Stupid chemistry question (sucrose)?

Question

okay, im no good at chem in the least, and im trying to find a picture of the chemical structure of sucrose. I google imag searched for C12H11O11 and sucrose, and got a lot of different ones. why are there so many different structures? Which one is the most commonly used notation?

I got 3 different ones here:

http://mbs.cbrc.jp/EzCatDB/Compound/JPEG/C02048.jpg

http://www.nutritionmd.org/images/photos/sucrose.gif

http://www.vectorsite.net/tpchem_07_08.png

is the first one sucrose? there are no carbons in it?

sorry for such a dumb question - thanks

Answer 1

To start with, sucrose is C12H22O11. Also, there are several different ways of representing molecular structures. Often, for simplicity with complicated molecules, the carbons of large ring structures or long chains are not shown, just crossed lines with functional groups attached. Sometimes they don't even show the hydrogens, just non-hydrogen groups (as in your second reference). I would say the second reference was closest, their structure was the same as I have, except that the carbon in the 6-membered ring, (where the connection to the other ring is), has an OH group and my reference says a hydrogen is there. The first reference had 2 6-membered rings which is some kind of sugar, but not sucrose, which is a 6-membered ring linked to a 5-membered ring. The 3rd reference claimed I didn't have authorization to look at it, I don't know why.

Added:

The structure on your 4th site, while technically correct, does not show any of the stereochemistry. For many molecules, the are are several different configurations are possible, however only one might be biologically active (such as for  medicinal compounds). The one from "nutrition.org" shows the stereochemistry (some OH's "up", some "down"; yes, this does make a difference, because the 2 positions are NOT equivalent!)

Answer 2

For the first website, the vertices of the hexagon are the Carbon, it is just not written. The second website is correct as well. There are different ways to write sucrose because it has isomers (same chemical formula, but structural formula, or different ways to write it). You can use any of the ways to draw the structure of sucrose.