jV-Aryldiazoamides undergo facile intramolecular aromatic substitution to form 2(3/f)-indolinones in high yield when these reactions are performed in the presence of a catalytic amount of rhodium® acetate. Diazoacetamides react smoothly at room temperature in dichloromethane, whereas the corresponding less reactive diazoacetoacetamides respond in refluxing benzene. A meta methoxy substituent directs substitution solely to its para position, but a meta methyl substituent offers virtually no selectivity for substitution. JV-a-Naphthyldiazoacetamide undergoes exclusive intramolecular substitution at the /3-position. The perfluororesinsulfonic acid Nafion-H also catalyzes the decomposition of N-aryldiazoacetamides, but not IV-aryldiazoacetoacetamides, and yields of 2indolinones are even greater than those obtained with rhodium carboxylate catalysis even though higher reaction temperatures are required to initiate decomposition.
Ascorbic acid reacts with arenediazonium salts to form stable compounds whose structures have been spectroscopically identified as 3-0-arenediazoascorbic acids. The pK, values of the p-nitro-and p-chlorobenzenediazo derivatives are 10.2 and 10.1, respectively, which also correspond to arenediazonium ion attachment at the 3-hydroxyl position of ascorbic acid. These diazo ethers are stable in the pH range of 3 to 11, and they are resistant to nucleophilic displacement and electron-transfer reactions that commonly occur with the unassociated diazonium ions. Reaction rates for diazo ether formation are first order in ascorbic acid and arenediazonium ion concentrations, and they exhibit inverse first-order dependence on the hydrogen ion concentration over the pH range of 6.0-8.0.
Students at two-year colleges and small four-year colleges have often obtained their exposure to NMR spectroscopy through “canned” spectra because the cost of an NMR spectrometer, particularly a high-field spectrometer, is prohibitive in these environments. This article describes the design of a NMR site at Trinity University in which spectral data from student samples from community colleges and several four-year colleges are obtained on a 300 MHz NMR spectrometer. The unprocessed free induction decay (FID) is distributed to the students via the Internet and then processed by the students at their local institutions. The success of the NMR site at one two-year college, Palo Alto College, is described along with details of the experiments chosen for analysis. Two other two-year colleges, San Antonio College and Northwest Vista College, provide additional information about the effectiveness of the site.
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