Nucleophile Aromatic Substitution to Aniline Rings

Video thumbnail (Frame 0) Video thumbnail (Frame 12828) Video thumbnail (Frame 25481) Video thumbnail (Frame 38134) Video thumbnail (Frame 50787) Video thumbnail (Frame 63439) Video thumbnail (Frame 64473) Video thumbnail (Frame 67440) Video thumbnail (Frame 70407)
Video in TIB AV-Portal: Nucleophile Aromatic Substitution to Aniline Rings

Formal Metadata

Title
Nucleophile Aromatic Substitution to Aniline Rings
Title of Series
Part Number
23
Number of Parts
27
Author
License
CC Attribution - ShareAlike 3.0 USA:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor and the work or content is shared also in adapted form only under the conditions of this license.
Identifiers
Publisher
Release Date
2015
Language
English

Content Metadata

Subject Area
Abstract
This is the third (and final) 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: 00:22 - Reaction of Primary Amines with Nitrous Acid 08:42 - Using Diazonium Salts in Synthesis 17:39 - Use of Nucleophilic Aromatic Substitution to Make Substituted Aniline Rings 26:35 - Mechanism: Addition Elimination 33:28 - Amines in Condensation Reactions: The Mannich Reaction 43:12 - Carbohydrates 44:26 - Monosaccharides
Phosphorus Meat Amine Hydrochloric acid Chlorine Chemistry Kaliumiodid Halogenation Benzene Sodium nitrite Beer Nitrosamine Substituent Dye Salpetrige Säure Alkylation Chemical reaction Cancer Wine tasting descriptors Acid Cyanidion Copper(II) chloride Benzodiazepine Amination Aromatic hydrocarbon Chemical compound Diazonium compound Phenols Isotopenmarkierung Copper(I) cyanide Copper Hydroxyl Wursthülle Aromaticity Diet food Chemische Synthese Smoking (cooking) Schweflige Säure Kernproteine Molecularity Stickstoffatom Bromide Aniline Cigarette Sodium nitrate Water Hydrogen Sodium Computer animation Functional group Radical (chemistry) Sodium thiosulfate Handelsdünger
Kohlenhydratchemie Halide Diazonium compound Amine Hydrochloric acid Chloride Atomic number Chlorine Chemistry Molecule Electron Halogenation Addition reaction Colourant Phenol Benzene Library (computing) Aryl halide Aluminium hydride Whitewater Walking Vinylverbindungen Chemical reaction River source Wine tasting descriptors Reducing agent Hypobromite Acid Cyanidion Zinc Chemical compound Amination Aage Diazonium compound Methanol Toluene Carboxylate Substitutionsreaktion Eliminierungsreaktion <beta-> Wursthülle Namensreaktion Aromaticity Methylgruppe Amalgam (chemistry) Fluoride Nitroverbindungen Mercury (element) Sodium hydroxide Chemische Synthese Cryogenics Kernproteine Lithium Mixture Process (computing) Palladium Hydrocarboxylierung Grading (tumors) Stickstoffatom Bromide Carbon (fiber) Aldehyde Carbonylverbindungen Flood Water Computer animation Functional group Base (chemistry)
Semiotics Übergangszustand Resonance (chemistry) Amine Chloride Hydrochloric acid Chlorine Steric effects Ethanol Electron Halogenation Addition reaction Octane rating Aldol Insertionselement Walking Chemical reaction Aldol reaction Food additive Iminiumsalze Iodide Acid Enol Amination Cobaltoxide Thermoforming Sunscreen Substitutionsreaktion Eliminierungsreaktion <beta-> Hydroxyl Aromaticity Fluoride Nitroverbindungen Human subject research Chemische Synthese Sodium hydroxide Fluoxetine Beta sheet Atom Hydrocarboxylierung Acyl Stickstoffatom Ketone Formaldehyde Carbon (fiber) Aldehyde Carbonylverbindungen Protonation CHARGE syndrome Computer animation Functional group Iron Base (chemistry) Enamine
Computer animation
Glucose Fructose Kohlenhydratchemie Chain (unit) Chemical property Stereochemistry Glykogen Chemical plant Topicity Organische Verbindungen Abundance of the chemical elements Water Starch Cellulose Computer animation Cell (biology) Hydrolysat Chemical compound Polymer Monosaccharide Thermoforming Body weight Biochemistry
Cheminformatics Glucose Fructose Kohlenhydratchemie Chain (unit) Stereochemistry Ketone Aldehyde Aldose Ketosen Sample (material) Computer animation Orlistat Chemical structure Thermoforming
so we left off last time talking about nitrous acid its generated instant you by treating nano2 sodium nitrite with hydrochloric acid and what you can do with this is it decomposes to nitro sodium ion and these are actually considered to be very very highly carcinogenic compounds so there is some concern if you look on the label when you eat any processed meat or hotdogs or things like that it says nano2 sodium nitrite that's what they used to preserve the meat and of course you have hydrochloric acid in your stomach so this sort of thing can happen in your stomach and so there's some concern about this it's been proven to cause things like stomach cancer and bladder cancer in animals but maybe not in humans the problem is is that it's ubiquitous they use nitrogen fertilizers and so even if you if you have to eat really healthy and you consume