What type of molecule typically acts as a Lewis base in a chemical reaction?

A molecule that acts as a Lewis base is characterized by its ability to donate a pair of electrons to a Lewis acid during a chemical reaction. According to the Lewis definition, a Lewis base is any species that can provide an electron pair, which is commonly found in molecules with lone pairs of electrons. These lone pairs can be used to form new bonds by interacting with electron-deficient species, or Lewis acids, that seek to accept those electrons.

For instance, ammonia (NH₃) is a classic example of a Lewis base, as it contains a lone pair of electrons on the nitrogen atom that can readily be donated in reactions with Lewis acids such as boron trifluoride (BF₃). This characteristic makes molecules with lone pairs of electrons essential players in various chemical reactions, particularly in coordination chemistry and catalysis.

The other options do not fulfill the criteria to act as a Lewis base effectively. A positively charged ion typically does not have extra electrons to donate and is more likely to act as a Lewis acid since it can accept electrons. Saturated hydrocarbons are primarily composed of carbon and hydrogen with single bonds, lacking lone pairs of electrons suitable for donation. Molecules with no available electrons cannot function as Lewis bases, as they lack the necessary electron