Bonding in Alcohols
Names and Lewis StructuresWe name alcohols as alkanols. Find the longest carbon chain that includes the OH group. The numbering of carbon atoms on the chain should put the OH group at the lowest number possible.
In the line drawings above, the end of every line is a carbon atom unless otherwise assigned. Every carbon atom makes for bonds. Any bond that is not specified is to a hydrogen atom.
Electron BookkeepingThe total electron count is the sum of the number of non-bonding electrons and bonding electron pairs around every atom. The bonding pairs are counted twice, once for each atom in a bond.
Each atom can have a maximum that is the same as the nearest noble gas. For hydrogen, the maximum electron count is 2. For carbon and oxygen, it is 8.
For oxidation state, break the bonds and give all bonding electrons to the more electronegative of the pair. Compare the sum of the electrons around an atom with its valence number. Use Roman numerals for oxidation state to differentiate from formal charge.
Molecular Orbital DiagramsWe'll use hybrid molecular orbital diagrams for these molecules because they have more than 2 atoms.
The first step is to decide on the hybridization of each atom. In this molecule, every carbon is 2sp3 hybridized, oxygen is also 2sp3 hybridized, and hydrogen uses it 1s orbital.There are a total of 12 + 20 + 4 = 36 atomic and hybrid orbitals.
Now use the atomic and hybrid orbitals to make 36 molecular orbitals with the same average energy as the orbitals they were made from:
The total number of electrons for the diagram is the sum of the valence electrons of C, H, and O: 5(4) + 12(1) + (6) = 38 electrons