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Benzidine rearrangement. XIV. The nitrogen kinetic isotope effect in the acid-catalyzed rearrangement of hydrazobenzene. [0/sup 0/C]

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00453a034· OSTI ID:7104380
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Rearrangement of hydrazobenzene was carried out at 0/sup 0/C in approximately 75 percent aqueous ethanol which was 0.1 M in HCl. Rearrangement products were isolated at 10, 20, 30, and 100 percent extents of rearrangement and converted into nitrogen gas whose /sup 29/N/sub 2///sup 28/N/sub 2/ contents were determined by isotope-ratio mass spectrometry. By this means the rearrangement was found to have a kinetic nitrogen isotope effect (k/sup 14//k/sup 15/) of 1.0203 +- 0.0007, demonstrating that breaking of the N-N bond in this two-proton rearrangement is part of the rate-determining step. The result is inconsistent with two mechanisms of the rearrangement which are found in the literature: the rate-determining formation of C/sub 6/H/sub 5/N/sup +/H/sub 2/N/sup +/H/sub 2/C/sub 6/H/sub 5/ followed by its rapid rearrangement; and rate-determining second protonation at C-1 carbon atom followed by the rearrangement of the ring-protonated dication. The isotope effect result is consistent with two pathways but cannot distinguish between them: preequilibrium diprotonation at the two nitrogen atoms followed by the rate-determining rearrangement of C/sub 6/H/sub 5/N/sup +/H/sub 2/N/sup +/H/sub 2/C/sub 6/H/sub 5/; and the rate-determining concerted scission of the N-N bond and approach of the second proton to C/sub 6/H/sub 5/N/sup +/H/sub 2/NHC/sub 6/H/sub 5/, the second proton being almost but not completely transferred in the transition state.
Research Organization:
Texas Tech. Univ., Lubbock
OSTI ID:
7104380
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 99:11; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ALCOHOLS
AMINES
AROMATICS
AZO COMPOUNDS
BENZIDINE
CATALYSIS
CHEMICAL REACTION KINETICS
ETHANOL
HYDROCHLORIC ACID
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INORGANIC ACIDS
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MASS SPECTROSCOPY
NITROGEN 15
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
REACTION KINETICS
SPECTROSCOPY
STABLE ISOTOPES