Question

Does a C2 bond exist? And is it stable, if yes what is its VSEPR structure?

Answer 1

Diatomic carbon (systematically named ethenediylidene and dicarbon(C—C)), also called dicarbon, is an inorganic chemical with the chemical formula C=C (also written [C
2] or C
2). It is a gas that only exists above 3,642 °C (6,588 °F),below which it aggregates into graphite or fullerenes.it us unstable at theother conditions..It occurs in carbon vapor, for example in electric arcs; in comets, stellar atmospheresand the interstellar medium; and in blue hydrocarbon flames.

Molecular orbital theory shows that there are two sets of paired electrons in a degenerate pi bonding set of orbitals. This gives a bond order of 2, meaning that there should exist a double bond between the two carbons in a C₂molecule. A 2012 paper by Shaik et al. has suggested that a quadruple bond exists in diatomic carbon, an interpretation that was disputed by Jörg Grunenberg.

Carbon with 4 single bonds is sp3. If it has a double bond it is sp2. If there is a triple bond it is sp hybridization. ""Valence bond theory predicts a quadruple bond as the only way to satisfy the octet rule for carbon. However, molecular orbital theory shows that there are two sets of paired electrons in the sigma system (one bonding, one antibonding), and two sets of paired electrons in a degenerate pi bonding set of orbitals. This adds up to give a bond order of 2, meaning that there exists a double bond between the two carbons in a C2 molecule.[citation needed] This is surprising because the MO diagram of diatomic carbon would show that there are two pi bonds and no sigma bonds."""