lots of fruits and vegetables you still will get these nitrosamine in your diet there's also a little bit in beer cigarette smoke things like that but what they found is that people who eat a lot of fruits and vegetables actually have lower risk of these cancers so that the mechanisms aren't aren't entirely understood but just to keep you a little aware so you'll see some meats there they claim to be healthier instead of using sodium nitrate they'll use celery extract well celery has a lot of sodium nitrite in it already and so if they're just really doing the same thing it just sounds healthier celery extract rather than sodium nitrite so um so something to be concerning but certainly we do need to preserve these meats because if you don't preserve the meat you're gonna get a lot sicker than right away you'll get sicker later on you'll get sicker if you get cancer right okay so we talked about the mechanism I do not ask this mechanism on the exam whatsoever and it's really not very synthetically useful for simple amines like this what we're word so we're not going to be doing this this is not where we're doing it actually is synthetically useful when you use aromatic amines okay so look let's label this this is a electrophile with a fantastic leaving group so can wreak all sorts of havoc in your body when you have a good great nucleus so we call it a really great alkylating agent alright so I'm the reaction with primary means primary aliphatic amines is not synthetically useful that's what I just showed you on the previous page but when you use primary aromatic amines it's actually very useful when animals allowed to react with nitrous acid dyes it ization occurs the same as we did here on the previous page and we form an arene diazonium salt as diazonium salt has a very good leaving group molecular nitrogen and undergoes substitution and so there's a bunch of different substitution reactions we can do with this let's first draw the arrow earring diazonium salt so this is the intermediate we have a positive charge on the nitrogen that's bonded to the benzene ring and then depending on what we use in this case we use hydrochloric acid we would have CL minus as our counter ion and this is stable at 0 degrees so it's stable enough at 0 degrees these when we do it with an aliphatic amine it is not stable at 0 degrees so this is stable at 0 degrees so we can form the diazonium salt in SU 2 and then we could treat it with a bunch of different nucleophiles so here's all the reactions we can do with this so this this reaction here it's called the San Meyer reaction and this is why you want to go back and you want to review aromatic chemistry you want to go back and review chapter 18 if you had me last quarter I talked a lot about problems with aniline and our ways to work around that if you didn't have me last quarter that is hand out under the practice link and you definitely want to take a look at that okay so and and even if you had me last quarter you definitely want to review that so I'm here's all the things that you can do here we can replace that diazonium salt with a bromine using copper bromide we can replace it with a chlorine using copper chloride we can replace it with an iodine using potassium iodide HB f4 and he will replace it with a fluorine so this is the first time we've been able to put a fluorine on an aromatic ring copper cyanide is a way to replace that diazonium salt with a cyano group so this is our first synthesis of a aromatic this is what this would be benzo nitrile aromatic nitrile benzo nitrile very synthetically useful if you treat this with water and sulfuric acid and heat so basically you just would use sulfuric acid as your acid and then you would just let this warm up you can now replace that diazonium salt with a hydroxyl group so this is now our first synthesis of phenols this is the first time we've been able to synthesize phenols and then a very kind of different reagent h3p o - it's actually called hypo phosphorus acts acid these numbers are not wrong it looks a little strange so hypo hypo phosphorus acid and if you do that you can replace the diazonium with a hydrogen why would you want to do that well there's instances where that would that's actually a very useful thing to be able to do all right so this can be can be used to remove an amine group and let's say we put in a mean group on the benzene ring and we use it to direct incoming substituents once it directs us it directs the incoming substituents we can take it right back off again when we're done with it so to remove an amine group that that's used to activate the benzene ring or direct an incoming substituent and and sometimes you can actually use it to also to block a position on the benzene ring that you don't want substitution on now as for the mechanism of this reaction it is not an sn1 it is not an sn2 I'm not going to ask you the mechanism because it's not completely understood probably involves radicals so not sn1 and not sn2 mechanism not exactly known and and probably involves radicals which means there's there's evidence to suggest that there's radicals as part of this reaction so one less mechanism you need to know but it's very useful in synthesis and and guaranteed you will have some synthesis on the final where you use the San wire reaction alright so let me give you an example of how you would use this in synthesis apart from just being able to
