I can't understand how the following compound with bridged benzene rings looks like:

enter image description here

  • 3
    $\begingroup$ this question will probably be downvoted because you haven't "done your due diligence" see the code of conduct. I recommend trying to create the molecule in a visualization software like Avogadro and see for yourself. $\endgroup$
    – Cody Aldaz
    Jun 12 at 8:15
  • $\begingroup$ Where is code of conduct $\endgroup$
    – Ritil
    Jun 12 at 16:19
  • $\begingroup$ chemistry.stackexchange.com/conduct $\endgroup$ Jun 13 at 2:55

1 Answer 1


This is a cyclophane, namely 4,8-dibromo[2.2]paracyclophane. Lonsdale et al. [1] first structurally characterized [2.2]paracyclophane in 1960:

The molecule consists of two facing benzene rings linked in para-positions by two $\ce{(CH2)2}$ bridges. As a result of steric hindrance, the benzene rings are each bent into a boat-shape, but even so, their maximum distance apart in the molecule is only 3.09 Å, whereas the normal van der Waals distance is upwards of 3.4 Å.


The angle of bending of the benzene ring (14°) does not change with temperature, but the aliphatic $\ce{CH2-CH2}$ bond appears to be unusually long at room temperatures* and has decreased by 0.07 Å at 93 °K. Moreover, although the distance between the two benzene rings does not change, there is a decrease of 0.03 Å in the overall length of the molecule from 291 to 93 °K.


Structure of [2.2]paracyclophane
Figure 4. Diagram showing projection of molecules at $0, 0, 0;$ $1/2, 1/2, 1/2$ and $0, 0, 1$ on to $(100).$

* The $\ce{CH2-CH2}$ bond length is 1.63 Å, which is above average 1.54 Å expected for the aliphatic $\ce{C-C}$ bond.

See CCDC entry DXYLEN for more details and an interactive 3D image.

Several related polysubstituted [2.2]paracyclophanes have been reported:


  1. Lonsdale, K. Y.; Milledge, H. J.; Rao, K. K. V. Studies of the structure, thermal expansion and molecular vibrations of di-p-xylylene, $\ce{C16H16},$ at 93 and 291 °K. Proc. R. Soc. Lond. A 1960, 255 (1280), 82–100. DOI: 10.1098/rspa.1960.0055.
  2. Atman Vorontsova, N. V.; Zhuravsky, R. P.; Antonov, D. Yu.; Sergeeva, E. V.; Godovikov, I. A.; Starikova, Z. A.; Vologzhanina, A. V. Synthesis of Bromo-Substituted 4-Hydroxy[2.2]Paracyclophanes and [2.2]Paracyclophane-4,7-Quinones as Versatile Chiral Building Blocks: [2.2]Paracyclophane Derivatives as Versatile Chiral Building Blocks. Eur. J. Org. Chem. 2015(2), 325–330. DOI: 10.1002/ejoc.201403316.
  3. Chow, H.-F.; Low, K.-H.; Wong, K. Y. An Improved Method for the Regiospecific Synthesis of Polysubstituted [2.2]Paracyclophanes. Synlett 2005, No. 14, 2130–2134. DOI: 10.1055/s-2005-872270.

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