okay so welcome to our final topic topic four for organic chemistry 2 I'm Dr SAA and this is our final lecture so lecture six and what are we going to do we're going to well I'm going to introduce you to carbonal compounds um in this lecture so we're GNA start with an overview of the functional groups we've looked at just in organic chemistry 2 we're going to go into what carbonal groups are and talk about the aspects of the carbonal couble bond o Bond and we're going to look at some reactions of these carbonal groups with the carbonal carbon behaving as an electrophile we're going to look at nucleophilic substitution reactions and this is where we actually have a leaving group off the carbonal we're going to find out why Al coxy is better than hydroxy for leaving group okay this is lots of words but this is letting you know what's happening and then we have feel like addition reactions we're going to look at and that's means if you don't have a good leaving group what do you do and I just want to let you know I've made another video with some supplemental information about arrows and this is found in your um Moodle h5p um oh not group book okay um so it's tucked in there this is just made because someone asked some questions about arrows and I thought I would help you by making a little video so let's stop off start off by looking at functional groups in organic chemistry what have we actually covered in organic chemistry too well we've covered quite a bit we've talked about alkanes alkenes alkin uh We've also talked about alcohols and ethers here we go and we have talked about Halo alkanes as well okay and we talking about air atic chemistry so arines as well and we mentioned amines and today we're going to be introducing you to this class of carbonal compounds aldhy ketones carboxilic acids all as we go across here so if you look at this thing we have covered a good chunk of functional groups of organic chemistry just in our six lectures so well done you for sticking with us so here we have a carbonal compound a carbon double bonded to an oxygen that oxygen has two lone pairs that carbon is bound to two other groups so that means B bound to something and we don't know what that's just sort of a wiggly line meaning there's something over here and there's something over there so all carbonal compounds contain this particular group this carbonal group and this is the most important functional group in organic chemistry so they are prevalent in um biological compounds in nature so look at this here's Cortisone and we've got one two three carbonal groups only on this one molecule it's there's a vast class of these compounds um carbonal compounds that contain this carbony group you may recognize alahh there's a carbonal group there Ketone there's a carbonal group there this one has one alkalol group one hydrogen this one has two alkal groups what you're going to learn is there's no good leaving groups with alahh or ketones and so because of that these two will undergo nucleophilic addition reactions I'll get to that in a later slide but remember that alahh and ketones don't have good leing groups and they don't they undergo nucleophilic addition reaction something is added to it then we look at this here we've got carboxilic acid there's your carbonal group you've got o here and we've got derivatives of carboxylic acid so we've got acid halides okay so there's a hallogen there acid and hydde there's an an hydde ester and amides there NH nr2 there could be nh2 NRH but we got an amide Esther and hydrides acid halides so for all of these what you'll notice you have your carbonal group with your double bond that carbon is bound to another carbon that's the R Group here and on the other side see there's an R Group there R Group R Group but the other side of the carbon is bound to a electr negative hetro atom so it's bound to something that's electronegative so that could be a hogen there in this case we've got oxygen in this case we've got oxygen there and this one we've got nitrogen so these are carboxilic acid derivatives and these compounds undergo nucleophilic substitution reactions and these groups all have good leaving groups we're going to explore what makes a good leaving group so no good leaving groups these have good leaving groups these undergo nucleophilic substitution reactions so there's a good leaving group good leaving group another one another one so that would be a halide okay so we can yeah anyway I'm going to get to that in one of the later lectures or slides so just off of this you're going to find out that carbonal groups are within carbonal compounds are are some of the most important and useful compounds that we have in organic synthesis so let's explore that carbonal group a little bit more to try to understand it so that carbon here is an SP2 hybridization okay and that means that this group is um is as well it's got 120 degree Bond angle from here to here from here to here and here to here it also means it is planer it's flat so we've got equivalent Bond angles and it's planer and because we have this Electro negative oxygen here this bond is polarized so oxygen again is electr negative it's pulling electrons towards itself so oxygen is more electronegative than carbon just stating that as a fact so it means we have a dipole here and we've got a partial negative um charge sitting next to the oxygen which means the carbon at this end is partially positive okay so it means that this carbon is electrophilic and there's a dipole showing the direction of the electrons and there's a positive little bar there suggesting to you and reminding you that this is the electrophilic end so here we go we have a carbon oxygen dipole and let's let's draw this out in another way let's draw some resonance structure so here is our carbonal group with that dipole so we know the electrons are being pulled towards that Electro negative oxygen let's push them formally up there so we're going to curly Arrow grab a pair