تفاصيل الوثيقة

نوع الوثيقة : مقال في مجلة دورية 
عنوان الوثيقة :
Solvent effects on ester linkage of 4-nitrophenyl acetate in aqueous and ethanol solutions with imidazole and hydroxide ion as nucleophiles
Solvent effects on ester linkage of 4-nitrophenyl acetate in aqueous and ethanol solutions with imidazole and hydroxide ion as nucleophiles
 
الموضوع : كيمياء 
لغة الوثيقة : الانجليزية 
المستخلص : The reaction of 4-nitrophenyl acetate in aqueous and ethanol solutions with imidazole as a nucleophile has been monitored spectrophotometrically. The second order rate constants of these reactions are 10 times higher in water than in alcoholic solutions. This is attributed to better solvation of the initial state and less solvation of the excited state in the alcohol medium. The entropy of activation in water is more negative indicating the greater structuredness of the excited state in water. In addition to the above, the base hydrolysis reaction of the ester using OH- as a nucleophile in buffered aqueous solutions has been followed spectrophotometrically as a function of pH The observed pseudo first order rate constant obeys the relationship k obs=ko+kOH [OH-] where ko represents the water reactions and the buffer dependent rate constant, and kOH is the rate constant for the OH- catalyzed (specific base) reaction. For both cases, a mechanism involving a tetrahedral intermediate and in which the nucleophile attacks at the electrophillic carbon of the ester C=O is proposed. 
ردمد : 0376-4710 
اسم الدورية : Indian Journal of Chemistry - Section A Inorganic, Physical, Theoretical and Analytical Chemistry 
المجلد : 47 
العدد : 10 
سنة النشر : 2008 هـ
2008 م 
عدد الصفحات : 6 
نوع المقالة : مقالة علمية 
تاريخ الاضافة على الموقع : Thursday, October 15, 2009 

الباحثون

اسم الباحث (عربي)اسم الباحث (انجليزي)نوع الباحثالمرتبة العلميةالبريد الالكتروني
سهام سليمان ابراهيم الطريريAl-Terairy, Seham Sباحثدكتوراهalterary_seham@yahoo.fr
سالم أحمد صالح باسيفBasaif, Sباحثدكتوراهsbasaif@yahoo.com
عباس عباس محمدالسعيد العوضيEl-El-Awady, A.Aباحثدكتوراهabbaselawady@hotmail.com

الرجوع إلى صفحة الأبحاث