TY - JOUR
T1 - A deep insight into the mechanism of theacid-catalyzed rearrangement of the Z-phenylhydrazoneof 5-amino-3-benzoyl- 1,2,4-oxadiazole in a non-polar solvent
AU - Frenna, Vincenzo
AU - Fontana, Gianfranco
AU - D'Anna, Francesca
AU - Marullo, Salvatore
AU - Macaluso, Gabriella
AU - Macaluso, Gabriella
AU - Marullo, Salvatore
AU - Frenna, Vincenzo
AU - D'Anna, Francesca
AU - Fontana, Gianfranco
AU - Spinelli, Domenico
PY - 2011
Y1 - 2011
N2 - The conversion of the Z-phenylhydrazone of 5-amino-3-benzoyl-1,2,4- oxadiazole (1a) into the relevant 1,2,3-triazole (2a) has been quantitatively studied in toluene in the presence of several halogenoacetic acids (HAAs, 3a-h). Again, the occurrence of two reaction pathways has been pointed out: they require one or two moles of acid, respectively, thus repeating the situation previously observed in the presence of trichloroacetic acid. The observed rate constant ratios (kIII/kII) are only slightly affected by the nature of the acid used. To gain a deeper insight into the action of the acids used we have measured the association constants of the HAAs (3a-h) with 4-nitroaniline (4) in toluene. Also in this case, the formation of two complexes requiring one (K2) or two (K3) moles of acid has been evidenced, but now the K3/K2 ratios are significantly affected by the strength of the acid examined. The variation of the K 3/K2 ratios larger than those concerning the k III/kII ratios appears useful to enlighten the very nature of the acid-catalyzed pathways in toluene, which has been elucidated also carrying out the rearrangement in the presence of mixtures of tribromo- and trichloro-acetic acids at different concentrations.
AB - The conversion of the Z-phenylhydrazone of 5-amino-3-benzoyl-1,2,4- oxadiazole (1a) into the relevant 1,2,3-triazole (2a) has been quantitatively studied in toluene in the presence of several halogenoacetic acids (HAAs, 3a-h). Again, the occurrence of two reaction pathways has been pointed out: they require one or two moles of acid, respectively, thus repeating the situation previously observed in the presence of trichloroacetic acid. The observed rate constant ratios (kIII/kII) are only slightly affected by the nature of the acid used. To gain a deeper insight into the action of the acids used we have measured the association constants of the HAAs (3a-h) with 4-nitroaniline (4) in toluene. Also in this case, the formation of two complexes requiring one (K2) or two (K3) moles of acid has been evidenced, but now the K3/K2 ratios are significantly affected by the strength of the acid examined. The variation of the K 3/K2 ratios larger than those concerning the k III/kII ratios appears useful to enlighten the very nature of the acid-catalyzed pathways in toluene, which has been elucidated also carrying out the rearrangement in the presence of mixtures of tribromo- and trichloro-acetic acids at different concentrations.
UR - http://hdl.handle.net/10447/53117
M3 - Article
VL - 24
SP - 185
EP - 192
JO - Journal of Physical Organic Chemistry
JF - Journal of Physical Organic Chemistry
SN - 0894-3230
ER -