The crystal structure of orthorhombic hexatriacontane, C₃₆H₇₄

Abstract

Single crystals of the orthorhombie form of hexatriacontane C3sH~4 have been shown to have space group Pca21 with unit-cell dimensions a ----7.42, b ----4.96, c ----95.14 /~. The crystal structure has been determined from Fourier syntheses of the electron density projected down the three principal crystallographic axes and from observations of the agreement between observed and calculated structure factors. The molecular chains are regular and periodic within experimental error, with a C-C bond length of 1.533 A and a zigzag bond angle of 112 °. The side-by-side packing of chains is identical with that found in the monoclinie form and in polythene. Intermolecular distances are given and discussed briefly in relation to the polymorphism, the stability and the anisotropic thermal vibrations and expansion coefficients of long chain hydrocarbons.

Polytypic structures of n-C28H58 (octacosane) and n-C36H74 (hexatriacontane)

“…With identical morphologies (rhombic platelets), the polymorphs differ only in the orientation of the paraffinic chains: in the monoclinic phase the chains are inclined relative to the (001) plane (Shearer & Vand, 1956), whereas in the orthorhombic phase they are perpendicular to this plane (Teare, 1959). The crystals obtained belonged to neither phase, but to a new orthorhombic phase, space group Pbca with a = 7.42, b = 5"59, c= 84"5 A, Z=4.…”

New insights on the crystalline forms in binary systems of n-alkanes: Characterization of the solid ordered phases in the phase diagram tricosane + pentacosane

“…In the M hkl notation, the ͑hkl͒ describes the plane formed by the methyl end groups (CH 3 ) in the referential of the orthorhombic subcell. Two orthorhombic forms are observed: O p (P ca21 , Z 4 7 ) and O II (P bcn , Z 4 or P bca , Z 4 8 ). The latter is observed only in C 36 H 74 8,23 which results from an alternative stacking of molecular layers of type M 011 and M 011 .…”

Electron diffraction intensities from bent molecular organic crystals

“…A review of the crystal structure of orthorhombic n-paraffins (Teare, 1959) is given here in order that the following arguments based on this will be clear. As is shown by the (010) and (100) projections in Fig.…”

“…n-tetracosane, C2aHs0 (Aldrich Chemical Co. Inc., Milwaukee, WI), n-hexacosane, C26H54 (Eastman Organic Chemicals, Rochester, NY), n-octacosane, nC28Hs8 (Aldrich Chemical Co. Inc., Milwaukee, WI), n-dotriacontane, nC 32H66 (Eastman Organic Chemicals, Rochester, NY), n-hexatriacontane, C36H74 (Aldrich Chemical Co. Inc., Milwaukee, WI), n-tetracontane, C40H82 (Pfaltz & Bauer Inc., Stamford, CT), and n-tetratetracontane, C44H90 (Supelco Inc., Bellefonte, PA) were grown as the orthorhombic polymorph (Teare, 1959) by rapid evaporation of dilute hexane solutions onto carbon-Formvar-covered electron-microscope grids.…”

“…Quantitative comparison of the whole zonal data set to the kinematical data has not been made, because no Okl pattern has been recorded yet which adequately satisfies mm symmetry in intensity. However, systematic absences for the (100) zone are correct as well as location of Okl intensity maxima (see Teare, 1959). An attempt to use the Okl data from the pattern schematized in Fig.…”