put these groups on a benzene ring and we'll do some more in discussion next week so here's an example let's say we want to synthesize the following compound from toluene so if you think about synthesizing that bro means an ortho para director methyls and ortho para director how are we gonna get those things meted to each other okay so that's that's a turkey that's a tricky problem if you brominate toluene you will get and let's say we use two equivalents two equivalents of bromine toluene is an ortho para director so our major is going to be one bromine in the ortho position in one bromine in the para position that's our major and minor because it's a little bit more sterically hindered would be to have both means in the ortho position so that's going to be a minor product and that's only because it's more sterically hindered but not even close to what we want to make all right so let's let's see how we can do this and get things going exactly like we would want them to go so instead what we can do is nitrate the benzene ring and put it in and change that to aniline okay so but nitrate reduce that and use the amine group as a directing group so get all that aromatic chemistry should come flooding back to you hopefully at this point we will get ortho and para so we would isolate the para nitro toluene we reduce it with h2 palladium now what do we know about this compound if we brominate that where where the bromine is going to go so so that I mean and and so again you want to look at that problems with a mean that is a very highly activating group you will get both ortho ortho positions filled okay and you don't want to use febr3 because this is so activated that you just throw bromine in and they're gonna go right on the ring even at low temperature so you're just going to say to be R to febr3 is not needed so you see where we're going here we've introduced in a mean and that amine is doing a great job for us it's is it's directing where these bro means are going to go notice both bro means our meta to the methyl group which is exactly where we want them to be and now we can get rid of that amine group so we're gonna do a dies it ization so nano2 h2so4 and you can use hydrochloric acid you can use h2 so4 your choice those are the two common ones h2 so4 water that makes the diazonium salt that makes the diazonium salts and then we use again you just want to get these numbers right for this one it's really common for students to write to change this around h3p oh - I won't tell you the common mistakes because then you'll do that on the final but it is a ch3 po2 so it looks a little strange and then we get exclusively the product that we want with the bro means the two bro means and the methyl meta to each other alright so now I've had students say oh I have a better approach that doesn't use that so let me give you an alternate approach to this molecule that also works that you might have thought of if you hadn't had this problem on if I hadn't shown you this so let's do a different approach all right so we start with toluene and this is going to bring back some old chemistry from chapter 18 so one of the things that we can do is we can convert that into a carboxylic acid remember how to do that kmno4 our favorite purple reagent came in a forest sodium hydroxide heat and followed by and that should be a 2 followed by acid why do we have to follow by acid because we're making a carboxylic acid in base so it will be deprotonated so we need to make sure to throw in acid here that gives us the carboxylic acid which is a meta director and now we can promenades of bromine febr3 we definitely the febr3 here and and i honestly don't care which method you use here whatever works if as long as all the steps work all the steps work now we need to convert that carboxylic acid back into a methyl group so the way to do that would be to reduce it with lithium aluminum hydride first and so the reason I'm showing you this is I do try as much as possible to bring up old chemistry so that when you see it on exams you will be ready for it you'll you'll remember what that was so lithium aluminum hydride this goes back to chapter 20 and then PCC we convert this to an aldehyde and now what would we do from 51b to possible name reactions here to get rid of that carbonyl hmmm Clemmensen or wolf cushion I kind