1 Lecture 6 Structural Isomers ? Just how many structures can you make from a simple formula? 1. methane: CH4 C H H H H CH4 C H H H H condensed formula 2D formula 3D formula methane 2. ethane: C2H6 Once the two carbons are connected, there are only six additional bonding sites and these are filled by the six hydrogen atoms. Ethane is a saturated molecule. C2H6 is completely unambiguous. C2H6 C H C H H condensed formula 2D formula 3D formula H H H CC H H H H H H You can twist about this single bond generating different conformations. Build a model and try it. condensed line formula CH3CH3 ethane The carbon-carbon single bond allows rotation of one group of three C-H sigma bonds past the other