Kinetic secondary deuterium isotope effects for substituted benzaldehyde cyanohydrin formation

Journal Article · Wed Jul 07 00:00:00 EDT 1976 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00430a032· OSTI ID:7356846

Okano, V; do Amaral, L; Cordes, E H

..cap alpha.. secondary deuterium isotope effects have been measured for the observed rate constants for addition of cyanide ion to a series of substituted benzaldehydes in aqueous solution at 25/sup 0/C. Under the experimental conditions employed, these reactions did not proceed to completion, and the observed isotope effects were corrected to account for the influence of the reverse reaction employing measured equilibrium constants for cyanohydrin formation and previously determined secondary deuterium isotope effect for the equilibrium constant for 4-methoxybenzaldehyde cyanohydrin formation. In the four cases studied, values of k/sub D//k/sub H/ varied from 1.15 to 1.20, only slightly lower than the calculated maximal value for complete formation of the anionic tetrahedral species which is the immediate product of the rate-determining step, 1.21. A trend in isotope effect as a function of substrate reactivity could not be definitively established. The results suffice to establish that addition of cyanide to benzaldehydes proceeds via transition states in which rehybridization of carbonyl carbon to the tetrahedral geometry is nearly complete.

• Research Organization: Univ., Sao Paulo, Brazil
• OSTI ID: 7356846
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 98:14; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ALDEHYDES
CHEMICAL REACTION KINETICS
CYANIDES
DEUTERIUM
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MEDIUM TEMPERATURE
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PH VALUE
REACTION KINETICS
STABLE ISOTOPES