Ionization Constants of Mandelic Acid Derivatives.

Klingenberg, J. J.; Thole, J. P.; Lingg, Robert D.

doi:10.1021/je60028a026

Cited by 6 publications

(4 citation statements)

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“…This assumption is supported by the fact that the dissociation constants for substituted mandelic acids vary only slightly [13], and that the formation constants for cerium(1V) complexes with substituted benzyl alcohols are not very sensitive to electronic effects [6,14]. Therefore the trend of the relative rates (CH3 > H < C1 < NOz) found in the present investigation would reflect the effects of the substituents on the rate-determining step and would be compatible with the path A since the carbon radical is expected to be stabilized by both electron-donating and electron-withdrawing groups.…”

Section: Resultsmentioning

confidence: 93%

Substituent effects on the kinetics of the cerium(IV) oxidation of mandelic acids in sulfate media. Anomalous kinetic behavior of the methoxy derivative

Calvaruso

Cavasino

Sbriziolo

1981

Int J of Chemical Kinetics

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The kinetics of the cerium(1V) oxidation of p-nitro and p-methoxymandelic acids have been investigated in H2S04-MHS04 (M+ = Li+ , Na+, K+) and H2S04-MC104 (M+ = H+, Na+) mixtures a t a constant total electrolyte concentration of 2.00 mol/dm3. The oxidation of p-nitromandelic acid proceeds through two [H+]-independent paths, as was also observed for some substituted mandelic acids studied previously. The kinetic behavior of the pmethoxy derivative differs from that of the other mandelic acids in that (1) the oxidation occurs via two [ H+]-dependent paths, (2) the reaction rate is anomalously high, (3) the activation enthalpy and entropy of the overall process are markedly lower. It provides strong support to the suggestion that a different mechanism is operative. The substituent effects and the reaction mechanism are discussed.

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Section: Resultsmentioning

confidence: 93%

Substituent effects on the kinetics of the cerium(IV) oxidation of mandelic acids in sulfate media. Anomalous kinetic behavior of the methoxy derivative

Calvaruso

Cavasino

Sbriziolo

1981

Int J of Chemical Kinetics

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“…Hydroxy(4‐methoxyphenyl)acetic Acid ( rac ‐2f): Yield: 73 % (according to Method B); white solid; m.p. 104–106 °C ( n ‐hexane/AcOEt) [ref . 108 °C (no data)].…”

Section: Methodsmentioning

confidence: 99%

“…104-106°C (n-hexane/ AcOEt) [ref. [66] 108°C (no data)]. 1 Hydroxy(2-naphthyl)acetic Acid (rac-2g): Yield: 75 % (according to Method B); white solid; m.p.…”

Section: Preparation Of the Racemic Mandelic Acid Derivatives Rac-2a-mentioning

confidence: 99%

Chemoenzymatic Preparation of Enantiomerically Enriched (R)‐(–)‐Mandelic Acid Derivatives: Application in the Synthesis of the Active Agent Pemoline

2017

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The enantioselective resolution of several racemic derivatives of mandelic acid methyl ester catalyzed by lipases from Pseudomonas fluorescens (Amano AK) or Burkholderia cepacia (Amano PS‐C II and Amano PS‐IM) has been achieved. A gram‐scale lipase‐mediated kinetic resolution approach has been developed that allows the facile synthesis of the corresponding methyl (R)‐(–)‐mandelates with excellent enantiomeric excesses (up to >99 % ee) and reaction enantioselectivity (E values up to >200). The dopaminergic agent pemoline, used in the treatment of attention‐deficit hyperactivity disorder (ADHD) and narcolepsy, was synthesized with 98 % ee in a straightforward route by condensing the prepared methyl (R)‐(–)‐mandelate with guanidine hydrochloride under basic conditions. The desired (R)‐(+)‐pemoline in optically pure form (>99 % ee) was obtained after two recrystallizations from ethanol. However, it was confirmed by chiral HPLC that optically active pemoline undergoes racemization in methanol solution.

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“…Prior to 1966 values had been reported only for mandelic acid (7) and m-halo (7), o-, m-, and p-nitro (3), and p-bromo (2) derivatives of mandelic acid. In 1966 Klingenberg, Thole, and Lingg (5) published ionization constant values for 13 mandelic acid derivatives. Table I is a summary of the values reported.…”

Section: Literature Citedmentioning

confidence: 99%