Farbloses und farbiges Triphenylmethyl

Abstract

wu& unter Bildung der um 2 Wasserstoffatome reicheren T'erbindung Gs&rN* (IV): CH.C(CsH5):N.NH.CsHs CH.C(CsH5):N.NH.C& '. IV. *. Durch die Analyse kann zwischen beiden Formeln nicht entschieden werden; die ausgefiihrte Stickstoffbestimmung entspricht beiden in gleicher Weise. Dagegen spricht die Darstellung eines B e n z y l p h e n y l o s a z o us mittels des unsymmetrischen Benzylphenylhydrazins zugunsten der Formel IV. Man verfuhr dabei ebenso wie bei der Umsetzung mit Phenylhydrazin. SO wurde zunachst ein rotgelbes 0 1 erhalten, welches schliefilich in farblosen Nadeln krystallisierte. Schmp. logo. Es loste sich in konzentrierter Schwefelsaure mit gelber Farbe, die mit Eisenchlorid in rotbraun umschlug. CH.C(CsH5):N.N.csHs CH. C(CsH5): N. N. CsHs! 111. 0.0699 g Sbst.: 5.8 ccm N (19.5O, 745 mm). Dnnach kann dem Korper die Formel C,sIIa,jNd. Ber. N 9.4. Gef. N 9.2. CH. c (c&) : N. N (CT&) CsH.5 CH. c(C~d&) : N. N (CTH~) CsHs zugeschrieben werden. Doch ist diese, ebeoso wie diejenige des Phenylhydrazinderivates nur mit Vorbehalt anzunehmen. Mangel an Material verhinderte uns leider, sie noch weiter zu erharten. B r a u n s c h w e i g , Chem. Laborat. der Techn. Hochschule. 48. Julius Schmidlin: Farblosea und fsrbiges Triphenylmethyl. [Mitteilung aus dem Chem. Laboratorium des Schweizerischen Polytechnikums in Zarich.] (Eingegangen am 30. Juni 1908.) SDas Triphenylmethyl bildet, frisch dargestellt, f a r b l o s e Krystalle; seine Losungen sind dagegen i m n i e r gelb gefarbta. So lautet der

Sizing the role of London dispersion in the dissociation of all-meta tert-butyl hexaphenylethane

“…1 In addition, the neat colourless hydrocarbon was found to be in equilibrium with a coloured form in solution. 8 This triggered an intense discussion regarding the proper structure of triphenylmethyl where, apart from the highly symmetric HPE structure, 9 quinoid structures H- 2 10 and H- 3 11 were suggested (Scheme 1). In an early review Gomberg described an equilibrium between an associated and a free radical, the monoquinoidal structure, and HPE.…”

A Perspective on Free Radical Autoxidation: The Physical Organic Chemistry of Polyunsaturated Fatty Acid and Sterol Peroxidation

“…The rearrangement is clearly dissociative. The mechanistic picture for the [3,2] rearrangement of simple allylic peroxyl radicals was much more difficult to unravel, however, and this provided a stimulus for one thread of our research for a decade.…”

“…Allylic [3,2] rearrangements are mechanistically important in the free radical oxidation of oleic acid. 90 The oxidation of oleates proceeds by abstraction of an allylic hydrogen at C-8 or C-11 of the acid, as shown in Scheme 7A for abstraction at C-8.…”

“…(E)-10-peroxyl-8-ene and (Z)-8peroxyl-9-ene compounds. Allylic [3,2] peroxyl radical rearrangements shown in Scheme 7B give the two (E) peroxyl radicals that are trapped to give the thermodynamic (E)-8 and -10-hydroperoxides. As shown in Scheme 7B, of the three hydroperoxide products shown, one is a kinetic product, one is a thermodynamic product and one ((E)-10-hydroperoxyoctadeca-8-enoic acid) is formed both kinetically and thermodynamically.…”

“…Indeed, a critical piece of evidence supporting the notion that he had prepared triphenylmethyl was the fact that his species reacted with molecular oxygen to form a symmetrical peroxide in a non-chain reaction. 3 The color of the radical disappeared when oxygen was admitted to solutions of the dimer, only to appear again once oxygen was excluded and dissociation of the dimer gave more radical. Subsequent experiments by Mike McBride and his coworkers at Yale in the early 1970s on the reactions of triphenylmethyl radical with oxygen shed light on Gomberg’s experiments and showed that a free radical chain reaction of the dimer with oxygen led to products that complicated Gomberg’s analysis.…”