Some Reactions and Properties of Molecular C2. An Experimental and Theoretical Treatment

Article abstract of DOI:10.1021/ja00194a042

Diatomic carbon, C2, reacts with propylene and (E)- and (Z)-2-butene in the condensed phase at 77 K.Products can be rationalized by a mechanism involving initial addition of C2 to the alkene to generate a 1,4-diradical.This diradical may then either abstract hydrogens or add another alkene molecule to give a 1,6-diradical which disproportionates to an enyne.Thus, reaction of C2 with propene gives 1-pentyne, 3-methyl-1-butyne, 4-methylhept-6-en-1-yne, 6-methylhept-1-en-4-yne, and oct-1-en-4-yne.Ab initio calculations at the HF/3-21G level predict that both ¹C2 and ³C2 will add to ethylene without barrier.At the MP2/6-31G^*//3-21G level, the triplet adduct is calculated to be more stable than ³C2 and ethylene by 46.0 kcal/mol.The reactions of ¹C2 and ³C2 with methane and hydrogen have also been investigated theoretically.