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Video transcript

you can make mez lights and toss lights from alcohols and you might want to do this because mess lights and toss lights are better leaving groups so if we look at a general reaction to format oscillate you would start with an alcohol and you'd add tousle chloride and also pyridine and you would form your tousle 8 over here on the right we look at the mechanism we start with tousle chloride and if you if you focus in on the sulfur here the sulfur is bonded to two oxygens and a chlorine and we know that oxygen or chlorine are more electronegative than sulfur so they're going to withdraw some electron density from that sulfur and so since sulfur is losing some electron density the sulfur becomes partially positive and we have an electrophilic Center so the sulfur wants electrons it can get electrons from the alcohol so lone pair of electrons on the alcohol here can attack the sulfur so nucleophile attacks the electrophile and these electrons could kick off onto the chlorine here to form the chloride anion and let's go ahead and draw what we would make so we would have an R group we would have an oxygen the oxygen would now be bonded to sulfur all right we would also have still a hydrogen attached to that oxygen and we still have a lone pair of electrons on that oxygen so the oxygen gets a +1 formal charge the sulfur is still double bonded to this oxygen and to another oxygen and then we still have our ring attached to the sulfur so put in our PI electrons here and that was a bad one let me fix that so we have our PI electrons right here and then a methyl group like that so let's go ahead and follow those electrons so the electrons in magenta right here on the oxygen alright formed a new bond to the sulfur so here are those electrons in magenta right in the next step we're going to take the proton off the oxygen here and so the pyridine is going to function as a base right the lone pair of electrons on nitrogen is going to take this proton leaving these electrons behind on the oxygen so let's go ahead and draw what we would form we would have our R group we would have an oxygen right and our oxygen would have now two lone pairs of electrons and we have our sulfur double bonded to this oxygen don't want to this oxygen and then we would have our ring like this so let me just sketch that in really quickly so we would have electrons here here here our methyl group and let's let's follow some of those electrons so the electrons in this bond right now end up on the oxygen like that and we formed our toluene at sulfonate ester so also called eight oscillate so this is the exact same thing right so this compound and this compound are the same alright the top way is just a way to abbreviate it and so we formed our tousle 8 alright so one reason to format oscillate would be to have a better nucleophilic substitution reaction so let's let's look at first forming 8 oscillate from this alcohol over here on the left and so we know that this carbon is a chiral Center right so that is a chiral Center but if we're forming a tosylate the tosylate forms at this oxygen here alright so let's go ahead and draw the product right we would we would now have we still have a wedge here because again the reaction does not occur at the chirality Center the reaction occurs at the oxygen here's the oxygen would now be bonded right so we'd form a tosylate group which is a much better leaving group right then then this Oh H over here so the toss lights an excellent leaving group for nucleophilic substitution reactions so if we go went ahead and did a nucleophilic substitution reaction we could add something like sodium bromide so na plus and BR minus alright so if this was an sn2 type mechanism right the bromide anion would attack this carbon right here which is a little bit positive so we have a partially positive carbon right here and then we get nucleophilic attack from the bromide anion so it attacks right here and then sn2 type mechanism you're going to get inversion of configuration so you go ahead and draw your product like that and so and so the formation of itas light just makes this process much easier we could talk about formation of another good leaving group and that's a meso late so very similar to a tosylate so if you look at the general reaction once again we start with an alkyl all this time we add meso fluoride and this time triethylamine is as the base that we will use to form our bezel age over here on the right the mechanism is a little bit different from the formation of at oscillate so let's let's go ahead and look at see what happens first the triethylamine is going to function as a base and take this proton right here so these electrons are going to remain behind on this carbon so trial amine reacts with this is methyl chloride right here so if we if we take a proton off let's go ahead and draw what we would have we would have our sulphur double bond to this oxygen sulfur double bonded to another oxygen a chlorine right here and we would now have a carbon bonded to only two hydrogen's right and a lone pair of electrons on this carbon so it's a carb anion so it's a negative one formal charge so let's show those electrons so these electrons in this bond right we're left behind on the carbon to form our carb anion so in the next step these electrons in magenta are going to move in here to form a double bond between the sulfur and the carbon and that would kick these electrons off onto chlorine to form the chloride anion and let's go ahead and draw what we would make all right so now we would have sulfur so four would be double bonded to an oxygen sulfur is double bonded to another oxygen and now there's a double bond between sulfur and this carbon and this carbon is bonded to two hydrogen's like that once again we can think about sulfur as being electrophilic because this sulfur right here is bonded to these oxygens which are more electronegative they're going to withdraw electron density from that sulfur leaving that sulfur partially positive and so our electrophilic Center all right once again we're going to have our alcohol functions in nucleophile so a lone pair of electrons on our alcohol are going to go all the way to here right they're going to attack our electrophile and when they do that right now push these electrons back off onto the carbon so let's get a little more space down here so we can draw so we can draw what happens so this is a sulfon right here so the alcohol attacks the Saltine nucleophile electrophile and let's go ahead and draw what we would make alright so now we would have an R group group bonded to an oxygen right we would have a hydrogen and this is the oxygen from the alcohol which attacked the sulfur's now there's a bond between the oxygen and the sulfur there's still a lone pair of electrons on that oxygen giving it a +1 formal charge and the sulfur is bonded to double bonded to this oxygen double bonded to this oxygen and bonded to this carbon this carbon has two hydrogen's on it it also has a lone pair of electrons so that's a negative 1 formal charge so once again let's identify those electrons so these electrons right here alright moved off on to the carbon to form our carb anion and we could we could identify some of the electrons on our alcohol too so let's say let's say let's make it red here these electrons are right here on the oxygen alright those are the ones that form the bond between the oxygen and the sulfur so you could say that those electrons are these electrons in here and so in the last step of our mechanism the the carb anion is going to function as a base and this lone pair of electrons here is going to take this proton leaving these electrons behind on our oxygen so let's go ahead and draw we would make all right so we would have an R group over here right we would have an oxygen and the oxygen would have two lone pairs of electrons the oxygen is bonded to a sulfur the sulfur is del bond to this oxygen don't want this oxygen and then we would have a ch3 group over here all right so a ch3 group because this carbon go ahead and identify it in magenta this carbon right picked up this proton here so you could say you could say it's that one if you want it to and we formed our methyl 8 so this is the this is the exact same thing we could just abbreviate it here we could say it's our O and then an MS here so that's how to form bezel eights and toss lights which are excellent leaving groups