The mechanism of the aqueous perchloric acid isomerization of oleic acid to γ‐stearolactone

Shepherd, I. S.; Showell, John S.

doi:10.1007/bf02544372

Cited by 12 publications

(6 citation statements)

References 10 publications

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“…Their methodology required vigorous reaction conditions to achieve the necessary isomerization of the ∆9 double bond of oleic acid to the ∆4 position before ring closure resulted in the γ-lactone (Scheme 1). Shepherd and Showell (7) confirmed the mechanism proposed by Showell et al (6) for double bond migration prior to lactonization.…”

supporting

confidence: 60%

Synthesis of δ‐stearolactone from oleic acid

Cermak

Isbell

2000

J Americ Oil Chem Soc

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δ-Stearolactone was prepared from oleic acid using concentrated sulfuric acid under various conditions in the presence of polar, nonparticipating solvents. δ-Stearolactone was formed in as high as 15:1 ratios over the thermodynamic product, γ-lactone, in the presence of methylene chloride, 100% wt/vol, at room temperature with two equivalents of sulfuric acid for 24 h. This procedure is applicable to other olefinic fatty acids such as estolides and fatty acid methyl esters. Temperature plays a role in the regioselectivity of the cyclization for δ-lactone, as lower temperatures (20°C) gave higher δ/γ ratios. At higher temperatures (50°C) in the presence of sulfuric acid and methylene chloride the yield of lactone was 75% but with a δ/γ ratio of only 0.3:1. Cyclization of oleic acid to lactone also occurred with other acids. Oleic acid underwent reaction with perchloric acid, one equivalent, in the absence of solvent at 50°C, which yielded δ-lactone in a modest yield with a 3.1 δ/γ ratio. The same temperature effect was observed with perchloric acid that was observed in the case of sulfuric acid. Because δ-stearolactone is much more reactive than the corresponding fatty acid, fatty acid ester, or γ-lactone, we believe that it will be a useful synthon for many new industrial products including new biodegradable detergents.

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supporting

confidence: 60%

Synthesis of δ‐stearolactone from oleic acid

Cermak

Isbell

2000

J Americ Oil Chem Soc

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“…If the reaction contains sufficient energy, this species will be protonated and establish an equilibrium with the starting unsaturated fatty acid. Since the carbocation can lose a proton at C-6 or at C-4, double-bond migration occurs and has been demonstrated elsewhere (11,12). Under thermodynamically controlled conditions, the carbocation formed at C-4 will be captured by the carboxyl group to form the more stable γ-lactone, with the thermodynamic equilibrium favoring this product.…”

Section: Resultsmentioning

confidence: 94%

“…γ-Lactones have been synthesized previously (10) from meadowfoam fatty acids and mineral acid catalysts utilizing methodology developed by Swern et al (11) and Shepherd and Showell (12). Swern developed a methodology for a perchloric acid-catalyzed isomerization of oleic acid into γ-stearolactone (Scheme 2).…”

mentioning

confidence: 99%

A highly regioselective synthesis of δ‐lactones from meadowfoam fatty acids

Isbell

Plattner

1997

J Americ Oil Chem Soc

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Meadowfoam fatty acids, when treated with mineral acid catalysts in the presence of polar nonparticipating solvents, undergo a facile ring closure to form δ-lactones. Perchloric and sulfuric acids catalyze the cyclization at concentrations of 0.6-13 mole equivalents, both neat and in the presence of solvent. Under constant acid concentrations, methylene chloride was found to increase the rate of reaction, the regioselectivity for the formation of δ-lactone, and the overall yield. In the absence of solvent, increased acid concentration improved the yield of lactone but reduced regioselectivity for the δ-isomer. Solvent polarity plays a significant role in the regioselectivity of the cyclization for δ-lactone, with solvents of higher dielectric strength providing larger δ/γ ratios (38:1) and higher yields up to 92%. JAOCS 74, 153-158 (1997).

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“…Lactonization of oleic acids in acidic conditions has been reported (32,33). This reaction is an acidcatalyzed reaction occurring with or without migration of the double bond.…”

Section: A Closer Look At Mechanistic Pathways Of Polysorbate Degradamentioning

confidence: 97%