Equilibrium acidities and homolytic bond dissociation enthalpies of m- and p-substituted benzaldoximes and phenyl methyl ketoximes

✍ Scribed by F. G. Bordwell; Yongyu Zhao; Jin-Pei Cheng

• Book ID: 101286235
• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 120 KB
• Volume: 11
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199801)11:1<10::aid-poc967>3.0.co;2-f

✦ Synopsis

The equilibrium acidities in DMSO of nine p-and m-substituted benzaldoximes and eight p-substituted phenyl methyl ketoximes were measured. Estimates of the homolytic bond dissociation energies (BDEs) of the acidic O-H bonds in these compounds were made by combination of their pK HA values with the oxidation potentials of their conjugate bases, E ox (A À ), using the equation BDE = 1.37pK HA 23.06E ox (A À ) 73.3 kcal (1 kcal = 4.184 KJ). Plots of E ox (A À ) vs pK HA for p-substituted benzaldoximes and p-substituted phenyl methyl ketoximes were linear with slopes near unity. Consequently, as required by the above equation, the BDEs estimated for the O-H bonds in these oximes were constant, being 88.3 AE 0.3 and 89.2 AE 0.4 kcal, respectively.