Melanin. 2. Electrochemical study of the oxidation of .alpha.-methyldopa and 5,6-dihydroxy-2-methylindole

Young, Thomas E.; Babbitt, Brion W.; WOLFE, L. A.

doi:10.1021/jo01302a029

Cited by 26 publications

(9 citation statements)

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“…Young and Babbitt detected the oxidation peak due to 5 ⇀ 6 at pH 7.68 and a temperature of 35 °C . Or they also did by using an authentic sample of 5 . Hawley et al observed the oxidation peak due to 5,6-dihydroxy- N -methylindole from the adrenaline pathway .…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Study of Dopamine at Electrode Fabricated by Cellulose-Assisted Aqueous Dispersion of Long-Length Carbon Nanotube

Muguruma

Inoue

Inoue³

et al. 2016

J. Phys. Chem. C

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A long-length (hundred micrometers) carbon nanotube is successfully dispersed in aqueous solution with surfactant cellulose while maintaining its length. An electrochemical study of the synthetic pathway of dopamine (DA), dopamine-o-quinone (DAQ), leucodopaminechrome (LDAC), and dopaminechrome (DAC) at the electrode fabricated by the long-length carbon nanotube dispersed solution is presented. The sequence DA ⇌ DAQ ⇀ LDAC ⇌ DAC for the reaction is electron transfer-chemical reaction-electron transfer (ECE)-type, which is a chemical reaction (DAQ ⇀ LDAC, C) interposed between two electron transfer reactions (DA ⇌ DAQ and LDAC ⇌ DAC, E). The salient electrochemical signals due to both DA ⇌ DAQ and LDAC ⇌ DAC can be obtained at the long-length carbon nanotube electrode, unlike other carbon electrodes such as carbon paste, graphene, fullerene, nanofiber, and graphite. The overall reaction is dominated by step DAQ ⇀ LDAC and is sensitive to pH. With cyclic voltammetry in acidic media, the peak current due to LDAC ⇀ DAC disappeared at a higher scan rate because the reaction rate for DAQ ⇀ LDAC was so slow that DAQ was completely consumed in the electron transfer of DAQ ⇀ DA before the chemical reaction of DAQ ⇀ LDAC could go forward. In alkaline media, the peak height due to DAC ⇀ LDAC became as high as that due to DA ⇀ DAQ because the DAQ ⇀ LDAC rate became fast enough that a sufficient amount of LDAC was generated for the subsequent reaction of LDAC ⇀ DAC. Concomitantly, the reaction DAQ + LDAC ⇌ DA + DAC was generated. Quantitative and selective detection of dopamine based on the signal due to LDAC ⇀ DAC is possible just as in the conventional strategy of direct oxidation of dopamine (DA ⇀ DAQ).

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Section: Resultsmentioning

confidence: 99%

Electrochemical Study of Dopamine at Electrode Fabricated by Cellulose-Assisted Aqueous Dispersion of Long-Length Carbon Nanotube

Muguruma

Inoue

Inoue³

et al. 2016

J. Phys. Chem. C

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“…The addition of excess diethyl malonate (DEM; [DEM]/[1] = 11) had no effect upon the cathodic peak height (ip,c,i) for the reduction of 1. However, DEM did cause the anodic peak which was present near 0.04 V in aprotic media to disappear and a second, large cathodic peak (i 2/¿p c l = 1.2) to appear near -2.0 V. On the basis of product and cyclic voltammetric studies which will be described below, the species that is reduced at the potential of the second cathodic wave is the alcohol F1HC(CH3)20H (2).…”

Section: Resultsmentioning

confidence: 99%

Electrochemical studies of the reduction of 6,6-dimethyldibenzofulvene oxide and tetraphenyloxirane

Nuntnarumit¹,

Null²,

Hawley³

1984

J. Org. Chem.

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“…15,16,17 These studies provided the first order rate constants for the cyclisation of the free amines (k 2 , Scheme 3) as well as the overall rate constants for aminochrome formation (k f , Table 2 Scheme 3) is the rate limiting process. Subsequently, a combined theoretical and kinetic study of the oxidation of L-dopa using mushroom tyrosinase under acidic conditions (pH 5.0-6.0) was able to derive values of the rate constants for both the first order deprotonation step (k 1 ) and the cyclisation step (k 2 )(Scheme 3).…”

Section: Methodsmentioning

confidence: 99%

ortho-Quinone amines and derivatives: the influence of structure on the rates and modes of intramolecular reaction

Land¹,

Ramsden²,

Riley³

2006

Arkivoc

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The influence of N-substituents and chain length on the mode and rate of intramolecular reaction of ortho-quinone amines is reviewed. These reactions have been the subject of a series of studies over the last decade using a combination of pulse radiolysis, enzyme oximetry and preparative chemistry. Alternative reactions are cyclisation, spirocyclisation and para-quinomethane formation. The observed mode of reaction is determined by both the length of the ortho-quinone side chain and the nature of the N-substituents. The rates of the competing reactions are discussed and compared with rates determined by other workers using cyclic voltammetry. Formation of a para-quinomethane is relatively slow and only occurs when cyclisation is unfavourable due to steric, entropy or electronic effects. Spirocyclisation is rapid and usually reversible but in one case a stable spirocyclic product has been isolated.

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Melanin. 2. Electrochemical study of the oxidation of .alpha.-methyldopa and 5,6-dihydroxy-2-methylindole

Cited by 26 publications

References 0 publications

Electrochemical Study of Dopamine at Electrode Fabricated by Cellulose-Assisted Aqueous Dispersion of Long-Length Carbon Nanotube

Electrochemical Study of Dopamine at Electrode Fabricated by Cellulose-Assisted Aqueous Dispersion of Long-Length Carbon Nanotube

Electrochemical studies of the reduction of 6,6-dimethyldibenzofulvene oxide and tetraphenyloxirane

ortho-Quinone amines and derivatives: the influence of structure on the rates and modes of intramolecular reaction

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