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A theoretical and experimental investigation of acid catalyzed rearrangements of small [ n ]cyclophanes
Author(s) -
Kostermans Gerardus B. M.,
Kwakman Pieter J.,
Pouwels Petra J. W.,
Somsen Gus,
De Wolf Willem H.,
Bicklehaupt Friedrich
Publication year - 1989
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610020405
Subject(s) - chemistry , mndo , protonation , deprotonation , cyclophane , adduct , reactivity (psychology) , proton affinity , mindo , computational chemistry , catalysis , proton , gas phase , acid catalysis , medicinal chemistry , stereochemistry , organic chemistry , molecule , medicine , ion , physics , alternative medicine , pathology , quantum mechanics
The difference in reactivity of small [ n ]cyclophanes towards CF 3 CO 2 H is discussed in terms of charge densities, strain energies and proton affinities. These data are calculated with MNDO and MINDO/3 for para ‐, meta ‐ and ortho ‐cyclophanes and for their ipso ‐protonation products; an attempt is made to transform gas phase Δ H f 0values into liquid phase Δ H 0 f values. Experimental evidence is presented that the acid catalyzed rearrangement of [5]paracyclophane to its ortho ‐isomer proceeds via two consecutive 1,2‐carbon shifts without deprotonation; intermediate adducts were identified by NMR‐spectroscopy. Thus, a gradual shift in reaction pattern in the series [4]‐, [5]‐ and [6]paracyclophane is observed experimentally, in line with the calculational results.
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