Acta Crystallographica Section C

Crystal Structure Communications

Volume 69, Part 2 (February 2013)

organic compounds

Acta Cryst. (2013). C69, 204-208    [ doi:10.1107/S0108270113002485 ]

Relative influence of noncovalent inter­actions on the melting points of a homologous series of 1,2-dibromo-4,5-dialk­oxy­benzenes

A. Fonrouge, F. Cecchi, P. Alborés, R. Baggio and F. D. Cukiernik

Abstract: Crystal structures are presented for two members of the homologous series of 1,2-dibromo-4,5-di­alk­oxy­benzenes, viz. those with decyl­oxy and hexa­decyl­oxy substituents, namely 1,2-dibromo-4,5-bis(decyl­oxy)­benzene, C26H44Br2O2, (II), and 1,2-dibromo-4,5-bis(hexa­decyl­oxy)­benzene, C38H68Br2O2, (III). The relative influences which halogen bonding, [pi]-[pi] stacking and van der Waals inter­actions have on these structures are analysed and the results compared with those already found for the lightest homologue, 1,2-dibromo-4,5-dimeth­oxy­benzene, (I) [Cukiernik, Zelcer, Garland & Baggio (2008). Acta Cryst. C64, o604-o608]. The results confirm that the prevalent inter­actions stabilizing the structures of (II) and (III) are van der Waals contacts between the aliphatic chains. In the case of (II), weak halogen C-Br...(Br-C)' inter­actions are also present and contribute to the stability of the structure. In the case of (III), van der Waals inter­actions between the aliphatic chains are almost exclusive, weaker C-Br...[pi] inter­actions being the only additional inter­actions detected. The results are in line with commonly accepted models concerning trends in crystal stability along a homologous series (as measured by their melting points), but the earlier report for n = 1, and the present report for n = 10 and 16, are among the few providing single-crystal information validating the hypothesis.

Formula: C26H44Br2O2 and C38H68Br2O2

hkldisplay filedownload file

Structure factor file (CIF format) (263.9 kbytes)
[ doi:10.1107/S0108270113002485/uk3060IIsup2.hkl ]
Contains datablock II

hkldisplay filedownload file

Structure factor file (CIF format) (337.9 kbytes)
[ doi:10.1107/S0108270113002485/uk3060IIIsup3.hkl ]
Contains datablock III


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