The hydrolysis of N-substituted acetimidate esters

Abstract

facilitation of hydrolysis attributable to the 6-methyl and 6-chloro groups in this series.Methyl 2-Formyl, 2-Acetyl-, and 2-Benzoylbenzoates. In the three unsubstituted esters, methyl o-formylbenzoate (111)) methyl o-acetylbenzoate (11)) and methyl o-benzoylbenzoate (I), the alkaline hydrolysis may conceivably proceed via two mechanisms: (1) attack of hydroxide ion at the carbonyl function as in the case of the 6-substituted esters, and (2) the normal attack of the hydroxide ion at the carbomethoxy function. Since Bender has shown that I11 hydrolyzes lo5 faster than methyl p-formylbenzoate the main path undoubtedly involves carbonyl attack.With the unsubstituted benzoyl esters the situation is reversed. Methyl pbenzoylbenzoate hydrolyzes 1.46 times faster than I. Thus attack of hydroxide ion on the carbomethoxy group may be the rate-controlling step for I.The rate of hydrolysis of I1 is intermediate between that of I11 and I. Since I1 and I11 hydrolyze at so much greater rates than does I, the rate-controlling step may be the forward reaction in eq 1. Unfortunately, we have been unable to find a comparative study involving benzophenone, acetopheone, and benzaldehyde in order to estimate the relative rates of such a reaction.Although we were unable to prepare pure samples of the normal methyl esters of 6-methyl-and 6-chloro-2-formylbenzoic acids, mixtures of normal and pseudo esters were obtained. Qualitative tests showed that these esters hydrolyzed more rapidly than did methyl 2-formylbenzoate, but the rates were so rapid that further kinetic work on the ester mixtures was not done. Thus, a steric effect to accelerate the hydrolyses is probably present in these cases also but further work is required before a suitable system for measurement can be found.Acknowledgment. We thank Professor Jack Hine for valuable discussion concerning the kinetic results. (31) M. L. Bender, J. A. Reinstein, M. S. Silver, and R. Mikulak, J . Am. Chem. SOC., 81, 4545 (1965). Methyl 2-Formylbenzoates.serve similar functions, namely, to keep the ester carbonyl group out of the plane of the ring to which it is attached. This nonplanarity facilitates the intramolecular nucleophilic attack of the neighboring 0-function in two ways: (a) there is a more favorable orientation,3 and (b) the carbonyl group carbon of the ester is more electrophilic since there is less distribution of positive charge to the aryl ring. The fact that VI1 hydrolyzes appreciably faster than IV is explained by the greater inductive effect of C1 as compared to CHI on both K and kl, since the steric effect of each should be about the same. 30Methyl 2-Acetylbenzoates. In this series the rates for V and VI11 are also greater than that for the unsubstituted ester I1 but the rate ratios for V (1.4) and VI1(7.4) as compared to I1 are appreciably less than the ratios for IV (4.3) and VI1 (32.2) as compared to I. The steric explanation for the rate increase is similar to that described for the methyl 2-benzoylbenzoates. However, the fact that there is a greater increase in r...

Models for polyurethane hydrolysis under moderately acidic conditions: A comparative study of hydrolysis rates of urethanes, ureas, and amides

“…A relevant case is the comparative hydrolysis of N-substituted acetimidate esters. 33 During acid hydrolysis, the tetrahedral intermediates from addition of water are similar for the imidate (6) and carbamate cleavage of the C= N bond with ethyl N-phenylacetimidate significantly faster than an N-alkylacetimidate. Kinetic analysis showed that addition of water to the N-protonated acetimidates was the key discriminating factor.…”

Poly(dipeptamidinium)‐Salze: Definition und Methoden zur präparativen Herstellung

“…[I], S . 24 Die Stabilitat von Amidinium-Salzen des Strukturtyps 17a bzw. 16a gegeniiber Hydrolyse ist stark vom pH-Wert der Losung abhangig.…”

“…In den NMR-Spektren sind die Signale dieser Endgruppe nicht auszumachen, und es ist moglich, dass die Konstitution dieser Kopfgruppe nicht einheitlich ist. Nach Literaturdaten [24] konnte die Imidthioester-Gruppe zwar die durch die Bedingungen der Polykondensation (gepufferte wasserige Losung pH &7/0") gegebene Hydrolyse-Gefahr uberstehen, doch besteht letztere vor allem auch wiihrend der Aufarbeitung, da dieselbe saure Phasen durchlauft. Es ist wahrscheinlich, dass die Kopfgruppe zumindest zum Teil als primare Amid-Gruppe vorliegt.…”

“…: C 53,66, H 7,77, N 17,90. N C 18,97,H 5,57,CI 28,00,N 22,13,S 25,33;gef. : C 19,11,H 5,66,CI 28,30,N 22.05,S 25,24. Boc-Glycin-thioamid liess sich ebenfalls rnit TsOH .H,O in heissem EtOH entschutzen. Das in 78% Ausbeute erhaltene, plattchenformig kristallisierende Glycin-thioamid-O, -toluolsulfonat) erwies sich laut 'H-NMR und DC als einheitlich und liess sich rnit Amberlite CG-400 (CI--Form) quantitativ in 12 (X = Cl) uherfuhren.…”

“…fur C2,H,,N406S: C 56,08, H 6,55, N 11.37, S 6,51; gef. : C 56,19, H 6.55, N 11,24, S 6,50. b) Ausgrhend uon 14b. Eine Lsg.…”