Lecture 4: Unimolecular Elimination

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Lecture 4: Unimolecular Elimination
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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: 00:11 - The Stereochemistry of the E2 Reaction 08:23 - Competition between Sn2 vs E2 28:43 - Rate Law and Mechanism of the E1 Reaction
Übergangszustand Forkhead-Gen Transport Eliminierungsreaktion <beta-> Chemistry Electron Sequence alignment Colourant Common land Active site Elektronentransfer Chemical reactor Seafloor spreading Carbon (fiber) Chemical reaction Kupplungsreaktion Systemic therapy Hydrogen Song of Songs Computer animation Tiermodell Functional group Ion channel Home remedy Aage Base (chemistry) ISO-Komplex-Heilweise Thermoforming Isotopenmarkierung
Waterfall Species Carbon (fiber) Ocean current Chemical reaction Molecule Hydrogen Acid Computer animation Metabolic pathway Shear strength Functional group Essenz <Lebensmittel> Base (chemistry) Conjugated system
Area Alkylation Alchemy Eliminierungsreaktion <beta-> Carbon (fiber) Steric effects Hydrogen Computer animation Functional group Human body temperature Chemical structure Substrat <Chemie> Base (chemistry)
Stop codon Ethylene Sense District Ionenbindung Nitrogen fixation Eliminierungsreaktion <beta-> Solvent Human body temperature Storage tank Conjugated system Periodate Oxide Pilot experiment Öl Death by burning Octane rating Inorganic chemistry DNS-Synthese Chemical reaction Alcohol Water Hydrogen Sodium Acid Computer animation Functional group Dimethylformamid Yield (engineering) Acetone Substrat <Chemie> Base (chemistry) Soap Extract
Species Activity (UML) Octane rating Haloalkane Walking Eliminierungsreaktion <beta-> Operon Chloride Chemical reaction Hydrogen Computer animation Ageing Halogenation Human body temperature Essenz <Lebensmittel> Controller (control theory) Cryogenics Base (chemistry) Mixture Stuffing
OK arts and here's where we left off last time when we were talking about the nature of products from this particular I'm out of here alive and we saw that we got 44 per cent of the train so let's label that only 41 per cent of that something could someone adjusted over there trends you know is you could talk about the overhead projector being old technology but it's such a lot more dependable than the spread argues that France was 1 is says and this 1 here is substituted all right so much show how we get to do what we can easily see how we can get the least substituted by eliminating right here in in this car ,comma father pointing all right let's see how we can assist in the transition so here is and I just put this in this orientation put it into a new projections so you can see where that comes from the consulates fall down a little bit of here so was volunteers are leaving here's our hobby freedom hydrogen so leaving In himself a place and so that's on the back cover of in the way I haven't thought and we eliminates the leading group and that they the hydrogen they get this 1 is going to be the those things like that and now but if we rotate knows we have never stupid hydrogen is here we have this 1 here only have this 1 here and so everywhere take down we change the color that images wrote to the city .period drawing on the top suggesting a remedy this hydrogen right here that's going to rotate down so it's and tied to the living room and that's what we want so now that hydrogen is right here and heroes oral leaving groups staying the same and it's just going the company will the pace of his are Inga never played a hydrogen and everyone in various conceded that nite conceded the Ethel and therefore not to be on the same style so we have a common problem volunteer the 2 hydrogen around the same size over this really have and in the side we have them so that's how we got system the trailers and we want to have the Balkans groups on opposite sides of this one's going to be more stable both the screws on the opposite side so that's something to be the most stable can therefore it's going to be a major product and so we definitely see that that is the major product appear questions arose about that problem anybody in public that yes show the errors for elimination is confident on ornament projections the least substituted a move yes let's do that right here since there is no way of stereo chemical issues are known different ways to drop the unconventional system transplants and ended will just not I'm not going put into Newman's projections soldiers try right here In a way I usually drawn is 1 of modern minimum projection as I definitely put the hydrogen on the opposite side of the weaving through the entire carry playing so our base is a fox scientists understand appreciate that each the alignment investors coming around the Bay hydrogen the opening of electrons here to between those 2 carbons reading groups can only a song giving its like Paris and that's what like effect so that all 3 products so if the reacted only has 1 hydrogen bonded to the beta carbon there's only 1 couple were restricted to be eliminated inside the particular isolated form depends on the configuration of the reactor so that we don't automatically to all the transfers you might not be able to get the train is that if you showing stare chemistry in the reactor in mildly will again into an orientation to give the transport so this is a good example right here Of this 1 only has 1 hydrogen other only on the substituted that's going to give them most substituted outlining OK so this is our fate hydrogen here so you eliminate a financial model lease at the low substituted carbon that would give you the most substituted talking so we certainly can eliminate 1 of this 1 of these data packages but that's not going to give us the most substituted out he announces trying to draw the sites have Ericsson we only have 1 and so when the base comes in Fox signed treatment that had a hydrogen so here's some more Arab wishing me a lot of practice with this particular mechanism because it's just a strange reaction looking reactions to can there is only 1 product that we can get so we can say that we can't really even get any of the product whereas the channel and the hydrogen trees to each other that's the only party that we can get all
