Lecture 2: Alkenes Structure and Stability

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Lecture 2: Alkenes Structure and Stability
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UCI Chem 51B: Organic Chemistry (Winter 2015) Instructor: Susan King, Ph.D. This is the second quarter of the organic chemistry series. Topics covered include: Fundamental concepts relating to carbon compounds with emphasis on structural theory and the nature of chemical bonding, stereochemistry, reaction mechanisms, and spectroscopic, physical, and chemical properties of the principal classes of carbon compounds. Index of Topics: 00:47 - Relative Stabilities of Alkenes 11:07 - The Mechanisms of Elimination 20:10 - The Effect of the Base 21:02 - Solvent Effects 24:24 - Leaving Group Effects 25:19 - Structure of the Substrate 33:35 - Regioselectivity of the E2 Reaction: The Zaitsev Rule
Alkene Biosynthesis Computer animation Recreational drug use Chemical property Functional group Plastic Chemical compound By-product Ausgangsgestein Gene Chemical reaction
Chemical element Hydrogen Computer animation Addition reaction Battery (electricity) Formaldehyde Covalent bond Chemical reaction
Metal Sense District Hydrogen Computer animation Ageing Substitutionsreaktion Covalent bond Katalase Sea level Wursthülle
Systemic therapy Slighting Computer animation Tiermodell Etomidate Substitutionsreaktion Eliminierungsreaktion <beta-> Elektronentransfer
Übergangszustand Ionenbindung Forkhead-Gen Activation energy Species Eliminierungsreaktion <beta-> Organische Verbindungen Wursthülle Ethanol Halogenation Essenz <Lebensmittel> Ausgangsgestein Transformation <Genetik> Conjugated system Oxide Periodate Oceanic basin Bromide Octane rating Concentrate Alkylation Hydrogen bond Walking Carbon (fiber) Chemical reaction CHARGE syndrome Electronic cigarette Hydrogen Klinische Chemie Computer animation Covalent bond By-product Acetone Base (chemistry) Cobaltoxide Isotopenmarkierung
Übergangszustand Ionenbindung Activation energy Haloalkane Eliminierungsreaktion <beta-> Chloride Wursthülle Methylgruppe Origin of replication Molecule Solvent Shear strength Sequence alignment Essenz <Lebensmittel> Area Bromide Octane rating Alkylation Hydrogen bond Carbon (fiber) Chemical reaction River source Buffer solution Hydroxide Electronic cigarette Wine tasting descriptors Lone pair Hydrogen Song of Songs Gesundheitsstörung Computer animation Tiermodell Covalent bond Acetone Turbulence Substrat <Chemie> Base (chemistry) Stuffing
Sense District Separation process Ionenbindung Activation energy Left-wing politics Recreational drug use Substitutionsreaktion Eliminierungsreaktion <beta-> Chemical plant Ocean current Wursthülle Aromaticity Methylgruppe Alkene Ethanol Lead Halogenation Lactitol Cell (biology) Common land Active site Benzene Storage tank Sea level Conjugated system Beer Metal Bromide Drainage divide Hydrogen bond Carbon (fiber) Chemical reaction Herzfrequenzvariabilität Electronic cigarette Wine tasting descriptors Hydrogen Computer animation Tiermodell Bicarbonate Attitude (psychology) Covalent bond Chemical compound Priel Cobaltoxide Base (chemistry) Satellite DNA
so let's keep going through talking about 1 of the it's an properties instability and so the reason our kids are really important functional group because the carbon-carbon double bonds easily converted into many other compounds as you will see when we get to Chapter 10 you'll be shocked at the number of reactions that we can do without being so being able to make our genes from Apple Hill is a really important skill so by the time they get to check pretended to be making our opinions In 1 of mostly to different ways and then doing reactions on our so are we going to get to that point 1st fell on so we can synthesize drugs pesticides and valuable chemicals but the byproduct largest thing we use of his supporters making policy paper so millions of parents are used to make policy so all the plastics
you have everywhere that's all formalities
polarizing Our itself but in this chapter is going to be really important that we know relative stability is about things because we're going to be making our and we want to be able to protect sometimes we can make more than 1 of the Montebello predict the best 1 the 1 that's going to be a major product and so we need to know a little bit about stability there's only we can figure out stability is to use elements of the needs of
hydrogenation and what we do is we taken out emptiness this is our reaction on a talk about Chapter 12 you don't need to know this reaction right now but what we do is we take the happiness that we and the elements of hydrogen across the double bonds of the double bond goes away so this is an addition reaction play under the double 1 goes away and we can measure the knowledge he has given up because the product is lower energy than the started hero so it is with this measure and this will instead OK is the batteries get back to you OK so we just add the elements of hydrogen across the double bond right here on the double goes away so we have decided that we measure the hydrogenation stands doing years were just
