Organic compounds proton-transfer reactions

Several types of proton transfer reactions can be studied conveniently by a neutral product analysis. Until now, the most extensive investigations have been concerned with (1) proton transfer from H3+ and CH5 + to various hydrocarbon molecules, and (2) the transfer of a proton from carbonium ions to larger olefins or other organic compounds. 

Photoinduced proton transfer reactions, undoubtedly, belong to the most important transformations in chemistry [20], Proton transfers can take place both in the ground and excited states of organic compounds, and the most important for... 

Steeghs M, Bais HP, de Gouw J, Goldan P, Kuster W, Northway M, Fall R, Vivanco JM (2004) Proton-transfer-reaction mass spectrometry as a new tool for real time analysis of root-secreted volatile organic compounds in arabidopsis. Plant Physiol 135 47-58... 

MDGC, and comprehensive two-dimensional GC, or GCxGC), faster separation techniques (fast GG), fast methods for quality assessment or process control in the flavour area ( electronic noses and fingerprinting MS) and on-line time-resolved methods for analysis of volatile organic compounds (VOGs) such as proton-transfer reaction MS (PTR-MS) and resonance-enhanced multi-photon ionisation coupled with time-of-flight MS (REMPI-TOFMS). The scope of this contribution does not allow for lengthy discussions on all available techniques therefore, only a selection of developments will be described. 

Lindinger, W., Hansel, A., Jordan, A. (1998) Proton-transfer-reaction mass spectrometry (PTR-MS) on-line monitoring of volatile organic compounds at pptv levels. Chem. Soc. Rev. 27 347-354. 

Lindinger, C., Pollien, P., Ali, S., Yeretzian, C., Blank, I., Mark, T. (2005) Unambiguous identification of volatile organic compounds by proton-transfer-reaction mass-spectrometry (PTR-MS) coupled with GC-MS. Anal. Chem. 77 4117-4124. 

Performance characteristics and applications of a proton transfer reaction-mass spectrometer for measuring volatile organic compounds in ambient air. Environmental Science and Technology, 36 (7), 1554—60. 

Most of the principles used to explain the acidity of compounds are also used to explain the reactivity and stability of organic compounds in general. Also, proton transfer reactions are often the first step in most organic reactions. For this reason, if we can thoroughly comprehend proton transfer, then we have a solid basis for understanding most organic reactions. 

The traditional equilibrium method of flavor release study mentioned above is extremely time consuming, and several weeks are commonly needed to obtain full release profiles of flavors from powders. Recently, thanks to the pioneering work of Dronen and Reineccius (2003), proton transfer reaction mass spectrometry (PTR-MS) has been used as a rapid analysis to measure the release time-courses of flavors from spray-dried powders. The PTR-MS method has been applied extensively to analyze the release kinetics of volatile organic compounds from roasted and ground coffee beans. The release profiles could then be mathematically analyzed by means of Equation 1.1 to obtain the release kinetic parameters, A and n (Mateus et al., 2007). 

The development of proton-transfer-reaction mass spectrometry (PTR-MS) as a tool for the analysis of volatile organic compounds (VOCs) is described. PTR-MS is based on the rapid, non-dissociative transfer of protons from H30 to most common VOCs, but not to the principal gases in the air sample. Recent developments in the design of PTR-MS instruments allow detection of some VOCs in the parts per trillion by volume range. This sensitivity and the capability of PTR-MS instruments to be operated for extended periods in both laboratory and field settings has allowed exploration of many aspects of VOC analysis in environmental, food and medical applications. 

We have briefly mentioned the use of data on IMR in plasma modeling and for the understanding of interstellar molecular synthesis as well as of ionospheric chemistry, and we also want to point out the applications of IMR in various methods of chemical ionization. The most recent one, developed in our laboratory, namely proton-transfer reaction mass spectrometry (PTR-MS), allows for on-line monitoring of volatile organic compounds at levels as low as a few parts per trillion and is therefore applicable for environmental, food, and medical research involving investigations of fast metabolic and enzymatic processes. 

Proton transfer reaction mass spectrometry (PTR-MS) was first developed at the Institute of Ion Physics of Innsbruck University in the 1990s. Nowadays, PTR-MS is a well-developed and commercially available technique for the on-line monitoring of trace volatile organic compounds (VOCs) down to parts per trillion by volume (ppt) level. PTR-MS has some advantages such as rapid response, soft chemical ionization (Cl), absolute quantification, and high sensitivity. In general, a standard PTR-MS instrument consists of external ion source, drift tube, and mass analysis detection system. Figure... 

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