Benzidine rearrangements. 16. The use of heavy-atom kinetic isotope effects in solving the mechanism of the acid-catalyzed rearrangement of hydrazobenzene. The concerted pathway to benzidine and the nonconcerted pathway to diphenyline

Journal Article · Wed May 05 04:00:00 EDT 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00373a028· OSTI ID:6862781

Shine, H J; Zmuda, H; Park, K H; Kwart, H; Horgan, A G; Brechbiel, M

Kinetic isoptope effects (KIE) in the acid-catalyzed rearrangement of hydrazobenzene to benzidine and diphenyline have been measured. Nitrogen KIE were determined by whole-molecule mass spectrometry on each of the products obtained at low and 100% conversions from mixtures of hydrazobenzene and (/sup 13/N,/sup 15/N') hydrazobenzene. The results were k(/sup 14/N)/k(/sup 15/N) = 1.0222 for benzidine and 1.0633 for diphenyline. Carbon KIE were determined with both /sup 14/C and /sup 13/C labeling, using counting techniques for the former and whole-molecule mass spectrometry for the latter. Again measurements were made on both products isolated from low and 100% conversions. Use of mixtures of hydrazobenzene and (4-/sup 14/C) hydrazobenzene gave k(/sup 12/C)/k(/sup 14/C) = 1.0284 for benzidine and 1.0011 for diphenyline. Use of mixtures of hydrazobenzene and (4,4'-/sup 13/C/sub 2/) hydrazobenzene gave k(/sup 12/C)/k(/sup 13/C) = 1.0209 for benzidine and 1.000 for diphenyline. The results show that the formation of benzidine is a concerted process while the formation of diphenyline is a dissociative process involving the formation of an intermediate (possibly a ..pi.. complex or pair of caged radical ions) in the rate-determining step. Calculations of the KIE were made on simplified models of transition states for concerted and dissociative processes and were found to be in reasonable agreement with the experimental results. In harmony with the concerted formation of benzidine (the major product) we found also by whole-molecule mass spectrometry and with the use of mixtures of hydrazobenzene and (4,4'-/sup 2/H/sub 2/) that the disappearance of hydrazobenzene has an inverse secondary deuterium KIE, k(/sup 1/H)/k(/sup 2/H) = 0.962.

• Research Organization: Texas Tech Univ., Lubbock
• OSTI ID: 6862781
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 104:9; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
AMINES
AROMATICS
BENZIDINE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CARBON 13
CARBON 14
CARBON ISOTOPES
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CONVERSION
DATA
DEUTERIUM
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
INFORMATION
INORGANIC ACIDS
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MINUTES LIVING RADIOISOTOPES
NITROGEN 13
NITROGEN 15
NITROGEN ISOTOPES
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
RADIOISOTOPES
REACTION KINETICS
STABLE ISOTOPES
STEREOCHEMISTRY
SYNTHESIS
YEARS LIVING RADIOISOTOPES