Published online by Cambridge University Press: 11 May 2021
Morgan and Parker proved that if G is a group with ${\textbf{Z}(G)} = 1$, then the connected components of the commuting graph of G have diameter at most
$10$. Parker proved that if, in addition, G is solvable, then the commuting graph of G is disconnected if and only if G is a Frobenius group or a
$2$-Frobenius group, and if the commuting graph of G is connected, then its diameter is at most
$8$. We prove that the hypothesis
$Z (G) = 1$ in these results can be replaced with
$G' \cap {\textbf{Z}(G)} = 1$. We also prove that if G is solvable and
$G/{\textbf{Z}(G)}$ is either a Frobenius group or a
$2$-Frobenius group, then the commuting graph of G is disconnected.
This work was supported by NSF Grant DMS-1653002.