Question

Whar are Lewis acids?

Answer 1

a compound or ionic species which can accept an electron pair from a donor compound.

Lewis acids accept an electron pair. Lewis Acids are electrophilic meaning that they are electron attracting. When bonding with a base the acid uses its lowest unoccupied molecular orbital or LUMO.

• Various species can act as Lewis acids. All cations are Lewis acids since they are able to accept electrons. (e.g., Cu2+, Fe2+, Fe3+)
• An atom, ion, or molecule with an incomplete octet of electrons can act as an Lewis acid (e.g., BF3, AlF3).
• Molecules where the central atom can have more than 8 valence shell electrons can be electron acceptors, and thus are classified as Lewis acids (e.g., SiBr4, SiF4).
• Molecules that have multiple bonds between two atoms of different electronegativities (e.g., CO2, SO2).