Reactivity toward metals

One approach (.40) has been to conduct the reaction in the presence of a more electropositive metal, often as an alloy. In the presence of magnesium, tin reacts with ethyl bromide to give tetraethyl tin, and various additives promote the reaction, the sequence of effectiveness being carbitols I > tetrahydrofuran, tetrahydrothiophene > ether triethylamine Br the ions ClOj, PFg, BFj, and BPhj are without effect. It is suggested that this reflects the coordination of the additive (L) to the Grignard reagent that is first formed, making it more reactive towards metallic tin. 

Hydrocarbons lacking directing substituents are not very reactive toward metal-lation, but it has been found that a mixture of n-butyllithium and potassium r-butoxide66 is sufficiently reactive to give allyl anions from alkenes such as isobutene.67... 

In this chapter we will not attempt to give an overview of all of the knowledge on the reactivity of chalcogen-donor molecules towards di- and inter-halogens, since some aspects of this are discussed in other chapters. Instead, this chapter is dedicated exclusively to the analysis of the chemical bond and structural features of C.-T. adducts between LE chalcogen-donor molecules (E = S, Se) and di- and inter-halogens, and their reactivity towards metal powders. 

The early patent disclosures have claimed the application of a wide spectrum of gas-evolving ingredients and phosphorus-based organic molecules as flame retarding additives in the electrolytes. Pyrocarbonates and phosphate esters were typical examples of such compounds. The former have a strong tendency to release CO2, which hopefully could serve as both flame suppressant and SEI formation additive, while the latter represent the major candidates that have been well-known to the polymer material and fireproofing industries.The electrochemical properties of these flame retardants in lithium ion environments were not described in these disclosures, but a close correlation was established between the low flammability and low reactivity toward metallic lithium electrodes for some of these compounds. Further research published later confirmed that any reduction of flammability almost always leads to an improvement in thermal stability on a graphitic anode or metal oxide cathode. 

A novefroute to l//-l-benzazepin-9-carboxylic acid, which capitalizes on the reactivity towards metal exchange of a methoxy group ortho to an oxazoline function, is outlined in Scheme 15 (81JOC783). 

Structural studies suggest that when the active site selenocysteine group is in the reduced form TrxR displays a high reactivity toward metal ions [85, 86]. It is possible that gold(III) compounds such as auranofin exert their cytotoxic effects by causing direct mitochondrial damage through selective modification of the selenol... 

V-Benzylthieno[3,2-6]pyrrole (18) was lithiated and upon treatment of the lithio derivative with methyl chloroformate, 2-methoxycarbonyl-lV-benzylthieno[3,2-f>]pyrrole (51) was obtained (Scheme 10). The a-proton in the thiophene ring is more reactive towards metal-hydrogen exchange compared to the proton at C-5. 

A series of 4-alkylamido-2-hydroxybenzoic acids containing a different number of carbon atoms in the alkyl-amido group has been studied as model ligands for metal ion extraction in aqueous micellar solutions of nonionic surfactants. Their acid-base properties and reactivity towards metal ions in the presence of micelles were investigated. By operating at a proper temperature, the separation of the iron (III) chelate complexes into a micellar rich phase was achieved and the extraction efficiency was correlated with the ligand hydrophobicity. 

The x-ray photoelectron spectra for both dissolved and solventless polyamic acid have been reported in the literature [2-8], It has been noted previously by us [5-7], that the spectra for solventless PAA and PI exhibit a pronounced deficiency for the Cls and Ols carbonyl emission. This, together with an analysis of the Nls lineshape and the Ols and Cls shake up features, allows us to derive conclusions on the chemical nature of solventless polyamic acid and to explain it s high reactivity towards metals as discussed below. 

Ophthalmic ointments are marketed in a metal tube with an ophthalmic tip. Ophthalmic ointments that are reactive toward metal may be packaged in a tube lined with an epoxy or vinyl plastic coating. 

Because of the diversity displayed, tabulation of the properties of the whole of Gp.VIB is not very helpful the elements range from the very electronegative, non-metallic oxygen to the metallic polonium. Reactivity towards metals and hydrogen decreases from oxygen to tellurium. Sulphur, selenium and tellurium react energetically with fluorine and chlorine, rather less activity with bromine ... 

Q9.6 Homo-allylic alcohols, where the alcohol group is removed one extra carbon from the double bond, also show increased reactivity toward metal catalyzed epoxidations by f-BuOOH.3 Explain why this might be so. 

Thiophene. Recent work in the authors laboratories has demonstrated that the directed metalation concept works well in substituted thiophenes once a certain limitation is realized—namely, that the 2,5-positions of thiophene are much more reactive toward metalation than are the 3,4-... 

If this conclusion is valid, a sodium dispersion should approach the degree of reactivity toward metal halides that is shown by sodium addition compoimds or liquid ammonia solutions of sodium. 

Glycols are highly reactive towards metal alkoxides to form homoleptic and mixed alkoxo-glycolate derivatives. This alcohol exchange reaction (see Section 7.10.3.1.3) is driven by the formation of chelated or bridged structures with both (dianionic) OCR2CR2O—... 

Reaction conditions can be modified to accelerate the rate of lithiation when necessary. Addition of tertiary amines, especially tetramethylethylenediamine (TMEDA), accelerates lithiation by coordination at the lithium, which promotes dissociation of aggregated structures. Hydrocarbons lacking directing substituents are not very reactive toward metalation, but it has been found that a mixture of fi-butyllithium and potassium f-butoxide is sufficiently reactive to give allyl anions from alkenes such as isobutene and 2,3-dimethyl-l,3-butadiene. ... 

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