of favor wolf cushion I mean Clements and myself we'll just do Clemmensen reduction zinc mercury amalgam HCL so I'm hoping that like many light bulbs are going off in your head to remind you of these these reactions so that's another way to do it both of those would get equal credit on the exam even though the first the first mechanism I mean the first synthesis has a little bit more pizzazz to it you know we do like pizzazz especially when we're grading you know you grade 370 eggs you know exams and you like when somebody does something interesting okay so it's it's delightful to see all right questions anybody we are adding I'm adding two new reactions on to this chapter just for fun and so with the one of the reactions I'm adding is nucleophilic aromatic substitution which is in Chapter is in the newest edition of Smith I did not
have time to cover it last quarter it is in chapter 18 okay if you have the third edition how many people have the third edition I will put some practice problems for you I will cover as much as you need to know about this reaction and I will put some practice problems for you under the practice links so that you will not have any disadvantage over people who have the fourth edition okay and I do believe that forces you is on is on reserve in the library can anybody verify that is it on reserve it usually is okay should be in the library if you want to take a look at it alright so nuke we covered in chapter 18 we covered electrophilic aromatic substitution and that is where the benzene ring acts as a nucleophile and attacks electrophiles right so we made all sorts of souped-up electrophiles and the benzene ring attacked this is the opposite this is nucleophilic aromatic substitution and now the benzene is acting as an electrophile and nucleophiles are attacking it so if we want benzene and we read so we're used to seeing electron-rich benzene in chapter 18 and we'd have electron donating groups to make that benzene really electron rich if you if you if now you want the opposite and you want benzene to be electron poor what would you put on that benzene ring electron withdrawing groups right the more the merrier the better the more electron withdrawing groups so so back in chapter 18 when benzene was acting as the nucleophile if you put electron withdrawing groups on it it slowed down the reaction you got meta substitution and you had to heat it up a lot higher here I'm putting lots of electron withdrawing groups actually enhances the reaction that makes it work better so let me show you what it looks like so chapter 18 fourth edition aromatic rings don't react easily with nucleophiles nucleus can't displace aryl halides in highly deactivated benzene derivatives via addition elimination mechanism alright so let me show you what I mean by highly deactivated so and in our criteria is going to be a little more strict than the general criteria for a highly deactivated we want to nitro groups or to cyano groups or and I guess we'll do court or to carbonyls where of course the carbonyl is bonded directly to the aromatic ring and so we want two of them two of these or you could have a nitro on a cyano group but two deactivating groups ortho or para to a halogen especially fluorine so I'm gonna make these very very recognizable to you okay you see a benzene ring you see two nitro groups to say honor groups two carbonyl groups are two of any mixture ortho or para to a fluorine and that should just jump right out at you because we barely use fluorine at all right so those are the best cases and that's what we're gonna be looking for all right so that's that's our criteria so on fluorines better this one it uses chlorine though but notice the chlorine is ortho and para two deactivating group to strongly electron withdrawing groups and this is what and so the reason we're introducing this here is this is a way to make aromatic amines another way to make aromatic amines so our our nucleophile as is na NH two it is displacing the chloride what do we know about this Rex isn't an SN water an sn2 what do you think essent - we Essen - we don't want sp2 hybridized right so it's not going to be sn2 because we can't do backside attack is it going to be sn1 yeah if it's sn1 we certainly wouldn't want a lot a bunch of electron withdrawing groups on a benzene ring if it's us and one we'd have to make a carbo cadion with on the benzene ring you know we would have to make a phenol carbo cation and having a bunch of electron withdrawing groups on a carbo cadion is going to not be a good thing so it's not sn1 it is not sn2 so let's look at the characteristics of the reaction strong nucleophile required so absolutely strong nucleophile required water wouldn't work but methanol wouldn't work calories can't proceed by an sn1 because the Itron withdrawing group would destabilize this intermediate so let's draw that the