Effects of mixed H2O‐CH3CN solvents on the rate of hydrazinolysis of N‐phenylphthalimide: Spectral and kinetic evidence for the occurrence of N‐aminophthalimide on the reaction path

Ariffin, Azhar; Leng, Sim Yoke; Lan, Lai Chwee; Khan, M. Niyaz

doi:10.1002/kin.20057

Cited by 3 publications

(2 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The change in coplanarity between the o -OMe substituent and the benzene ring due to significant steric hindrance of o -OMe with imide functionality reduces the electron-donating ability by resonance of o -OMe compared to p -OMe. However, the values of k OH seem to be almost insensitive to polar and resonance effects of substituents attached to the leaving aryl group for the reason that k OH values are almost the same for hydrolysis of p -PT and N -(phenyl)phthalimides . This is plausible in view of the reaction mechanism shown in Scheme , which predicts a significant sensitivity of k OH values to substituents of leaving aryl groups only when the k 2 7 step is the rate-determining step.…”

Section: Discussionmentioning

confidence: 93%

Efficient Rate Enhancement Due to Intramolecular General Base (IGB) Assistance in the Hydrolysis of N-(o-Hydroxyphenyl)phthalimide

2007

Self Cite

View full text Add to dashboard Cite

The rates of the hydrolyses of N-(o-hydroxyphenyl)phthalimide (1) and N-(o-methoxyphenyl)phthalimide (2), studied at different pH, show that the hydrolysis of 1 involves intramolecular general base (IGB) assistance where the o-O- group of ionized 1 acts as IGB and H2O as the reactant. The rate enhancement due to the IGB-assisted reaction of H2O with ionized 1 is>8x10(4)-fold. Pseudo-first-order rate constant for the reaction of water with 2 is approximately 2x10(3)-fold smaller than the first-order rate constant (0.10 s-1) for pH-independent hydrolysis of 1 within the pH range of 9.60-10.10. Second-order rate constants (kOH) for hydroxide ion-assisted hydrolysis of ionized 1 and 2 are 3.0 and 29.1 M-1 s-1, respectively. The solvent deuterium kinetic isotope effect (dKIE) on the rate of alkaline hydrolysis of 1 and 2 reveals that the respective values of kOH/kOD are 0.84 and 0.78, where kOD represents the second-order rate constant for DO--assisted cleavage of these imides (1 and 2). The value of kwH2O/kdD2O is 2.04, with kwH2O and kdD2O representing pseudo-first-order rate constants for the reactions of ionized 1 with H2O and D2O, respectively.

show abstract

Section: Discussionmentioning

confidence: 93%

Efficient Rate Enhancement Due to Intramolecular General Base (IGB) Assistance in the Hydrolysis of N-(o-Hydroxyphenyl)phthalimide

2007

Self Cite

View full text Add to dashboard Cite

show abstract

“…The value of secondorder rate constant (k OH ) for hydroxide ion-catalyzed hydrolysis of 6, 36.0 M −1 s −1 (=k 0 /[NaOH], where the k 0 value is calculated from Eq. (6)), is nearly 31% smaller than k OH (= 52.0 M −1 s −1 ) for alkaline hydrolysis of N -(4-methoxyphenyl)phthalimide [8] and k OH (= 51.0 M −1 s −1 ) for alkaline hydrolysis of Nphenylphthalimide [20].…”

Section: Effects Of Mixedmentioning

confidence: 99%

Intramolecular carboxylic group‐assisted cleavage of N‐(2‐hydroxyphenyl)phthalamic acid (7) and N‐(2‐methoxyphenyl)phthalamic acid (8): Absence of intramolecular general acid catalysis due to 2‐OH in 7

Sim

Ariffin

Khan

2006

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

The values of pseudo first-order rate constants (k obs ) for the cleavage of N-(2-hydroxyphenyl)phthalamic acid (7), obtained at 4.9 × 10 −2 M HCl, 35 • C, and within CH 3 CN content range 2-80% (v/v) in mixed aqueous solvent are smaller than k obs for the cleavage of N-(2-methoxyphenyl)phthalamic acid (8) INTRAMOLECULAR CARBOXYLIC GROUP-ASSISTED CLEAVAGE 747 by nearly 1.5-to 2-fold. These observations show the absence of expected intramolecular general acid catalysis due to 2-OH group in 7. The values of k obs for the cleavage of 7 and 8 decrease by more than 20-fold with the increase in the content of CH 3 CN from 2 to 80-82% (v/v) in mixed aqueous solvent. The kinetic data reveal that in acidic aqueous cleavage of 7, N-cyclization (leading to the formation of imide) and O-cyclization (leading to the formation of phthalic anhydride) vary from ∼10 to 15% and ∼90 to 85%, respectively, with the increase in CH 3 CN content from 2 to 80% (v/v). Similar increase in CH 3 CN content causes increase in N-cyclization from ∼0 to 5% and decrease in O-cyclization from ∼100 to 95% in the acidic aqueous cleavage of 8. Some speculative, yet conceivable, reasons for nearly 10 and 0% N-cyclization in the cleavage of respective 7 and 8 at low content of CH 3 CN have been described.

show abstract

Workable Synthetic Route to Functionalized 1,6-Benzodiazocines

Proust¹,

Preston²,

Paquette³

2009

HETEROCYCLES

View full text Add to dashboard Cite

Effects of mixed H₂O‐CH₃CN solvents on the rate of hydrazinolysis of N‐phenylphthalimide: Spectral and kinetic evidence for the occurrence of N‐aminophthalimide on the reaction path

Abstract: Kinetic study on the cleavage of N-phenylphthalimide (NPhPT) in the presence of 0.05 M NH 2 NH 2 and mixed H 2 O-CH 3 CN solvents reveals the occurrence of reaction scheme

Cited by 3 publications

References 20 publications

Efficient Rate Enhancement Due to Intramolecular General Base (IGB) Assistance in the Hydrolysis of N-(o-Hydroxyphenyl)phthalimide

Efficient Rate Enhancement Due to Intramolecular General Base (IGB) Assistance in the Hydrolysis of N-(o-Hydroxyphenyl)phthalimide

Intramolecular carboxylic group‐assisted cleavage of N‐(2‐hydroxyphenyl)phthalamic acid (7) and N‐(2‐methoxyphenyl)phthalamic acid (8): Absence of intramolecular general acid catalysis due to 2‐OH in 7

Workable Synthetic Route to Functionalized 1,6-Benzodiazocines

Contact Info

Product

Resources

About