Über organische Schwefelradikale, III. Organische Schwefel‐Radikalionen (Sulfiniumsalze)

Abstract

Durch ESR‐Messung werden in den mit K2S2O8 oxydierten Lösungen von Diarylthioäthern in konz. Schwefelsäure beständige Sulfinium‐Radikalionen Ar‐S⊕‐Ar nachgewiesen. Diese bilden sich auch aus den entsprechenden Sulfoxyden in Schwefelsäure oder Polyphosphorsäure ohne zusätzliches Oxydationsmittel. Stabiler sind die Radikalionen aus Tetraphenylthiophenen und p‐Phenylendimercapto‐diaryläthern. Substitution der Phenyle durch Elektronendonatoren stabilisiert die Radikale. Bei der Oxydation der Thioäther mit Halogen in SnCl4 fallen die stabilen, aber sehr feuchtigkeitsempfindlichen “Sulfinium”‐hexachlorostannate aus, die sich mit Anisol zu den entsprechenden Sulfoniumsalzen umsetzen. Die oft beschriebene Bildung von Sulfoniumsalzen aus Sulfoxyden und Phenolen in starken Säuren dürfte in vielen Fällen über “Sulfiniumsalze” verlaufen.

Kinetics and Mechanism of the Reaction of Peroxy-compounds with Phosphites, Sulphides, and Aromatic Amines

“…in media where the radical cations are stabilised). The experimental hyperfine coupling constants (a^ = a^ = 1.35 Oe) are close to those measured for the same radical-cations obtained in the oxidation by persulphate ions 78 . This result is important; it can be regarded as confirmation of the suggested mechanism for the formation of free radicals in the reaction of hydroperoxides with aliphatic sulphides 77 .…”

“…Subsequently Schmidt et al 78 observed by ESR the formation of the radical-cations of derivatives of diphenyl sulphide [di-(4-methylphenyl), di-(4-methoxyphenyl), di-(4-methoxy-3-methyl), di-(2-chloro-4-methoxyphenyl), di-(4-hydroxyphenyl), di-(3,6-dichloro-4-hydroxyphenyl), and di-(6-chloro-4-hydroxyphenyl) sulphides] in their oxidation by persulphate ions in concentrated sulphuric acid solution at 20°C. For example, the ESR spectrum of the radical-cation of di-(4-methoxyphenyl) sulphide (^-factor = 2.0079) consists of nine lines with a splitting of 1.25 Oe owing to the coupling of the unpaired electron with the eight equivalent protons of the aromatic rings (probably the unpaired electron density at the ortho-and raeta-protons is the same); the observed ratios of the hyperfine structure intensities (0.6 : 7 : 27 : 54 : 70: 53 : 23 : 4: 0.6) proved to be close to the ratios expected for the proton structure (1 : 8 : 28 : 56 : 70 : 56 : 28 : 8 :1).…”

Violene/Cyanine Hybrids as Electrochromic Systems: A New Variation of the General Structure

“…[5] The complex events were followed later by analytical methods. [6] Finally, we adopted the synthesis of tetraphenylthiophene from diphenylacetylene and sulfur [7] for the pyridine series. Indeed, 4,4Ј-dipyridinio-acetylene (1), now relatively easily accessible, [8] yielded 28% of 3 in the first run.…”