Pure, single-component even and odd n-alkanes exhibit distinct packing symmetries, with even n-alkanes favoring monoclinic unit cells and odd n-alkanes packing in orthorhombic symmetry. With small amounts of impurities, however, even n-alkanes adopt orthorhombic packing which may explain the preponderance of orthorhombic forms with polyethylene-like domains in plant waxes. Odd n-alkanes with 11 or more carbons (n ≥ 11) consistently adopt orthorhombic symmetry. Smith reported a structure solution for the n = 23 alkane (n carbon atoms) with Pbcm space group symmetry. In Smith's structure, the long chain end-to-end packing is along the c-axis such that mirror planes at c/4 and 3(c/4) coincide with the molecular mirror symmetry. Dorset, in contrast, has reported odd n-alkanes packing with A21am symmetry when prepared with a benzoic acid epitaxial template to yield crystals with chains perpendicular to the electron beam in SAED. In the A21am unit cell, the long chains are likewise along the c-axis, but with the molecular mirror planes at c/2 and c. The difference in chain packing is perhaps most noticeable in two visualizations, depicted in Figure (1) When viewed along chains, i.e., along [001] and here denoted the 'down-chain' orientation, the offset between sequentially stacked chains differs (see also Figure ), and (2) when viewed with the chains flat, i.e., perpendicular to [001] in these orthorhombic unit cells and here denoted the 'chains-flat' orientation, the sequential chains along the c-axis in the A21am structure are rotated by 180°. Irrespective of the precise unit cell for alkane lamellae, additional disordered states have been identified with chains slipping across lamellar regions giving rise to "nematic" phases. Earlier XRD analysis by Lüth provides further evidence of this general characteristic, where longitudinal molecular disorder within individual lamellae was proposed to compensate copacking of dissimilar chain lengths. These "nematic" phases draw parallels with the 'brick and mortar' model proposed for the structure of the IW layer comprised of both ordered and disordered regions.