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I'm writing a publication in which I compare the effect of alkyl, alkene and similar chains of different length connected to a N-atom of a heterocyclic organic compound. Often I have to refer to these chains, without the N-atom.

Right now I'm using something like "the ethyl/propyl/etc. group connected to the N-atom", which feels awkward. Is there a better chemical term I could use? Based on my online research, amine group or amine substituent appears to be the closest, but it includes the nitrogen itself.

Some examples (not from my work):

a few examples

Is there a term that properly describes the encircled parts?

Mithoron
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Neinstein
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  • Though I asked the question in general, the molecule I'm concerned with has the nitrogen in a ring structure, like my examples. If there's no general name, one applying for this specific case would also suffice. – Neinstein Jan 23 '23 at 13:05
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    o.O Looks like you have a fundamental misunderstanding. Substituents are named for what they are, not what they are connected to. – Mithoron Jan 23 '23 at 13:52
  • @Mithoron I know how it looks like, but (I think) it's not a misunderstanding. I'm working with molecules with different length of CH-groups attached to a the N-atom of a pyrinide ring. I'm comparing certain (density-like) quantities on the ring (including the N) and on the connected group (excluding the N). It's kind of awkward to refer to this "tail" as "the ethyl/propyl/etc. group connected to the N-atom", so I was looking for a general way to refer them at. – Neinstein Jan 23 '23 at 14:12
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    Amyl is an old name for pentyl, so you at least have a misunderstanding. Substituents are substituents, in particular alkyl, or aryl groups. – Mithoron Jan 23 '23 at 14:51
  • @Mithoron That was a mental typo on my part. fixed. – Neinstein Jan 23 '23 at 16:29
  • See nomenclature in resources learning chemistry, especially the Blue Book (or chapter 4, P-44 of Moss' compilation): first you define the senior chain/cycle/motif of structure; second the substitutents/side chains. But the name of an "ethyl", "acetyl", or "3-methoxyphenyl" side chain is not determined by what atom of the more senior motif binds to this side chain. – Buttonwood Jan 23 '23 at 16:35
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    Where is the problem ? Your first molecule is N-ethylpyrrole; the second is N-acetylpyrrole. – Maurice Jan 23 '23 at 17:56
  • @Maurice I need a general word to refer to the circled groups, ot the name of the molecules. – Neinstein Jan 24 '23 at 07:44
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    If general, what about "N-substituent", "N-substituent in X" or "R-N" in a formula? – Poutnik Jan 25 '23 at 10:14
  • @Poutnik wouldn't that still include the N-atom? I arrived to a phrase like "N-bound chain" but it feels a bit clumsy. – Neinstein Jan 25 '23 at 10:57
  • As I assume N may be bound by various ways, I doubt there could be a general name covering N implicitly. Try a general name without the substituent. – Poutnik Jan 25 '23 at 11:01

2 Answers2

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I think "N-substituent" is just fine.

A substituent refers to whatever is sticking off something. The prefix "N-" doesn't change that; rather, it qualifies what it is sticking off. So the N-substituent doesn't mean "the nitrogen plus the substituent", but rather "the substituent sticking off the nitrogen".

(As a parallel example: in, say, aromatic rings it is common to refer to a C-2 substituent or an ortho-substituent or something. This doesn't include the carbon on the ring, it just refers to whatever's sticking off it.)

orthocresol
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Inspired by the locant N- and by biochemical nomenclature for glycolisation, I could see use of the term “N-linked moiety”.

Karsten
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