# Does carbon monoiodide (CI) exist?

Many of my students get chlorine $$\ce{Cl}$$, confused with carbon monoiodide $$\ce{CI}$$, despite my promises to use serif fonts whenever possible and to never give them carbon monoiodide in a question.

Everything I know about chemical bonding tells me carbon monoiodide should not exist ($$\ce{CI4}$$, sure), but weird things happen sometimes. My only results from internet searches for carbon monoiodide bring up a set of Quizlet flash cards.

Will my students prove me wrong if I tell them that carbon monoiodide does not exist (except possibly in extreme laboratory conditions).

• Impossible to prove a negative so for the moment a comment rather than a answer as I can't provide a reference. No, a simple diatomic CI molecule does not exist as something you can put in a bottle and use later. Compounds with the stoichiometry CI do exist, such as C2I2 (sciencemadness.org/member_publications/diiodoacetylene.pdf) but that's as close as you can get. But personally I think the kids are taking the proverbial. – Ian Bush Nov 25 '18 at 11:04
• Define "exist." – Zhe Nov 26 '18 at 18:40

Provided that mellitic anhydride ($$\ce{C12O9}$$, empirical formula $$\ce{C4O3}$$) is considered one of carbon oxides, then e.g. hexaiodobenzene ($$\ce{C6I6}$$, empirical formula $$\ce{CI}$$) could be considered a form of carbon(I) iodide, formally. But please rather don't teach that in regular lectures.
Formula:    CI
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