Hydrogen/Deuterium (H/D) Exchange Catalysis in Alkanes

Sattler, Aaron

doi:10.1021/acscatal.7b04201

Cited by 86 publications

(57 citation statements)

References 228 publications

(286 reference statements)

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“…-CH 2 ·). A second possibility is di-adsorption, which includes αα, αβ and αγ types (Sattler, 2018). Bond (2006) suggests that αβ is the favored exchange mechanism for small straight-chain alkanes.…”

Section: Position-specific Exchange Mechanismsmentioning

confidence: 99%

“…Thus, this mechanism also predicts faster central exchange and slower terminal exchange. A third possibility is ionic exchange, which is involves the dissociation of either proton or hydride (Schimmelmann et al, 2006;Sattler, 2018). Alexander et al (1984) reported that alkyl H exchange happens exclusively on the position adjacent to the position that is more stable for carbocation.…”

Section: Position-specific Exchange Mechanismsmentioning

confidence: 99%

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Position-specific hydrogen isotope equilibrium in propane

Xie

Ponton

Formolo

et al. 2018

Geochimica et Cosmochimica Acta

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Intramolecular isotope distributions can constrain source attribution, mechanisms of formation and destruction, and temperature-time histories of molecules. In this study, we explore the D/H fractionation between central (-CH 2 -) and terminal (-CH 3 ) positions of propane (C 3 H 8 ) -a percent level component of natural gases. The temperature dependence of position-specific D/H fractionation of propane could potentially work as a geo-thermometer for natural gas systems, and a forensic identifier of specific thermogenic sources of atmospheric or aquatic emissions. Moreover, kinetically controlled departures from temperature dependent equilibrium might constrain mechanisms of thermogenic production, or provide indicators of biological or photochemical destruction. We developed a method to measure position-specific D/H differences of propane with high-resolution gas source mass spectrometry. We performed laboratory exchange experiments to study the exchange rates for both terminal and central positions, and used catalysts to drive the hydrogen isotope distribution of propane to thermodynamic equilibrium. Experimental results demonstrate that D/H exchange between propane and water happens easily in the presence of either Pd catalyst or Ni catalyst. Exchange rates are similar between the two positions catalyzed by Pd. However, the central position exchanges 2.2 times faster than the terminal position in the presence of Ni catalyst. At 200°C in the presence of Pd catalyst, the e-folding time of propane-water exchange is 20 days and of homogeneous exchange (i.e., equilibrium between central and terminal positions) is 28 minutes. An equilibrated (bracketed and time-invariant) intramolecular hydrogen isotope distribution was attained for propane at three temperatures, 30°C, 100°C and 200°C; these data serve as an initial experimental calibration of a new position-specific thermometer with a temperature sensitivity of 0.25‰ per ˚C at 100 ˚C. We use this calibration to test the validity of prior published theoretical predictions. Comparison of data with models suggest the most sophisticated of these discrepant models (Webb and Miller, 2014) is most accurate; this conclusion implies that there is a combined experimental and theoretical foundation for an 'absolute reference frame' for positionspecific H isotope analysis of propane, following principles previously used for clumped isotope analysis of CO 2 , CH 4 and O 2 (Eiler and Schauble, 2004;Yeung et al., 2014;Stolper et al., 2014).

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Section: Position-specific Exchange Mechanismsmentioning

confidence: 99%

Section: Position-specific Exchange Mechanismsmentioning

confidence: 99%

Position-specific hydrogen isotope equilibrium in propane

Xie

Ponton

Formolo

et al. 2018

Geochimica et Cosmochimica Acta

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“…Это обычный многоступенчатый синтез с использованием дейтерированных реагентов или дейтерирование родительского соединения методом Н/D изотопного обмена [5]. Изотопный протий-дейтериевый обмен (H/D) зависит от рН и природы катализатора [3,15].…”

Section: отличие дейтерия от протия с позиции фармацевтической химииunclassified

The Influence of Deuterium on the Properties of Pharmaceutical Substances (Review)

Сыроешкин¹,

Елизарова²,

Плетенёва³

et al. 2020

Razrabotka i registraciâ lekarstvennyh sredstv

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Introduction. The study discusses the hydrogen isotope 2 H effect on the biological activity of pharmaceutical substances.Text. Two aspects of the deuterium effect on the properties of active pharmaceutical ingredients and excipients are considered. The first one involves the use of deuterated substances, new compounds or substituted counterparts. Replacing protium with deuterium is used to reduce the rate of biotransformation. The kinetic isotope effect (KIE), expressed in a decrease in the rate of biotransformation as a result of deuteration, allows us to predict the rapid development of new directions in the development of pharmaceuticals. With the same therapeutic effect, an improvement in pharmacokinetic characteristics, a decrease in toxicity, a blocking of the epimerization of optically active substances, a change in the mechanisms of action are observed. The second aspect of the deuterium effect is associated with an increase in KIE of known pharmaceutical substances in aqueous solutions with a deuterium/protium ratio (D/H) lower than in natural water. For the first time, dose-response diagrams for deuterium demonstrate identity with essential microelements. There is a safety zone for the certain D/H relationship, beyond which the organism's vitality decreases. Improved kinetic characteristics are demonstrated for molecular level and for biological objects of various hierarchical levels. In particular, they include the possibility of increasing the dissolution rate of substances, the influence on the processes of mutarotation and the optical activity of chiral substances, the degree of accumulation of necessary elements in medicinal plants, and other processes.Conclusion. The results make it possible to predict the mechanisms of deuterium influence on the biochemical transformations of pharmaceutical substances in the body.

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“…It is, therefore, anticipated that advances in material science or inorganic catalysis will also enrich the armory of HIE reaction methods in the future. For readers interested in the HIE reactions at alkane C–H bonds in hydrocarbons, we like to direct you to the recent review of Sattler …”

Section: Aliphatic C(sp3)‐h Hydrogen Isotope Exchange Reactionsmentioning

confidence: 99%