TPPI

If direct homolysis occurs in the case of tetraphenylphosphonium tetrafloroborate, triphenylphosphonium ylide was expected to function as a photoinitiator of radical polymerization because of its similar structure. Therefore, another milestone was reached by Kondo and colleagues [50] who investigated the use of triphenylphosphonium ethoxycarbonylmethylide (TPPY) (Scheme 22) as an effective photoinitiator for the polym-... 

The proposed mechanism is based on the basis of the fact that ylides (Scheme 23 and Scheme 24) undergo bond fission between the phosphorus atom and the phenyl group in TPPY as reported by Nagao et al. [51] and between the sulfur atom and the phenyl group in POSY as observed in triphenylsulfonium salts [52-55] when they are irradiated by a high-pressure mercury lamp. The phenyl radicals thus produced participate in the initiation of polymerization. 

Applications TPPy-MAB-MS (Ar, N2) was recently used for the analysis of bis(l,2,2,6,6-pentamethyl-4-piperidinyl) sebacate in a PUR-based car paint [71a],... 

Similarly, toluene suspensions of the polystyrene housing of TV sets were examined by means of TPPy-FTMS (300-1200 K) [224], Diphenylether (DPE) was evidenced by peaks at m/z 141, 142 and 170 and decabromobiphenyl (DBBP) by m/z 943 and 864. Decabromodiphenyl ether (DBDPE) was recognised by thermal degradation products around m/z 800... 

Fig. 4. The HNCO-TROSY experiment for recording solely interresidual 1HN, 15N, 13C correlations in 13C/15N/2H labelled proteins. All 90° (180°) pulses for the 13C and 13C spins are applied with a strength of 2/ /l5 (p/ /3), where 2 is the frequency difference between the centres of the 13C and 13Ca regions. All 13Ca pulses are applied off-resonance with phase modulation by Q. A = 1/(4/hn) Tn = l/(4/NC ) S = gradient + field recovery delay 0 < k < TN/z2,max- Phase cycling i = y 4>2 = x, — x + States-TPPI 03 = x 0rec = x, — x.

Fig. 14. SeqHNCA-TROSY experiment for establishing sequential 1HN(i), 15N(i), 13Ca(i— 1) correlations in 13C/15N/2H enriched proteins. Durations of transfer delays A = 1/(4/Hn) 2Ta = 20-27 ms, depending on rotational correlation time of protein 2Tc = 5-7 ms S = gradient + field recovery delay 0 < k < Ta/t2,max- Phase cycling i = y (j>2 = y, — y + States-TPPI 0 = x 0ret. = x, — x. Semi-selective decoupling of 13C spins is attained using a SEDUCE-1 decoupling sequence.95...

Fig. 19. Pulse scheme of the MP-HNCA-TROSY experiment. Delay durations A = 1/(4/hn) 2T a = 27 ms 2Ta= 18-27 ms 2TN = 1/(2JNC-) <5 = gradient + field recovery delay 0 < k < Ta/t2,inax- Phase cycling scheme for the in-phase spectrum is 0i = y 02 = x, — x + States-TPPI 03 = x 0rec = x, — x 0 = y. For the antiphase spectrum, f is incremented by 90°. The intraresidual and sequential connectivities are distinguished from each other by recording the antiphase and in-phase data sets in an interleaved manner and subsequently adding and subtracting two data sets to yield two subspectra.

Proton-proton homonuclear decoupling has been performed by the ESLG decoupling sequence [46]. Quadrature detection in coj was achieved by using the time proportional phase increment method (TPPI) [47]. During the acquisition period, two pulse phase modulation (TPPM) heteronuclear decouphng ]48] was applied (Figure 7.6). 

Fig. 1. Pulse sequence of the C HSQC experiment with a spin-lock pulse for the suppression of signals from protons not bound to C. Narrow and wide bars denote 90° and 180° pulses, respectively. The spin-lock pulse is labeled SL. r is set to 1/[2J( C, H)]. The detection period is symbolized by a triangle. Phase cycle ] = 8(y) 4>2 = 2 x,x,y,y) 03 = 4 = 4n = 8(x) 05 =4(x,—x) 05 = 4(x),4(—x) acquisition = 2(x,—x,—x,x). The phases of the C pulses before U (03 and 0.5) are subjected to the States-TPPI scheme [38].

Aliasing is a term for choosing slower digitization than required by the Nyquist-theorem to cover the full spectral window, while sign discrimination is accomplished by simultaneous acquisition of real and imaginary phase components (called also complex acquisition) [10, 12]. Sequential acquisition for sign discrimination (either TPPI, or the Redfield-Kunz... 

Thefree-energy changes (AG) for ET from 90a to DCA, MB and 2,4,6-triphenylpyrylium perchlorate (TPPY+) are —18.4, —10.6 and —32.5 kcalmoD , respectively, indicative of exothermic electron transfer. The rate of disappearance of 90a was enhanced by addition ofMg(C104)2 (Table 20). 

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