e --> i in some instances: no pattern listed

henchir - to fill, to fill up
comedirse - to be restrianed
concebir - to imagine, to plan
derretir - to melt, to thaw
desmedirse - to go to far, to go over the top
despedir - to say goodby to
expedir - to send, to dispatch, to issue
henchir - to fill / to fillup
impedir - to prevent
pedir - to ask for, to order
preconcebir - to preconceive