2-Ethylpentanone vs 2-Ethylpentanal

[Lizzy]

Homework Statement

Is the name of this particular molecule 2-ethylpentanone or 2-ethylpentanal?

Homework Equations

The Attempt at a Solution

 

[Borek]

Why the problem? What kind of functional group do you see?

 

[Lizzy]

I see a Aldehyde group which would be an -al ending...so I am going to conclude 2-ethylpentanal is the right answer here? Do you always count the longest chain possible starting at the Aldehyde group?

 

[Borek]

Yes, it is an aldehyde, so 2-ethylpentanal is the right answer.

Do you always count the longest chain possible starting at the Aldehyde group?

No. You have to choose the chain with the highest precedence group. When there is aldehyde only, it will have the highest precedence obviously.

 

[Lizzy]

Thank you very much borek:) , but how do you determine which group (if there were multiple) takes higher precedence?

 

[Borek]

There is a list to remember. I don't deal with organic chemistry so I long forgot it, but it can't be difficult to google.

 

[Teemo]

If you are wondering: http://www.masterorganicchemistry.c...functional-group-priorities-for-nomenclature/