Rename small part of multiple files in middle of name using Bash?

Question

I\'d just like to change this

cc211_AMBER_13062012i.II  cc211_GROMOS_13062012i.II
cc211_CHARM_13062012i.II  cc211_OPLS_13062012i.II

to

Answer 1

A pure bash solution:

for i in cc*; do
  mv "$i" "${i/_13/_15}"
done