I don't understand why this molecule is assigned S instead of R. ![enter image description here][1] The H is assigned a priority of 4; the methyl group on the chiral carbon gets 3; the left carbon gets 1 and the right carbon gets 2. The rotation should therefore be clockwise. I guess what I have an issue with is assigning priorities in cases like these: what does moving away from the chirality center mean? Do I choose the H? The C? The other C? ![enter image description here][2] Do we just ignore the attached hydrogens? It seems like the hydrogen on the carbon left of the chirality center is ignored. ![enter image description here][3] ![enter image description here][4] And in the above case, why are we comparing an O with a C? The first atom to the left of the chirality center is a C, not an O. ![enter image description here][5] [1]: https://i.sstatic.net/ZYqU4.png [2]: https://i.sstatic.net/HHejM.jpg [3]: https://i.sstatic.net/WBOB9.png [4]: https://i.sstatic.net/uX8DS.png [5]: https://i.sstatic.net/yI0WH.jpg And in the last picture I give my configuration for the molecule in the first picture. Why doesn't the upper right carbon have a priority of 2? Double bonded carbon counts twice; the rest are hydrogens.