Enlarged deuterium isotope effects in oxyanion-catalyzed 1,3 proton transfer competing with 1,2 elimination as a probe of a common tightly hydrogen-bonded intermediate

Journal Article · Wed Feb 23 04:00:00 EST 1983 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00342a035· OSTI ID:6164076

Thibblin, A

The reaction of 1-(2-acetoxy-2-propyl)indene (1-h) or 1-(2-acetoxy-2-propyl)(1,3-/sup 2/H/sub 2/)indene (1-d) with p-NO/sub 2/PhO/sup -/ in methanol buffered with p-NO/sub 2/PhOH results in base-catalyzed 1,3 proton transfer, yielding 3-(2-acetoxy-2-propyl)indene (2-h) and 3-(2-acetoxy-2-propyl)(1,1-/sup 2/H/sub 2/)indene (2-d), respectively, in competition with base-promoted 1,2 elimination producing 1-isopropylideneindene (3-h) and 1-isopropylidene(3-/sup 2/H)indene (3-d), respectively. The overall deuterium isotope effect on the reaction of 1 was measured as (k/sub 12//sup H/ + k/sub 13//sup H/)/(k/sub 12//sup D/ + k/sub 13//sup D/) = 5.2, which is composed of the rearrangement isotope effect k/sub 12//sup H//k/sub 12//sup D/ = 12.2 +- 1.0 and the elimination isotope effect k/sub 13//sup H//k/sub 13//sup D/ = 3.6. The enlarged rearrangement isotope effect shows that the intramolecularity of the 1,3 proton-transfer reaction is substantial. The intramolecularity was determined as ca. 87% for (p-NO/sub 2/PhOH) = 0.24 M and ca. 80% for (p-NO/sub 2/PhOH) = 0.71 M by analyzing the /sup 2/H content of the product 2-d. The amplified isotope effect on the 1,3-prototropic shift together with the attenuated elimination isotope effect shows that the two reactions are coupled via at least one common intermediate, which is concluded to be a tightly hydrogen-bonded complex between the protonated base and the carbanion. An increase in basicity of the oxyanion favors elimination at the expense of rearrangement. Reaction of 2-h and 2-d predominantly give 1,4 elimination accompanied by a trace of competing 1,3 proton transfer. The isotope effect k/sub 23//sup H//k/sub 23//sup D/ was measured to 2.5; it is small owing to a large amount of internal return.

• Research Organization: Univ. of Uppsala, Sweden
• OSTI ID: 6164076
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 105:4; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
AROMATICS
CHEMICAL REACTIONS
CONDENSED AROMATICS
DATA
DEUTERIUM
EXPERIMENTAL DATA
HYDROCARBONS
HYDROGEN ISOTOPES
INDENE
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
REACTION KINETICS
STABLE ISOTOPES