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HOBt Hydrate

N-Hydroxybenzotriazole, developed by W. König and R. Geiger in 1970 was the most popular additive during the last decades.
CAS: 123333-53-9

Synonym: Hydroxybenzotriazole




Molecular Formula


Molecular Weight

135.12 [gr/mol]


White to off-white crystalline powder

Storage Conditions

Store in a cool and dry place


  • HOBt is one of the most effective suppressors of racemization in carbodiimide-mediated reactions.
  • The most important drawback of the additive lies in its explosive character, especially in water-free form. Therefore, its availability is more restricted today but it can be substituted by more stable additives as OxymaPure and K-Oxyma.
  • Polymer-bound HOBt is used for the formation of medium ring lactams with DCC in the presence of resin-bound esters and also for amides synthesis.


  • Kinetics of Amide Formation through Carbodiimide/N-Hydroxybenzotriazole (HOBt) Couplings
    L. C. Chan and B. G. Cox J. Org. Chem., 2007, 72, 8863-8869.
    Read Article
  • Explosive properties of 1-hydroxybenzotriazoles
    K. D. Wehrstedt, P. A. Wandrey, and D. Heitkamp Journal of Hazardous Materials, 2005A126, 1–7.
    Read Article

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