What is the IUPAC name of $\ce{(CCl3)3CCl}?$

The answer I got was 1,1,1,2,3,3,3-heptachloro-2-(trichloromethyl)propane. But when I looked up the question online, most sources say the answer is 2-(trichloromethyl)-1,1,1,2,3,3,3-heptachloropropane, even though ‘chloro’ comes before ‘trichloromethyl’ alphabetically. What is the reason ‘chloro’ is written after ‘trichloromethyl’?


1 Answer 1


According to Chemdraw JS' Structure to Name feature which generally gives the PIN of the molecule, the PIN for $\ce{(CCl3)3CCl}$ is 1,1,1,2,3,3,3-heptachloro-2-(trichloromethyl)propane

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From Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book),


Alphanumerical order has been commonly called ‘alphabetical order’. As these ordering principles do involve ordering both letters and numbers, in a strict sense, it is best called ‘alphanumerical order’ in order to convey the message that both letters and numbers are involved

Alphanumerical order is used to establish the order of citation of detachable substituent prefixes (not the detachable saturation prefixes, hydro and dehydro), and the numbering of a chain, ring, or ring system when a choice is possible.


P-14.5.1 Simple prefixes (i.e., those describing atoms and unsubstituted substituents) are arranged alphabetically; multiplicative prefixes, if necessary, are then inserted and do not alter the alphabetical order already established.

Here we have two main groups attached to $\ce{C-2}$, the (trichloromethyl) group and the (chloro) group.

P-14.5.2 The name of a prefix for a substituent is considered to begin with the first letter of its complete name.

Taking the example of 7-(2,4-dimethylpentyl)-5-ethyltridecane from the Blue Book, we see that in such a case, the di- is considered to be a part of the complete name and so needs to be considered as well.

Therefore the two names in the nomenclature of our compound would be 1,1,1,2,3,3,3-heptachloro and 2-trichloromethyl. Our parent chain is propane and so the PIN for the given compound becomes 1,1,1,2,3,3,3-heptachloro-2-(trichloromethyl)propane which is the same name as suggested by Chemdraw JS.

Therefore, your proposed answer is correct and the source online is wrong when it comes to the PIN.


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