Solvent isotope effects on the kinetics of nucleophilic addition of water to a. beta. -nitrostyrene

Journal Article · Fri Sep 23 00:00:00 EDT 1983 · J. Org. Chem.; (United States)

DOI:https://doi.org/10.1021/jo00167a026· OSTI ID:5557729

Crowell, T I

The hydrolysis rate of 3,4-(methylenedioxy)-..beta..-nitrostyrene (S) has been measured in H/sub 2/O and in 99% D/sub 2/O buffer solutions from pH -0.9 to 10.6. The kinetic solvent isotope effect (KSIE), k(H/sub 2/O)/k(D/sub 2/O), is 6.2 at pH 2.5, where k is independent of pH in both solvents and attains a higher value, approximately 22, at about pH 6.2. The isotope effects k/sub i/(H/sub 2/O)/k/sub i/(D/sub 2/O) on the rate constants for the individual steps of the mechanism have been determined and their contributions to the overall KSIE evaluated. Accordingly, the KSIE on the pH-rate plateau at pH 1-4 can be separated into two factors: 5.0 for K/sub 12/, the ionization constant of S as a pseudo-base in water; and 1.4 for k/sub 3//sup H/, the rate constant for rate-controlling protonation of the resulting anion by H/sub 3/O/sup +/. At pH 6.2, the higher KSIE (7.6) on k/sub 3//sup H/sub 2/O/ becomes important while the uncatalyzed addition of water to the double bond is partly rate controlling. The rate at the midpoint of a proton-inventory plot (49.5% D/sub 2/O) shows a negative deviation from linearity of 18%. 2 figures, 2 tables.

• Research Organization: Univ. of Virginia, Charlottesville
• OSTI ID: 5557729
• Journal Information: J. Org. Chem.; (United States), Journal Name: J. Org. Chem.; (United States) Vol. 48:19; ISSN JOCEA
• 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)
ABSORPTION SPECTRA
ALCOHOLS
AQUEOUS SOLUTIONS
AROMATICS
BUFFERS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DEUTERIUM
DISPERSIONS
EXPERIMENTAL DATA
HEAVY WATER
HYDROCHLORIC ACID
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROLYSIS
HYDROXY COMPOUNDS
INFORMATION
INORGANIC ACIDS
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
LYSIS
METHANOL
MIXTURES
NITRO COMPOUNDS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXYGEN COMPOUNDS
PH VALUE
REACTION KINETICS
SOLUTIONS
SOLVOLYSIS
SPECTRA
STABLE ISOTOPES
WATER