 Okay, for the final reaction mechanism today, let's do this stereoselectivity and alcohol dehydration. So you can see here we've got this 3-pentanol, and we're reacting it with sulfuric acid, so dehydrating conditions of course, sulfuric acid and heat, and we're getting this mixture of products as you would imagine, right, but we're getting, of course, the trans product is the major product, and the cis product is the minor product, remember, trans, and trans is when they're on the opposite side, okay, and cis is when they're on the same side, right, or sometimes we call this Z, okay? So those are the products you would expect, but why do you get this stereoselectivity? Well, the reason you get it is because, of course, well, we can do the mechanism, but we'll talk about it first. The trans formed is, doesn't have that steric clash of the two groups bumping into each other, okay? So that's less favorable than the trans form. The cis form is less favorable than the trans because you've got kind of the steric hindrance of each other coming together, so let's go over the mechanism of this, and, okay, so sulfuric acid made by the alcohol, thank you to that good leaving group there, okay? So here you've got the hydrogens that you're going to deprotonate, so you can imagine this being an SN1 or an E1 or an E2 reaction. We'll look at it as an E1 reaction, so when we make that carbocat ion there, what's going to happen is the base here could be the newly formed water molecule, it could be the conjugate base of sulfuric acid, it could be either one. But anyways, let's just say general base will come in and deprotonate like that, making your double bond. And again, we're making the trans isomer over the cis isomer because it's more energetically stable because we don't have the steric interaction between the two groups, right? On this side we have a hydrogen, this side we have a hydrogen, so there's no, it's a small group, big group, small group, big group. On the other, with the other isomer, the cis isomer, which we do get as the minor product, we got the big group, big group on the same side, and the small group, small group on the same side. So this is going to be the minor, this is going to be the major due to that interaction. Any questions on that one? Okay, cool.