Tetrazine experiments

The time-resolved solvation of s-tetrazine in propylene carbonate is studied by ultrafast transient hole burning. In agreement with mode-coupling theory, the temperature dependence of the average relaxation dme follows a power law in which the critical temperature and exponent are the same as in other relaxation experiments. Our recent theory for solvation by mechanical relaxation provides a unified and quantitative explanation of both the subpicosecond phonon-induced relaxation and the slower structural relaxation. 

Attack of hydrazine on 1,2,4,5-tetrazines affords primarily ring-opened products, but these recyclize to 1,2,4,5-tetrazines to yield hydrazino-l,2,4,5-tetrazines in low yields, as shown by 15N-labeling experiments.216l 219 24,2 ... 

If this is the case, then crossing experiments should be successful in trapping the free components tetrazine and dienophile. This expectation is fully met. As Scheme 52 shows, both fragments of the yellow compound (295) obtained from 3-p-anisyl-l,2,4,5-tetrazine and ketene A,A-aminal (287) could be trapped by 3-p-chlorophenyl-l,2,4,5-tetrazine (297) to give a mixture of pyridazines (298) ... 

In a similar competition experiment, dipole (295) reacted in the presence of 9.5 equivalents of cyclooctyne to yield a 92 8 mixture of (300) and (301) besides the cycloaddition product of tetrazine and cyclooctyne. These crossing experiments prove beyond doubt that the yellow compound (295) in this system cannot be an intermediate in the cycloaddition reactions. Furthermore, all yellow dipolar species isolated dissolve with the typical violet color of tetrazines and yield the... 

Based on the H NMR and NOE experiments data, it was concluded that the tetrahydrotetra-zine ring of 3-phenyl-1,2,3,4-tetrahydro-1,7-dimethyl-6-oxo-27/,47/-[l,2,4]triazino-[4,3-h][ 1,2,4,5] tetrazine (2) adopts a half-chair conformation (Figure 1). The ring is found to be more flattened in DMSO-dfi than in CDCI3 <88T2249>. 

A high-performance liquid chromatographic/atmospheric pressure chemical ionization-mass spectrometric (HPLC/APCI-MS) method has been developed for the determination of the pesticide clofentezine (3,6-bis(2-chlorophenyl)-l,2,4.5-tetrazine) in plum-, strawberry-, and blackcurrant-based fruit drinks <1995RCM1441>. The structural characterization and the mass spectrometric behavior of pyridazinofurocoumarins, prepared by the inverse electron demand Diels-Alder reaction between furocoumarinones and 3,6-bis(methoxycarbonyl)-l,2,4,5-tetrazine, were studied under electron ionization conditions via sequential product ion fragmentation experiments <2004RCM564>. 

These states can be used to store population data and to perform hole-burning experiments. Experiments of this type have been performed with the probe molecule 3,6-dimethyl-l,2,4,5-tetrazine in a series of -alkane host materials <1996MCL97>. 

The difunctionality of NH2 moiety in the methylhydrazine derivatives has also been underlined by the reaction of (156) with trimethylorthobenzoate to afford the l-phospha-2,3,5,6-tetrazine derivative (163), which on oxidation with benzoquinone can be transformed to the radical species (164). EPR and ENDOR spectroscopic experiments clearly point to a spin polarization through the spirocyclic phosphorus atom to the other phosphorus and nitrogen nuclei in the phosphazene ring of (164). ... 

Time-resolved laser-induced fluorescence experiments have demonstrated that the photodissociation of T-Ar is preceded by intramolecular vibrational redistribution (IVR) processes in which the pumped level C. develops into levels C of the complex which are not accessible by optical excitation because they include highly excited van der Waals vibrations. The isoenergetic levels C and C of the cluster are characterized by different vibronic states of the tetrazine moiety. 

Very few experiments providing direct information about the pathways of intramolecular energy flow in van der Waals complexes have been reported to date. In most cases studied so far, distinct channels for IVR and vibrational predissociation (VP) could not be detected separately. Among the polyatomic van der Waals complexes the cluster T Ar of s-tetrazine and argon is one of the few favourable exceptions. It exhibits several channels for... 

Time-resolved experiments revealed that each of the observed VP processes is preceded by at least one IVR step in which the vibrational energy initially present in a ring mode is redistributed between the vibrational modes of tetrazine and the van der Waals vibrations. During such an IVR process the initially prepared state of the complex develops into a state from which the complex may dissociate. The cluster states and are characterized by vibronic states v and v of the tetrazine molecule. The energy difference (e - e ) between the molecular states v and v is taken up by the relative motion of the two constituents of the complex as vdW vibrational energy. Subsequent dissociation of the complex leads to the formation of electronically excited tetrazine in a specific vibronic state... 

The two theories therefore predict much different appearance kinetics for individual vibronic states of solute/solvent clusters generated by IVR and the bare chromophore molecule generated by VP. While the interpretation of wavelength and time resolved measurements does not depend on the theoretical model imposed or envisioned, the interpretation of the cw experiments is indeed highly model dependent. Thus, in the absence of temporal resolution, the assumption of only parallel or only serial relaxation processes is important for the data interpretation. The question of serial yLLi parallel processes for vibronic dynamics can in any cases be uniquely answered by time resolved studies. Indeed, we have shown zpreviously for tetrazine(Ar)i,2b and herein for aniline(Ar)i, (N2)i, (CH4)i, that the serial IVR/VP process is the appropriate one. 

Studies of IVR and VP in molecular clusters available in the literature come from the laboratories of Levy,. 5 ito,6 Soep, Rice,8 Paramenter,9 Rettschnick,iO and Bernstein.il In most of these instances cw (pulse width greater than 5 ns) experiments are performed on the clusters and dynamical behavior is inferred from the dispersed emission. Some time resolved dynamical studies have recently appeared on tetrazine/argon,8.l0 p-difluorobenzene/argon, the dimethyltetrazine dimer,5.i2 and the benzene/phenol dimeri3 which will be briefly discussed below. 

Furthermore, experiments in which model reactions were performed in cell media and in cell lysate produced >80% yield of adduct (analyzed by ESI-MS against an internal standard), indicating that the reaction is tolerant to a broad range of biological functionality. In spite of these encouraging results, 3,6-di-(2-pyridyl)-5-tetrazine was also observed to undergo... 

Hydrazine hydrate is known to react with acetonitrile in the presence of sulfur or ethanol to form 4-amino-3,5-dimethyl-l,2,4-triazole or 3,6-disubstitued-l,2-dihydro-l,2,4,5-tetrazines. The initial product, which is disubstituted l,2-dihydro-l,2,4,5-tetrazine, is readily oxidized to the pink colored 1,2,4,5-tetrazine it may also rearrange at elevated temperature or on treatment with an acid to the corresponding 1,2,4-triazole. The triazole compound is obtained by the reaction of hydrazine hydrate and acetonitrile in the presence of CO2. The presence of CO2 in the formation of the six-membered ring intermediate is essential, and has been confirmed by repeating the experiments in the absence of CO2. However, the exact role of CO2 in this reaction is not clear. Figure 6.1 gives a possible mechanism for the formation of the triazole from hydrazinium hydrazine carboxylate and acetonitrile. 

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