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Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide

The apparent second-order rate constant (k(OH)) for hydroxide-ion-catalyzed conversion of 1 to N-(2'-methoxyphenyl)phthalamate (4) is similar to 10(3)-fold larger than k(OH) for alkaline hydrolysis of N-morpholinobenzamide (2). These results are explained in terms of the reaction scheme 1 ->...

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Main Authors: Ariffin, Azhar, Khan, M.N., Sim, Y.L.
Format: Article
Published: 2008
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QD Chemistry
Online Access:http://eprints.um.edu.my/8067/
http://pubs.acs.org/doi/pdfplus/10.1021/jo702695k
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spelling my.um.eprints.80672019-08-27T06:09:29Z http://eprints.um.edu.my/8067/ Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide Ariffin, Azhar Khan, M.N. Sim, Y.L. QD Chemistry The apparent second-order rate constant (k(OH)) for hydroxide-ion-catalyzed conversion of 1 to N-(2'-methoxyphenyl)phthalamate (4) is similar to 10(3)-fold larger than k(OH) for alkaline hydrolysis of N-morpholinobenzamide (2). These results are explained in terms of the reaction scheme 1 -> 3 -> 4 where 3 represents N-(2'-methoxyphenyl)phthalimide and the values of k(2obs)/k(1obs) Vary from 6.0 x 10(2) to 17 x 10(2) within [NaOH] range of 5.0 x 10(-3) to 2.0 M. Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of 1 decrease from 21.7 x 10(-3) to 15.6 x 10(-3) s(-1) with an increase in ionic strength (by NaCl) from 0.5 to 2.5 M at 0.5 M NaOH and 35 degrees C. The values of k(obs), obtained for alkaline hydrolysis of 2 within [NaOH] range 1.0 x 10(-2) to 2.0 M at 35 degrees C, follow the relationship k(obs) = k(OH)[HO(-)] + k(OH)'[HO(-)](2) with least-squares calculated values of k(OH) and k(OH)' as (6.38 +/- 0.15) x 10(-5) and (4.59 +/- 0.09) x 10(-5) M(-2) s(-1), respectively. A few kinetic runs for aqueous cleavage of 1, N'-morpholino-N-(2'-methoxyphenyl)-5-nitrophthalamide (5) and N'-morpholino-N-(2'-methoxyphenyt)-4-nitrophthalamide (6) at 35 degrees C and 0.05 M NaOH as well as 0.05 M NaOD reveal the solvent deuterium kinetic isotope effect (= k(obs)(H2O)/k(obs)(D2O)) as 1.6 for 1, 1.9 for 5, and 1.8 for 6. Product characterization study on the cleavage of 5, 6, and N-(2'-methoxyphenyl)-4-nitrophthalimide (7) at 0.5 M NaOD in D(2)O solvent shows the imide-intermediate mechanism as the exclusive mechanism. 2008 Article PeerReviewed Ariffin, Azhar and Khan, M.N. and Sim, Y.L. (2008) Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide. Journal of Organic Chemistry, 73 (10). pp. 3730-3737. ISSN 0022-3263 http://pubs.acs.org/doi/pdfplus/10.1021/jo702695k 10.1021/jo702695k
institution Universiti Malaya
building UM Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Malaya
content_source UM Research Repository
url_provider http://eprints.um.edu.my/
topic QD Chemistry
spellingShingle QD Chemistry
Ariffin, Azhar
Khan, M.N.
Sim, Y.L.
Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide
description The apparent second-order rate constant (k(OH)) for hydroxide-ion-catalyzed conversion of 1 to N-(2'-methoxyphenyl)phthalamate (4) is similar to 10(3)-fold larger than k(OH) for alkaline hydrolysis of N-morpholinobenzamide (2). These results are explained in terms of the reaction scheme 1 -> 3 -> 4 where 3 represents N-(2'-methoxyphenyl)phthalimide and the values of k(2obs)/k(1obs) Vary from 6.0 x 10(2) to 17 x 10(2) within [NaOH] range of 5.0 x 10(-3) to 2.0 M. Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of 1 decrease from 21.7 x 10(-3) to 15.6 x 10(-3) s(-1) with an increase in ionic strength (by NaCl) from 0.5 to 2.5 M at 0.5 M NaOH and 35 degrees C. The values of k(obs), obtained for alkaline hydrolysis of 2 within [NaOH] range 1.0 x 10(-2) to 2.0 M at 35 degrees C, follow the relationship k(obs) = k(OH)[HO(-)] + k(OH)'[HO(-)](2) with least-squares calculated values of k(OH) and k(OH)' as (6.38 +/- 0.15) x 10(-5) and (4.59 +/- 0.09) x 10(-5) M(-2) s(-1), respectively. A few kinetic runs for aqueous cleavage of 1, N'-morpholino-N-(2'-methoxyphenyl)-5-nitrophthalamide (5) and N'-morpholino-N-(2'-methoxyphenyt)-4-nitrophthalamide (6) at 35 degrees C and 0.05 M NaOH as well as 0.05 M NaOD reveal the solvent deuterium kinetic isotope effect (= k(obs)(H2O)/k(obs)(D2O)) as 1.6 for 1, 1.9 for 5, and 1.8 for 6. Product characterization study on the cleavage of 5, 6, and N-(2'-methoxyphenyl)-4-nitrophthalimide (7) at 0.5 M NaOD in D(2)O solvent shows the imide-intermediate mechanism as the exclusive mechanism.
format Article
author Ariffin, Azhar
Khan, M.N.
Sim, Y.L.
author_facet Ariffin, Azhar
Khan, M.N.
Sim, Y.L.
author_sort Ariffin, Azhar
title Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide
title_short Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide
title_full Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide
title_fullStr Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide
title_full_unstemmed Kinetics and mechanism of large rate enhancement in the Alkaline Hydrolysis of N '-Morpholino-N-(2'-Methoxyphenyl)Phthalamide
title_sort kinetics and mechanism of large rate enhancement in the alkaline hydrolysis of n '-morpholino-n-(2'-methoxyphenyl)phthalamide
publishDate 2008
url http://eprints.um.edu.my/8067/
http://pubs.acs.org/doi/pdfplus/10.1021/jo702695k
_version_ 1643688209177116672
score 13.211869

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