right and so that was users to buy competition between Athens University each year Our exit or don't talk about all the aspects of the tsunami that talk about competition between the essence you need to because as into interactions are competition with each other in the Arab leaders favor 1 or the other let's show bolstered the reactions here so this is the ability of the finals /slash just put based here it's the same species most of the examples we don't use the cited sustained things we just calling it something different but cultures can be used interchangeably so I'm Nunavut base last week the file we call them have already passed here call that a weird it was in a removes the beta hydrogen we break the carbon hydrogen bomb to making final between carbon and there are leading group so it is with 2 pathways right here and I'm product is they so this right the conjugate base and we have our leaving the events excellence right alternatively I will call this 1 pathway beating down here the negative on backside attack so that would be coming in from the back side here and check the carbon break in current acts volunteers should look like that those are related to things that were comparing yes conjugated acid U.S. News thank you thank you for catching the far-right so In actually
contracted it's much easier for the new goes to reach this hydrogen here this on the periphery of the molecule much much easier it is for it to do backside status Thursday when we have a very candid carbon bonded to the living room OK so that's really going to be the whole entire thing it's all about security interests in the office of him I it's also about strength of that of the base last found the more basic nuclear fall get more more favorite you'll be over a century all right so what determines which is going to be the major major pathways he is the structure of
the alchemy like the structure of the base and temperature so as not to know where temperature favors elimination definitely temperature favors elimination so this is the structure of a /slash nucleophile here so let's 1st look at the structure of the alkyl here I need read Pariseau Ekinci 1st substrate we haven't really nice primary on June the lines errands out so it's going to be really easy for the new good father came in an attack not very much steric hindrance the carbonates bonded to the meeting because 2 hydrogen 1 on protests was primarily the Sydney variously for the new cathartic turning it into backside attack kick off the leading group which finale groups are all Halliburton's but when we get to Chapter 9 and see that they don't always have to be held agents operating area all right so so what we see here is that the attack on the current unhindered we so
therefore into this thing her In the 2nd example we have a little bit different issue here we
have a very printed out till he lied it's tertiary there will be and we talked about the fact last quarter that we don't even get and other out here like but we do get you to tertiary out of life so this is waits 204 1st substitution but it is actually going because of that whole idea is going to favor allowances will we have stopped doing here that this has been a favor the base in acting as a base so the base slashed nucleophile is going to act as a base instead every move their hydrogen so we got 9 different data hydrogen is to remove we can review any 1 of those lines by men take the 1 that is in a tight period playing all these bonds can rotate so early in these hydrogen scandal moved out to pick the ones yet I can claim the naked mutable volunteer and leaving groups believe so what you see is that attack occurring as what so that the 2 workers so it's it's really easy to make a decision will have a primary researcher Sheri substrate is not easy to make a decision on the a secondary has now because the rates of those 2 reactions are going to be much closer together so let's look at some examples that that tends to be a good way to see what's going to happen so it's a real examples of that and run with primary secondary and tertiary out of life in the world are doing is reducing topside bionic arm so that's a good thing but pilots also good base in the temperature is 55 for all this so it's a little bit elevated temperature elevated temperature favors the 2 but was just see what we owe our actual outcome so for a primary out of here alive here we Attleboro line you don't get Mosley as in tune with the topside so let's see what members began here so our criteria for the instant she needed began to take a little and will practice to be able to draw these products quickly lose easily it's an S to and we get 90 per cent the 2 reactions His ethylene as a product and that's 10 per cent so when I'm asking for the major product which is what I do most often I wanna see only the has sent product for a primary on of him I that's what happens with the secondary store the products and oldest ,comma summarized here this is our 21 per cent not very good at home 21 per cent per cent you it should yes let's fix that every can sleep that class despite only has 1 of 2 when the possibility to product and that 79 per cent alright so Sosa secondary occupation Lawrence was favored with the side so oxide is a good good about it's also fairly strong Have we know it's a fairly strong based on what we we do is we look at the Peking the conjugate OK so let's look at the PGA of conjugate at stake is pleasant little houses here Ferdinand calling about that he gave the conjugate acid in that's 1 of the ones I want you to know rounded to the nearest 15 it's an alcohol since about 15 the crisis of we want we want things that are very strong bases things about above key 8 issue for the for the college classes the Nine Inch and that's well above that so that's a fairly strong pace in so with the secondary on alive In a