Heavy-atom kinetic isotope effects and mechanism of the acid-catalyzed o-semidine and p-semidine rearrangements and disproportionation of 4,4'-dichlorohydrazobenzene

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6855644

Rhee, E S.J.

In acidic 60% dioxane solution at 0/sup 0/C, 4,4'-dichlorohydrazobenzene (14) underwent concurrent disproportionation to form p-chloroaniline and 4,4'-dichloroazobenzene and o- and p-semidine rearrangement. In the p-semidine rearrangement one of the chlorine atoms of 14 is displaced, in essence, as Cl/sup +/. This requires participation of a second molecule of 14 in a redox reaction. The overall fate of 14, therefore, was to give 11% of o- and 12% of p-semidine rearrangement (along with 12% of 4,4'-dichloroazobenzene), and 60% of disproportionation, which accounts for 95% of 14. Nitrogen and carbon kinetic isotope effects (KIE) were determined for each of these reactions, with the use of (/sup 15/N,/sup 15/N')14, (2-/sup 14/C)14,(4-/sup 14/C)14, and (4,4'-/sup 13/C/sub 2/)14. Isotope ratios were measured in the trifluoroacetyl derivatives with a combination of scintillation counting, whole-molecule-ion mass spectrometry (WMMS), and isotope-ratio mass spectrometry (IRMS), and in no care was a KIE other than unity obtained. These results show that o-semidine formation from 14 complies with the expectation that a (1,3)-sigmatropic shift should not be a concerted process. Although a concerted (1,5)-sigmatropic shift is possible, the p-semidine results suggest that the p-semidine rearrangement of 14 does not proceed by a concerted process. However, in this case, the relevant KIE are for a bond-forming reaction, so that a firm decision either for or against concertedness is not possible. Finally, the results indicate that disproportionation involves one (or both) of the two semidine rearrangement intermediates. The most likely one is that of the p-semidine rearrangement.

• Research Organization: Texas Tech Univ., Lubbock (USA)
• OSTI ID: 6855644
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
AROMATICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 13
CARBON 14
CARBON ISOTOPES
CHEMICAL REACTIONS
CHLORINATED AROMATIC HYDROCARBONS
DECOMPOSITION
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HALOGENATED AROMATIC HYDROCARBONS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
NITROGEN 15
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RADIOISOTOPES
STABLE ISOTOPES
YEARS LIVING RADIOISOTOPES