of electrons and let's push them onto that oxygen okay remember curved Arrow you're moving a pair of electrons and this is a resonance Arrow so this is a resonance contributor so we're drawing a structure here that look at this we've broken that double bond and we push that pair of electrons up here so now we have a formal negative charge and a formal positive charge but of course they're resonant structures so we can actually there's your dipole we can push those electrons back and form your this this carbonal structure here so in real life it's it's a sort of a blend of both of those but if you can see we said that that carbon is an electrophile you can see there is really a positive charge sitting there or a CH positive dipole there on carbon so carbon is the electrophile and it's because of that bond to the oxygen so if we look at alide here an alkal group an AO group here and a hydrogen and we look at a ketone and compare it to carboxilic acid what we're going to find out that there are poor leaving groups this is a very poor leaving group hydrogen breaking that that carbon hydrogen bond is very difficult and breaking an alky bond that carbon carbon bond is also very difficult so that's a poor leaving group poor leaving group poor leaving group and you'll also find out oh that these undergo nucleophilic addition reactions we're going to get to that I'm just hammering it into your head it means we can add a nucleophile to it but we're not substituting anything and again breaking that o Bond on the carboxilic acid is tricky so that is a poor leaving group too but when you get to these carboxilic um acid derivative this is an acid halide and hydride an Esther an amide you're going to find out you have better leaving groups so look at these leaving groups here that we have so these are good which means that these compounds can undergo nucleophilic substitution so we can have a nucleophile attack at that electrophilic carbon and then we can drive off those groups as leaving groups whereas here the nucleophile is going to attack the electrophilic carbon but we're going to have something else happen because we don't have any good leaving groups okay so back to the carbonal we've got that dipole there we can actually do as we we showed you before we draw resonance structures to show a formal positive charge here and a formal negative charge here we've identified this carbonal carbon is electrophilic it means it's craving electrons so if you have this is a general carbon if you have a nucleophile it's going to attack at that carbo um the carbon carbon so that makes sense positive end here negative end here so your nucleophile can attack and push a pair of electrons here onto that carbon so you're forming a bond between the carbon and the nucleophile and at the same time it means you have to break this Bond and push that back up onto the oxygen and that goes well so now we formed this was SP2 hybridized this is now sp3 hybridized tetrahedral okay it's not drawn that way but that's tetrahedral and we have that formal negative charge on the oxygen here so SP2 to sp3 so carbon can be attacked by nucleophiles at the base you're going from a planer structure to a tetrahedral intermediate so let's look over here at aldah eyeses and ketones we got that dipole here oxygen is pulling electrons um to itself and what can happen is through that Sigma bond that single Bond we can share some electron density from the alkal group okay so there's because we have a dipole here we could share some electron density to try to help stabilize that partial positive charge here it's very difficult to share electron density on the carbon hydrogen bond that PO hydrogen doesn't have much to give we've sort of drawn that before to sort of show what's happening in other structures but it's also showing that that in other structures when that happens can make that more acidic but in this case it's not okay so if we look here the Ketone is being stabilized um through that alkalol group but then we have a second alcoholic group so this is more stabilized than this group which means in terms of reactivity oh this is I'm trying to say R contributes more electron density than the hydrogen so in terms of being susceptible to a nucleophilic attack this is going going to be the most reactive to a nucleophile because it's going to be the most exposed partial positive charge here whereas a ketone you've got two alkal groups contributing as much as they can to supporting that um partial positive charge here so a nucleophile attack is going to be faster than an aldah than a ketone now let's compare that to an Asel halide and we're going to find mind that that is going to be even slower than a ketone an Esther is going to be even slower and an amide the slowest okay so these are not as susceptible to a nucleophilic attack on that carbonal car compound they still are but this is going to be the fastest and the next fastest now how can we explain that well we've got something called dipole resonance so if we think that let's use y to signify that hogen that Esther that amide so that X the O the N okay if we draw that compound there your carbonal bound to the Y bound to the Y bound to the Y bound to the Y and you notice each one of them has a lone pair sitting on it well we can push those electrons around so we're going to push those electrons up here first and we show resonance structure that we have that formal negative charge here formal positive charge but now this this this atom next to it which could be the hogen the oxygen or the the nitrogen can say okay I can actually help out I want to push my pair of electrons here to try to support um that and reduce that positive charge so if we do that we form a resonance structure here so now we have a negative charge here and a positive charge here here and then we can go back and push the electrons back around okay so this dipole resonance stabilizes that partial positive charge at the carbon through resonance