N-Allylthiourea: Uses and Chemical Reactions

What is N-Allylthiourea？

N-Allylthiourea (ATU) is a white crystalline solid with a slight garlic odour. It is soluble in water and ethanol, slightly soluble in ether and insoluble in benzene. ATU has been used as a nitrification inhibitor in studies of the transformation of diclofenac, naproxen and bisoprolol under aerobic and anaerobic conditions. It is used in medicine to reduce scar tissue and to combat a form of dermatitis. In addition, ATU was used as an electrolyte additive in aqueous zinc ion batteries to establish a stable zinc electrolyte interface in a weakly acidic electrolyte, optimising the performance of zinc ion batteries. It was also used to prepare a chelating material, N-allyl thiourea chitosan (ATUCS), for the removal of arsenic azo III (As (III)) dye from aqueous solutions.

Chemical Reactions

N-Allylthiourea (ATU) has often been studied as a substrate (A) in various systems of photooxidation sensitized by dyes (S). ATU is generally considered a singlet oxygen (¹0₂) acceptor, but neither the site of this reaction (thiourea or allyl moiety) nor its rate constant in aqueous solutions has been established experimentally. Besides the possible participation of ATU in the singlet oxygen mechanism and in sensitized photooxidations, it can also react via a free radical mechanism (type I), since it reacts moderately fast with the triplet state of some sensitizers (³S) by the following mechanism:

Experiments on the photooxidation of N‐allylthiourea, thiourea, and N‐allylurea sensitized by the dye phenosafranine show that in N‐allylthiourea the thiourea group is the site of singlet oxygen attack, while the allyl moiety neither reacts with nor quenches this metastable form of O2 (in neutral aqueous solutions). Low concentrations of N‐3 (a known quencher of singlet oxygen) strongly reduce the photooxidation of allylthiourea by a mechanism which apparently obeys simple competition kinetics. From these results the rate constant of the reaction between allylthiourea and singlet oxygen is obtained (k= 4 × 106M‐1 s‐1; pH = 7.1).

References:

[1] SYRYLL OLIDAN . Zn dendrite suppression and solid electrolyte interface control using N-allylthiourea as an electrolyte additive for aqueous Zn-ion batteries[J]. Electrochimica Acta, 2023. DOI:10.1016/j.electacta.2023.143704.  

[2] I. KRALJIĆ  H. K. ON THE REACTION OF SINGLET MOLECULAR OXYGEN WITH N‐ALLYLTHIOUREA IN AQUEOUS SOLUTION[J]. Photochemistry and Photobiology, 1978. DOI:10.1111/j.1751-1097.1978.tb07557.x.

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