Atom count?

[mphilippe]

I was wondering if I could get any help in sorting out the mollecular formula of dinoprostone based on looking at its stick figure.

Thanks for the help!

 

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

[John Cuthber]

That wiki page gives the molecular formula.

[mphilippe]

yes that's right but I would like to see how to count it from the stick figure

[hermanntrude]

each corner in the skeletal diagram is a carbon atom. the ends of lines are also carbon atoms. each carbon has enough hydrogens attached to make up its four bonds, although they aren't shown either, except when it's important to show them for some reason or other. Other atoms are shown as normal

[vedmecum]

yep !interesting problem . i think it is better to write in its simple form and then find the correct molecular formula . mine ans is C19H30O5.

[mphilippe]

Thanks Hermann, your answer helped a bit. According to the formula that is given on the wikipedia site, I get the carbon atom count right : 20.

I get the oxygen atom count right also : 5.

 

However I can't get the hydrogen count right. If each carbon has 4 bonds, so I would count that it has 4 hydrogen atoms attached. Right?

 

And to those that have an oxygen, I would count 2 hydrogen attached to the carbon, is that correct?

 

And what about the two bonds in the mollecule that are double bonds? How many hydrogen atoms would be there?

 

That way, I count 42 hydrogen and there is supposed to be 32. What do I do wrong?

 

Thanks a million for the help!

[ChemSiddiqui]

This type of structures are called skeletal structure. You might like to google how to deduce the MF from these type of structure. Good Luck!

[hermanntrude]

Thanks Hermann, your answer helped a bit. According to the formula that is given on the wikipedia site, I get the carbon atom count right : 20.

I get the oxygen atom count right also : 5.

 

However I can't get the hydrogen count right. If each carbon has 4 bonds, so I would count that it has 4 hydrogen atoms attached. Right?

 

And to those that have an oxygen, I would count 2 hydrogen attached to the carbon, is that correct?

 

And what about the two bonds in the mollecule that are double bonds? How many hydrogen atoms would be there?

 

That way, I count 42 hydrogen and there is supposed to be 32. What do I do wrong?

 

Thanks a million for the help!

 

Carbon has four bonds in total. So for a carbon in a chain (which already has two other carbons attached) there are two hydrogens. For a carbon which has a single bond to one carbon and a double bond to another carbon, there is only one hydrogen. and so on.

 

THIS PAGE, the wikipedia page that chemsiddiqui was referring to, has two more examples.

[mphilippe]

Ah yes ok your explanation was clearing it !

 

thanks a lot!