds are incorporated into double-base propellants to increase the reaction rate in the dark zone. 

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