کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1171652 1491181 2006 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Stability of sotolon in acidic and basic aqueous solutions
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
پیش نمایش صفحه اول مقاله
Stability of sotolon in acidic and basic aqueous solutions
چکیده انگلیسی
Up to 50 °C, sotolon 1 slightly decomposed to acetoin 5 in aqueous sodium hydroxide solution under nitrogen and in the absence of light, and this degradation was irreversible, but at 80 °C it was rapidly decomposed according to two other reaction pathways. The first one (kinetic route) was new: it gave rise to the novel 3-methyl-2-oxopent-3-enoic acid 11 by opening of the lactone cycle. The second one (thermodynamic route) was the reverse of the formation of 1 from ethanal 9 and 2-oxobutyric acid 8, giving also propionic acid 10 by decarbonylation of 8. As shown in dilute potassium hydroxide added with potassium fluoride, the initial addition of hydroxide ion to 1 distinguished between the processes at 50 and 80 °C. At 50 °C, the ion added to the soft electrophilic carbon of the conjugated lactone (1,4-addition), whereas at 80 °C, it added to the hard electrophilic carbonyl carbon (1,2-addition). Under acidic conditions, 11 was easily cyclised back to racemic 1, whereas 1 formation from ethanal and 2-oxobutyric acid was very slow and unspecific, as reported previously. Furthermore, 5,5,5[2H3]-3-methyl-2-oxopent-3-enoic acid d3-11 was produced from 1, when its degradation was carried out in sodium deuteroxide at 80 °C. Its cyclisation in deuterated acid solution gave rise to 3-hydroxy-4-methyl-5-[2H3])-methylfuran-2(5H)-one d3-1, which was shown to be chemically and isotopically stable in strong acidic conditions. d3-11 was used as internal standard in a new stable isotope dilution assay method to quantitate 1 in wine. As 1 was shown to decompose slowly to the above degradation products in dilute sodium carbonate at room temperature, but faster in the presence of cupric ion (mainly oxidation to 5), a purification procedure using the favoured partition of hydrophilic 1 in dilute aqueous acid allowed to obtain extracts suitable to quantitate specifically 1. This method allowed the quantitative determination of 1 in Petit and Gros Manseng dry and sweet Jurançon wines (9-24 years ageing), with levels below its olfactive perception threshold (15 μg L−1).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Analytica Chimica Acta - Volume 563, Issues 1–2, 23 March 2006, Pages 365-374
نویسندگان
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