4,4 -Azoxydianisol

One performance validation material that is often used is 4,4 -azoxydianisol, which undergoes a solid-to-liquid crystal (anisotropic) transformation at around 115°C, followed by an anisotropic to isotropic conversion at around 134°C. 4,4 -Azoxydianisol can be thermally cycled and used repeatedly. This sample enables resolution, sensitivity, and signal and noise to be established quickly on any DSC system. Figure 2.14 shows the data from a single 4,4-azoxydianisol sample, but displayed at two different sensitivities, so that small transitions at 135°C can easily be seen. This material has been suggested as a useful sample to compare the performance of various DSC systems (6). 

Fig. 22. The results of the experiment shown in Fig. 21 on 4,4 -azoxydianisole (top).32 (a) The 2H DQ spectrum, showing resolution of the signals from the methyl and aromatic 2H. This is the projection in the f dimension of the two-dimensional experiment, (b) The associated/) projections showing the spinning sideband patterns arising from quadrupole coupling at the methyl and aromatic 2H sites.

Azoxyonisole or Azoxydianisole (called Azoxyanisol or Dimcthoxy-azoxybenzol in Ger), ClV0 C6H4(Na0) C6H4-0-CHa mw 258.27, N 10.85%. Three isomers are described in the literature o,o -Azoxy-atiisols (Ref l)j rn,m -Azoxyatiisois (Ref 2) and p,p -Azoxyanisole (Ref 3). The nitro derivs of Azoxyanisole may be of interest as expl ingredients... 

A solution of (Z)-6-phenylhex-2-ene (2 g, 12.5 mmol) in cyclopentane (200 mL) saturated with argon was irradiated with a Hanovia low-pressure Hg lamp (253.7 nm) for 3 h to consume over 90% of starting material. The bulk of the solvent was evaporated on a rotary evaporator at 25 °C and the residue molecularly distilled the material passing over at 40-87°C/1.5 Torr was collected and yielded 1.55 g (9.69 mmol) of distillate (78%) and 0.33 g (17%) of residue. Preparative GC of the distillate in 50 pi quantities on a 20 M Carbowax column at 160°C and molecular distillation gave the two photoproducts 4 and 5 0.70 g (total yield 35%). These products were separated by injecting 4 pi samples onto a 15% azoxydianisole column. After 59 injections 63.6 mg and 63 mg of each isomeric product were collected. 

Pines, A., and Chang, J. J. (1974). /. Amer. Chem. Soc. 96, 5590. Effect of Phase Transitions on Carbon-13 Nuclear Magnetic Resonance Spectra in p-Azoxydianisole, a Nematic Liquid Crystal. 

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