Question

I'm working with 1,1-diphenylethylene and I've observed that, if left at room temperature in the air atmosphere, a white insoluble powder forms. I'm unable so dissolve this powder in every solvent that I've tried (acetonitrile, acetone, ethyl acetate, hexane, water, etc), so I can't get an NMR spectrum. Moreover, I can't find any paper or information online about this subproduct/impurity.

Edit: The melting point of this powder is around 120-130 ºC.

1,1-Diphenylethylene has to be stored between 2-8 ºC, but the safety data sheet doesn't say that it has to be stored under an iner atmosphere. However, we have it stored under argon in the refrigerator and the impurity only appears when leftovers of 1,1-diphenylethylene are left outside in a vial, for example. Futhermore, I observed that 1,1-diphenylethylene is also oxidized to benzophenone when left outside.

Answer 1

The white powder is likely a product of 1,1-diphenylethylene oxidation or polymerization, insoluble due to high molecular weight or cross-linking. Other analytical techniques, like IR or MS, may help to identify it.

Step-by-step explanation:

The white insoluble powder that forms when 1,1-diphenylethylene is left at room temperature in air is likely due to oxidation or polymerization reactions. Given that you've observed the compound oxidize to benzophenone under these conditions, it's plausible that the powder could be a more heavily oxidized product or a polymer derived from 1,1-diphenylethylene. The insolubility of the powder in common organic solvents and inability to produce an NMR spectrum are consistent with a polymer or cross-linked material, which tend to have high molecular weights and/or are not soluble in most solvents. The procedures provided exemplify the isolation and purification of different chemical compounds, suggesting careful handling and controlled conditions to prevent unwanted side reactions.

The melting point range of 120-130 °C you have determined for the white powder does offer a clue to its identity but without further spectral or analytical data, identifying this substance definitively is challenging. You may try alternative analytical techniques such as infrared spectroscopy (IR), mass spectrometry (MS), or scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX) to gather more information about the compound's structure and composition.