Carboxylic acids from alkane oxidation

The much higher yields of 1-chloropropane than 2-chIoropropane reported by Gol dshleger et al. (34) do not arise necessarily from preferred attack at the terminal carbon of the alkane, as the internal isomers are themselves oxidized faster than the terminal isomer. If 1-chlorohexane or a mixture of 2- and 3-chlorohexanes was used as the reactant, then, when the 2- and 3-isomers had been consumed, 75% of the 1-isomer still remained (84). The ultimate oxidation product, carbon dioxide, was not formed, and it is thought that the major product from alkane oxidation are polychlorinated carboxylic acids formed by chlorination and reaction with the solvent. These acids are difficult to find in the reaction mixture and despite strenuous efforts have not been identified. 

Alkanes are formed when the radical intermediate abstracts hydrogen from solvent faster than it is oxidized to the carbocation. This reductive step is promoted by good hydrogen donor solvents. It is also more prevalent for primary alkyl radicals because of the higher activation energy associated with formation of primary carbocations. The most favorable conditions for alkane formation involve photochemical decomposition of the carboxylic acid in chloroform, which is a relatively good hydrogen donor. 

In fluorosulfonic acid the anodic oxidation of cyclohexane in the presence of different acids (RCO2H) leads to a single product with a rearranged carbon skeleton, a 1-acyl-2-methyl-1-cyclopentene (1) in 50 to 60% yield (Eq. 2) [7, 8]. Also other alkanes have been converted at a smooth platinum anode into the corresponding a,-unsaturated ketones in 42 to 71% yield (Table 1) [8, 9]. Product formation is proposed to occur by oxidation of the hydrocarbon to a carbocation (Eq. 1 and Scheme 1) that rearranges and gets deprotonated to an alkene, which subsequently reacts with an acylium cation from the carboxylic acid to afford the a-unsaturated ketone (1) (Eq. 2) [8-10]. In the absence of acetic acid, for example, in fluorosulfonic acid/sodium... 

CIS-[Ru(H20)2(dinso) ] is made from as-RuClj(dmso) and Ag(BF ) in aq. EtOH. The system c/s-[Ru(H20)j(dmso) ] Vaq. Na(ClO) or TBHP/CH Cl oxidised alkanes such as adamantane, cyclo-octane, -heptane and -hexane to the corresponding alcohols and ketones as did [Ru(Hj0) PWjj(0)3g ] . A free-radical mechanism may be involved for the TBHP oxidations, but those with (C10) probably involve oxoruthenate(VI) or oxoruthenate(IV) intermediates [823], The oxidative destruction of a-chlorinated alkenes by CM-[Ru(HjO)2(dmso) ] Vaq. Oxone /Me(CH3) jN(HSO ) MCj to carboxylic acids and ultimately to CO and HCl was reported [946],... 

The direct catalyzed or uncatalyzed oxidation of alkanes with oxygen is an important reaction in the industrial production of carboxylic acids, hydroperoxides (for production of epoxides from alkenes), alcohols, ketones, or aldehydes [60],... 

Introduction.—The oxidative dehydrogenation of alcohols to aldehydes and ketones over various catalysts, including copper and particularly silver, is a well-established industrial process. The conversion of methanol to formaldehyde over silver catalysts is the most common process, with reaction at 750—900 K under conditions of excess methanol and at high oxygen conversion selectivities are in the region 80—95%. Isopropanol and isobutanol are also oxidized commercially in a similar manner. By-products from these reactions include carbon dioxide, carbon monoxide, hydrogen, carboxylic acids, alkenes, and alkanes. 

Because oxidative decarboxylation of carboxylic acids by lead tetraacetate depends on the reaction conditions, the co-reagents, and the structures of the acids, a variety of products such as acetate esters, alkanes, alkenes, and alkyl hahdes can be obtained. Mixed lead(IV) carboxylates are involved as intermediates as a result of their thermal or photolytic decomposition decarboxylation occurs and alkyl radicals are formed. Oxidation of alkyl radicals by lead(IV) species gives carbocations a variety of products is then obtained from the intermediate alkyl radicals and the carbocations. Decarboxylation of primary and secondary acids usually affords acetate esters as the main products (Scheme 13.41) [63]. 

