Diazoacetaldehyde: completion of the rate profile for hydration of its photo-Wolff rearrangement product, ketene, in aqueous solution and kinetics and mechanism of acid-catalyzed hydrolysis of the diazoaldehyde
Y. Chiang et al., Diazoacetaldehyde: completion of the rate profile for hydration of its photo-Wolff rearrangement product, ketene, in aqueous solution and kinetics and mechanism of acid-catalyzed hydrolysis of the diazoaldehyde, J CHEM S P2, (6), 1999, pp. 1107-1109
Citations number
18
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
Ketene was generated flash photolytically by the photo-Wolff reaction of di
azoacetaldehyde and rates of its hydration to acetic acid were measured in
dilute aqueous sodium hydroxide solution. The results give the isotope effe
ct, k(HO)/k(DO) = 0.87, on the hydroxide-ion catalytic coefficient for this
reaction, and, together with literature information, they provide a comple
te rate law for the hydration of ketene in aqueous solution promoted by sol
vent related species: k(obs)/s(-1) = 1.01 x 10(4)[H+] + 3.65 x 10(1) + 5.26
x 10(4)[HO-]. Rates of hydrolysis of diazoacetaldehyde in dilute perchlori
c acid solution were also measured and an inverse hydronium ion isotope eff
ect was found: k(H)(+)/k(D)(+) = 0.55. That, plus the fact that hydrogen ex
change of the diazo hydrogen atom of diazoacetaldehyde takes place more rap
idly than its hydrolysis, shows that hydrolysis occurs through a mechanism
involving pre-equilibrium protonation of diazo carbon followed by rate-dete
rmining loss of nitrogen.