How do i name this compound according to IUPAC system?,

This is 10-Ethyl-4-Methoxy-8-Methylspiro[4.5] Decane, but why we can't start numbering from the carbon atom attached to Oxygen atom and name this compound as 1-methoxy-6-ethyl-8-methylspiro [4.5] Decane?

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1 Answer
May 18, 2018

You have the correct numbering, but there are still four mistakes in your name.

Explanation:

When different directions around the ring are competing for numbering, you choose the ones that give the lowest numbers at the first point of difference.

You can go clockwise or counterclockwise, so you must choose the correct direction in each ring.

Numbering

The competing choices are

#color(red)(1)","color(white)(l)color(orange)(6)","color(white)(l)"8#
#"4,8,10#

The lowest number in the five-membered ring is #color(red)(1)#.
The lowest number in the six-membered ring is #color(white)(l)color(orange)(6)#.

PubChem got the numbers wrong for both rings, but it also lists the same compound with the correct numbering.

Your numbers are correct! However, there are four mistakes in your name: you inserted two spaces, you capitalized "decane," and you put "ethyl" second in the alphabetical order.

The correct name has no spaces and the first letter is capitalized only at the beginning of a sentence.

The IUPAC name is 6-ethyl-1-methoxy-8-methylspiro[4.5]decane.