Related Experiment Video
Updated: May 3, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Substituent Effects on the Formation and Nucleophile Selectivity of Ring-Substituted Phenonium Ions in Aqueous
Yutaka Tsuji1, Shin Ogawa1, John P Richard2
1Department of Biochemistry and Applied Chemistry, Kurume National College of Technology, Komorinomachi, Kurume 830-8555, Japan.
Abstract:
The reaction of 2-(4-methyphenyl)ethyl tosylate (Me-1-OTs) in 50/50 (v/v) trifluoroethanol/water at 25 °C is first-order in the concentration of azide anion nucleophile. A carbon-13 NMR analysis of the products of the reactions of Me-1-[α- in 50/50 (v/v) trifluoroethanol/water at 25 °C shows the formation of Me-1-[β-, Me-1-[β- and Me-1-[β- from the trapping of a symmetrical 4-methylphenonium ion reaction intermediate Me-2+. The formation of Me-1-[α- by concerted bimolecular displacement of azide ion at Me-1-[α- (kN = 3.8 × 10-6 M-1 s-1) and of Me-1-[α- and Me-1-[α- by concerted bimolecular displacement of solvent (ksolv = 1.8 × 10-8 s-1) is also observed. An analysis of the rate and product data provides a value of kaz/ks = 32 M-1 for partitioning of Me-2+ between addition of azide ion and solvent that is nearly 3-fold smaller than kaz/ks = 83 M-1 reported in an earlier study on the partitioning of MeO-2+ [J. Org. Chem.2011, 76, 9568]. This change is attributed to a decrease in nucleophile selectivity with increasing electrophile reactivity for the activation-limited addition of solvent and azide anion to X-2+. These data set a limit of 1/ks ≥ 10-7 s for the lifetime of Me-2+ in aqueous solution.
More Related Videos
Related Concept Videos
Predicting Products: SN1 vs. SN2
With increased substitution on the alkyl halide,...
Directing Effect of Substituents: ortho–para-Directing Groups
Nucleophilic Substitution Reactions
In 1896, the German chemist Paul Walden discovered that he could interconvert pure enantiomeric (+) and (-) malic acids through a series of reactions. This conversion suggested the involvement of optical inversion during the substitution reaction. Further, in 1930, Sir Christopher Ingold described for the first time two different forms of nucleophilic substitution reactions, which are known as SN1 (nucleophilic substitution unimolecular) and SN2 (nucleophilic substitution...
Nucleophilic Aromatic Substitution: Elimination–Addition
Nucleophiles
Directing and Steric Effects in Disubstituted Benzene Derivatives