doing that during that exact thing for measuring the needs of hydrogenation for each of these outlines and all these outings and always Albany going to the same product so it turns out that if you do that experiment with this don't Will you age not equals minus 30 . 3 k accounts for more if we do the same thing with the 2nd Elkins a notice some the 1st docking we had an apple attached to the arcane we have 3 hydrogen only have 2 metals attached that 2 hydrogen and measure that we get Delta each nods equals minus 27 . 6 he acknowledged from all and then under certain when hearing adult age nods equals minus 20 8 K accounts for 28 . 6 actually key Kallstrom and if you'll notice something here all these going the same product so the is anything if we can actually compared the heats of hydrogenation see which 1 is more stable because we can't we have the same product for all of these so we have this 1 here we have this 1 year we have this 1 it's all the same and so on what we can do it again unseeded relative stability so this can be shown graphically investment values is waited all boys get get the hang of this year the rights so the first one gives all
minus 30 OK so that's number 1 will call this my number 1 will call this 1 number 2 will call this number 3 here's the energy of the product and it's the same for all of us saying product so far exceed this 1 here number 1 gives off the minus 30 . 3 following go should like this and get sense of 30 believable why is 30 . 3 and then the 2nd 1 only gives minus 27 . 6 0 with the SEC only gives off my needs 27 . 6 innings and had to start off at a lower energy level like that so it they're all belong to the same thing so this is number 2 I think I'm pressing the button accidentally so number 2 cats minus 27 . 6 k Kallstrom In an anniversary that gives operates 28 . 6 0 that's actually means that must have started off a little higher and higher than number 2 but lowered the number 1 so this is number 3 and so that off from minus 28 . 6 this article I can't put it at the same level as 1 kind now the case will that will go with that of a scenario means is that I'm number 2 is the most stable of all 3 of number 1 is the least stable and it turns out that the stability of knocking increases with the number about the groups the this substitute on the columns of the double bonds so if we move this up a little here we can see that for the
1st 1 we haven't won our group of bonded to the Al-Qaeda right here the 2nd 1 we have to our group responded to the AL team that's going to make them more stable this is trained to recognize transparent says that what we can see is that these guys are both more stable than the 1 that strands is more stable than and that recent attacks experiments that we can do on to figure out what we have going on here that we don't want to these different experiments and we could end up getting something that looks like a but we see on the next page the writers of the Rockies we've got more that in
which groups a chance to each other more stable than the corresponding says something and noticed that I had all these flights made on a on a Mac endowment and putting them on a PC it's sometimes scrolling them a little differently and the only reason the only way to fix that estimated in a PD up that doesn't have this feature where you can write hazardous waste so if you see something a little scholarly little bit differently it's not a problem but are a do this of a series of knocking them so you can see that we have a lot of times substituting is going to be the hiatus energy the rights movement substituted here no groups invited to the Albertine here we have 1 of our group onto the all-consuming :colon models substituted for the 1 group and then we have the to groups bonded to the since we know says we know France there's transpired here on this 1 here is called him the 2 are groups around the same problem on those are approximately equal to system GM there is a slight difference instability there were not going to worry about a recall those 2 equal so sisters about equal to the general that we have the transfer and we have to try substituted and we have touch substitute and so as you can see the more are groups we have bonded to the all keen to more stable than it's so so bad let's write that down more substitution equals more peoples are more stability and by substitution were looking for the number of our groups similar substitution would be more art groups where are groups bonded To the outline there so that and 2 years and then on these all 3 of these are diced substituted it will notice that fraud I substituted Trans it's more stable then sales for GM so it just right Jansher pesos transfer stable consists of question on those trends anyway yes they also do the once their lowest energy are more stable yes absolute that's absolutely right yet we're not going to go into the details of that dumb you could talk to me after class about that became more questions about alright let's look at the mechanism of eliminations amid elimination actually already were introduced to it there are 2 types of
elimination mechanism C 1 which competes with arson 1 entity to which competes with Massengill so we're going to have to keep track of these awarded the other half will have to make decisions about what the product is so in a start like I did with Chapter 7 I started with the eats you I'm really do the same thing here and started with a view to an organ move on to the E 1 so let's go on to the next stage again it's putting this on the top the bottom of that page mergers can ignore that
hopefully that is not it's studies for anybody here I can
