Organic Chemistry - Naming Compound

[YouKnowWhatAmine]

Was practicing naming organic compounds. Made this and found out it is called 1,1-dimethylaminoethane.

 

Question: Why isn't it called 1,5-dimethyldiaminoethane?

 

Thank you in advance.

[studiot]

A really well asked question +1

 

Naming is based on the longest carbon chain, which in this case is C2 - C3 and is two atoms long or an ethane base.

 

So the there are two identical nitrogen based groups attached to one of these carbons (C2 here) so the diaminomethyl must be a repeat of the same carbon number, either 1,1 or 2,2

 

So 1,5 is out.

 

Convention dictates we use 1,1 as the lowest carbon.

 

It might be important if there was another functional group then you might get 1-something, 2,2 dimethylamino.

 

Does this help?

[YouKnowWhatAmine]

That clears it up, thanks a lot.

[John Cuthber]

The problem is that

1,1 dimethylaminoethane isn't the same as

1,1di(methylamino)ethane

I think that stuff should be 1,1 bis(methylamino) ethane

[studiot]

The problem is that

1,1 dimethylaminoethane isn't the same as

1,1di(methylamino)ethane

I think that stuff should be 1,1 bis(methylamino) ethane

 

 

Thank you for your improved information.

 

Can you not post some formulae to explain in more detail?

[hypervalent_iodine]

You would also see it named N,N'-dimethylmethylethane-1,1-diamine. Both this and the 1,1-bis(methylamino)ethane would be correct.

 

 

 

Thank you for your improved information.

 

Can you not post some formulae to explain in more detail?

 

In this case, 1,1-dimethylaminoethane should also lead you to the same structure, but only because the other interpretation gives 1,1-dimethylethane, which is an incorrect name (it would be 2-methylpropane). It is still a little ambiguous on first glance. Typically when you are naming functionalised or branched substituents, you would separate their naming into brackets so as not to confuse with the naming of the parent chain. It is also for simplicity. When you have larger molecules that have a lot of functionality and branch points, having the various bits in brackets makes it easier to construct a mental image of the structure. For example:

 

 

The above is named 2-chloro-N-(4-chloro-6-methoxypyrimidin-2-yl)pentanamide. Without the brackets there, the numbering on the pyrimidine ring becomes ambiguous, since there is no clear way to tell if the numbers refer to the ring or to the parent chain.