 Okay, so let's go ahead and do this second mechanism that was on the quiz so this one said draw the mechanism from propanolic acid to propanol bromide using phosphorus tribromide So Remember just like every time we do a mechanism. What are we going to do? We're going to erase everything that's not needed in the first step and we're going to expand the bonds Okay, if we do that it really helps us to remember What things are breaking and what things are forming and I'd also like to put the lone pairs in okay? So let's go ahead and do that. Don't forget where we're going to though because if we forget oftentimes we won't get there, okay? phosphorus is oxyphilic, so Even though it's got those lone pairs on there, and we don't often like to Attack things with lone pairs phosphorus can Be attacked at that position. So that's what's going to happen. It's oxyphilic. So the oxygen will attack it So it'll be actually the heart hydroxyl group portion of the carboxylic acid so Going to take those electrons And attack that phosphorus out Okay, that's not the only thing that happens right? We're also going to knock off one of these bromines So what we're doing essentially is taking a bad leaving group the OH group here and turning it into a good leaving group Which is that oh connected to the phosphorus and all those okay, so So here Remember this carbon is electrophilic the carbonyl carbons always electrophilic and hopefully you can see right this is Going to be that good leaving group that we talked about in class. Okay, so this thing is going to Attack the bromide ion is going to attack the carbonyl carbon Which is going to induce those electrons to go there just like So we're going to get that tetrahedral intermediate that we see Final step is going to be these electrons coming back down Making the carbonyl again kicking out those electrons to allowing them to rest on that Okay, so when that happens, let's just draw that final product The organic product that we're interested in if you remember how to name those things and then This is an organic product, which we as organic chemists of course aren't interested. Questions on that mechanism? Makes sense You sure? Shut it off. Okay