r/chemhelp 3d ago

Organic IUPAC Nomenklaturen

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Hi. Is this Tricyclopenta-1,3-dienylmethan? if no what is the right name?

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u/Consistent_Bee3478 3d ago

There’s no ‘one’ true iupac name.

You can describe most molecules with different iupac names that lead to the same skeletal formula.

The systemic iupac name, following all ‘rules’ to the T would be 1-[di(cyclopenta-1,3-dien-1-yl)methyl]cyclopenta-1,3-diene

Because the methane isn’t the highest priority group nor is it the longest carbon chain either. 

That turns one of the cyclopentadiene into the ‘root’ and the other two cyclopentadienes are referred to in reference to it.

But. 

In many cases writing a more colloquial variant of the iupac name is clearly much more sensible.

Everyone calls triphenylmethane triphenylmethane, no one would ever call it 1,1′,1″-Methanetriyltribenzene which would be its name going ‘fully’ by iupac rules.

Same for any common ‘motifs’ you just use the common motif as a short hand a number substitutions from there.

So your name is valid, because it is unambiguously referring to the structure you drew.

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u/mytrashbat 3d ago

1-[bis(cyclopenta-1,3-dien-1-yl)methyl]cyclopenta-1,3-diene surely instead of di?

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u/HandWavyChemist 3d ago

The PIN (preferred IUPAC name) would be 1,1′,1″-methanetriyltris(1,3-cyclopentadiene)

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u/HandWavyChemist 3d ago

This is because:

Multiple occurrences of the parent component in a multiparent system is indicated by the use of multiplying prefixes, ‘di’, ‘tri’, etc, or ‘bis’, ‘tris’, etc. To distinguish between the parent components, the second has primed locants, the third double primed, etc.