Secondary deuterium isotope effects on formyl transfer reactions between sulfur and oxygen nucleophiles

Journal Article · Wed Apr 09 04:00:00 EST 1980 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00528a041· OSTI ID:5130229

Pohl, E R; Hupe, D J

Secondary deuterium isotope effects have been measured for formyl and deuterioformyl transfer between oxygen and sulfur nucleophiles at 25/sup 0/C in aqueous solution. Most data were obtained on p-nitrophenyl formate and deuterioformate, and on p-nitrothiophenyl formate and deuterioformate. The nucleophiles that were used are a series of aromatic and aliphatic thiol anions and oxy anions having a broad range of pK/sub a/ values. The value of k/sub D//k/sub H/ is larger for oxy anion attack (approx. 1.22) on esters than for thiol anion attack (approx. 1.00). The effects on k/sub D//k/sub H/ of changing from an aryl to an alkyl anion nucleophile are discussed. No measurable effect on k/sub D//k/sub H/ is observed with changing nucleophile basicity, suggesting little Hammond postulate type of change in transition-state structure. This lack of change is found even in regions where ..beta../sub nuc/ varies substantially for oxy anions. Data are presented which suggest that the use of absolute values of k/sub D//k/sub H/ for determining transition-state bond orders can give values much different than other indexes of transition-state structure. The possibility that changes in frequencies other than C-H stretching and bending modes may result in a variation in k/sub D//k/sub H/ is considered.

• Research Organization: Univ. of Michigan, Ann Arbor
• OSTI ID: 5130229
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 102:8; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ACYL RADICALS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DATA
DEUTERIUM
ESTERS
EXPERIMENTAL DATA
FORMIC ACID
FORMYL RADICALS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MONOCARBOXYLIC ACIDS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
RADICALS
REACTION KINETICS
STABLE ISOTOPES