So, in the first step, this pi bond acted as a lewis base, donating this pair of electrons and this h atom on this compound on the hydrochloric acid active as a lewis acid, donating that h, donating that empty one s orbital. And likewise, here, this is the lewis acid because it has an empty two p orbital. And this is the lewis base because it has a pair of non bonding electrons. So, what exactly is a lewis athens based reaction? So, a lewis athens based reaction is the interaction between a filled molecular orbital, as we saw here, and an antimolecular orbital. And this is known as a homolumo interaction.