okay so this going to be the least reactive more reactive even more reactive even more reactive and even more reactive okay towards a nucleophilic attack at that carbon so these two undergo nucleophilic addition the nucleophile is going to attack and add to the compounds these are going to have the nucleophile attack even if it's slower they can still attack and it's going to substitute and you're already thinking because I've told you these are good leaving groups nucleophile is going to come in and substitute this this or this so nucleophilic substitution reactions it's a curring mechanism so once you get used to seeing the pattern you can apply it so what you need for a substitution is you need a good leaving group on your carbonal and a good leaving group is an electr negative substituents okay so that um and can act as a a good leaving group so once it's leaving it's quite stable okay so if you had an Al coxy group or a chloride or that's a good leaving group as we've seen aldhy and ketones they don't have good leaving groups all they have is an R an alkal group or a hydrogen and both of those are extremely poor leaving groups okay so there's no nucleophilic substitution with them so let's just for example look at an acid halide or an Esther okay so we're going to look at that is a leaving group and that is a leaving group well we know this is SP2 hybridized so it's planer we've got that dipole so they've got the partial positive and partial negative charge we know that that carbonal is electrophilic so your nucleophile can come and push its electrons to that carbon and for example we've got some nucleophiles we use a hydride H minus we could use a grard remember how we made gards from alkoh halalyes in this um lecture two remember alky haly we've inserted magnesium between um an alkal um halide like and what it actually is is you're generating your alkal group which has got a formal negative charge on it okay you could use hydroxide alky lithium could also do the same thing so it's a similar way of generating that um negative alkal anide so anyway your nucleophile can then attack that carbonal group come on carbonal group and then you push electrons up and you formed this tetrahedral intermediate now we have the nucleophile that's bound on there and the electrons are up here on the oxygen sitting there so I've told you you have a good leaving group because the word leaving group is on here so now we have this SP sp3 tetrahedral compound and we're going to push electrons back down here to reform your carbon and then we're going to push off your leaving group which means that now we have a substitution of the nucleophile so nucleophilic substitution of that leaving group we reformed your carbonal compound SP2 planer and we've produced your leaving group okay now I've told you here this is a leaving group but how would you identify this on a real compound well that can be a little bit tricky but let me try to show you here so here's a carile one and two just got numbers there to indicate the two different things on that carbonal so it's SP2 planer and your nucleophile I'm going to call number three so that's going to attack the carbonal which is electron electrophilic which shows electrons up and we form this tetrahedral intermediate so at this point you're gonna have to decide which one of these three so you have to stop when the minute you've made this this structure here stop smell the roses and scrutinize each one of these which is the best leaving group well how do you know this this is this is so I'm going to push this down I'm going to tell you in this case one is the best leaving group just as an example and I'm just showing you that mechanism again so if one is the best leaving group we now have this nucleophilic substitution and we substituted nucleophile for one and we produced this there's your Le Group which should be stable and leaving group needs to be a stable sync for electron density what does that mean so you can see as we push our electrons down here we're pushing electrons onto that group that group has to be stable and able to support that negative charge being pushed onto it so once you push it onto that and you break that Bond can it sort of sit there by itself is it stay able so you have to have something that's able to accept those electrons and and and still be stable so oh that should say leaving groups from annion such as chloride Al oxide and this is the annion you get when you break off the um acid acetic and hydride if you can spit those off these are stable leaving groups they're able to take a negative charge on and sit there quite cly okay so we need to identify which is a good leaving group we've just said that there either neutral molecules or stable annion so how do we know this well we're going to find out the weaker the basic strength of the group is the better the leaving group okay so this is a lot of words I'm going to show you um what this really means so a good leaving group has a low PKA value of its conjugate acid don't worry I'm going to show you what this means so it needs to be less than 13 usually and that usually means your leaving group is stable so let's look at this we here have an acid chloride okay so there's a carbonal there's an alkal group and there's a chloro group there if your nucleophile and we'll use hydroxy group here comes in here and attacks so this oxide the base of the carbon because that's electrophilic and we're going to push electrons up we form this species here okay so now our instinct is to push this back down and reform the carbonal but we have to consider each one of these um um substituents which one is going to be the one that forms the best anine and or um yeah anine and is stable so if we push this down and we break this Bond here we're going to we're going to imagine that chloride is our e leaving group and that means if we do that we have formed look at this this um carboxilic acid so if we say the leaving group is chloride