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The rate coefficients for elimination from 24 substrates in the series 2-Z-phenylethyl p-Y-arenesulphonate with potassium t-butoxide in t-butyl alcohol at 40 "C have been correlated with the Hammett equation. The reaction constants pz decrease linearly with the electronic properties of the group Y only for the most electron-withdrawing substituents, indicative of a shift to transition states with less carbanion character. The reaction constants py become less positive as Z becomes more electron-withdrawing, suggesting that increased C, q-H bond breaking is accompanied by decreased C, -X bond breaking, and a shift to a transition state with greater carbanion character. This result supports earlier secondary deuterium isotope studies in establishing a new interpretation of the reactivity ratio koTe/kBr as a measure of C-X bond breaking.

The b a s i c i t y (pKa) of a s e r i e s of p a r as u b s t i t u t e ? . M -p h e n y l p i p e r i 6 i n e s h a s b e e n measured u s i n g u l t r a v i o l e t a b s o r p t i o n s p e c t r o s c o p y . A v e r y good c o r r e l a t i o n was o b t a i n e d for s u b s t i t u e n t s of known H a m m e t t c o n s t a n t s ( a -) and t h i s h a s beefi u s e d t o e v a l u a t e p r e v i o u s l y u n r e p o r t e d p a r a m e t e r s .44 7

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Abstract-An NMR method is described for assaying the enantiomer composition of the pharmacologically active material penicillamine (l), using tris-(3-heptafluorobutyryl-d-camphorato)europium. The L enantiomer can be detected at levels of 0.4 to 0.5% in DL mixtures. Problems due to the insolubility of penicillamine in nonpolar solvents can be overcome by a two step derivatisation procedure.

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Die Kinetik der Hydrolyse der Titelverbindungen (I) [über die Stufe (II)] bzw. (IV) zu den Produkten (III) bzw. (V) wird hinsichtlich des Einflusses des Heteroarylsubstituenten bzw. der Halogensubstituenten eingehend untersucht.

The first and second hydrolysis rate coefficients for the title compounds are discussed in terms of variation of the heteroaryl substituent (substituted phenyl, furyl, pyrrolyl, or thienyl) and of the halogen substituents (X = F, CI, I, or CCI,).Electron-withdrawing substituents in the aryl rings enhance the rate coefficients, which are linearly related to the pK, values of the analogous dioxo-products (111) for phenyl. thienyl, or pyrrolyl substituents. Evidence is presented to show that the rate-determining step in the hydrolysis is nucleophilic attack on the triazine rather than carbon-halogen bond rupture.PART I V 1 described the mechanism of hydrolysis of 2,4-dichloro-6-(N-methylpyrrol-2-yl)-s-triazine in a range of aqueous dioxan solutions of varying acidity. The SCHEME 1 kinetics for the initial hydrolysis in alkaline media did not require the intermediacy of a hydrate, as has been