Basicity constants of cyclopolymethylenetetrazoles in formic acid solutions

Erlich, Ronald H.; Popov, Alexander I.

doi:10.1021/j100697a019

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“…Some intramolecular analogs of the preferred mechanism 4 for the metal ion catalyzed exchange of V are not excluded by the kinetics. In one variation (eq 11) (V)Cu2+(H20)"_i + OH-X (V)Cu0H+(H20)*_2 + h2o XI (11) XI -> (VII)Cu2+(H20)"_2(HD0) -> products 1/JTcuT Cu2+(H20)n + V:?=±-(V)Cu2+(H,0)"_l X X + :B -4-(VII)Cu2+(H20)"_1 ->--VI (9) this exchange. If both OHand water can act as the attacking base (B) to remove the proton at C5 from the intermediate l-methyltetrazole-Cu2+ complex (X), then, assuming that the first step of mechanism 9 is a rapid preequilibrium and that other processes are not important, the rate is:…”

Section: Results and Interpretationmentioning

confidence: 99%

Dependence of mechanism on pH for deuterium-hydrogen exchange in 1-methyltetrazole-5-d. Transition metal ion catalysis of a deprotonation process

1972

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pared from the monoetherates by adding the more polar solvent and distilling out the ether under vacuum.The complete removal of ether from the THF solutions required evaporation to dryness twice, followed by dilution with enough THF to bring the sample to the required concentration.Samples for electronic spectra were transferred to evacuated cells by means of breakseal tubes. Spectra were run at approximately 10-2 and 10~3 M using a 1.0-mm cell equipped with a removable 0.9-mm spacer. The spectra were recorded on a Cary 14 spectrophotometer.The nmr samples were filtered through a sintered glass filter into an nmr tube attached to the vacuum apparatus and sealed under vacuum.Spectra were recorded on a Varían HA 100 spectrometer in frequency sweep mode using solvent peaks for a lock. Frequency measurements were made using a frequency counter and the chemical shifts were referenced to TMS by adding the chemical shift of the lock peak. In THF and HMPA the methylene protons could not be observed because of overlap with the solvent peaks.In the case of THF this was remedied by the use of THF-c/g as a solvent. TMS was used for a lock in these samples.Temperatures were measured using the Varian-supplied methanol and ethylene glycol samples. Frequency measurements of the methanol peaks in the -5 to +10°range were not reproducible be-cause the peaks are very broad. Interpolation was therefore necessary. In the vicinity of 40°, temperature measurements with the two samples agreed to ± 1 °.Chemical Shifts of Naphthalene in THF and HMPA. The 100-MHz spectra of 0.20 M solutions of naphthalene in CCU, THF, and HMPA were obtained. The patterns were all very similar, but reasonably large shifts in the a and ß proton patterns were apparent.Using the value of Cooper and Manatt51 for the chemical shift between the a and ß protons (35.7 Hz) and the midpoint between their patterns in the CC14 spectrum (7.56 ppm), the chemical shifts are calculated to be 7.74 and 7.38 ppm, respectively, for the 0.2 M solution.52 In THF the a and ß patterns were 0.06 and 0.04 ppm downfield from the corresponding patterns in CC14. The a and ß chemical shifts in THF are then approximately 7.80 and 7.42 ppm, respectively. In HMPA the patterns were shifted downfield 0.22 and 0.12 ppm, making the approximate chemical shifts 7. 96 and 7.50 PPm.

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Section: Results and Interpretationmentioning

confidence: 99%