By analogy with the Stone-Wales rearrangement in sp(2)-hybridized carbon allotropes that involves turning one CC bond by 90 degrees in a graphene sheet and reconnecting it cross-wise with two carbon atoms, the similar rearrangement for the diamond lattice was called connected exchange. In this case one C-C bond in the diamond lattice involving sp(3)-hybridized atoms is switched such that two anti bonds exchange one of their endpoints. As a result of this connected exchhange one obtains a defect in the diamond lattice with four 5-membered and four 7-membered rings. For the hydrocarbon pyracyclene with sp(2)-hybridized atoms, the Stone-Wales rearrangement is degenerate (automerization). By analogy, one can imagine a hydrocarbon having sp(3)-hybridized atoms that could undergo a degenerate connected exchange. (C) 2013 Elsevier B.V. All rights reserved.