In this paper, the Arrhenius curves of selected hydrogen-transfer reactions for which kinetic data are available in a large temperature range are reviewed. The curves are discussed in terms of the onedimensional Bell-Limbach tunnelling model. The main parameters of this model are the barrier heights of the isotopic reactions, barrier width of the H-reaction, tunnelling masses, pre-exponential factor and minimum energy for tunnelling to occur. The model allows one to compare different reactions in a simple way and prepare the kinetic data for more-dimensional treatments. The first type of reactions is concerned with reactions where the geometries of the reacting molecules are well established and the kinetic data of the isotopic reactions are available in a large temperature range. Here, it is possible to study the relation between kinetic isotope effects (KIEs) and chemical structure. Examples are the tautomerism of porphyrin, the porphyrin anion and related compounds exhibiting intramolecular hydrogen bonds of medium strength. We observe pre-exponential factors of the order of kT/hy10 13 s K1 corresponding to vanishing activation entropies in terms of transition state theory. This result is important for the second type of reactions discussed in this paper, referring mostly to liquid solutions. Here, the reacting molecular configurations may be involved in equilibria with non-or less-reactive forms. Several cases are discussed, where the less-reactive forms dominate at low or at high temperature, leading to unusual Arrhenius curves. These cases include examples from small molecule solution chemistry like the base-catalysed intramolecular H-transfer in diaryltriazene, 2-(2 0 -hydroxyphenyl)-benzoxazole, 2-hydroxy-phenoxyl radicals, as well as in the case of an enzymatic system, thermophilic alcohol dehydrogenase. In the latter case, temperaturedependent KIEs are interpreted in terms of a transition between two regimes with different temperature-independent KIEs.

Using dynamic solid state 15N CPMAS NMR spectroscopy (CP = cross polarization, MAS = magic angle spinning), the kinetics of the degenerate intermolecular double and quadruple proton and deuteron transfers in the cyclic dimer of 15N labeled polycrystalline 3,5-diphenyl-4-bromopyrazole (DPBrP) and in the cyclic tetramer of 15N labeled polycrystalline 3,5-diphenylpyrazole (DPP) have been studied in a wide temperature range at different deuterium fractions in the mobile proton sites. Rate constants were measured on a millisecond time scale by line shape analysis of the doubly 15N labeled compounds, and by magnetization transfer experiments on a second timescale of the singly 15N labeled compounds in order to minimize the effects of proton-driven 15N spin diffusion. For DPBrP the multiple kinetic HH/HD/DD isotope effects could be directly obtained. By contrast, four rate constants k 1 to k 4 were obtained for DPP at different deuterium fractions. Whereas k 1 corresponds to the rate constant k HHHH of the HHHH isotopolog, an appropriate kinetic reaction model was needed for the kinetic assignment of the other rate constants. Using the model described by Limbach, H. H.; Klein, O.; Lopez Del Amo, J. M.; Elguero, J. Z. Phys. Chem. 2004, 218, 17, a concerted quadruple proton-transfer mechanism as well as a stepwise consecutive single transfer mechanism could be excluded. By contrast, using the kinetic assignment k 2 ≈ k 3 ≈ k HHHD ≈ k HDHD and k 3 ≈ k HDDD ≈ k DDDD, the results could be explained in terms of a two-step process involving a zwitterionic intermediate. In this mechanism, each reaction step involves the concerted transfer of two hydrons, giving rise to primary kinetic HH/HD/DD isotope effects, whereas the nontransferred hydrons only contribute small secondary effects, which are not resolved experimentally. By contrast, the multiple kinetic isotope effects of the double proton transfer in DPBrP and of the triple proton proton transfer in cyclic pyrazole trimers studied previously indicate concerted transfer processes. Thus, between n = 3 and 4 a switch of the reaction mechanism takes place. This switch is rationalized in terms of hydrogen bond compression effects associated with the multiple proton transfers. The Arrhenius curves of all processes are nonlinear and indicate tunneling processes at low temperatures. In a preliminary analysis, they are modeled in terms of the Bell−Limbach tunneling model.

Using dynamic NMR spectroscopy, the kinetics of the degenerate double proton transfer in cyclic dimers of polycrystalline (15)N,(15)N'-di-(4-bromophenyl)-formamidine (DBrFA) have been studied including the kinetic HH/HD/DD isotope effects in a wide temperature range. This transfer is controlled by intermolecular interactions, which in turn are controlled by the molecular conformation and hence the molecular structure. At low temperatures, rate constants were determined by line shape analysis of (15)N NMR spectra obtained using cross-polarization (CP) and magic angle spinning (MAS). At higher temperatures, in the microsecond time scale, rate constants and kinetic isotope effects were obtained by a combination of longitudinal (15)N and (2)H relaxation measurements. (15)N CPMAS line shape analysis was also employed to study the non-degenerate double proton transfer of polycrystalline (15)N,(15)N'-diphenyl-formamidine (DPFA). The kinetic results are in excellent agreement with the kinetics of DPFA and (15)N,(15)N'-di-(4-fluorophenyl)-formamidine (DFFA) studied previously for solutions in tetrahydrofuran. Two large HH/HD and HD/DD isotope effects are observed in the whole temperature range which indicates a concerted double proton transfer mechanism in the domain of the reaction energy surface. The Arrhenius curves are non-linear indicating a tunneling mechanism. Arrhenius curve simulations were performed using the Bell-Limbach tunneling model. The role of the phenyl group conformation and hydrogen bond compression on the barrier of the proton transfer is discussed.

Abstract. The study of emotion in human beings has traditionally been a research interest area in disciplines such as psychology and sociology. The appearance of affective computing paradigm has made it possible to include findings from these disciplines in the development of affective interfaces. Still, there is a lack of applications that take emotion related aspects into account. This situation is mainly due to the great amount of proposed theoretical models and the complexity of human emotions. Besides, the importance that mobile computing area is acquiring has made necessary to bear context related aspects in mind. The proposal presented in this paper is based on a generic ontology for describing emotions and their detection and expression systems taking contextual and multimodal elements into account. The ontology is proposed as a way to develop a formal model that can be easily computerized. Moreover, it is based on a standard, the Web Ontology Language (OWL), which also makes ontologies easily shareable and extensible. Once formalized as an ontology, the knowledge about emotions is used in order to make computers more accessible, personalised and adapted to user needs.