intermediate that you would use for this that we're not going to use definitely that's looking really bad we've got two really powerful electron withdrawing groups so no sn1 let's put a big X through that okay reaction cannot proceed by an sn2 like vinyl halides arrowheads cannot achieve the correct geometry for backside displacement aromatic ring box approach to the nucleophile to the back of the carbon bearing the leaving group so let's just draw this out just for a reminder of this because it's been a while since we've had this so here's benzene on its side so I'll wedge it to show that it's kind of going on so it would be floating above your page so we know we've got overlap on the top and the bottom and just for a moment here let's leave off the nitro groups to make this a little easier to see let's put our chlorine here can we do backside attack I mean basically what this means is this this electron rich nucleophile so we've got this electron rich we've got these electrons circulating on the top of the bottom and this electron ray what's going to happen when this nucleophile approaches that pi electron cloud it's going to be repelled right so is that going to be able to sneak in here into the middle of that doughnut hole and do backside attack and kick off chloride no not the million years is that going to happen okay so impossible to have sn2 impossible to have sn1 let's do this a different color so you can see what I'm talking about here there's got to go in here not going to happen so none of this either so sn2 requires backside attack which is impossible here and there is no and we already talked about this multiple times there's no sn2 on sp2 hybridized atoms all right so Essen ones out sn2 is out um the other thing that's that's really kind of wonky here is that the fluorides are much better leaving group than iodide so we definitely isn't we're not looking at sn2 so recall in sn2 and sn1 even iodide it's a better leaving group than bromide which is a better leaving group than chloride which is a better
leaving group than fluoride and here fluorides better so definitely we're not talking about the same reaction and this is worse leaving group and in fact we've never seen fluoride as a leaving group in this class so what if we but we are doing a substitution so what kind of substitution do we do when we have an sp2 hybridized atom what did we do instead of sn1 sn2 what do we do what do we do and all throughout chapter 20 when we wanted to do substitution of an acyl acid chloride for example what is that what was what does that call addition elimination right right you attacked the carbon eel you kick electrons up onto oxygen electrons come down and you do an elimination so it's the same thing here it's addition elimination alright so let's look at it addition elimination now III have so many choices here III can what I'm going to do is I'm going to actually tack the carbon that's bonded to the leaving group I'm not going to do direct displacement though I'm going to do addition elimination so I'm gonna have this nitrogen attack here that carbon I'm going to move electrons over and I can go all the way up on to the Nitro group there should be a positive charge on that Nitro group by the way that's addition a little bit longer a little more arrows than attacking carbon eel but that's essentially what we're doing and that is the slow rate determining step now there is there are a bunch of resonance structures we can draw I'm not going to draw all of them I'm going to do the two main ones so I pushed electrons on to one of the Nitro groups I can also push electrons on to the other Nitro group and that's why these two nitro groups need to be ortho or para to the leaving group because if they're ortho repaired to the leaving group then we're going to be able to especially stabilize we know we've we've disrupted aromaticity so we need to do some stabilization of this high energy intermediate here and that's nitrogen here let's put the nitrogen there all right and that was so much fun I'm gonna push on to the other nitro group here okay again we're leaving out the extra resonance structures there's a bunch but what I can do is I can because of the orientation of these two nitro groups I can go all the way on to the other nitro group and in fact I could have gone on to this nitro group at the start so you see why we need two of them so this is a possible mechanism for the final and of course we can push this charge onto the ring three places in the ring in addition to these two resonance structures so my recommendation to you is know how to draw a nitro group that's the wrong spot there know how to draw a nitro group for the final and know how to draw resonance structures for a nitro group okay so there's our slow rate determining step it's a high energy intermediate because we've disrupted aromaticity and now we want to