[SimoneMeyer]

I was asked to draw the condensed structural diagram of 1,3,5-trimethylcyclohexane.
This is what I drew, I'm just wondering if this is in fact the way to draw a condensed diagram.



Also, what would a non-condensed version look like?

[Fridushka]

1st of all you don't need to write the H₂ on the position 2 and 4..

[MrTeo]

If you want something really condensed you don't need to write any C or H but simply draw the strcuture 

[cliverlong]

As I understand it ..

Condensed formulae were created to give some sense of the strucutre of an organic compound with chains of carbon atoms when the typography was limited to characters typed in straight lines on a typewriter with possibly subscripts. See

http://dl.clackamas.edu/ch106-01/condense.htm

However this form of representaiton is severely limited with cyclic compounds, and in my opinion pointless since more sophisticated tools for drawing structural formulae are available to anyone with access to a psersonal computer

See the comment on:

http://en.wikipedia.org/wiki/Structural_formula "Text formulas"

so in my opinion (although it doesn't help you) is that for your example, attempting to write an accurate condensed formula for your compound doesn't help develop a skill that will be of any value in communicating the structure of a chemical compound.

The simplest form of representation (apart from the systematic name) I would use would be your diagram but eliminate the C and H (as Mr Teo has written above). The convention being:

At the "unconnected" end of any single line will be a hydrogen atom
At the intersection of two or more lines will be a carbon atom
Lines represent bonds between the carbon and or hydrogen atoms as identified above
Double and triple bonds are repesented by double and triple parallel lines
All non carbon and hydrogen atoms , such as O for oxygen, are explicitly identified by the letter in the appropriate place in the structure.

Can you redraw your structure as a skeleton?

Have a look at any chemistry paper and this convention will be used to show the molecule. Also molecules of a compound can take different forms and these have to be represented

look at the example

http://en.wikipedia.org/wiki/Glucose

to see this convention in action.

question is, do you want to confront your teacher / professor with this argument?

Clive

[cliverlong]

<< snip >>
At the "unconnected" end of any single line will be a hydrogen atom
<< snip>>

Sorry, that is incorrect

What I should have written:
At the "unconnected" end of any single line will be a carbon atom
Once all carbons and other non-carbon atoms have been accounted for in the structure, hydrogens are "added" at any "line end", whether "unconnected" or "connected" to other lines in the skeleton so that each carbon has four bonds

For example

-  is ethane becasue there are 2 Cs at the end of the lines, the 2 Cs are bonded by the line and 6 Hs to make up 4 bonds on each Carbon

Similarly

= is ethene.

-= is propene

This convention doesn't deliver much benefit for small molecules but really pays off when the structure has, say, 5 or more carbons, or especially when the structure involves rings.

[SimoneMeyer]

Then would that be a normal structural diagram?

Does the following make sense as a condensed diagram? But, if I don't put the C's, H3C and CH2's, will they know what I am referring to if I just put the four lines?

[Fridushka]

Well your strucure is wrong, since you have drawn an extra CH₃ on the position 4! what you have drawn is:1,3,4,5-tetramethylcyclohexane
did you get it?
Good Luck

[cliverlong]

Does the following make sense as a condensed diagram?

No, it's a skeletal diagram. But as I wrote in detail above, I feel it is almost impossible to write a meaningful condensed formula for a cyclic compound. I won't repeat my whole argument again. I am interested if anyone can come up with an unamiguous condensed formula for a cyclic compund that uses only letters and numbers in one line. I suppose one could use abbreviations such as CycHex to represent cyclohexane or Ph to represent the phenyl group.

But, if I don't put the C's, H3C and CH2's, will they know what I am referring to if I just put the four lines?

Well, apart from adding an extra CH₃ group (note the cheeky use of condensed formula there) I feel your diagram is accurate and unambiguous and adheres to the conventions as I understand them and see used all over the place in what chemical literature I read. What more could you ask for?

So my statement to someone who challenges the skeletal form would be "show me where the ambiguity is and show me how to write a condensed formual that is strictly a line of letters and numbers". Also do a quick scan of chemical literature and show the relative abundance of skeletal formulae against condensed formulae for anything other than trivial compounds.

And to be honest, even if you could represent this molecule in a condensed form you get absolutely no sense of its structure without drawing it out in 2D anyway.

Clive

[SimoneMeyer]

Is this now correct?

[Fridushka]

Yeah now is true good job

[cliverlong]

I will certainly be interested in your teacher's/professor's view of what is the correct solution. Can you post on this thread what is the answer you are given when you receive it?

Thanks

Clive