Reactions hydrogen exchange

Beside these two labeling strategies, there are also different modes of exchange reactions that can be used to best capture the dynamics of the protein sample. The two most common methods are deuterium on-exchange and deuterium off-exchange reactions, which are applicable to both continuous 

The hydrogen exchange between amide and ammonia in the gas phase at 300it2 K was investigated by the selected-ion flow tube (SIFT) technique. The following reactions and rate constants of amide consumption were found [1]  

The hydrogen exchange between NH2 and liquid NH3 has a rate constant of k= 1.5 x 10 L-mol s at 298 K which was determined from the change of the relaxation time in the NMR spectra with temperature and amide concentration. The activation parameters are AH =16.7 + 2.1 kJ/mol and AS= —51.5 + 8.4 J-K moPV The large entropy indicates a considerable rearrangement in the solvation sphere when the reactants form the activated complex [2]. 

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Schnieder L, Seekamp-Rahn K, Wede E and Welge K H 1997 Experimental determination of quantum state resolved differential cross sections for the hydrogen exchange reaction H -r D2 -> HD -r D J. Chem. Phys. 107 6175-95... 

Neuhauser D, Baer M, Judson R S and Kouri D J 1989 Time-dependent three-dimensional body frame quantal wavepacket treatment of the atomic hydrogen + molecular hydrogen exchange reaction on the Liu-Siegbahn-Truhlar-Horowitz (LSTH) surfaced. Chem. Phys. 90 5882... 

The stereochemistry observed in hydrogen-exchange reactions of carbanions is very dependent on the conditions under which the anion is formed and trapped by proton... 

Electrophilic aromatic hydrogen exchange reactions fall into two classes, namely those reactions catalysed by acid and those reactions catalysed by base. Of these the former are by far the most common and have been subjected to the most extensive and intensive kinetic studies. 

On the basis of these correlations, Gold and Satchell463 argued that the A-l mechanism must apply (see p. 4). However, a difficulty arises for the hydrogen exchange reaction because of the symmetrical reaction path which would mean that the slow step of the forward reaction [equilibrium (2) with E and X = H] would have to be a fast step [equivalent to equilibrium (1) with E and X = H] for the reverse reaction, and hence an impossible contradiction. Consequently, additional steps in the mechanism were proposed such that the initial fast equilibrium formed a 7t-complex, and that the hydrogen and deuterium atoms exchange positions in this jr-complex in two slow steps via the formation of a a-complex finally, in another fast equilibrium the deuterium atom is lost, viz. 

Secondly, destannylation appears to be more sterically hindered than the hydrogen exchange reaction, since in the latter the a-position of naphthalene is rate-... 

R=COPh) loses its proton in hydrogen-exchange reactions 6000 times more... 

Similar behavior was found for carbanions generated by base-catalyzed hydrogen exchange (Reaction 12-1) ... 

E. Wrede, Energy-Dependent Investigation of the Hydrogen-Exchange Reaction Ph.D. thesis. University of Bielefeld, Germany, 1998. 

Kaesz et al. have shown that simple, primary amines (e.g. MeNH2) will react with Ru3(CO)12 to form p-acetamido ligands at temperatures as low as -15°C. We find that simple primary, secondary and tertiary alkyl amines will react with Ru3(CO) 2 at temperatures of 70-150°C to undergo catalytic deuterium for hydrogen exchange reactions on the hydrocarbon groups and transalkylation (52). We have found that a... 

Fig. 1. Potential energy surface and classical trajectory calculations on the H + H2 hydrogen exchange reaction. Note the orbiting trajectory in the vicinity of Lake Eyring . Despite the unrealistic nature of a well near the transition state of this reaction, many of the modern ideas of chemical reaction theory can be seen in action already in this work. (See Ref. 1.)...

The closely related topics of hydroformylation (55-65) and hydrogen exchange reactions (66-68) are not covered in this chapter. 

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