do the fast now we want to do the fast step fast elimination alright so in addition we add electrons we push electrons up on to the oxygen and then elimination electrons come down and kick and now they're gonna kick off the fluoride let's see we'll go from we'll do it from this one we could do it from either one there's a negative charge here let's go here just like that so electrons on oxygen come back down and we kick off fluoride as a leaving group can you think of a possible reason why fluoride would be a better leaving group than say let's do the other extreme iodine why would fluoride be a better leaving group than iodide for example here there's two reasons so maybe you can guys can come up with one of them hmm well let's draw the product first while you mull that over yeah fluoride ion versus I'd I would both be yeah actually that would both be cooking off so that's not that wouldn't be the reason so substitution think about sterics here the cervix is one of the factors here look at where the look at where the amine is attacking do you see any possible advantage for that leaving group to be as small as possible because it's it's attacking on the same side all right so it's attacking on the same side and it's also more electronegative so let's let's so so carbon with the remember we want this ring as electrode electron withdrawing as possible we want it to be very activated fluorides more electronegative than iodide so it's going to make that ring even more electrophilic and that's what we want so carbon with fluorine attached has larger passo positive charge therefore it is more subject to nucleophilic attack in the rate-determining step and the other thing is of course the size of the fluorine in sn2 we have backside attack so size doesn't matter here believing group ability in nucleophilic aromatic substitution na s attack is from the same side so the fact that chlorine is smaller is better questions on nucleophilic aromatic substitution anybody all right we've got one more reaction to talk about that's the manic reaction all right so when an aldehyde or ketone is heated with an acid catalyst in the presence of formaldehyde and an amine this is the most standard version of the Manik there's other versions of this but this is the one that we're going to be using the product is a beta amino carbonyl compound that should be that should be the symbol beta rather than that so turn that into a real looking beta there so I'm going to go through
this the mechanism and then we'll then we will look at the product part one and I'm not going to go through all the steps because we've already done this and you can go back and check how to do this part one we form a mininum ion of formaldehyde all right so here's formaldehyde and we're going to form into mini mi on so not an amine and not an enamine so normally when we use isness a secondary amine which we're doing here we form an enamine can we form an enamine from formaldehyde no there's you need a carbon here right but we deprotonate that Carmen and we form an enemies so this is the what you put you form the can't form an enemy we can't form an enamine so we form an iminium ion and that's definitely going to be electrophilic the mechanism for this is page 46 of your notes okay so take a look at that so this is a this would be a possible mechanism on the on the final also because it's got its got new one now it's got something from midterm one it's got something from midterm two and then it's got something from this third section of the class so part two is acid catalyzed aldol like reaction so the first part part one is from midterm one the second part is from midterm to material and so let's go through that acid catalyzed aldol we've done that before but let's do it again because this is a little bit different so acid catalyzed reaction we protonate the carbonyl first we've got a hydrochloric acid I'm just going to use hydrochloric acid to do this so remember in the acid catalyzed reaction and enol is our reactive intermediate so we're gonna make the enol from this alright so we've got two bases here we got chloride iron we have ethanol we you can use either I'm not going to be particular about this ethanol or you can use CL - I'll just use ethanol here we're going to remove this acidic proton push electrons up on to oxygen so remember in acid college reaction enol is our reactive intermediate alright so now that rather than in the aldol reaction we would attack another protonated carbonyl but instead we have the somany am i on that we just made in the first part so that's what we're going to attack so electrons on oxygen come down we attack this carbon you know we kick electrons up onto nitrogen so hopefully this is all looking very familiar to you it's just a little bit of a twist on that reaction and what you see is going to happen is we've got this amine and we're