try to fix that I'm going to try to fix that because I think it has to do with the sponsors like this that's not the font you see when I use a larger fonts of schooling differently so I may have to fix that are so on the 2nd elimination the 42 is the dominant reaction of tertiary organized in the presence of a strong base and competes with the essence you reaction for secondary and primary health care realize that 100 Let's go into more detail here simply to figure out what's going on here so following the 1st things we did all we talked about it send to reaction is a measure of the rate loss and how we do that as we change the concentration of the alkyl here like to see what effect it has on the right there were change that the concentration of the nuclear file was solid effect it had on the right and if those changes affect the rate and that means that both of those species appear in the rate determined steps so we do the same thing here and also I notice here and I have days written but that's really the same species the in the in the 2 it's acting as a need to it's acting as a along the way to do that OK and that he too is acting as a babies In the US into its acting as a nuclear power but it's still the same species so the most common 1 for example would be a fox In the US into its acting as a nuclear power in the 2 it's acting as a base as someone that means is that both of the outlook a light at the end of the nuclear file have or nuclear file /slash face have to collide in the rate determined steps so that means that the outfield parents the /slash nuclear file must collide in rate determined steps so I do RDS related training staff that's the rate determined that determines that that's a step determines the rate for a reaction all right so here's a mechanism and that so we know that in this case are our hobbies such new good followers of side we know that it has acquired with the help of human predetermined steps in and so that's what we have going on here right so inner mechanism here I'm going to put my mole appears on all my reacting species so I'm pretty happy with that name this depends on his good will hear somebody working on getting it down a little better but when I have a because wherever the canyons and puts a doctor c mon and also ordered this figured out but the oxygen 3 sensible pairs right on redistricting my mechanisms I definitely I'm asked I actually on mechanisms in my closet helps you learn the material and I'm pretty strict about some points on a test so any many species that are reacting In a mechanism and maybe I just have to slow down but that's a good thing for that's good that's a good thing for you alright so I want long periods on the arm oxygen and I want appears on the bromide consoles are both going to be involved in the raid determined step so there's going to come from a long here it's going to grab this data hydrogen we're going to break this carbon hydrogen bond it's going to move over here between these 2 comments to make on the double bond and reintegrate the carbon bromine bond so noticed the error in staring at that moment here so you guys are not going to have to call me on this you know what it's supposed to look like but was wiser during the annual OK but that that's got 6 pairs it's grabbing the hydrogen were breaking the carbon hydrogen bonding the leading group was leading them so that leaves us with H 2 doubly bonded stupid chasing carbon and we have a CH 3 and we have a CH 3 here we also have a conjugate base because of oxide is acting as a base in this reaction so we're going to have ethanol please our side project now we have relied on it now you'll find a way to introduce a new reaction and I draw the side product and that's the last time tendency to outside products if I'm asking for the product of this reaction on a test I just want the European product I know that this is a organic that's the ethanol's organic puts aside product we're looking at what the major transformation here is with the outflow feline questions on that mechanism anybody we have questions already the 2nd mechanism evolving it's a removal of the of Proton by Basin loss of the hairline is called in the 2 mechanism so as we talked about last time let's label what we're talking about here let's go blue here that carbonates bonded to the leading group is out and the carbon it's right next door is data and so this is a debate hydrogen we shall all that means is it's bonded to debate a carpenter and that's what we're eliminating an immunity to reaction Iran's civilian to die earlier this season Jaguars will look a lot like Anderson to energy diagram so we start up the Obdulia light in our base /slash nuclear file we have energy of activation for really any Stephanie interaction and we end up getting are keen on this oxide and rely on and so this right here is the overall Delta H Mart reaction that the energy difference between the reactants the products and somewhat strongly a strong transition state this is not an easy transition state to draw but was doing anyway the case that have oxide coming in clinic ,comma rather the hydrogen so the bonded the hydrogen and carbon is breaking by the way I usually don't have the draw scientists we have a single von between this carbon and Vijay Singh ,comma there were actually can be making a double bond so this is dotted to so this is a little bit of a beast that some transition state and now I have to use the eraser here we go because I step