鎖中央に側鎖をもつ長鎖アルカンの合成と結晶構造解析

概要

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We synthesized two samples of branched long chain $n$-alkane with methyl and ethyl side groups at the middle of the main chain with the same carbon number of 39, (abbr. M39 and E39, M : methyl and E : ethyl group) and performed SEM, DSC, and X-ray diffraction measurements on solution- and bulk-crystallized samples. The melting temperatures $T_m$ of M39 and E39 were 54.3$^\circ$C and 44.3$^\circ$C, respectively, being considerably lower than $T_m=78.9^\circ$C of corresponding linear $n$-alkane, C39. Direct observation of morphology by SEM as well as X-ray scattering profiles revealed that crystal structure of E39 was more distorted than M39. M39 and E39 crystals both gave a new peak with $d=4.54\AA$ at $2\theta=19.6^\circ$ not oserved for C39 which takes the orthorhombic type of crystal lattice, and also a broad peak at around $2\theta=23.5\circ$. The latter broad peak for M39 tended to split into two peaks with increasing temperature, possibly being due to appearance of the rotational phase near $T_m$. Those results strongly suggest that the subcells of M39 and E39 are the triclinic type.
2000-06-30