going to do an intramolecular deprotonation and and remember it in order to do an intramolecular deprotonation we need to have a five or six membered ring in transition state so if we count this is one two three four five six so that's exactly what we're looking for so we're going to deprotonate intraocular deprotonation so this nitrogen is going to be protonated and then you can see step two in step two of our reagents step two we add sodium hydroxide so then we will just deprotonate this so here's our final product so remember in an aldol reaction we get a beta hydroxy carbonyl here we get a beta amino carbonyl so if you see that functionality you know we could make that using a manic reaction so let's go ahead and draw that up here yeah doesn't like being up there questions anybody on the manic reaction all right so possible mechanism for the final manic reaction is used as a key step in the synthesis of Prozac we're not going to do the whole synthesis of prozac but you can see that this is Prozac and maybe my one on your own think of how to finish this synthesis alright so we've got our ketone we've got formaldehyde we have methylamine here we have an acid catalyst and this is ethanol as our solvent so maybe you want to practice the mechanism on this one and sodium hydroxide and then think about how we would take that and you prozac so at what you can see here is that we have this part done right here so basically but this is a ketone we need that to be reduced and but just think about how else how you might finish that synthesis to make prozac questions anybody alright we're going to I'm going to save this page and then we're gonna start chapter 27 so we're almost done here so let me close this
any questions while we're waiting for that to save anybody
all right carbohydrates so you probably mostly a little know a little bit about carbohydrates from bio right so we're going to just using that use that as a jumping off point to go a little bit more in depth in Jakarta hydrates the carbohydrates are the most abundant class of organic compounds in the plant world so super importance so they're synthesized by nearly all plants and animals they use them to store energy and deliver to the cells and then most living organisms take carbohydrates for which they extract glucose they oxidize it to get co2 and water and energy and that's not certainly not a topic for this class that would be a topic for your your your class your bio class starch glycogen and cellulose are all polymers of glucose plants store energy by converting glucose to start starch animals store energy by converting glucose to glycogen and plants use cellulose as the structural material to support the weight of the plant all of these are polymers of glucose with subtle stereochemical differences which make profound differences in the physical properties of these compounds all right we're gonna start by classification two carbohydrates so there's a little bit of a I guess you could call it nomenclature of carbohydrates that we need to make sure we're all on the same page here so monosaccharides are carbohydrates that cannot be broken down into simpler units by hydrolysis you can take a monosaccharide and convert it into smaller units by other means but not by hydrolysis so monosaccharides two examples are glucose and fructose this is drawn in the open chain form which you're not used to seeing it in but certainly there is a small amount of
the open chain form when you have a sample of glucose and so basically we see an aldehyde here so this is an aldose so os-- means sugar and al means it's an aldehyde you won't be able to tell it's an ally when you look at the closed form the ring form which is the most predominant form but if you have the open chain form you'll see that it's an aldehyde d-fructose on the other hand is not an aldehyde it's a ketone so it is a ketose all carbohydrates end in O so that means you just have a sugar or a carbohydrate and ketose means that you have a ketone so that's classification number one that we all need to get get down the other thing is that and I pretty much use Fischer projections exclusively for carbohydrates Fischer projections are introduced in chapter what's the stereochemistry chapter 5 so Fischer projections are introduced there but I don't talk about it in my class I wait till now so let's talk about Fischer projections we definitely need to know what to do with Fischer projections so they look like this and there's some rules here most highly oxidized and carbon on top so the most highly oxidized is the aldehyde so that's on the top here most highly oxidized is as close to the top as we can get it second from the top it looks like these are Lewis structures but this is actually conveying stereo chemical information we don't have to talk to
time to talk about that now we will continue this on Friday you
Feedback