A-hydroxy-phthalimide (NHPI) acts as a catalyst for transformation of alkanes to alcohols, ketones, carboxylic acids, and/or nitroalkanes under mild oxidation conditions [64]. Koguchi et al. [64] used NHPl-Co(OAc)j-02 system for the oxidation of alcohols in ionic liquids. They found that NHPI is separated easily from ionic liquid... 

As mentioned above, the hydrophilic head group may be unionised [e.g., alcohols or poly(ethylene oxide) (PEO) alkane or alkyl phenol compounds], weakly ionised (e.g., carboxylic acids), or strongly ionised (e.g., sulphates, sulphonates, and quaternary ammonium salts). The adsorption of these different surfactants at the A/W and O/W interfaces depends on the nature of the head group. With nonionic surfactants, repulsion between the head groups is small and these surfactants are usually strongly adsorbed at the surface of water from very dilute solutions. Nonionic surfactants have much lower cmc values when compared to ionic surfactants with the same alkyl chain length typically, the cmc is in the region of... 

Determination of the residual antioxidant content in polymers by HPLC and MAE is one way to determine the amoimt needed for reasonable stabilization of a material, and also to compare different antioxidants and their individual efficiencies. During ageing and oxidation of PE, carboxyhc acids, dicarboxylic acids, alcohols, ketones, aldehydes, n-alkanes and 1-alkenes are formed [86-89]. The carboxyhc acids are formed as a result of various reactions of alkoxy or peroxy radicals [90]. The oxidation of polyolefins is generally monitored by various analytical techniques. GC-MS analysis in combination with a selective extraction method is used to determine degradation products in plastics. ETIR enables the increase in carbonyls on a polymer chain, from carboxylic acids, dicarboxyhc acids, aldehydes, and ketones, to be monitored. It is regarded as one of the most definite spectroscopic methods for the quantification and identification of oxidation in materials, and it is used to quantify the oxidation of polymers [91-95]. Mechanical testing is a way to determine properties such as strength, stiffness and strain at break of polymeric materials. 

There have been several attempts to obtain oxygenated products from lower alkanes (C2 - C5) by using heteropoly catalysts. It has been reported that the hydrogen form of H3PM012O40 catalyzes the oxidation of lower alkanes to aldehydes and carboxylic acids [8] and that the substitution of for Mo modified the catalytic activity and selectivity [1, 9 - 12]. 

The degradation of alkanoic acids by P-oxidation has been noted parenthetically above, but alternative pathways may occur. For example, the metabolism of hexanoic acid by strains of Pseudomonas sp. may take place by co-oxidation with subsequent formation of succinate and 2-tetrahydrofurany-lacetate as a terminal metabolite (Kunz and Weimer 1983). In a strain of Cory neb acterium sp., the specificities of the relevant catabolic enzymes are consistent with the production of dodecanedioic acid by co-oxidation of dode-cane but not of hexadecanedioic acid from hexadecane (Broadway et al. 1993). Hydroxylation at subterminal (co-1, co-2, and co-3) positions of carboxylic acids with chain lengths of 12 to 18—and less readily of the corresponding alcohols, but not the carboxylic acids or the alkanes—has been observed (Miura and Fulco 1975) for a soluble enzyme system from a strain of Bacillus megaterium. Whereas in this organism co-2 hydroxylation is carried out by a soluble cytochrome P-450 BM 3 (Narhi and Fulco 1987), co-hydroxylation in P. oleovorans that carries the OCT plasmid is mediated by a three-component hydroxylase that behaves like a cytoplasmic membrane protein (Ruettinger et al. 1974 Kok et al. 1989). 

---