Diazald (N-methyl-N-nitroso-p-toluenesulfonamide) is used as a relatively safe and easily handled precursor to diazomethane, which is toxic and unstable.[2] Diazald has become the favored commercially available precursor for the synthesis of diazomethane, compared to reagents like N-methyl-N-nitrosourea and N-methyl-N'-nitro-N-nitrosoguanidine, which are less thermally stable and more toxic and mutagenic, respectively.
Upon the addition of a base such as sodium hydroxide or potassium hydroxide and mild heating (65–70 °C) in a mixture of water, diethyl ether, and a high boiling polar cosolvent (e.g., diethylene glycol monomethyl ether[3]), the N-nitrososulfonamide undergoes successive elimination reactions to produce diazomethane (which is codistilled as an ethereal solution) as well as a p-toluenesulfonate salt as a byproduct, according to the following mechanism:
Like other nitroso compounds, it is thermally sensitive, as a result of its weak N–NO bond whose bond dissociation energy was measured to be 33.4 kcal/mol.[4]
References
- ^ External MSDS, Sigma Aldrich
- ^ Diazald in Chemical Synthesis, Sigma Aldrich
- ^ "Diazomethane". www.orgsyn.org. Retrieved 2018-07-27.
- ^ Zhu, Xiao-Qing; Hao, Wei-Fang; Tang, Hui; Wang, Chun-Hua; Cheng, Jin-Pei (March 2005). "Determination of N−NO Bond Dissociation Energies ofN-Methyl-N-nitrosobenzenesulfonamides in Acetonitrile and Application in the Mechanism Analyses on NO Transfer". Journal of the American Chemical Society. 127 (8): 2696–2708. doi:10.1021/ja0443676. ISSN 0002-7863. PMID 15725027.
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