What is the name of the alkane? I circled it in red. I am having trouble..

 

Thanks!!

Well you've got a five membered ring so you have cyclopentane. The substituents are isopropyl and ethyl (of which the isopropyl is higher prioritry).

 

So itl be 1-(S)-isopropyl - 3-(S)-ehtyl cyclopentante

Thank you! I wasad kind of close..this may seem like a stupid question but what do the S represent?

Thank you! I wasad kind of close..this may seem like a stupid question but what do the S represent?

 

You need to basically indicate whether the groups are pointing out or into the page. Therefore, you need to use R (clockwise) or S (counterclockwise) to label the chiral centers.

Yep, the two groups are chiral centres and you need to indicate which is which. See Gold-Ingham rules for how to identify chiral centres if your unsure how to do it

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Edited June 23, 201015 yr by Nerddoc

Well you've got a five membered ring so you have cyclopentane. The substituents are isopropyl and ethyl (of which the isopropyl is higher prioritry).

 

 

So itl be 1-(S)-isopropyl - 3-(S)-ehtyl cyclopentante

 

Why have you chosen isopropyl as the highest priority? According to my textbook, substituents of arenes are prioritised alphabetically (lower first). Or am I missing something else?

Why have you chosen isopropyl as the highest priority? According to my textbook, substituents of arenes are prioritised alphabetically (lower first). Or am I missing something else?

 

You are right that for arenes you name them alphabetically. But this example is not an arene. An arene is a aromatic system with a delocalised pi system in it (like benzene). In this case you simpley have a 5-membered cycle so you order them accordinging to which has the highest priority.

 

P.S. Sorry for the VERY late reply

Edited July 17, 201015 yr by Horza2002

Thanks. That was actually pretty quick.

The correct IUPAC name is (1S,3S)-1-ethyl-3-(propan-2-yl)cyclopentane. You can get the details at IUPAC nomenclature exercises in organic chemistry at AdiChemAdi.