General TRIPLE

A refinement of the ENDOR experiment is electron-nnclear-nnclear triple resonance, now commonly denoted TRIPLE. In TRIPLE experiments one monitors the effect of a simnltaneons excitation of two nnclear spm transitions on the level of the EPR absorption. Two versions, known as special TRIPLE (ST) and general TRIPLE (GT), are rontinely perfonned on connnercially available spectrometers. 

Biehl R, Plato M and Mdbius K 1975 General TRIPLE resonance on free radicals in solution. 

Still, it is true that in general triple bonds are more susceptible to nucleophilic and less to electrophilic attack than double bonds, in spite of their higher electron density. One explanation is that the electrons in the triple bond are held more tightly... 

Upon treatment of 2,5-dihydro-1,2,3,5-thiatriazole 1-oxides with sodium or potassium (4.20.5.1) in 1,2-dimethoxyethane 2,5-dihydro-l,2,3,5-thiatriazol-5-yl radicals are formed which have been studied by means of ESR, ENDOR, and general triple resonance spectroscopy <90JCS(P2)1619>. 

Dihydro-l, 2,3,5-thiatriazole 1-oxide radicals were generated from the thiatriazole oxides upon hydrogen abstraction in the reaction with thermally formed bis(4-methylphenyl)aminyl (4.20.5.1). Only radicals with aryl substituents in positions two and four are persistent, radicals with alkyl groups in these positions could not be detected. The radicals were investigated by ESR, ENDOR, and general triple resonance spectroscopy <92MRC84>. 

The data on electron spin resonance (ESR), electron-nuclear double resonance (ENDOR), and general triple resonance spectroscopy for 2,5-dihydro-l,2,3,5-thiatriazole-5-yl radicals was reviewed by Holm and Larsen <1996CHEC-II(4)733>. There are no new data on this subject. 

In general, triple stage quadrupole mass spectrometer with ESI in positive ion mode is perceived as the most appropriate MS technique available at present for small—mostly basic—molecules and was used for the assay of nilotinib [112], sorafenib [115,116], lapatinib [117], sunitinib [113,114], bosutinib [88], vatalanib [119] axitinib [120], vandetanib [118] neratinib [87], and crizotinib [125], The latter assay for crizotinib was developed for preclinical experiments and does not contain... 

Readability refers to the smallest measurement that a balance can indicate and that can be read by an operator when the balance is being used as intended. Generally, triple-beam balances have a readability of 0.1 g, centigram balances have a readability of 0.01 g, and analytical balances have a readability of 0.0001 g. 

Another method that is important for structure assignment is the electron-nuclear-nuclear triple resonance (TRIPLE) spectroscopy (Endeward et al., 1998 Makinen et al., 1998), which is an extension of the ENDOR method. In the general TRIPLE experiment, transitions of different nuclei are driven simultaneously. One ENDOR transition is irradiated saturating rf power at a constant frequency, while the entire ENDOR frequency range is swept to obtain the TRIPLE spectrum. 

Biehl R, Plato M and Mobius K 1975 General TRIPLE resonance on free radicals in solution. Determination of relative signs of isotropic hyperfine coupling constants J, Chem. Phys. 63 3515-22... 

In general, triple bonds are stronger than double or single bonds between the same two atoms and have higher frequencies of vibration (higher wavenumbers) ... 

While g-factors are measured by ESR, there are several methods like ESR, CW and pulsed ENDOR, special and general TRIPLE to determine the strength of the magnetic coupling i.e. hyperfine coupling) between the electronic and nuclear magnetic moments in liquid solution. The method chosen therefore depends both on the system and the available equipment. The various possibilities are summarised in Table 3.1. 

A nucleus with spin / gives rise to 21 + 1 hyperfine lines in ESR while only two lines occur in the ENDOR specttum corresponding to the electronic quantum numbers ms = /2 for an 5 = V2 species. The relative signs of several isotropic hyperfine coupling constants in a radical can be determined by the general TRIPLE method as described in Chapter 2. The number of equivalent nuclei in the radical systems discussed below can be obtained from the line intensities in ESR, Special TRIPLE, and pulsed ENDOR, but usually not from CW-ENDOR for reasons discussed in the previous chapter. 

INDO calculations. Flash phot. EPR study. Relative signs determined by general triple resonar ice. ... 

EPR spectroscopists together with more accurate values for other larger hyperfine coupling constants. The application of the general TRIPLE technique has enabled relative values to be obtained for the hyperfine coupling constants which has proved to be of great help in the assignment of the values. 

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