Benzylamine is a primary amine. Now a primary amine has the general formula R-NH₂ where R is an alkyl or aryl group. So here R will be equal to $\ce{C6H5CH2}$. But $\ce{C6H5CH2}$ is neither an alkyl group nor an aryl group. So why benzylamine is a primary amine?
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5$\begingroup$ Benzylamine falls in to the category of RCH2NH2 - in this case R=Ph but it is still a primary amine because 1 - it is attached to an alkyl carbon 2 - the N bears 2 hydrogens. $\endgroup$– WaylanderCommented Dec 20, 2023 at 11:43
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$\begingroup$ Does this mean NH(2) does not directly need to be attached to the R functional group to be called an anime? @Waylander $\endgroup$– Rajesh PaulCommented Dec 20, 2023 at 11:50
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$\begingroup$ Also I think an alkyl carbon is a carbon atom that is part of an alkyl group. An alkyl group is a fragment of an alkane molecule that has one hydrogen atom removed.So I am unable to understand how the carbon attached to the nitrogen will be an alkyl carbon (I am unable to see how the carbon is the part of an alkyl group.As I think there is no alkyl group present) @Waylander $\endgroup$– Rajesh PaulCommented Dec 20, 2023 at 11:55
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$\begingroup$ IF A is X and B is X then C as combination of A and B is usually X too. R need not to be even a hydrocarbon group and it would still be an amine, (or a compound with an amine group if nomenclature chooses different category name). $\endgroup$– PoutnikCommented Dec 20, 2023 at 12:31
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$\begingroup$ @Poutnik can you please briefly explain what you meant.I tried to understand what you are saying, but failed $\endgroup$– Rajesh PaulCommented Dec 20, 2023 at 12:34
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1 Answer
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The IUPAC gold book defines amines as:
Compounds formally derived from ammonia by replacing one, two or three hydrogen atoms by hydrocarbyl groups, and having the general structures RNH2 (primary amines), R2NH (secondary amines), R3N (tertiary amines).
https://doi.org/10.1351/goldbook.A00274
And it defines hydrocarbyl as:
Univalent groups formed by removing a hydrogen atom from a hydrocarbon, e.g. ethyl, phenyl.
https://doi.org/10.1351/goldbook.H02891
I would have said making a bond between ammonia and any organic molecule, replacing one hydrogen atom bound to nitrogen on ammonia, and one hydrogen of a C-H bond in the organic group, but that would also give rise to multifunctional molecules, e.g. with a hydroxyl and an amino group.
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$\begingroup$ Thanks for your reply @Karsten.Your answer made perfect sense after all these wasted hours of searching. Every article I read was all about R can only be an alkyl or aryl group. $\endgroup$ Commented Dec 20, 2023 at 12:40
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$\begingroup$ People posting on the internet often have beginning students as audience, and their definition is a bit quicker to write (and perhaps a bit easier to remember). Good for you discovering the inconsistencies and asking about them. $\endgroup$– Karsten ♦Commented Dec 20, 2023 at 13:15
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1$\begingroup$ @RajeshPaul You can see benzylamine as a primary alkylamine (methylamine) substituted by an aryl(phenyl). $\endgroup$– PoutnikCommented Dec 20, 2023 at 13:43
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$\begingroup$ Thanks! @Poutnik for pointing that out.I didn't know one can substitute, then check if the compound is a primary amine $\endgroup$ Commented Dec 21, 2023 at 2:36
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$\begingroup$ The simplest amino acid glycine NH2-CH2-COOH is an acid in spite of the amine group and at the same time a primary amine, in spite of carboxy group. Due formal naming group priority, it is called aminoacid and not carboxyamine. $\endgroup$– PoutnikCommented Dec 21, 2023 at 7:57