Mechanisms of Lactone Hydrolysis in Neutral and Alkaline Conditions

Abstract

The neutral and base-catalyzed hydrolysis of nine carboxylic acid esters was studied using a hybrid supermolecule-PCM approach including six explicit water molecules. The molecules studied included two linear esters, four β-lactones, two γ-lactones, and one δ-lactone: ethyl acetate and methyl formate, β-propiolactone, β-butyrolactone, β-isovalerolactone, diketene (4-methyleneoxetan-2-one), γ-butyrolactone, 2(5H)-furanone, and δ-valerolactone. DFT and ab initio methods were used to analyze the features of the various possible hydrolysis mechanisms. For all compounds, reasonable to very good qualitative and quantitative agreement with experimental work was found, and evidence is provided to support long-standing hypotheses regarding the role of solvent molecule as a base catalyst. In addition, novel evidence is presented for the existence of an elimination-addition mechanism in the basic hydrolysis of diketene. A parallel work addresses the acid-catalyzed hydrolysis of lactones.

Quantitative Determination of Andrographolide and Related Compounds in Andrographis paniculata Extracts and Biological Evaluation of Their Anti-Inflammatory Activity

“…Nevertheless, for mixtures such as B and C where the quantity of 2 is not negligible, the inhibitory activity increases. These results could explain those reported in the literature [31], showing that there were other compounds than andrographolide in A. paniculata extracts that act as an immunostimulant, and we proved herein that there was a complementary activity of 2 at the studied concentrations.…”

“…Further identification by NMR spectroscopy ( 1 H, 13 (Figure 4) were obtained by treatment of 1 according to the procedure described in the literature [30] (Scheme 1). Compound 7 came from the standard isomerization of Compound 5 and the semi-synthetic Compounds 8 and 9 were obtained after treatment of 1 with MeONa in MeOH [31] at room temperature (Scheme 2) according to the mechanism proposed in Scheme 3. Compound 7 came from the standard isomerization of Compound 5 and the semi-synthetic Compounds 8 and 9 were obtained after treatment of 1 with MeONa in MeOH [31] at room temperature (Scheme 2) according to the mechanism proposed in Scheme 3.…”

“…Compound 7 came from the standard isomerization of Compound 5 and the semi-synthetic Compounds 8 and 9 were obtained after treatment of 1 with MeONa in MeOH [31] at room temperature (Scheme 2) according to the mechanism proposed in Scheme 3. Compound 7 came from the standard isomerization of Compound 5 and the semi-synthetic Compounds 8 and 9 were obtained after treatment of 1 with MeONa in MeOH [31] at room temperature (Scheme 2) according to the mechanism proposed in Scheme 3. Sample preparations were made according to the following procedure: About 1 mg of crude extract was accurately weighted and methanol was added to obtain a 1 mg•mL −1 solution.…”

Experimental and theoretical studies on the tautomerism and reactivity of isoxazolo[3,4-b]quinolin-3(1H)-ones

“…36 Recently, it has been found that the base-catalysed hydrolysis of esters and lactones proceeds in aqueous solution, and therefore, the structure of the transition state incorporates two water molecules hydrogenbonded to the nucleophile (OH -group), two solvating the incipient charge in the carbonyl group, and one bound to those solvating the hydroxide ion. 37 However, the transformation of 3 to 6 was accomplished with use of an eight-fold excess of powdered NaOH in anhydrous…”

Comparison of Microwave Assisted Thermo-Chemical Procedures in the Production of Adsorbents for Wastewater Treatment

“…The region 1640-1850 cm −1 correspond to C=O vibration characteristic of lactones, esters (triglycerides) or aldehydes that decreased intensity or disappeared after activation with NaOH [18]. Lactones and esters of carboxylic acids are known to undergo hydrolysis under alkaline conditions [19]. The peaks at bandwidths 1540-1610 cm −1 are usually associated to N-C-O symmetric stretch, especially in adsorbents treated with NaOH [20].…”