Aliphatic glycol oxidation

Habid and Malek49 who studied the activity of metal derivatives in the catalyzed esterification of aromatic carboxylic acids with aliphatic glycols found a reaction order of 0.5 relative to the catalyst for Ti(OBu)4, tin(II) oxalate and lead(II) oxide. As we have already mentioned in connection with other examples, it appears that the activation enthalpies of the esterifications carried out in the presence of Ti, Sn and Pb derivatives are very close to those reported by Hartman et al.207,208 for the acid-catalyzed esterification of benzoic and substituted benzoic acids with cyclohexanol. These enthalpies also approach those reported by Matsuzaki and Mitani268 for the esterification of benzoic acids with 1,2-ethanediol in the absence of a catalyst. On the other hand, when activation entropies are considered, a difference exists between the esterification of benzoic acid with 1,2-ethanediol catalyzed by Ti, Sn and Pb derivatives and the non-catalyzed reaction268. Thus, activation enthalpies are nearly the same for metal ion-catalyzed and non-catalyzed reactions whereas the activation entropy of the metal ion-catalyzed reaction is much lower than that of the non-catalyzed reaction. 

Prior to 1978, the work in this area mainly dealt with the synthesis of tri-, tetra-, and pentavalent metal and metalloid derivatives of aliphatic (glycol) and aromatic (catechol/substituted catechol) diols (6, 423), of a wide variety of structural types. These types depended on (a) the nature of the metal and metalloid and their oxidation states, (b) the type of diol, and (c) the reactants stoichiometries. Out of a large number of structural possibilities, the common types reported earlier are shown in Fig. 65, without X-ray crystallographic authentication. 

Treatment of these samples with SF4 gas to convert the carboxylic acids produced in the weathering process into carbonyl fluorides showed [2, 11] that the acids are actually a mixture of aliphatic and aromatic acids (Figure 18.12). Aromatic acid species are by far the predominant ones, however. The origin of these acids will be discussed below in conjunction with the overall mechanisms of photodegradation. Aliphatic acid species were detected by GC/MS in the artificial device exposure of PECT [11], Note that the PECT copolymer produced more aromatic acids with the same exposure as PET but that the aliphatic acid production was several times higher for the PECT copolymer. The photo-oxidation of the co-glycol must be the reason for this difference. 

We note also that the schemes discussed until now only show the oxidation of the ethylene glycol moiety. In the PECT copolymer, the 1,4-cyclohexylenedi-methylene moiety is also available for oxidation. Indeed, given that the oxidizable hydrogens are tertiary, one reasonably expects a greater ease of production of a radical from that center. Grossetete et al. [11] reported such to be the case with the observation that photo-oxidation reactions occurred much faster with the PECT copolymer than with PET itself. The aliphatic acids that they reported, as identified by the SF4 treatment, could also account for previous aliphatic acid reports [25], This is also additional support that the photo-oxidation mechanism is operating as proposed (Scheme 18.4). 

Direct electrochemical oxidation is not a convenient way for a preparative production of carbonyl compounds from alcohols due to the unselectivity caused by the high oxidation potentials of alcohols. Thus, there have been only a few compounds (some aliphatic alcohols, glycols, and related alcohols) that have been oxidized by the direct method, while the indirect method has often been used to oxidize selectively a variety of alcohols, since it does not... 

Glycols and related alcohols In contrast to aliphatic monoalcohols (1), 1,2-glycols and related compounds (2-methoxy alcohols, 1,2-amino alcohols) can be easily oxidized by the direct electrochemical method [12]. For example, 1,2-cyclopentanediol (9) affords diacetal (10) in 56% yield as the main product (Eq. 3). 

This enzyme [EC 1.1.3.15] (also referred to as glycolate oxidase, hydroxy-acid oxidase A, and hydroxy-acid oxidase B) catalyzes the reaction of an (5)-2-hydroxy acid with dioxygen to produce a 2-oxo acid and hydrogen peroxide. FMN is the cofactor for this enzyme. This oxidase exists as two major isoenzymes. The A form preferentially oxidizes short-chain aliphatic hydroxy acids whereas the B form preferentially oxidizes long-chain and aromatic hydroxy acids. 

Grosjean, D., Atmospheric Chemistry of Toxic Contaminants. 2. Saturated Aliphatics Acetaldehyde, Dioxane, Ethylene Glycol Ethers, Propylene Oxide, J. Air Waste Manage. Assoc., 40, 1522-1531 (1990b). 

Chemical properties of glycols. They are similar to those of aliphatic alcohols and the glycols may be oxidized (in the vapor phase and in the presence of catalysts) to the corresponding acids. They are easily estertfied by inorganic and organic acids to form, esters. Ethers (such as methyl, ethyl etc) may be prepd by treating... 

Direct Oxidation. Direct oxidation of petroleum hydrocarbons has been practiced on a small scale since 1926 methanol, formaldehyde, and acetaldehyde are produced. A much larger project (29) began operating in 1945. The main product of the latter operation is acetic acid, used for the manufacture of cellulose acetate rayon. The oxidation process consists of mixing air with a butane-propane mixture and passing the compressed mixture over a catalyst in a tubular reaction furnace. The product mixture includes acetaldehyde, formaldehyde, acetone, propyl and butyl alcohols, methyl ethyl ketone, and propylene oxide and glycols. The acetaldehyde is oxidized to acetic acid in a separate plant. Thus the products of this operation are the same as those (or their derivatives) produced by olefin hydration and other aliphatic syntheses. 

Trimethylene glycol occurs in the glycerin which is produced by fermentation. There is no harm in leaving it in glycerin which is to be used for the manufacture of explosives. It may however be separated by fractional distillation. When pure it is a colorless, odorless, syrupy liquid, specific gravity (x°/4°) 1.0526 at 18°. It mixes with water in all proportions and boils at atmospheric pressure at 21 i° without decomposition. At temperatures above 15° or so, it is oxidized rapidly by nitric acid or by mixed acid. It is accordingly nitrated at 0-10° under conditions similar to those which are used in the preparation of ethyl nitrate and other simple aliphatic nitric esters (except methyl nitrate). 

The vanadium(V) oxidation of the sulfide PhCH=CHSPh has been studied in aqueous acetic acid containing perchloric acid. The reaction is first order in vanadiiun(V) and fractional order in sulfide. An intermediate complex of vanadium and the sulfide forms and its decomposition is the slow step of the reaction.181 Two Indian groups have reported on the use of ruthenium(VI) and ruthenium(III).182 183 The kinetics and mechanism of the oxidation of diethylene glycol by aqueous alkaline potassium bromate in the presence of Ru(VI)182 and the Ru(III)-catalysed oxidation of aliphatic alcohols by trichloroisocyanuric acid183 have been examined. 

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