Reactivity series

Résumé

In chemistry, a reactivity series (or activity series) is an empirical, calculated, and structurally analytical progression of a series of metals, arranged by their "reactivity" from highest to lowest. It is used to summarize information about the reactions of metals with acids and water, single displacement reactions and the extraction of metals from their ores. Going from the bottom to the top of the table the metals: increase in reactivity; lose electrons (oxidize) more readily to form positive ions; corrode or tarnish more readily; require more energy (and different methods) to be isolated from their compounds; become stronger reducing agents (electron donors). There is no unique and fully consistent way to define the reactivity series, but it is common to use the three types of reaction listed below, many of which can be performed in a high-school laboratory (at least as demonstrations). The most reactive metals, such as sodium, will react with cold water to produce hydrogen and the metal hydroxide: 2 Na (s) + 2 H2O (l) →2 NaOH (aq) + H2 (g) Metals in the middle of the reactivity series, such as iron, will react with acids such as sulfuric acid (but not water at normal temperatures) to give hydrogen and a metal salt, such as iron(II) sulfate: Fe (s) + H2SO4 (l) → FeSO4 (aq) + H2 (g) There is some ambiguity at the borderlines between the groups. Magnesium, aluminium and zinc can react with water, but the reaction is usually very slow unless the metal samples are specially prepared to remove the surface layer of oxide which protects the rest of the metal. Copper and silver will react with nitric acid; but because nitric acid is an oxidizing acid, the oxidizing agent is not the H+ ion as in normal acids, but the NO3− ion. The reactivity series is sometimes quoted in the strict reverse order of standard electrode potentials, when it is also known as the "electrochemical series". The following list includes the metallic elements of the first six periods. It is mostly based on tables provided by NIST.

Source officielle

https://en.wikipedia.org/wiki/Reactivity_series

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Publications associées (8)

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Thorium nitrides are likely intermediates in the reported cleavage and functionalization of dinitrogen by molecular thorium complexes and are attractive compounds for the study of multiple bond formation in f-element chemistry, but only one example of thorium nitride isolable from solution was reported. Here, we show that stable multimetallic azide/nitride thorium complexes can be generated by reduction of thorium azide precursors─a route that has failed so far to produce Th nitrides. Once isolated, the thorium azide/nitride clusters, M3Th═N═Th (M = K or Cs), are stable in solutions probably due to the presence of alkali ions capping the nitride, but their synthesis requires a careful control of the reaction conditions (solvent, temperature, nature of precursor, and alkali ion). The nature of the cation plays an important role in generating a nitride product and results in large structural differences with a bent Th═N═Th moiety found in the K-bound nitride as a result of a strong K–nitride interaction and a linear arrangement in the Cs-bound nitride. Reactivity studies demonstrated the ability of Th nitrides to cleave CO in ambient conditions yielding CN–.

2022

The development of an unusual oxidative alkene difunctionalization using methyl formate and syn-thetic studies towards alkaloid natural products provide the basis of the thesis. The first chapter details the development of a method that forges methoxycarbonyl radical direct-ly from its most accessible precursor: methyl formate. Although the aforementioned transfor-mation was documented in the literature, no synthetically useful method was developed at the time. We were able to identify conditions that transform methyl formate and simple styrene de-rivatives to value added ï¢-methoxy alkanoates and cinnamic acid derivatives under copper cataly-sis. We also demonstrated that by tethering nucleophilic moieties to the styrene substrates, we could access medicinally important heterocycles such as pyrrolidines, tetrahydrofurans and ï§-lactones. Our method proved to be scalable on each classes of substrates. Mechanistic studies re-vealed that methyl formate has an unprecedented double role in the transformation. It acts as a precursor for methoxycarbonyl radical; furthermore, it is the direct source of the ï¢-methoxy func-tion in the synthesis of ï¢-methoxy alkanoates. A ternary ï¢-diketiminato-Cu(I)-styrene complex, fully characterized by NMR spectroscopy and X-ray crystallographic analysis is capable of catalyz-ing the same transformation. We hypothesize that pre-coordination of electron-rich double bond to copper might play an important role in the polarity-mismatched addition between nucleophilic methoxycarbonyl radical and electron rich olefins. Synthetic studies toward the total synthesis of koumine is discussed in the second chapter. Our synthetic strategy features an oxidative ring closing, Fukuyama indole synthesis and an enantiose-lective Diels-Alder cycloaddition for the construction of the core of koumine skeleton. We designed a rapid route to access 1,2-dihydropyridine derivatives and these compounds were examined as dienes in the Diels-Alder cycloaddition reaction. Despite our efforts, we were unable to effect the [4+2] cycloaddition, which eventually lead us to decide to discontinue our campaign. In chapter three, our synthetic efforts toward voacafricine A and voacafricine B is presented. In our pursuit towards the natural products, we devised and followed a divergent and potentially en-antioselective strategy. We successfully developed a synthetic route to reach the key intermediate in five steps. Despite our efforts, we were not able to construct the remaining F ring of the natural product. Our conformational analysis of advanced intermediates suggest that epimerization of the C14 stereocenter potentially unlocks the desired reactivity and enables us to reach the target mol-ecules. Work towards the total synthesis of voacafricine A and voacafricine B is underway and may focus on the conformational manipulation of advanced intermediates to allow the elaboration of the F ring and complete the synthesis.

EPFL2020

Investigations of the Chemistry of 1-Alkynyltriazenes

Florian Gérald Abela

The chemistry of aromatic triazenes is well known, and has been explored for more than a century. These compounds have emerged as very useful intermediates, because of their unique reactivity. This functionality can notably be used to access many other functional groups, and it is present in certain bioactive compounds. Recently, our laboratory has reported a novel synthesis of triazenes using nitrous oxide, which allows the synthesis of 1-alkynyltriazenes. These compounds are poorly known, as their synthesis is not trivial by other routes. This thesis aims to explore the reactivity of these compounds. We have shown that the chemical reactivity of 1-alkynyltriazenes parallels what has been observed for ynamides. The similarity in reactivity of these two classes of compounds is demonstrated by addition reactions with acids and by cycloaddition reactions with ketenes and tetracyanoethene. The presence of the reactive triazene groups in the products allowed for subsequent transformations. We also studied the reactivity of these substrates in Ru-catalyzed [2+2] cycloadditions. The triazenes serve as unique vinyl cation surrogates. Under acidic conditions, the triazene functionality can be replaced by a variety of groups including halides, alkoxides, sulfoxides, amides, arenes and heteroarenes, providing efficient access to a pool of chiral and achiral polycyclic compounds The formation of very reactive cations using cyclic alkenenyl triazenes is described in a short study. It seems that the strained vinyl cation can be formed, but that its high reactivity prevents it to react selectively with weak nucelophiles. In the final part of this work, first results of a rhodium-catalyzed reaction with bifunctional boronic acids are presented. We show that 1-alkynyltriazenes react in the presence of rhodium to form indene derivatives. The unique reactivity of the triazenes lead to the formation of unexpected compounds. Overall, our results suggest that 1-alkynyltriazenes will become valuable reagents in synthetic organic chemistry.

EPFL2018

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Investigations of the Chemistry of 1-Alkynyltriazenes

Florian Gérald Abela

EPFL2018

EPFL2020