we need to think about its conjugate acid so the conjugate acid of that is HCl then we look at the pka of the conjugate acid it's minus 7 if the pka pka of the cont acid is less then then okay if it's less than 13 so it's a very good leaving group if it's if it's more than 13 it's a poor leaving group so what this means is this is a very good leaving group what if we push these electrons down and we we Tred to spit off an O group this hydroxy group hydroxide this is that we' form this this um acid chloride here and this would be our leaving group so we look at the conjugate acid of that leaving group which is water what's pka of water 15.7 that is greater than 13 so this is a poor leaving group well let's explore what happens if we try to push our electrons down here and kick off methyl this methyl Anon well if we do that oh we form this funny sort of creature here and there is our leaving group let's look at the conjugate acid which is methane what is the pka of methane B methane 48 oh that is a dreadful awful awful awful leaving group so if we compare these three we're going to find the better leaving group here is a chloride anion it's better than the hydroxide and hydroxide is better than the methyl that's a really bad one so now we already have three ranks so we know the reaction if we're going to do this we're going to lose the chloride group and to form this species so we've already Rank and we know this is awful awful awful horrible this is really not good and this is good what happens if our leaving group we've got the option between an Aly group or a hydroxy group okay so let's look at this compound here here we've got an Esther there's a methyl on this side and then methoxy group on that side we're going to use the hydroxide as a nucleophile it's going to push at the base of that carbonal because of that dipole that Electro or electropositive carbon we're going to push our electrons there there and push them up okay and now we form this tetrahedral intermediate at this point stop and consider where if we push try to push these electrons down is one of these three going to be a good leaving group oops so Al oxy groups Al coxy groups when they become leaving groups they become Al coxy ANS or Al oxides remember that from the alcohol um lecture and we find out the pka of the conjugate acid of an Al alkoxide which is an alcohol so an Al oxide the conjugate acid is RO so it's an alcohol and it's around 16 so that normally means that this would be a worst leing group than the hydroxide okay so if we lost that because we just saw that on the the previous slide so if we tried to push electrons here and we wanted to push this Al oxide off methoxide the conjugate acid of the methoxide is methanol pka of methanol is around 16 so that would indicate it's a poor leaving group what if we push the electrons down down here and try to push off the O Group Well the conjugate acid is water PKA is 15.7 so this is also a poor leaving group and you would think that the O would be a better leaving group because of that than the methoxide and also if we push the electrons down here and try to push off the methy group well we know the conjugate acid is methane PKA is 48 really bad leaving group so we don't even think about pushing our electrons that way so based on this one would predict that this is a better leaving group than the AL oxide so you'd think the hydroxy group would be a better leaving group than the AL coxy group but the truth is alkoxy groups are better leaving groups than hydroxy groups just remember that and I'm going to try to explain it here in a little story so just imagine you had a strong base imagine okay we're going into fantasy land that we had a strong base and a strong base comes along and it's going to look at this hydroxy group and we're going to maybe pretend that we could deprotonate this hydroxy group okay so we're going to use hydroxide in this case as a base in this case it was a nucleophile because it's attacking a carbon in this case we're going to use use it to pretend to deprotonate this proton here so let's do that this is still in fantasy land and let's push the electrons onto that oxygen so now we've got this pretend dot dot dot showing you it doesn't happen um species here where you have o minus as well as the one up here oh now let's pretend that if we push your electrons here we're going to push this off off so we already have o minus the electrons here would add to this with another electron and we would generate a species which is O2 minus oh this is going to have your organic chemistry brains ringing its alarm Bells going no this doesn't feel right those dotted lines means that doesn't happen I'm just showing you what could happen if we imagined so this would be a horrible horrible leaving group so that's not going to happen because as we know this space is not going to deprotonate a proton this o because we learned that in a lecture three about alcohols so that doesn't happen this is not going to happen so what it means is by default the AL oxy group is a better leaving group than the hydroxy despite the fact that it's got a similar PKA so what's going to happen is we're going to push electrons here we're going to lose that methoxy group and we form a carboxilic acid through a nucleophilic substitution we're substituting that leaving group for your nucleophile oops for that nucleophile sorry um and then let's think about ordering these things so what we've learned from this slide is methoxide oxides are better leaving groups than hydroxides okay so this is a better leaving group the alkoxy group than the hydroxy group and that's much better than the methyl anion so my question to you is can you rank these in your heads in the previous slide we said chloride was better than hydroxide which was better than a methy so can you in your heads rank this now so chloride or haly is going to be better than Al oxide which is better than hydroxide which is better than this methy an i okay