Parathion Hydrolysis Revisited: In Situ Aqueous Kinetics by 1 H NMR

Orth

2019

J. Braz. Chem. Soc.

Is the broad mechanistic versatility of imidazole towards organophosphates (OPs), that has inspired many catalysts and sensors, beneficial? Herein, a thorough analysis is given seeking to unravel this puzzle. For OPs from the P=O family, imidazole attacks the phosphorus atom exclusively (N-phosphorylates). With the P=S family which are less reactive, an unusual N-alkylation predominates. Surprisingly, imidazole reacts with methyl parathion exclusively at the aliphatic carbon, whilst for the ethylated analogue parathion, imidazole reacts by two pathways: at both the phosphorus and aliphatic carbon, with predominance for the latter. The preference for the electrophilic center can be modulated by the pH. Overall, a mechanistic structure-related trend is observed: imidazole tends to prefer other electrophilic centers than the phosphorus for less reactive OPs. Moreover, this gives important insights concerning the challenging chemistry of imidazole alkylation and the outcomes for monitoring systems that depend on the detection of degradation products. Finally, a thorough comparison with the literature is presented seeking to understand how imidazole reacts towards various OPs. We suggest that the promiscuity of imidazole boosts up its versatility.

Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Nmr Studymentioning

confidence: 99%

“…7), the reactions occur exclusively at the aliphatic carbon. 27 In fact, this pH dependence is also an important ally when targeting specific reactions pathways.…”

Section: Imidazoles: Versatile or Promiscuous?mentioning

confidence: 99%

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Are Imidazoles Versatile or Promiscuous in Reactions With Organophosphates? Insights From the Case of Parathion

Orth

2019

J. Braz. Chem. Soc.

“…It is also noticeable that hydroxide commonly reacts via the phosphorus moiety for both P=S and P=O organophosphates, while with water both phosphorus and aliphatic carbon could react. [12,13] This changes with other nucleophiles, not following any evident pattern.…”

Section: Introduction: Why Nucleophilic Reactions With Organophosphates?mentioning

confidence: 91%

Nucleophilic Neutralization of Organophosphates: Lack of Selectivity or Plenty of Versatility?

Campos

Pavez

et al. 2021

The Chemical Record

Neutralization of organophosphates is an issue of public health and safety, involving agrochemicals and chemical warfare. A promising approach is the nucleophilic neutralization, scope of this review, which focuses on the molecular nucleophiles: hydroxide, imidazole derivatives, alpha nucleophiles, amines and other nucleophiles. A reactivity mapping is given correlating the pathways and reaction efficiency with structural dependence of the nucleophile (basicity) and the organophosphate (electrophilic centers, P=O/P=S shift, leaving and nonleaving group). Reactions extremely unfavorable (> 20 years) can be reduced to seconds with various nucleophiles, some which are catalytic. Although there is no universal nucleophile, a lack of selectivity in some cases accounts for plenty of versatility in other reactions. The ideal neutralization requires a solid mechanistic understanding, together with balancing factors such as milder conditions, fast process, selectivity and less toxic products.

Puzzling Reaction of Imidazole with Methyl Parathion: P=S versus P=O Mechanistic Shift Dilemma in Organophosphates

Nascimento

Nunes

et al. 2018

Chemistry A European J

Organophosphates (OPs) constitute many toxic agrochemicals and warfare and can undergo a wide spectrum of mechanisms, some which are fairly unexplored. In this sense, concise mechanistic elucidation stands out as a strategic tool for achieving efficient detoxification and for monitoring processes. Particularly intriguing is the effect of substituting the oxygen atom of the phosphoryl moiety (P=O) in OPs with a sulfur atom to give the thio‐derived OPs (i.e., OTPs, P=S). In general, imidazole (IMZ) reacts very efficiently with OPs by targeting the phosphorus atom, although herein we evidence a thio‐driven shift with OTPs: IMZ undergoes unusual nucleophilic attack at the aliphatic carbon atom of methyl parathion. Alkylation of IMZ under mild conditions (aqueous weakly basic medium) is also novel and should be applicable to other novel IMZ‐based architectures, and thereby, it can be a great ally for organic synthesis. Overall, a broader understanding of the mechanistic trend involved in such highly toxic agents is provided.