Ethenium
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2H+
5)
In chemistry, ethenium, protonated ethylene or ethyl cation is a positive ion with the formula C
2H+
5. It can be viewed as a molecule of ethylene (C
2H
4) with one added proton (H+
), or a molecule of ethane (C
2H
6) minus one hydride ion (H−
). It is a carbocation; more specifically, a nonclassical carbocation.
Ethenium has been observed in rarefied gases subjected to radiation.[1] Another preparation method is to react certain proton donors such as H+
3, HeH+
, N
2H+
, and N
2OH+
with ethane at ambient temperature and pressures below 1 mmHg. (Other donors such as CH+
5 and HCO+
form ethanium preferably to ethenium.)[2]
At room temperature and in a rarefied methane atmosphere, ethanium slowly dissociates to ethenium and H
2. The reaction is much faster at 90 °C.[1]