G. A. Melkonian

Polarographische Bestimmung der Hydrolysegeschwindigkeit acylierter p-Nitroverbindungen

I n t he series of homologous c o m p o u n d s in sec t ion (1) a n d (2) of t he tab le 1, t he redox po ten t i a l s of t he qu inones and t he radii of t he s u b s t i t u e n t s increase s imu l t aneous ly . I n a g r e e m e n t w i th our p red ic t ion th i s is a c c o m p a n i e d b y an increase of t h e s t r e n g t h of p a r a m a g n e t i c absorp t ion . The s u b s t a n c e s in sec t ion (3) requi re a more de ta i led discussion, which wilt be g iven e lsewhere . F u r t h e r m e a s u r e m e n t s , wh ich should give i n f o r m a t i o n a b o u t t h e m a g n i t u d e of the s ingle t t r ip le t sp l i t t ing are be ing carr ied ou t a t p resen t . A n u m b e r of o ther proper t ies of some of t hese bi radicaI c o m p o u n d s s u p p o r t t he p ic tu re we h a v e g iven above. T he solu t ions of c o m p o u n d s der ived f rom (I) in s t r o n g l y po la r so lven t s are deep blue-redid). Solut ions in non -po la r so lvents , however , are nea r l y colourless, b u t on add i ng to th i s colourless so lu t ion wa t e r or acetoni tr i le , t he s ame in tense b luered colour appears . This is w h a t we m i g h t expec t if t he complex spl i ts preferent ia l ly in to t he u n c h a r g e d componen t s , A and D, in t he nonpolar solvent , whe reas in po la r so lven t s dissociat ion in to ions, A a n d D +, occurs . In s u p p o r t of th i s we h a v e found t h a t a d i lu te so lu t ion of (I) a n d (II) g ives an opt ical abso rp t ion s p e c t r u m in t h e vis ible r ange nea r l y ident ica l to t h a t of t h e s ing ly cha rged ion of (I). W e are i ndeb ted to t he t3ri t ish Council for t h e awa rd of a schola rsh ip (H. K.), Oxford U n i v e r s i t y for t he awa rd of a Pressed Steel C o m p a n y L imi t ed resea rch fel lowship (D. B.) and the D e p a r t m e n t of Scientific and I n d u s t r i a l R e s e a r c h for a m a i n t e n a n c e g r a n t (A. C. R.-I .) d u r i n g t he t e n u r e of wh ich these researches were carr ied out .