Note: "Bis" is used to avoid ambiguity, since diketene is sometimes used for dimeric ketene.
Examples to Rule C-321.1
(see Rule C-321.3)
321.2 - Ketenes in which the carbon atom of the CH2 group of ketene has been incorporated into a ring system are named by use of the prefix "carbonyl-".
321.3 - An acyl derivative of ketene may be named as a polyketone.
Example to Rule C-321.2
Note: In such cases the use of "carbonyl" for =CO is analogous to use of "methylene" for =CH2.
See Recommendations'93 R-5.6.3
Example to Rule C-321.3
(see Rule C-321.1)
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