stop sign a loyalty to his favorite soap I'm asking for the major hurricane with only trolley elimination questions so far in vain yes over the top I'm I would provide any details that are not the 811 and on numerous occasions yes it's still would be under Major would be get absolutely as a question a resident beaches out of alliance Welch's American Americanized still do to right so no I sent to for a tertiary Here lies therefore the 2 only Her Excellency currently only have 1 possible problems with this particular asking with this particular I'll kill him right 100 per cent at the outset excellent happens if we changed to upon the outcome of all the days so when take a primary article him I usable strong pace so how about Turkey topside that rather than and and I and I would recommend that you keep going back to this page because this is actually these things come back this is the page I often refer to the students asking questions OK so we haven't had a
primary outcome realize we have of their thoughts on oil and so little time that was hindered the the thought side that we have to be talks and we actually get so this when we get 96 per cent S 2 and 1 per cent each year I don't temperature on this 1 it's probably a lower temperature makes sense probably along temperature this particular of experiment I don't have temperature or you'll also notice that the numbers are not adding up to 100 we got 96 per cent 1 per cent so when that happens it means these are isolated deals rather than I From what I wanna say ideally yields but the 2 isolated fields when they don't add up to 100 per cent but then in a 2nd example do the same number of people interviewed talks and we get only 12 per cent N 2 In 85 per cent of the 2 so the message here is that you can actually determine which part of the EU wall by choosing the correct base give a primary out here like and anyone elimination undulated major-party better use of all the pace he don't want elimination on Friday then you could get anyone is an unhindered on elimination of primary energy continues in normal and on and I mean if I said that if you want substitution you would just using you know you're not going to have to worry too much about elimination with the primary out of here alive question yes the on the alcohol was the solvents it's very common with some Fox Idaho Cox basis to have the alcohol as a solvent bank can you make those by taking an alcoholic itself of sodium to them became so that's the most common of solvent used that far more questions including yes but then OK occasionally good questions so I'm pleased U.S. faster and more exotic solvent quarry products although is often not the the most convenient and so on there is still some already solvents like you wanna give you some examples the 2 most common that we use in this class DMF Indiana itself those solvents are a little bit problematic because of have higher boiling points so you know once you isolate your products you can easily remove the solvent that's a problem of the 2nd problem is have you guys done extraction unit allowed the DNA in the catalog right in itself but also you know you have to and that's how you often isolate products inorganic chemistry is unity and also in the last day or 2 later it is it make every water will not promise of where the Senecal or difficult to isolate your product so that's why we don't use acetone in like seated as well as oxide ordering acetone why not just use acetone instead you know why why not and the reason is that the sodium of oxide doesn't dissolve in a hospital it's 0 so there's also the problems so fervently Hassan warned you would we have to use products although there for the S & T wheat With Our it's got a little bit left
so you over essence you used secondary evoking a license strongly basic and revoking England files increasing temperature also favors elimination over substitution so there's where we talk about the increasing temperatures To Samar essence you over the Tsuen were especially good up to worry about this was secondary out of the alliance we want low temperature so room temperature for example of weekly basic unhindered the files that's a tall order telling there's a lot of are also strong so what kind of files are really looking for I'm here some examples of things that files basis all of the halogen success Florida lots of it I don't following another 1 is and 3 minor chloride can also be obtained these are sort of like going to good files with bases so these guys are good news their files and we face so when you're doing secondary operability really going to have to choose from these fights because as you saw with the thoughts either in a major product is elimination on rights that means directly into the E 2 which will just start to the Americans spend very much time on opening the EU underwriters dangerous time on the 1 but we want them cover things I want to point out is that number 1 the rate was exactly the same as the S 1 instead of 1 the 1st step of the US and what is actually this is exactly the same as the 1 so the 1st step of and 1 we have leaving so what draws their signed in include were waiting for this to do whatever it it does OK so we have a leading through these 1st steps we make a copycat right so that should look very familiar to you so the leading the lease and that's why we only have the alkyl halide appearing the rate determined stuff that is the rate In the 2nd step of basics abstracts and the hydrogen so I'm going to redraw the species fear corporate Karin with just looks like that so relating bit hydrogen let's label that for you here's how how their status so we get age plus family there are alright so that's the same Kirkland scenes in the US
and 1 reaction that you want the as someone reactions are in competition with each other and generally you will get mixtures of products that we have very little control because the rate determining step is the same for both the other 2 steps for the S & verses that you want the loyalty of activation very competitive .period or about that next time