Describe the differences between carbenes and carbanions.

Carbenes are neutral species with a divalent carbon atom, while carbanions are negatively charged species with a trivalent carbon atom.

Carbenes are highly reactive species that possess a divalent carbon atom with two unpaired electrons. They can be classified into two types: singlet carbenes and triplet carbenes. Singlet carbenes have a paired set of electrons in the ground state, while triplet carbenes have two unpaired electrons in the ground state. Carbenes can be generated by various methods, such as thermal decomposition of diazo compounds, photolysis of ketenes, and metal-catalyzed decomposition of diazo compounds.

On the other hand, carbanions are negatively charged species that possess a trivalent carbon atom with one unpaired electron. They are formed by the loss of a proton from a carbon atom that has a lone pair of electrons. Carbanions are highly reactive species and can be stabilized by resonance. They can be classified into three types: sp3 hybridized carbanions, sp2 hybridized carbanions, and sp hybridized carbanions.

In summary, carbenes and carbanions are two different types of reactive intermediates that possess a carbon atom with unpaired electrons. While carbenes are neutral species with a divalent carbon atom, carbanions are negatively charged species with a trivalent carbon atom. Both species play important roles in organic chemistry and are widely used in various synthetic transformations.