✍ Scribed by Hernqvist, L. ;Larsson, K.
No coin nor oath required. For personal study only.
Based on X‐ray single crystal data of the β′‐form of triundecanoin the general features of the molecular arrangement in this crystal form have been derived. The unit cell contains eight molecules arranged according to space group P2~1/c~, with alternation of the tilt of the hydrocarbon chains in adjacent bimolecular layers. The structure within the molecular layer is quite similar to that of the β‐form; the main difference being the chain packing. A second β″‐form, β′~2~, of triundecanoin has been observed and it differs from the one mentioned above in the orientation of the chain packing subcell 0° in relation to the true unit cell. The polymorphic transitions have been followed by recording of the diffraction pattern versus temperatures. The polymorphic transitions α · β′ · β can be regarded mainly as different lateral arrangement of a dimeric unit. In the α‐form the chains are disordered near the methyl end groups, and due to this disorder the structure is closely related to the lamellar liquid‐crystalline phase. It is also possible to classify β′‐forms according to short‐spacing data into a β′~1~‐type and a β′~2~‐type, and these groups can be identified also in complex triglycerides.
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