there breaking respond here to the meeting are you glad don't put does want it's a lot going on here I draw this because I want to see what this looks like his word and you're looking at this reaction and will look at animations next time for all these reactions so this is our transition state but we have some charges so in our transition state so do that we looked down here we have had a negative charge on oxygen right here in no negative charge on oxygen here in the product we also have neutral bromine and we have negative bromine over here so let's go ahead and add this going ahead and partial negative charge on the bromine impartially discharge on the oxygen so there's a lot going on in this reaction is a one-step reaction so all this is happening in a concerted fashion the bonds are being made and broken other jurists time all right so just like I did with the other as interior actually talk about the
effect of the base /slash nuclear file and I talk about the effect of the alkyl him lied and I talk about anything else that has to do with that once we know all that stuff that we can make predictions about what's going to happen operates on the basis of /slash appears in the rate equations of the rate of 82 reaction increases as the strength of the base increases than experts said the stronger the babies the faster the reaction we're going to have feature reactions are generally run was strongly negative charge basis like hydroxide and or minor source Fox too strong and the hindered bases called and indeed you also sometimes used these this is TV end this is deviousness other bases that you will see that in the 2 reactions solid effects are the same as the instant you Polaroid songs increase the rate of the 2 reactions the widest product solvents increase rate the 2 reactions they don't solid and very well OK they don't Holly in it's very well there there for the base it is not well 1 way to say this is shackled right is if you have you know it's going to have this very strongly solvated it's going to have trouble getting in there to remove that a hydrogen so order to remove debris hydrogen has to move the solvent that's in between it and hydrogen and and it's easy to do applaud products although not as easy to do In a polar and predicts officers not shackled arms With solvent and is more free to react and by the way on the DPU when the DB and I don't use also very often but those are used when he was just an elimination to happen anonymous substitution because the 2 are going to be in competition with each other and so these are unhindered basis the essence here was in competition with the 2 and if you if you have a very winter days was seconded to the US and the reaction Rivera members are from Chapter 7 yes and you reaction if you look at the transition so we have 5 groups around carbonates and varied handed the transition state so anything that candidates this slow that reaction down so the alkyl halide has hinted that was slow down if the bases hinted that will also slow it down so I want favor just elimination we want a user base that's hindered so that's 1 of the things will be talking more about coming up surfing hindered based on has into what happened will be slow or will happen question so far they write forensic believing that protects there's not a whole lot to say we need a good living this reaction as you can see the base comes in removes the big hydrogen at the same time that Leading Group 1 starts to leave so we need to have a good living proof just like as 1 just like us into that's going to be the easiest part of this chapter we needed may be OK and so on the originality wide-eyed the fastest 2 because I dies at best leaving her he has the best leading Group the rights remember how we look at leaving her ability we won a very very big case I died is a much weaker based chloride so it's going to be a better living as simple as that area was littered the structure of the
substrates USA struck substrate I'm talking about the outlook on life so the outflow he alive you need to react in different group's affect the rate of reaction rate poking the uphill wives have an increased rate of reaction so this is not the same trend assessment used a lesson to you we want police police hinders right I'm in need to we want the most hindered the most tenders is going to be faster than it's been slow down the rate of innocent to so for hasn't she reaction fastest as followed by primary followed by secondary and tertiary there's no reaction for each year reaction churches but the fastest and if you think about it if you think about a church funeral turbulent bromide case so have a carbon with 3 medals in a bromide there's no way they're going to get any message reaction buffer based to come in and remove 1 of those hydrogen is at some outside periphery of the molecule that's really easy to do OK so we haven't got the opposite trend here and that's important for you to remember that so on tertiary no reaction within a and it's going to be the fastest with need to so that's going to make decisions about tertiary occupy a light under the 2 conditions and that and make that easier to decide so that the problems are going to be encountered in the secondary Apple Hill is also the ones that are going to be problematic in the transition state the double bonds partially also increasing the stability of the double bonds without situation stabilizes the transition state