Hydrolysis of imidate esters derived from weakly basic amines. Influences of structure and pH on the partitioning of tetrahedral intermediates

Concurrent general acid and general base catalysis in the hydrolysis of an imidate ester. 3. Ethyl N-p-nitrophenylformimidate

“…At pH >5 and at zero buffer concentration (30 °C, 2% CH3CN-H2O, µ = 0.5 with added KC1), the hydrolysis of the imidate ester obeys the rate law3 £obsd(s-1) = 4.4 X 104[H+] + 0.51 [OH-] + 1.4 X 10~4 (4) Spectrophotometric assay for p-nitroaniline after 6 or more half-lives of hydrolysis indicates that, at zero buffer concentration, the amine is formed in 100% yield at pH <4 and in <3% yield at pH >7.6 The sharp decrease in amine yield at intermediate pH conforms well to eq 2, with a midpoint at pH 5.7. 3 As with many other imidates, the change in the products of hydrolysis occurs in a pH range where there is no concomitant change in the rate law (at pH 7,97% of the reaction still occurs via hydronium ion catalysis), indicating that the product-forming steps are distinct from the rate-determining step.…”

Separation of oil from oily wastewater by sorption and coalescence technique using ethanol grafted polyacrylonitrile

“…In the first step, treatment of the -C N groups with acid in ethanol gave imidate esters [14]. In the second step, the imidate esters yielded amines and esters in acidic solution [15]. The alcoholysis of PANF was carried out as follows: 1 g of PANF was added to a 500 cm 3 round bottom flask (3-neck) with 50 g of ethanol and 16 g of H 2 SO 4 .…”

Synthesis of enantiopure 2‐aryl‐2‐methoxypropionic acids and determination of their absolute configurations by X‐ray crystallography

“…1) 8 (for the preparation of oxazolines and conversion to carboxylic acids) 14,15 (for the mechanism of the hydrolysis of imidate salts). [16][17][18] This method is generally applicable to amides formed from carboxylic acids with a quaternary stereogenic center and amino alcohols. We have therefore applied this method to amides (À)-13a, (À)-15a, (À)-16a, (À)-17a, (À)-18a, (À)-19a, and (þ)-19b as shown in Schemes 1-3.…”

“…The mechanism of the hydrolysis of imidate salts has been well studied (for the mechanism of the hydrolysis of imidate salts). [16][17][18] For example, the hydrolysis of an imidate salt with a mild base like aqueous NaHCO 3 yielded ester, but not amide, indicating that the CÀ ÀN bond cleaves first (for the mechanism of the hydrolysis of imidate salts). 18 Therefore, as shown in Scheme 4, the reaction proceeds through the intermediate 30b, in which the CÀ ÀN bond cleaves first with the participation of water affording ester intermediate 30c.…”