In molecule drawings, why does position matter?

Question

Let's say a molecule drawing is in the shape of a dog. If I turn the drawing upsidedown, rotate it...blah, blah, blah... will it change the actual molecule? In other words is it a different molecule if I only manipulate the position?

Disregarding any mentions of resonance....
A benzene molecule demonstrates my question well. The textbook says that the two diagrams used to represent the "real" molecule of benzene are different. However, a close look will tell you that they are the same. the second molecule is just the first one rotated 30 degrees.

Does it really matter whether I turn my head 30 degrees? Or MUST we pull resonance into the discussion and say this situation only happens if there is a case of resonance?

Answer 1

For your first example changing the way you look at the molecule will not change the molecule. For your benzene example if you look at the picture again it shows a double arrow between the two structures this means the structures are in resonance. The benzene molecule doesn't occupy either one of the structures it forms a superposition of both structures in other words it occupies both at the same time. But that's resonance. What you were talking about earlier was isomerization. This is changing the position of molecules with the same chemical formula. For example C2H6O like ethanol CH3CH2OH is a very different then dimethly ether CH3OCH3. They have the same number and types of elements but there positions are different. This results in two molecules with drastically different properties.

Answer 2

well, normally it's assumed that other chemists can do resonance structures well. Though your teacher may ask for a structure to be drawn a particular way to make grading easier or something.

You need to watch to make sure that things are in the correct position after doing a ring-flip on your benzene, though.

Remember, single bonds can rotate, double bonds can not.

Answer 3

Position doesn't always matter. It depends on the type of molecule to determind that. Yes, it matters if you turn your head 30 degress. If it was only 10 degrees then it wouldn't matter.