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I have a compound like this:

$$\ce{CH2=C=O}$$

I wonder if it is a functional group or a normal group. As a functional group I couldn't find out. Is it a normal compound or a functional group and what is it's IUPAC name

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According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) the name of the given compound is the systematically constructed name for ketones.

Therefore, the preferred IUPAC name (PIN) is ethenone.

The name ketene is retained, but only for general nomenclature.

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The compound you have drawn is called ketene, since the central carbon is part of both a ketone and an alkene. Ketene is the parent compound of the ketene functional group, where the terminal carbon is substituted with some more complicated structure.

Ketene itself is not stable and dimerizes to diketene by a [2+2]-cycloaddition. Diketene was commercially available and can be converted to ketene by thermal or photochemical conditions.

enter image description here

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  • $\begingroup$ Ketone - R-CO-R .. I mean that there are two Alkyl group but in the post there is only one. That part is troubling me out $\endgroup$ – frunkad Apr 28 '15 at 18:48
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    $\begingroup$ @Darshan Jain It's like you'd insert C between C and O in carbonyl group. $\endgroup$ – Mithoron Apr 28 '15 at 21:00
  • $\begingroup$ Yes, it is a ketone attached to a highly strained 2-membered ring (a double bond can be viewed as a 2-membered ring). It is the 2-membered ring analogue of cyclopropanone. $\endgroup$ – ron Apr 28 '15 at 23:31
  • $\begingroup$ Ketenes do not require photochemical conditions to do cycloaddition. It would be unwise to do so. You would not get that product but 1,2-cyclobutandione instead. Ketenes are reactive enough to do 2+2 with a little stirring. Light is incorrect. $\endgroup$ – DrAzulene Jul 6 '16 at 8:00

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