Abstract: Carbon is a crucial non-metallic element and serves as the foundation for all life on earth. Its chemical structure is typically governed by the “octet rule”. However, advancements in science have led to the discovery of various carbon species with unique valence electron configurations, such as radicals with seven valence electrons, carbocations, and carbenes with six valence electrons. These discoveries have significantly propelled the fields of organic synthesis, medicinal chemistry, and natural product chemistry. Conversely, carbon species with fewer than six valence electrons have been challenging to synthesize and characterize due to their inherent instability and the lack of suitable techniques. Recently, a breakthrough in this scientific challenge has been achieved through the diligent efforts of Bertrand and colleagues. This article primarily focuses on the synthesis, characterization, and reactivity of doubly oxidized carbenes with four valence electrons. It aims to provide students with insights into cutting-edge chemical research, stimulate their thinking, enhance their independent learning capabilities, and further ignite their interest in the study of chemistry.

Key words: Carbon, Octet rule, Doubly oxidized carbene, Valence electron