In Acid, the protonation of the HO in the hemiketal causes it to leave as H20 and thus allow for another nuc. to attack there due to the carbocation. However, in basic conditions, you can't protonate the OH group so it stops there.
In Acid, the protonation of the HO in the hemiketal causes it to leave as H20 and thus allow for another nuc. to attack there due to the carbocation. However, in basic conditions, you can't protonate the OH group so it stops there.