Section 50
Chapter 49,845

Packing conflicts in the Z' = 5 structure of CF (3) (CF (2) ) (3) (CH (2) ) (10) COOH

Lehmler, H.J.; Parkin, S.; Brock, C.P.

Acta Crystallographica. Section B Structural Science 60(Part 3): 325-332


ISSN/ISBN: 0108-7681
PMID: 15148436
DOI: 10.1107/s0108768104005609
Accession: 049844923

Dimers of the partially fluorinated amphiphile 1-(perfluorobutyl)undecanoic acid, CF(3)(CF(2))(3)(CH(2))(10)COOH, crystallize in the same basic packing arrangement found for many n-alkyl carboxylic acids. The unit cell of the fluorinated compound, however, contains five independent molecules rather than the one found for most n-alkyl carboxylic acids including CH(3)(CH(2))(13)COOH. The structures of the two C(15) acids are compared. The structural modulations that lead to the large value of Z' can be understood as resulting from the conflict between the necessity of filling space densely and uniformly and the tendency of unlike groups to be segregated spatially. The few other known structures of compounds with both (CF(2))(n) and (CH(2))(m) regions show evidence of the same conflict.

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