Unable to generate the structure for cycloprop-1-en-3-ylidene-1-nitrile

[vthimmakondu]

While OPSIN generates the structure if I type the name like cycloprop-1-en-1-nitrile (or simply cyclopropen-1-nitrile) , it complains that
nitrile is uninterpretable as soon as a carbene comes into the picture. Any thoughts?

I believe that nitrile takes precedence over carbene in functional group ordering. Please, let me know if I am wrong about this. Of course, if I do use "cyano" as prefix (1-cyanocycloprop-1-en-3-ylidene) then I could generate the structure. But, is that correct way of naming?

[dan2097]

As far as I'm aware the carbene takes precedence:
https://iupac.qmul.ac.uk/BlueBook/P4.html
According to that list radicals are the most preferred of all functional groups, while nitriles are rank 14.

So I think 1-cyanocycloprop-1-en-3-ylidene would be the preferred name.

IUPAC nomenclature does support a seldom used prefix ylo for indicating a radical using a prefix, but this is not supported by OPSIN.

[vthimmakondu]

Thank you. But, I am dealing with singlet carbenes here. They are NOT triplet carbenes. Electronic structure calculations that I did indicate that it is indeed a singlet. A triplet carbene could be considered as a biradical. But, what about singlet carbenes? Should we still consider them as radicals?

[dan2097]

I don't think IUPAC nomenclature directly allows the distinction between single and triplet carbenes to be captured:

"Systematic names are the preferred IUPAC names. The retained names carbene or methylene, nitrene or aminylene and carbyne, can be used in general nomenclature, with full substitution. The use of the systematic or retained names does not imply a specific electronic configuration. If needed, such a distinction would be made by using a separate word such as singlet or triplet, or a descriptive phrase."
Source: https://iupac.qmul.ac.uk/BlueBook/P7.html#71020201

[vthimmakondu]

Thank you.

[vthimmakondu]

Should the preferred IUPAC name for this carbene should be should be 1-cyanocycloprop-1-en-3-ylidene (as you stated earlier) or should it be 2-cyanocycloprop-2-en-1-ylidene? Because, if we have to give preference to carbene considering it as a radical (and thus functional group here) then 1-ylidene should be preferred than ending with 3-ylidene? Am i correct?

Because, even for the simplest case like cyclopropenylidene, the preferred IUPAC name is cycloprop-2-en-1-ylidene. Isn't it? If we use the same logic here then the preferred name should be 2-cyanocycloprop-2-en-1-ylidene. Please correct me if I am wrong about this.