Valence Compounds of the Inert Gases

Abstract

G. Closing Remarks situated, the hypoiodite reaction can lead to a homolytic substitution of iodine on the carbon by an oxy-radical. The action of lead tetraacetate on alcohols leads directly to high yields of tetrahydrofuran derivatives, without the formation of a "free carbonium ion", when all the participating centers are fixed in the arrangement which favors hydrogen abstraction. In the lead tetraacetate oxidation of alcohols in which the hydroxy groups and the attacked C-€3 bond are not fixed, acetoxylated or unsaturated 5or 6-membered cyclic ethers can be formed through intermediates with a carbonium character. Easily cleavable derivatives of homoallyl and homobenzyl alcohols are not suitable as starting materials for intramolecular substitution reactions, since in such cases the carbonyl-forming fragmentation competes successfully with the intramolecular hydrogen abstraction. This side reaction occurs in general when the carbon radical produced is stabilized. In the presence of acylates of tri-and tetravalent lead, the carbonylforming fragmentation may be reversible. The course of the intramolecular free-radical reactions can be changed by the addition of intermediately formed carbon radicals onto neighboring unsaturated systems such as C-C, C=O, or C EN groups. Received, October 9th, 1963 (A 372/169 IEI German version: Angew. Chem. 76, 518 (1964) Translated by Express Translation Service, LondonThe intramolecular substitution reactions of oxyradicals may be summarized as follows: In the photolysis of nitrites and hypochlorites only ligand transfers have been observed as primary processes (formation of 1,5-nitroso alcohols or 1,5-chlorohydrins). In the h,vpoiudite reaction, the principal process besides the ligand transfer (formation of 1,5-iodohydrins, which can then undergo intramolecular solvolysis, in the same way as the chlorohydrins, to yield tetrahydrofuran derivatives) is the oxidation of carbon radicals to carbonium ions. In contrast to the photolysis of nitrites and hypochlorites, in which only a single intramolecular substitution is possible, the same carbon atom may be doubly substituted in the hypoiodite reaction. The reason for this difference is that the hypoiodites are prepared from alcohols and split homolytically in situ, so that both the initially formed (monoiodinated) alcohols and the regenerated starting material can react further. The yields in the hypoiodite reaction are therefore generally higher than those of the analogous photolyses of nitrites or hypochlorites. The course of the reaction can be influenced by special steric relationships. If the reaction centers are suitably

The Synthesis of XeF2; a Predictable Outcome with a Significant Chemistry

“…[1] Following his more extensive report on XeF 2 in this Journal, Hoppe again focussed on solid state topics. Apart from contributions in several publications, [7,9,22] no further manuscripts dealing with noblegas chemistry were forthcoming from his laboratory.…”

“…[8]). According to Hoppe's own accounts, [9] his convictions grew out of deliberations within his research group in 1949/1950 concerning the possibility and the properties of xenon fluorides. From 1951 onwards, Hoppe affirms "we were convinced that XeF 4 and XeF 2 must be thermodynamically stable to decomposition into their elements".…”

“…The absence of molecular ion peaks attributable to higher xenon fluorides established that only XeF 2 was formed. Hoppe later stated [9] that it was due to his intention to secure the compound's chemical www.zaac.wiley-vch.de 1387 analysis by mass spectrometry that the results of his research on XeF 2 were only published in October 1962. Efforts to obtain the melting point of XeF 2 were hampered by its high vapor pressure at elevated temperatures, and only an estimated value of 120°C was reported.…”

Exploring the Limits of Transition‐Metal Fluorination at High Pressures

“…[1][2][3][4][5][6] One motivation for the synthesis of transition-metal fluorides in general is the generation of strong oxidizers. [2,3,7] Thef irst noble-gas compounds,X eF 2 , XeF 4 and what was likely salts containing XeF n + cations,were, for example,either made through electric discharges of xenon and afluorine source [8][9][10] or through oxidation of xenon with PtF 6 . [8,11,12] Transition-metal fluorides can also be used as fluorination agents and as precursors to obtain various other compounds.…”

“…[2,3,7] Thef irst noble-gas compounds,X eF 2 , XeF 4 and what was likely salts containing XeF n + cations,were, for example,either made through electric discharges of xenon and afluorine source [8][9][10] or through oxidation of xenon with PtF 6 . [8,11,12] Transition-metal fluorides can also be used as fluorination agents and as precursors to obtain various other compounds. [13] Fori nstance,M oF 6 is able to catalyze the fluorination of carbonyl groups to CF 2 groups.…”