کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9605467 | 44101 | 2005 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Reaction of singlet molecular oxygen, O2(1Îg), with the Cinchona tree alkaloids
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
بیو مهندسی (مهندسی زیستی)
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Reaction of singlet molecular oxygen, O2(1Îg), with the Cinchona tree alkaloids Reaction of singlet molecular oxygen, O2(1Îg), with the Cinchona tree alkaloids](/preview/png/9605467.png)
چکیده انگلیسی
Detection of O2(1Îg) emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, kT, and the reactive reaction rate constant, kR, for the reaction between singlet oxygen and the Cinchona tree alkaloids, cinchonidine, cinchonine, quinine and quinidine in several solvents. In most solvents, the kT values were close to 107 Mâ1 sâ1, indicating that these compounds are good singlet oxygen quenchers. The reactive rate constants are smaller than 104 Mâ1 sâ1, implying that quenching is essentially a physical process. The analysis of solvent effect on kT by using LSER equations indicates that singlet oxygen deactivation by these drugs is accelerated by solvents with large Ï* and β values, being inhibited by hydrogen bond donor (HBD) solvents. Correlations employing theoretical solvent parameters, TLSER, give similar results. These data support the formation of an exciplex with charge transfer character, resulting from the singlet oxygen electrophilic attack on the quinuclidine moiety nitrogen. In most solvents, cinchonidine is more reactive than cinchonine and quinine is more reactive than quinidine although reactivity differences are small and only in a few solvents kT values of the S,R-isomer are about twice than those of R,S-isomer. The higher reactivity of S,R-isomers in these solvents is explained by the geometrically favorable intra-exciplex stabilizing interaction between the non-bonded pernitrone oxygen and the hydrogen of the hydroxyl substituent at C(9).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 175, Issues 2â3, 31 October 2005, Pages 146-153
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 175, Issues 2â3, 31 October 2005, Pages 146-153
نویسندگان
Else Lemp, Germán Günther, Rafael Castro, Manuel Curitol, Antonio L. Zanocco,