Kinetics and mechanism for oxime formation from 4-dimethylaminobenzaldehyde and 4-trimethylammoniobenzaldehyde iodide

✍ Scribed by A. Malpica; M. Calzadilla; T. C. Cordova; S. Torres; G. H. Saulny

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 131 KB
• Volume: 31
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1999)31:5<387::aid-kin8>3.0.co;2-v

✦ Synopsis

The following lines of evidence establish that oxime formation from 4-dimethylaminobenzaldehyde and 4-trimethylammoniobenzaldehyde iodide occurs with a simple twostep mechanism. The pH-rate profile for the reaction of 4-trimethylammoniobenzaldehyde iodide exhibits, in order of decreasing pH, a negative deviation at pH near 2.0, corresponding to a transition from rate-determining step carbinolamine dehydration with acid catalysis to the uncatalyzed carbinolamine formation. In the case of the reaction of 4-dimethylaminobenzaldehyde, the pH-profile exhibits, in order of decreasing pH, a positive deviation at pH near 3.5 and then a negative deviation at pH near 2.0. These deviations have been interpreted in terms of i) transition of the rate-determining step, and ii) protolytic equilibrium of the substrate.