that we are more stable transition states that means we're going to have a lower energy of activation more stable transition state Cellucci asked for transition state the close of lower energy of activation well here lower energy of activation work I write so that means that we're making we just learned about stability about before making no change on that and only has 1 our group honored to have been cited as good as if we have making Elkington has 4 groups bonds the outfit we want to make this the the most stable keen most tables and have the most number of orders so we compare these 2 reactions here here we have a bromide ions this is a primary occupation like down here we have a tertiary out of life so why is the primary slower I'm well were starting to form a double bond the rate determined step that if we do elimination from a primary I'll kill the alignments do that by that time the scene on gaining get here so I'm going to be removing the fate of hydrogen hydrogen on the carbon adjacent to the carbon responded to the leading group I'm gonna break this carbon of hydrogen bond I'm moving down here and I would have a bromide ion leaves since it's involved in area pushing I'm going to put the lone pairs on the bromide ion so that reminds them so looks like that and it looks like it's consistently getting rid of 1 of my mom appears here so I hope that's not a problem must straight out again if I don't move will stay there and can I write so that since it would seem that the product as we have ch great CH there's also a hydrogen here we have a hydrogen here and hydrogen so the 1st learning curve in this chapter is being able to destroy all the elimination of part that's not so straightforward it's a lot more difficult to do than substitution I'm so that we do the same thing with the true Sharia appeal lied now going here grabbing hydrogen breaking the hydrogen and carbon bond moving it to midway between these 2 ,comma so they can double bonds In World War it's going away but if we do that in the current right responded to 2 methyl groups the carpet on the left responded to 2 hydrogen all right so we have a model substituted persons die substituted services moral substituted announces abbreviate that model substituted and therefore less stable the
transition stating where the into the model substituted product and all spend less stable so and is all it is is is also the less stable so be higher energy higher energy of activation are dies substituted so we're looking for are groups bonded directly to the carbon of the carbon-carbon double bonds and that's going to be more stable In the 1st a faster reactions all right questions anybody left How do get the product for this 1 here yeah it's it's very Gallagher said that's the biggest learning is at the very beginning of this chapter being able to draw the product so here's this common in this part let me know and I'll watch with the enormity of but we have this problem here let's call this program and Warren carbon too right over here this is probably 1 in this Parliament you so let's follow what's happening here and this may be good enough for me to effect so we have ,comma on ,comma to his car into an to hydrogen and as 3rd hydrogen Iowa eliminating hydrogen so every year it's got to hydrogen but breaking the sponsor moving it over here and then this group is and so this career responded to to mount so there's the 2 levels here but right Our rights you certainly can all variables method would serve privileged so yes it could eliminate a hydrogen from any 1 of those novel yes definitely are thinking radio selectively the meeting the 2 reaction and this is lasers to divide several you'll see on different kinds of Spelling's presides this is the 1 that makes more sense to me but there's there's many different ways spelled like Italy's 3 that I've seen to discovers so there's no way I'm going to spell but went 2 or more elimination character possible in each reaction the most stable out Keane will predominate so now and see what we have to know something about stability here so the most stable locking is going to predominate are so let's look at this reaction right here we have actually we have a fact site were solvent of ethanol 70 degrees and I want to drive attitude fossil products and then I'm going to show you how we get the products again learning curve number 1 is just being able to draw the products here and then some students so if you're having this problem some students have trouble seeing what we mean by substituted model substituted so that's very common so that's probably the learning curve number 1 what his friend Apple right here so I use the T abbreviation for Apple ,comma Maine so why should those Elkins is more stable yet the 1st ones try substituting OK so one's going to be found 69 per cent consumes only 31 per cent 69 per cent more stable and that's because it's try substituting we had 2 or 3 hours responded and this 1 is less stable so die substitute so on a test I will be very clear whether I want all the products are among the most the predominant product if I say I want the predominant product in you would only join the first one here by satellite all products and you do all the possible bomb OK there's 1 OK so let's see how we get these 2 different ones here so we have ,comma now what it's doing is it's scrolling take away some MySpace here which we don't like so maybe I can write off the margin I think I can write off margin here appeared several first one year astronomers OK so another thought communion grabbing a beer hydrogen breaking the carbon hydrogen bond moving over to the did to the carbon despondency in the leading group and they were going to have the current common bromine Bonebrake so we're going to have the leading the way that's how you get this 1 right here so you don't want to put this in the
