[AussieK]

I'm a bit stuck on a quesion at uni, even researching online i can't seem to find anything that matches to help me work this out.

Because the question is worth 3 marks surely its not as easy as just putting it into a formula c3h9 or (ch3)3.. because that wouldn't make it right anyway because carbon can only have 4 bonds which would give me a hydrogen left over.

Have i missed something about pentagon rings with a single double bond?  My study book briefly talks about hexagon rings with alternating double bonds, but still not much info.

Any help would be much appreciated.

[Burner]

Because the question is worth 3 marks surely its not as easy as just putting it into a formula c3h9 or (ch3)3.. because that wouldn't make it right anyway because carbon can only have 4 bonds which would give me a hydrogen left over.

Have i missed something about pentagon rings with a single double bond?  My study book briefly talks about hexagon rings with alternating double bonds, but still not much info.

Count the number of bonds(other than the non-visible C-H bonds) formed with each of the carbon atoms inthe pentagon ring and then deduce the number of H atoms bonded to each carbon atom. If a carbon atom has 4 bonds linked to other atoms, no more H atoms will be bonded to it since a carbon atom can form at most 4 bonds.

By the way, why did you draw an incorrect structure of propene which seems not related to the question? And what do you mean by 1 'H' leftover?

[AussieK]

Sorry you'll have to excuse my ignorance for chemistry, my background is finance and more so biology over chemistry.

What confuses me is the extra line in the pentagon (double bond???) How does this extra line affect how you would write the molecular formula?

My 2nd drawing was me trying to work out how many hydrogens could go onto the carbon.. obviously very wrong!

It frustrates me that the lecturer would put something like this, yet the information to learn it has not been supplied. So i'm clutching at straws trying to work it out.

Going by what you say if no more hydrogens can attach the formula would be c3h8?  Again im not sure of the impact of the double line in the pentagon, as to whether this affects the formula.

[Burner]

What confuses me is the extra line in the pentagon (double bond???) How does this extra line affect how you would write the molecular formula?

Yes, the extra line means a C=C bond(double bond). To put it simple, since carbon must have 4 bonds, if it has more bonds with carbon or other atoms, it has less bonds with hydrogen.

Consider the following diagrams. When a C-C bond(single bond) is replaced with a C=C bond, each of the two carbon atoms have 1 less hydrogen atom bonded to it, since carbon must have 4 bonds only. Try to count the number of 'lines'(bonds) besides each carbon atom.

Going by what you say if no more hydrogens can attach the formula would be c3h8?  Again im not sure of the impact of the double line in the pentagon, as to whether this affects the formula.

C₃H₈? Are you referring to the propene structure you drawn or to the structure of the original question?

[Borek]

c3h9

Sounds like you are completely missing the idea of the structural formula - every node is a carbon atom with all its bonds saturated with hydrogen - so no, the formula here is not C₃H₉, you have to count all carbon atoms (including those not named) and all hydrogens (including the implicit ones, not marked on the picture).



This is a shorthand notation for CH₃-CH₂-CH₂-CH₃.



This is a shorthand notation for CH₃-CH=CH-CH₃.