Cacodyl oxide is a chemical compound of the formula [(CH3)2As]2O.

This organoarsenic compound is primarily of historical significance since it is sometimes considered to be the first organometallic compound synthesized in relatively pure form.

[1][2] "Cadet's fuming liquid", which is composed of cacodyl and cacodyl oxide, was originally synthesized by heating potassium acetate with arsenic trioxide.

The molecular structure of [Ph2As]2O (Ph = phenyl), the tetraphenyl analogue of cacodyl oxide, has been established by X-ray crystallography.

[3] This article about an organic compound is a stub.