Oxidation of heptaldehyde

The photochemical oxidation of heptaldehyde has been studied in two extensive kinetic investigations [28,29] under slightly different conditions from the standpoint of temperature and solvents. (McNesby and Davis [28] solvent, cyclohexane oxygen pressure, 100—600 torr temperature, 20—35° C. Lemaire [29] solvent, decane oxygen pressure, 50—720 torr temperature, 0—17°C.) 

Although, in both cases, thermal initiation is negligible, somewhat contradictory results have been obtained with regard to the influence of oxygen pressure on the rate of oxidation which, in both studies was found to be proportional to the square root of the light intensity. According to McNesby and Davis, the order with respect to oxygen is probably 

Considering the low degree of experimental reproducibility obtained by these authors, it is more probable that the effect of oxygen is closer to that determined by Niclause and his coworkers [31] who show that, at very low pressures ( 10 torr), the rate of oxidation depends on Pq2 and is independent of po2 for pressures greater than 160 torr. In these pressure ranges, the expression for the rate of oxidation has the forms 

The X peroxides produced by the reaction of perheptanoic acid and heptanal would have the structures [30] 

Infrared spectra of Xj, X2 and X3 peroxides from perheptanoic acid and heptanai [30] in CCI4 solution Cell thickness, 1 mm. 

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Although aldehydes are more easily ozidized than alcohols, reagents and conditions are similar in the conversion of both substances to acids. Sulfuric-chromic acid mixture has been used to prepare propionic acid from the alcohol (65%), heptanoic acid from the aldehyde (70%), and furoic acid from furfural (75%). ° Alkaline permanganate is employed in the preparation of methyldiphenylacetic acid from the aldehyde (45%) and ethyl-n-butylacetic acid from the aldehyde or alcohol (74%). ° Acid permanganate is used for the oxidation of heptaldehyde to heptanoic acid (78%) and 6-methyl-l-octanol to 6-methyloctanoic acid (66%). ... 

Heptoic acid has been prepared by the oxidation of heptaldehyde with nitric acid, with potassium permanganate in alkaline aqueous solution or in acetone solution, and with potassium dichromate and sulfuric acid. ... 

Heptanoic Add, Enanthic acid oenanthic add oenanthylic acid n-heptoic add n-heptylic add. C,Hl40, mol wt 130.18. C 64.58%, H 10.84%, O 24.58%. CHj-(CHj)jCOOH. Found in the various fusel oils in appredable amounts. Has been observed in randd oils. Prepd by the oxidation of heptaldehyde with potassium permanganate in dil sulfuric add Ruhoff, Org. Syn. coll. voL II, 3]5 (1943). 

The chain unit in the thermal and photochemical oxidation of aldehydes by molecular dioxygen consists of two consecutive reactions addition of dioxygen to the acyl radical and abstraction reaction of the acylperoxyl radical with aldehyde. Experiments confirmed that the primary product of the oxidation of aldehyde is the corresponding peroxyacid. Thus, in the oxidation of n-heptaldehyde [10,16,17], acetaldehyde [4,18], benzaldehyde [13,14,18], p-tolualdehyde [19], and other aldehydes, up to 90-95% of the corresponding peroxyacid were detected in the initial stages. In the oxidation of acetaldehyde in acetic acid [20], chain propagation includes not only the reactions of RC (0) with 02 and RC(0)00 with RC(0)H, but also the exchange of radicals with solvent molecules (R = CH3). 

Although the data of Layng and Youker4 were obtained in a bulb type of apparatus, they show the progressively increasing rate of oxidation of n-heptane, heptaldehyde, and heptoic add and the stability of n-heptyl alcohol to oxidation (Fig. 32). No alcohol was found in the products from n-heptane oxidation. 

In 1927, Backstrom [4] succeeded, for the photochemical oxidation of benzaldehyde and heptaldehyde, in making the first quantitative measurement of the quantum yield and found that this is between 560 and 15,000 depending on the conditions. Because a photon can react only with a molecule, this specifically implied a radical chain mechanism. 

Pyrolytic Decomposition. The pyrolytic decomposition at 350—460°C of castor oil or the methyl ester of ricinoleic acid spHts the ricinoleate molecule at the hydroxyl group forming heptaldehyde and undecylenic acids. Heptaldehyde, used in the manufacture of synthetic flavors and fragrances (see Elavors and spices Perfumes) may also be converted to heptanoic acid by various oxidation techniques and to heptyl alcohol by catalytic hydrogenation. When heptaldehyde reacts with benzaldehyde, amyl cinnamic aldehyde is produced (see Cinnamic acid, cinnamaldehyde, and cinnamyl... 

The reaction mechanism was explained on the theory that the oxidative attack was through the methyl group, n-octane being converted to n-octaldehyde and this in turn to the next lower aldehyde, with the elimination of carbon monoxide. The degradative action was believed to be repeated step by step, through a nonstop run, to formaldehyde as the final product. n-Heptaldehyde and n-butvraldehyde gave essentially the same products. It was believed the luminescence was due to the chain reaction by which each aldehyde was converted to the next lower aldehyde with the elimination of carbon monoxide. 

Johnson et al. were the first to prepare enantiomerically pure aminosulfoxonium ylide 3.73 from 3.72, which on reaction with benzaldehyde gave (P)-styrene oxide (3.69) in 20% ee. The reaction of aminosulfoxonium ylide 3.74 with heptaldehyde gave the corresponding epoxide 3.75 with opposite enantioselectivity (39% ee, S) as expected. 

Heptaldehyde can be hydrogenated to heptanol or oxidized to heptanoic acid, which can be marketed. The ester cracking yield is up to 75 molar per cent of methyl undecenoate. 

When ozone is passed through n-heptylamine that is adsorbed on neutral silica gel, 1-nitroheptane is formed in 70% yield. This in turn may be converted into n-heptaldehyde by a new modification of the Nef reaction in which the nitroheptane is adsorbed on to basic alumina, and the heptaldehyde eluted with ether 48 hours later A complementary method involves the oxidative cleavage of nitronate anions under very mild conditions using t-butyl hydroperoxide and a vanadium catalyst. This method was exploited to provide an improved route to the prostaglandin intermediate anri-7-(diethoxymethyl)-5-norbornen-2-one (8) (Scheme 25). 

A stereospecific anionic polymerization of acetaldehyde was originally reported in 1960 [343, 344]. Two alkali metal compounds [341] and an organozinc [342] one were used as the initiators. Trialkylaluminum and triarylaluminum in heptane also yield crystalline, isotactic polymers from acetaldehyde, heptaldehyde, and propionaldehyde at -80°C [343]. Aluminum oxide, activated by diethylzinc, yields stereoblock crystalline polymers from various aldehydes [342, 344], Lithium alkoxide formed polyacetaldehyde is insoluble in common solvents. It melts at 165°C [341],... 

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