Related Experiment Video
Updated: Jun 10, 2026

Efficient Synthesis of Polyfunctionalized Benzenes in Water via Persulfate-promoted Benzannulation of α,β-Unsaturated Compounds and Alkynes
Published on: December 16, 2019
The biphenyl-monitored effective size of unsaturated functional or fluorinated ortho substituents
Renzo Ruzziconi1, Sara Spizzichino, Andrea Mazzanti
1Chemistry Department, University, Via Elce di Sotto 10, I-06100, Perugia, Italy. ruzzchor@unipg.it
Abstract:
The size of a series of typical substituents has been probed by dynamic NMR measurements of the barriers to aryl-aryl rotation of the corresponding biphenyls. The resulting B values are meaningful because only mono-ortho substituted compounds were investigated and thus the results are not compromised by the non-additivity of multiple steric effects. On the basis of the chosen model system ethynyl and cyano groups were found to be slightly smaller than a phenyl ring. In contrast, vinyl and, in particular, formyl groups proved to be larger than phenyl. The latter difference is due to the loss of conjugation forces at the planar transition state. Alpha-Hydroxyhexafluoroisopropyl is slightly more bulky than tert-butyl. Pentafluorophenyl and trifluoromethoxy exhibit nearly the same effective size as phenyl and methoxy, respectively. Trifluoromethyl is somewhat smaller than isopropyl.
More Related Videos
08:56Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions
Published on: November 30, 2022
06:56Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) Mass Spectrometry
Published on: June 10, 2018
Related Concept Videos
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
Nomenclature of Aromatic Compounds with a Single Substituent
Nomenclature of Aromatic Compounds with Multiple Substituents
For disubstituted benzene derivatives, with two groups attached to the benzene ring, three constitutional isomers are possible. For example, consider dimethyl benzene, often called xylene, where the second methyl group can be substituted at the second, third, or fourth carbon. The relative position of the substituents is represented by prefixes ortho, meta, or...
Directing Effect of Substituents: ortho–para-Directing Groups
Reactions at the Benzylic Position: Halogenation
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3