Talk:Imino acid

proline is an amino acid, not an imino acid. an imino group is C=N-R.

:Amino acids containing secondary amine group (the only natural compound of this type is proline) are sometimes named imino acids[1][2], though this usage is disputed by some.

Hydroxyproline also occurs in nature. N-methylated amino acids like NMDA also occur naturally and contain secondary amine groups.--Eloil 00:13, 17 April 2007 (UTC)

:My organic chemistry colleagues tell me that imino- should be reserved for -N= exactly as stated in the opening paragraph; proline is a secondary amine, not an imine. The problem is that its description as an imino acid appeared in a few older textbooks, particularly those written from a medical rather than chemical viewpoint. Like many textbook errors, this gets repeated in newer textbooks that copied their content from older ones. 96.54.32.44 (talk) 01:16, 20 February 2011 (UTC)

::Yes, so i 've learned it too, that there must be a double bond between the nitrogen]] and carbon. Thoses are amides from an imine and are called Iminamide. Examples: Sulfaguanidine , 1-(4-Nitrophenylethyl)piperidylidene-2-(4-chlorophenyl)sulfonamide. 77.177.43.109 (talk) 10:38, 30 December 2011 (UTC)

In reply to User:DMacks, the definition given talks about an imino group, which is specified as >C=NH, and this is also how my CRC Handbook and my American Heritage Dictionary define "imino". I know that the diagram shows an "imine" as having a radical attached to the nitrogen, not necessarily a hydrogen. That may be correct as the definition of an imine, but I don't think it's the correct definition of the term "imino". Maybe we should change that diagram. Eric Kvaalen (talk) 09:52, 6 June 2014 (UTC)

:I don't think there's as much structural-definition distinction between "imino" (adjective) and "imine" (noun), rather than just adjective vs noun. For example, Gold Book [http://goldbook.iupac.org/search.py?search_text=imino search for imino] finds lots of C=NR not just C=NH. But its [http://goldbook.iupac.org/I02959.html definition of "imino acid"] only mentions the C=NH derivative. That seems in keeping with IUPAC defining structure-classes by the parent structure. For example, that same definition says that the nomenclature suffix "imine" is the =NH group, but [http://goldbook.iupac.org/AT07329.html here] they use that nomenclature and interchangeably use imine/imino wording with examples that are =NR. I agree with changing the inline structure.

:Interestingly, amino acid (as well as many lay-reader and even intro school texts) define that that compound class contains the amino group specifically identified as "NH₂" despite proline. DMacks (talk) 14:24, 6 June 2014 (UTC)

::I notice that your link [http://goldbook.iupac.org/search.py?search_text=imino search for imino] uses the term "N-substituted imino group". So I think an acid with >C=N-R should be called an N-substituted imino acid. I would say that the 1-Pyrroline-5-carboxylic acid in the illustration is a sort of N-substituted imino acid – but it's not a very good example of that either, because the thing that substitutes the H on the N is part of the same chain that is attached by a double bond to the N! Unfortunately I don't know of any other example with a drawing we could use. Eric Kvaalen (talk) 18:55, 6 June 2014 (UTC)

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