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The kinetics and mechanism of alkaline hydrolysis of N ‐substituted phthalimides
Author(s) -
Khan M. Niyaz
Publication year - 1987
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550190206
Subject(s) - phthalimide , chemistry , reaction rate constant , phthalimides , substituent , nucleophile , medicinal chemistry , aqueous solution , ionization , hydrolysis , kinetics , alkaline hydrolysis , analytical chemistry (journal) , ion , organic chemistry , physics , quantum mechanics , catalysis
The aqueous cleavage of N ‐(2‐bromoethyl)phthalimide (NBEPH), N ‐(3‐bromopropyl)phthalimide (NBPPH), and N ‐carbethoxyphthalimide (NCPH) have been studied within the [ŌH] range of 5 × 10 −4 M to 2 × 10 −3 M, pH range of 8.82 to 10.62 and 8.06 to 8.66, respectively. The observed pseudo‐first‐order rate constants, k obs , reveal a linear relationship with [ŌH] with essentially zero intercept. The alkaline hydrolysis of N ‐(hydroxymethyl)phthalimide (NHMPH) has been studied within the [ŌH] range of 5.64 × 10 −6 M to 2.0 M. The [OH]‐rate profile reveals that both ionized and nonionized NHMPH are reactive toward ŌH. The second‐order rate constant, k OH , for the reaction of ŌH with non‐ionized NHMPH is ca. 10 4 times larger than that with ionized NHMPH. The values of k OH obtained for NBEPH, NBPPH, NCPH, and nonionized NHMPH show a reasonable linear relationship with Taft substituent constants, and the slope (ρ*) of the plot is 1.01 ± 0.10. The low value of ρ* of 1.01 is attributed to nucleophilic attack as the rate‐limiting. The k OH value for ionized NHMPH reveals nearly 10 3 ‐fold negative deviation from the linear Taft plot.