this meeting is being recorded in section 10 from chapter 7 we're introduced to um some additional sulfat or some additional substrates rather that can be used in addition to um alkalides such as um these sulfinates so we have these Alternatives um to our alkal halides and uh let's take a look at some of them that are shown here so we have this first group that's called a alkal mesilate that's formed so this is the mesilate group here uh this is a tosilate group shown here and we have this triflate group shown here um all three of these uh substrates have very good leaving groups so if you recall um the first step um in a sn1 or E1 reaction is to have this leaving group and generation of a carbocation occur uh or with sn2 and E2 reactions we have that concerted U mechanism where um the leaving group occurs uh as well so having a good leaving group facilitates a um more efficient reaction so um as mentioned um these sulfinates can be considered uh good leaving groups they are very stable um conjugate basis of strong acids that um result so we know that um either due to inductive forces or resonance stabilization um all of these would be good leaving groups and were're asked down here to determine based on PKA value um which of these sulfinates would be the best leaving group and we would look at the most acidic compound here um and find that its conjugate base would be the most stable so um this tfoh this Tri florom methane sulfonic acid and the resultant um TFO group that is used is uh considered the best leaving group of these three so let's look at um how sulphonates can be made from a corresponding alcohol so we have this alcohol here and um we treat it with what's called tsel chloride so we have this uh chloride attached to this tosilate um group here and uh what happens is we react um are compound with uh purine and uh after this uh first reaction occurs the purine can deprotonate the alcohol and we end up with this uh structure here this alkal tosilate and um we should note that uh alcohols when they are turned into tsat uh we do not change our configuration so there's no inversion of configuration when we prepare a tosilate and um overall nothing has changed besides this hydrogen is now replaced with that uh TS group so no change in configuration but when we have um our uh sn1 uh reaction occur we would see an inversion of configuration so now that we have our toilat we see a primary tosilate here or a secondary tosilate um either of these can be treated with a strong nucleophile strong base such as hydroxide and we would see a mix of products so for this first reaction uh mechanism we would see a mix of our major product our substitution product and then a minor elimination product then with our secondary tosilate shown down uh in the second row here we treat that with uh the same reagent the strong nucleophile strong base the hydroxide and now we'll see that with a secondary substrate our major product will be an elimination product and our minor product is now the substitution product so um again you should begin to uh look at the substrate to determine what um reaction mechanism will be your main uh mechanism whether it's elimination or substitution as we see with these cases here so alcohols uh can also be used in substitution and elimination reactions uh similarly to the toilat that we saw and um what we see here is a primary alcohol we can treat it with uh an alkal haly or with um this hydrobromic acid and produce an alkal halide in this case it's a primary uh alcohol so we would produce that primary bromide as our product and of course uh water as well right the O and the H form our other product so we would need uh strongly acidic conditions in order to accomplish this um because H2O is uh I'm sorry o is not a good leaving group but if we use something like hydrobromic acid to protonate the alcohol we can see here that water is a much better leaving group and that leaves the bromide ion available for nucleophilic attack at this site here and then that forces this uh water molecule to be objected and by that path we have our sn2 uh mechanism and our alcal Ali product produced so alcohols can participate in either sn2 or sn1 depending on what type of substrate so we see that primary alcohols are going to follow sn2 but secondary and tertiary alcohols will follow an sn1 pathway uh so that's what we see here we see this tertiary alcohol um we see that we are going to generate a carbocation intermediate in in this uh Second Step here um so first step we proteinate our alcohol we generate um this species here then we see that water molecule is ejected as a leaving group and then we have our carbocation generated here and then that nucleophilic attack happens in this step here and um we generate that tertiary bromide so we reviewed um different solvents can affect um reactions and we know that strongly acidic conditions are proteic conditions which would favor sn1 but since we know that these primary carbocations are too stable to form um primary alcohols would then react via the sn2 mechanism instead um they're unable to stay uh in that carbocation in the primary state so therefore um they follow that sn2 mechanism so then we look at alcohols and elimination reactions um alcohols will undergo E2 elimination um if we use the strong um acid here sulfuric acid so concentrated sulfuric and heat are the driving uh force of this reaction to take a tertiary alcohol and uh cause an elimination to occur and we generate this alken and of course water as a byproduct so once again we have these strongly acidic conditions these are proteic conditions um our solvent is a polar pric solvent and therefore um E1 uh would favor for secondary and tertiary substrates so we have that tertiary alcohol shown here we have our first step in the mechanism a proton transfer um here's our acid Source right this hydronium ion shown uh then we have our in step two loss of leaving group and um remember if we had a neutral uh leaving group we will have to have a third step here in our mechanism for a subsequent proton transfer to um create our final product so we'll take a look at uh synthesis in our next video