What do the hexagonal shapes mean in chemistry?

[FishmanGeertz]

In chemistry and biochemistry, what do the hexagons with letters in between them mean? Call me silly but for some reason they never taught this to us in school.

 

[Bogrune]

I don't know much because I never fully understood organic chemistry in High School A.P. Chemistry, but I do know enough to say that these are benzene molecules, and that these molecules normally need a catalyst in order to react with other molecules due to their electron cloud structures.

 

[QuarkCharmer]

These shapes are called skeleton formulas. It's a short hand way of representing a molecule. Lines for single bonds, double lines for double bonds etc. It's assumed that each intersection point of the line segments is a molecule, usually carbon, but you can have structures that are not consisting of carbon atoms, these are called heteroatoms and you represent them by noting the symbol for the atom in the chain like this:

In your posted image, you would assume (since there is no notation) that each point is a carbon atom. Interestingly enough, the only way they can maintain that hex form is by having alternating double bonds, hence the alternating double lines in your image. Hope that helps. I am sure you can find more info now that you know what they are called.

 

[Borek]

Note that alternating double bonds are just an early attempt at understanding http://en.wikipedia.org/wiki/Aromaticity

 

[Phrak]

C means Carbon. H means Hydrogen. Combined into a benzene ring, they look like b1) or b2). Carbon likes 4 lines to it. Hydrogen likes one line. These are called bonds, or atomic bonds.

All of your diagrams except perhaps a) are a Benzene molecule.

Sometimes for notational convenience and simplicity, the letter C is not included but everyone knows there's a Carbon there. This is the shown in diagram c).

To make it even simpler, the Hydrogen is left out. This is shown in diagram d).

Diagram a) is not the usual way to draw benzene.

Benzene can also be drawn as a hexagon with a circle in it. This one was not shown. This diagram means that it really doesn't matter if you choose diagram 1b) or 2b). They're really the same thing. When the hexagon with the circle is used, the symbols for Hydrogen are also left out.

 

[FishmanGeertz]

A molecule is a collection of two or more atoms, correct?

 

[Borek]

Neutral collection of bonded atoms.

 

[FishmanGeertz]

These shapes are called skeleton formulas. It's a short hand way of representing a molecule. Lines for single bonds, double lines for double bonds etc. It's assumed that each intersection point of the line segments is a molecule, usually carbon, but you can have structures that are not consisting of carbon atoms, these are called heteroatoms and you represent them by noting the symbol for the atom in the chain like this:

In your posted image, you would assume (since there is no notation) that each point is a carbon atom. Interestingly enough, the only way they can maintain that hex form is by having alternating double bonds, hence the alternating double lines in your image. Hope that helps. I am sure you can find more info now that you know what they are called.

Whats the difference between skeleton formula and a written-out chemical formula?

 

[Borek]

http://www.molport.com/buy-chemicals/molecular-formula/C6H8O2 can refer to hundreds of compounds, correctly written skeleton formula is unique.