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A Synthetic, X‐ray, NMR Spectroscopy and DFT Study of β‐Naphthil Dihydrazone, Di(β‐naphthyl)acetylene, Tetra(β‐naphthyl)cyclopentadienone, and Hexa(β‐naphthyl)‐benzene: C 6 (C 10 H 7 ) 6 Is a Disordered Molecular Propeller
Author(s) -
Harrington Laura E.,
Britten James F.,
Nikitin Kirill,
McGlinchey Michael J.
Publication year - 2017
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201600512
Subject(s) - chemistry , hexa , acetylene , conformational isomerism , benzene , tetra , molecule , crystallography , decarbonylation , nuclear magnetic resonance spectroscopy , yield (engineering) , ring (chemistry) , spectroscopy , medicinal chemistry , stereochemistry , photochemistry , organic chemistry , materials science , metallurgy , catalysis , physics , quantum mechanics
Treatment of β‐naphthil dihydrazone, 1 , with silver oxide yields di(β‐naphthyl)acetylene, 2 , which undergoes Diels–Alder cycloaddition with tetra(β‐naphthyl)cyclopentadienone, 4 , to give hexa(β‐naphthyl)benzene, 5 , upon decarbonylation. Molecules 1 , 2 and 4 have been characterised by X‐ray crystallography, but hexa(β‐naphthyl)benzene exhibits rotational disorder of the peripheral substituents. Nevertheless, calculations at the density functional level reveal the favoured structure of 5 to be a molecular propeller, in which the eight possible rotamers are essentially iso‐energetic. Variable‐temperature NMR spectroscopy studies yield a naphthyl rotational barrier of approximately 17 kcal mol −1 , similar to that previously found for meta ‐substituted phenyl groups. Enantiomerisation of hexa(β‐naphthyl)benzene engendered by rotation of a single naphthyl ring has been studied by DFT calculations, and the process has been represented pictorially.