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Abstract
Open-chain organic tetrasulfides can exist in three distinct conformations known as cis-cis, cis-trans, and trans-trans forms. Previously, the structure of only one other open chain organic tetrasulfide, benzylidenimine tetrasulfide, has been established and this compound has a cis-cis configuration. Now we can report that octadecyl tetrasulfide crystallizes in the trans-trans form, is nonbranched, nonplanar, and has two different sulfur-sulfur bondings. Its central S-S bond (2.060Å) is longer than the terminal S-S bond (2.018Å). The central bond length of 2.060Å is close to the average value of 2.08Å selected by Pauling as a normal S-S single bond. Terminal bond lengths of 2.018Å represent another type of S-S bonding that displays some double bond character. A central torsion angle (dihedral angle) is 65.3 (±2)° and this is considerably less than the optimum value of 90° postulated by Pauling. Octadecyl tetrasulfide crystallizes in the monoclinic space group C2/c with a = 5.44Å, b = 9.43Å, c = 78.3Å, β = 90.6°, and z = 4. The compound is stable at ordinary laboratory temperatures under indirect lighting.