AbstractThe reaction products and intermediates from the interaction of acetonitrile with olefins (oct‐1‐ene) or alcohols (tert‐butyl alcohol) in zeolite H‐ZSM‐5 at 296 K have been characterized with13C and15N solid‐state NMR. It has been shown that coadsorption of acetonitrile and olefin on H‐ZSM‐5 gives rise to the intermediateN‐alkylnitrilium cation represents a persistent species inside a zeolite under anhydrous conditions. Upon admittance of water to the pores of the zeolite, theN‐alkylnitrilium cation slowly converts intoN‐alkylamide in accordance with the classic Ritter reaction. In the case of acetonitrile and alcohol, just after coadsorption both the intermediateN‐alkylnitrilium cation and the finalN‐alkyl‐amide are identified simultaneously; the former slowly disappears over a few days. Thus, 1) it has been shown that the Ritter reaction can occur not only in liquid acidic media but also on a solid acid catalyst, zeolite H‐ZSM‐5; 2)N‐alkylnitrilium cations have been detected and characterized with solid‐state NMR as persistent intermediates in the Ritter reaction for the fir