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Why IUPAC Nomenclature of following amine is written as 2-methylpropan-2-amine and not as as 2,2-dimethylethanamine?

2-methylpropan-2-amine

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    $\begingroup$ "2,2-dimethylethanamine" is not only a wrong name, it also describes a different compound. $\endgroup$ – Loong Feb 13 at 19:35
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    $\begingroup$ This question is tagged with "amine"; however, the numbering of 2-methylpropan-2-amine is not limited to amines. You can see the analogous numbering for example in 2-methylpropan-2-ol and 2-chloro-2-methylpropane. Can you spot your mistake now? $\endgroup$ – Loong Feb 13 at 19:41
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The basic principle in nomenclature is to look for the longest carbon chain: here it is the chain with 3 carbon atoms so the suffix prop; since it is an amine connecting to the carbon 2 it gives the suffix propan-2-amine. As you have a $ \ce {CH_3} $ group grafted in position 2 of the main carbon chain, you must add the prefix 2-methyl

So you have 2-methylpropan-2-amine.

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    $\begingroup$ It is should be propan-2-amine right? $\endgroup$ – CrownedEagle Feb 13 at 7:22
  • $\begingroup$ Of course, i edit my post $\endgroup$ – Nicolas Feb 13 at 9:52
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It's so because while doing IUPAC naming we have to always choose longest branch where the number of functional group (here Amine) should be at least number. That's why we here call it 2-methylpropan-2-amine and not 2,2-dimethylethanamine. You can clearly see in the actual name it's propane which mean 3 carbon atom while as the name you want to give it has name ethan which means 2 carbon. Also if you will write 2,2dimethylethananime it means you are considering 2 methyl group which means only 1 carbon is left which will be called methane not ethane. Hope it helps

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  • $\begingroup$ "Also if you will write 2,2dimethylethananime it means you are considering 2 methyl group which means only 1 carbon is left which will be called methane not ethane." : There will be 2 carbons left if one considers 2 methyl group substitutions to Central Carbon, wouldn't there? H3C-C(CH3)2-NH2 $\endgroup$ – CrownedEagle Feb 13 at 7:24

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