Hybridization of Nitrogen, Oxygen, Phosphorus and Sulfur

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.

Key Terms

Make certain that you can define, and use in context, the key term below.

lone pair electrons

Study Notes

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.

Methylamine

The nitrogen is sp³hybridized which means that it has four sp³ hybrid orbitals. Two of the sp³hybridized 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 109.5^odue to compression by the lone pair electrons.

Methylamine

Methanol

The oxygen is sp³hybridized which means that it has four sp³ hybrid orbitals. One of the sp³hybridized 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 109.5^odue 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, phosphorusis 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 112^o.

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 sp³hybridized and the bond angles are much less than the typicall 109.5^o.