The synthesis of some model allene molecules and the study of molecular interlocking in their melts. Part I. Thermal properties of three aromatic allenes

Abstract

Methods of synthesis and purification are described for tetraphenylallene, α-naphthyltriphenylallene, and biphenyl-4-yltriphenylallene. These compounds were studied as the first representative members of a new class of hydrocarbon, which provides rigid, non-polar molecules for testing models of molecular interlocking in the liquid state. The chemical stability of the melts was found to be adequate to allow accurate determination of properties such as the molar volume and viscosity as functions of temperature.

As might be expected from the shapes of their repulsion envelopes, the molecules showed increasing tendency to interlocking in their melts in the sequence: Ph₂CCCPh₂ < Ph₂CCC(Ph)-α-C₁₀H₇ < Ph₂CCC(Ph)·C₆H₄Ph.

Various criteria for interlocking are examined and discussed. The melts supercool readily, particularly for the last two compounds, whose melts usually congeal to form stable non-polar glasses. Glass transition temperatures were observed at ca. 34° for α-naphthyltriphenylallene (m.p. 140°) and 35° for biphenyl-4-yltriphenylallene (m.p. 106°).