1.10: Hybridization of Nitrogen, Oxygen, Phosphorus and Sulfur
- Page ID
- 67048
Objective
After completing this section, you should be able to apply the concept of hybridization to atoms such as N, O, P and S explain the structures of simple species containing these atoms.
Make certain that you can define, and use in context, the key term below.
- lone pair electrons
Nitrogen is frequently found in organic compounds. As with carbon atoms, nitrogen atoms can be sp3-, sp2- or sp‑hybridized.
Note that, in this course, the term “lone pair” is used to describe an unshared pair of electrons.
The valence-bond concept of orbital hybridization can be extrapolated to other atoms including nitrogen, oxygen, phosphorus, and sulfur. In other compounds, covalent bonds that are formed can be described using hybrid orbitals.
Methyl amine
The nitrogen is sp3 hybridized which means that it has four sp3 hybrid orbitals. Two of the sp3 hybridized orbitals overlap with s orbitals from hydrogens to form the two N-H sigma bonds. One of the sp3 hybridized orbitals overlap with an sp3 hybridized orbital from carbon to form the C-N sigma bond. The lone pair electrons on the nitrogen are contained in the last sp3 hybridized orbital. Due to the sp3 hybridization the nitrogen has a tetrahedral geometry. However, the H-N-H and H-N-C bonds angles are less than the typical 109.5o due to compression by the lone pair electrons.
Methylamine
Methanol
The oxygen is sp3 hybridized which means that it has four sp3 hybrid orbitals. One of the sp3 hybridized orbitals overlap with s orbitals from a hydrogen to form the O-H signma bonds. One of the sp3 hybridized orbitals overlap with an sp3 hybridized orbital from carbon to form the C-O sigma bond. Both the sets of lone pair electrons on the oxygen are contained in the remaining sp3 hybridized orbital. Due to the sp3 hybridization the oxygen has a tetrahedral geometry. However, the H-O-C bond angles are less than the typical 109.5o due to compression by the lone pair electrons.
Methanol
Methyl phosphate
Phosphorus can have have expanded octets because it is in the n = 3 row. Typically, phosphorus forms five covalent bonds. In biological molecules, phosphorus is usually found in organophosphates. Organophosphates are made up of a phosphorus atoms bonded to four oxygens, with one of the oxygens also bonded to a carbon. In methyl phosphate, the phosphorus is sp3 hybridized and the O-P-O bond angle varying from 110 to 112o.
Methanethiol & Dimethyl Sulfide
In biological system, sulfur is typically found in molecules called thiols or sulfides. In a thiol, the sulfur atim is conded to one hydrogens and one carbon and is analogous to an alcohol. In a sulfide, the sulfur is bonded to two carbons. In both cases the sulfur is sp3 hybridized and the bond angles are much less than the typicall 109.5o.
Methanethiol
Dimethyl sulfide
Exercise
1) Insert the missing lone pairs of electrons in the following molecules, and tell what hybridization you expect for each of the indicated atoms.
a) The oxygen is dimethyl ether:
b) The nitrogen in dimethyl amine:
c) The phosphorus in phosphine:
d) The sulfur in hydrogen sulfide:
Solution
1)
a) sp3 hybridization
b) sp3 hybridization
c) sp3 hybridization
d) sp3 hybridization
Contributors and Attributions
Dr. Dietmar Kennepohl FCIC (Professor of Chemistry, Athabasca University)
Prof. Steven Farmer (Sonoma State University)