so let's keep going so now we know what to do if we have a nucleophile and it's attacking your carbon um then you form that um tetrahedral intermediate and then you try to reform you try to push your electrons down um and throw off a leaving group but what if you you don't have a decent leaving group okay that's not a good leaving group that's not a good leaving group those aren't good leaving groups so what do we do well what we find out is we have instead of a substitution reaction the nucleophile can still attack here but we can't substitute because there's nothing to substitute so in that case we have a nucleophilic addition reaction so when you see alahh and ketones you think about nucleophilic addition reactions so here we go here is a oh this is an R Group here and an R Group here this one is an alky this one is an A and let us oh just remind yourselves you've got your dipole there you've got your electrophilic carbon it's electronegative at that end because of the oxygen pulling the electron density let's introduce it to this nucleophile now this is a grard remember grard was an alkal halide where we shoved magnesium in between and by doing that you changed the carbon from a electrophile into a nucleophile so this is R minus so essentially what's going to happen is we're going to push those electrons to the base of the carbon here and then push his electrons up onto the oxygen so remember this is planer it's SP2 hybridized and your nucleophile now can attack push those electrons up and what do we well and that's your nucleophilic addition we've added to this compound so we've created this tetrahedral intermediate so the first thing you're going to do because you've been trained is you're going to say okay I'm going to look at the the three different groups here which of these is a good leaving group oh ch3 an alkal group that's not a good leaving group that's not a good leaving group and that's not a good leaving group so what do you do you're stuck aren't you you can't push your electrons down here because you have nowhere else to push electrons so what you need to do because you're stuck is you're going to work this up with acid okay so we're going to convert this o minus we're going to protonate it and this is now going to form o so it's an acidic workup H+ and solution aquous acid and I like to write aquous acid as h3o+ because I like Curly arrows you could also write it as h plus by itself so let's use that lone pair or that negative charge to attack that proton and we're deprotonated we're going to break this Bond and push the electrons onto the oxygen here and that means we're forming the bond between this oxygen and this this hydrogen here this proton and we're going to be oh look at that now we have o oh we've made a one to a tertiary um alcohol how about that and we've spat out water so and we've regenerated well we have an sp3 tetrahedral um compound so let's think about nucleophile so we've shown you some examples we have a hydride we have a grard which is essentially this alkal anion um hydroxide GNA is a nucleophile and here is another way of getting an alkal anine is through an alkal lithium so these nucleophiles if you imagine if each one of them attacks here r h o r minor okay if they attack they're going to be poor leaving groups so let's look here here we have an aril Ketone again and we have our nucleophile and in this case again is a grenard and the second stage is the um the acid workup oh I don't know why I was come on oh what's happened there oh I have no idea um well this could be the end of the lecture I'm sorry I'm just a bit discombobulated and I have no idea why I've I've I've um h hang on there is there is I don't want to have to re-record this entire lecture oh my goodness that would be horrible um for me and for you um so I'm just I'm just a bit perplexed I don't AR we at the end AR we at the end maybe maybe maybe well that seems like a bit antic antic doesn't it okay for some reason I've just drawn oh maybe to make it look a bit simpler than all of this I'm just showing you it's two steps okay so you've got your nucleophile adding nucleophilic condition and the second stage is a is is a workup so whenever you get to this Stage Stop do you have a good leaving group if not you acidify it oh that's what I was trying to say and you always think about this when you have an alahh or a ketone ha so I just want to end with the fact that we have gone in topic one gone through Alka halides topic two we've looked did alcohols and ethers topic three we've done aromatic compounds in chemistry and topic four we today we've G gone through carbonal compounds so I just wanted to make a little request here maybe maybe you might feel like helping me maybe not um just to give you some background I've been very fortunate I got the University of Glasgow teaching Excellence award this is overall Glasgow University um in 2020 um I was nominated and shortlisted for the best use of tech technology and teaching in the University uh also uh shortlisted for the best teacher in the College of science and engineering and also for the best advisor of studies in um science and engineering um twice in a row um but I would absolutely love to win an SRC award this year so when that comes around if you would think about me and you know if you want to be ause to feel like it um and if you want to share that with me that's great too because these Awards go to um your comments go to the SRC but they don't actually tell us what you said so if you feel like sharing some love that would be fantastic um I would absolutely be delighted to win an SRC award um if you feel it's appropriate so thank you very much it's an absolute treat to get to know you this year and I'm wishing you all the very very best and oh by the way I'll see you next if you're doing organic chemistry I'm teaching aromatic chemistry and I used to teach the carbonal chemistry but somebody else is now um so I'll look forward to seeing you next year