2nd 1 on the bottom of the page I think we're going to have to do is come back and take away all these these cells different fonts like this are taking a more space OK for the 2nd part so we have that we have the CH 3 right here what we have a bromide with its long pairs so there is going to come from a lone-parent oxygen with grabbed the hydrogen were going to break the hydrogen carbon bond moving over here to make a new double plant and then the leading the going lead Is that will give you this product questions that How do I get the percentage this right here don't mistake right here Our hydrogen should be gone so widespread and generational it's a scribbled that out OK that should not be there impact he made to answer questions that we get the 16 episodes 31 % we monitoring experiments will again that's not I mean I wouldn't ask you to come up with numbers if I might ask what's the major but I would ask you to come up with more questions anybody OK some important points and here's where it gets tricky the most stable Keane is usually the most substitute usually but not always most earmarking is usually 1 of the most substituted but aren't always so let's look at some examples here karadzic Look at this guy from current 1 the leading the result and the common it's right stores baby have 2 different problems next door so that was 1 good thing about covering spectroscopy early now we're able to recognize have different hydrogen so to hundreds of different so we have to possible products here weekend enough because we have 2 different data hydrogen so that's a bit of hydrogen here and there's a different being hydrogen right here and so on if we drop products from both of those I'm a dropout from eliminating the ban hydrogen on the left and the drug product eliminated from get back from eliminating the margin on the right OK so that's the product from the limiting debate hydrogen on the left In the end we also have departed from eliminating the bay hydrogen on the right which follows a similar substituted the the first one the 2nd 1 it may be easier for you to say I had stopped during the swearing-in may be here for you to see if I put the hydrogen and how many are appointed to this compound here we got metal methyl hydrogen they said the this 1 has to come out can't responded to the offer came OK so this 1 here is the least substituted so it's started substituted and this 1 is the most substituted it turns out that this was actually the 1 of the major product wondrously substituted can anybody think of a reason why that 1st product would be a major part yes yeah that's so he stadium said the benzene ring is contributing stability to the double bonds but if you had my class last quarter and we talked about the fact that this double bond here's conjugated With these double bonds in their so if you did not my class quarter Bhattarai conjugation just means we have alternating double bonds to double bond here single bond double 1 single 1 doubled 1 single 1 double those double bonds are all conjugated wanted to double bonds have a single bond between the conjugated and what that means is that we can actually draw raisins structures that makes the compound were stable so this 1 is the major this is so silly substituted by of the conjugated with aromatic ring me substituted for but conjugated with friend when things are conjugated there more stable so they're much more stable I'm not going to do it you really can't imagine that we can actually go there we can move this double bonds around here we can go and resident structures because of the location that double bond it's pretty powerful effect that's a pretty powerful effect that charge chased stay away from those once when they start to get really close I try to stay away from those on findings and picked up at the top it's usually the most substitute in this case it's not yeah so usually the most substituted but Mark they and we have a 2nd case here and if somebody anybody who has my life how we did experiment in the 1st week then you haven't done it yet there is something of today but I believe but in some elimination is a less stable option is major product we did it in my last 2 of his 1st Creek you guys have been anybody mass 51 doing it later in the quarter there so it turns out that we have hinted that they Bayside stumbling advised him to release any endured I'll kill him so this is a tertiary alive this is a tertiary the ball sparing injured and tertiary days also what happens in that situation is that the the base is going to remove the most accessible hydrogen that's not the most accessible hydrogen is only got 2 choices here we have big hydrogen right here the hydrogen right here there we had been hydrogen right here In here these guys are all the same it's much easier because this basis on as much easier for a tour eliminate 1 of those outside items rather than this it's time once installed a major participant actually least substituted but we're out of time so I will draw those we