Stereochemistry of Alkanes and Cycloalkanes

Up to this point, we ve viewed molecules primarily in a two-dimensional way and have given little thought to any consequences that might arise from the spatial arrangement of atoms in molecules. Now it s time to add a third dimension to our study. Stereochemistry is the branch of chemistry concerned with the three-dimensional aspects of molecules. 

We know from Sections 1.7 and 1.8 that an sp -hybridized carbon atom has tetrahedral geometry and that the carbon-carbon bonds in alkanes result from a overlap of carbon sp orbitals. Let s now look into the three-dimensional consequences of such bonding. What are the spatial relationships between the hydrogens on one carbon and the hydrogens on a neighboring carbon We ll see in later chapters that an understanding of these spatial relationships is often crucial for understanding chemical behavior. 

Some conformations of ethane. Rapid rotation around the carbon-carbon single bond interconverts the different conformers. 

Melvin S. Newman (1908-1993) was born in New York and received his Ph.D. in 1932 from Yale University. He was professor of chemistry at The Ohio State University (1936-1973), where he was active both in research and in chemical education. 

A sawhorse representation and a Newman projection of ethane. The sawhorse projection views the molecule from an oblique angle, while the Newman projection views the molecule end-on. 

---