Bicyclic compounds nomenclature

[gracy]

Homework Statement

Name the following molecule by the IUPAC system of nomenclature.

Homework Equations

There are some rules.

To name bicyclic alkanes, you follow these three steps:

1- Count the total number of carbons in the entire molecule. This is the parent name (eg. ten carbons in the system would be decane)

2-Count the number of carbons between the bridgeheads, then place in brackets in descending order. (eg. [2,2,1])

3-Place the word bicyclo at the beginning of the name.

The Attempt at a Solution

[/B]
I numbered the given structure as follows

And I considered the red line to be bridge

And I named it as Bicyclo [5,3]Decane
But it is wrong . Answer is Bicyclo[3,3,1]nonane

 

[Borek]

There is no carbon 6. To draw this molecules to scale you can't avoid an accidental crossing of the lines on the picture. Bonds go like 2-9 and 5-7 using your numbering scheme.

 

[DrClaude]

You counted the atoms incorrectly. There is no atom where you wrote the number 6. The figure is not well drawn, so I can understand the confusion, but look at it as two cyclohexane molecules stuck together.

 

[gracy]

To draw this molecules to scale you can't avoid an accidental crossing of the lines on the picture. Bonds go like 2-9 and 5-7 using your numbering scheme.

I did not understand.

 

[Borek]

There is no atom 6, there are no bonds 6-9, 6-7, 6-2 and 6-5. When you have something that is 3d, and you try to draw it on a flat surface of paper (which is always kind of projection), sometimes lines have to cross - but it doesn't mean they touch in the real molecule.

 

[gracy]

Where are bridgeheads in this case?

 

[DrClaude]

Where are bridgeheads in this case?

2 and 7.

 

[gracy]

I am confused. How to identify bridge heads?

 

[DrClaude]

I am confused. How to identify bridge heads?

They are the atoms that are part of the two rings.