Lecture 17. More Structure, Stereochemistry, & Reactions of Carbohydrates.


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Lecture 17. More Structure, Stereochemistry, & Reactions of Carbohydrates.
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Nowick, James
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This is the third quarter course in 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: 1:40-Aldotetroses 9:16-Aldopentoses 11:40-Ribose 18:02-Ketoses 22:47-Hydrolysis of Glycosides 36:34-Formation of Glycosides 43:51-Alcohol Groups in Sugars 48:05-Making Esters 51:03-Reactions of Aldo Sugars 55:32-Sugar Structure Determination 59:12-Reducing Sugars 1:00:07-Tollen's Test 1:05:26-Which Aldotetrose? 1:15:24-Kiliani-Fischer Synthesis
the Florida so what today I
would like to continue our discussion of the structure in Styria chemistry of sugars were going to bend talk about reactions of sugars and we're going to come back at the end interlocked if everything works out how and meal Fisher originally determined the structure in Styria chemistry of of sugars and what really was a tour de force working on review tiny taste of the flavor of the chemistry and the logic involved so I
mentioned Fisher and last time we introduced Fischer projections this way of drawing sugars that really pervade sugar chemistry and it's a very very useful tool for quickly thinking about
structure and scary chemistry and so we're going to use that along with hot worth projections and other projections in today's talk so I wanna start by just giving an overview of how we can look at some scary chemistry of sugars I'll take some very simple very small ones what we talked about glucose glucose is now although hex so we've talked about it and we talked about the line shows like doses is another Aldo Hector packed so speeches 6 carbon sugars at this point I just wanna start out to give you the simplest thing where we can get all the stereo chemical relationships in so I wanted us to to look at various temperatures 10 processor course for
carbon sugars and specifically Aldo Tetris is the elder low-tech
processes the sugars where they won isn't the 1 position is an elder rival waiters
see Quito sugars where you have not now the body Keaton group in all of these are carbohydrates so to get some flavor of exterior chemical relationships and maybe harkened back to 51 a letter brought out before the panel game Tetris is a mail for I'm going to qualify because you could also
say it's too depending on whether we're counting in India Mercer let's start with the natural
isomers so this shows there is for carbon share is DEA 306 and remember all of the sugar is by definition when we draw pressure projection this way all of the DEA sugars have the hydroxy group at the carbon next to the bottom position the bottom various center have that with the awaits pointing off to the right remember this representation has the backbone curving backwards snaking back in a series of zigzags and so this means this cell wages pointing out of the board of this hydrogen is pointing out of the board this C H 2 O H is pointing back and this the remainder of the changes pointing back and ended this representation we continue to point the elder high further back and so this hydrogen is pointing out and it's always disappointing about
what's nice about the fisher projections is weakening rapidly way out all different structures and compare them it's
quicker and easier and more intuitive than zigzags structures and so I'm going to draw another danger another day although tack trials so it's still going to be deed but now instead of having this so that means this hydroxy group Mister lofted the right but now instead of having a serious danger would be a too often the left we're going to have it all on the right and this 1 here is called the arrest and of course these 2 molecules here are various area mayors we talked about highest theory emerged last time we talked about for example
glucose and galacticos those who Merced different ones stereo center that we have a special name 1st stereo isomer that differs in Dyess theory murdered differs at 1 of many serious centers we call that an moral and then
we also talked about Styria chemistry at the at the oven at the carbon carbon in the cycle like former Indiana Meira carbon where you could have either the data or the alpha Styria chemistry we had a special name for that and anniversaries so are faded D glucose and Alford the glucose those to guys emerged in addition to being a tide of all of our EP murder would also referred to them as an enema anyway suggested Eric exterior murders and Apple Burma's I guess you would say Now I mentioned for a moment that I've slept all of the theory of centers and the molecule Weinberg them and so we go like this and again I think very rapidly representatives for a 306 example so now for the 3 I've let this area around the bottom so that by inherently is now going to be an algebra and if I flipped the others seriously injured lifestyle so now I made the molecule that's the mirror image for more specifically than Noland superimpose a ball mirror image I have represented the Indian here and of course that means this compound I've drawn is held 3 hours of sometimes the servers are referred to as the on natural sugars and that the sugars as
the natural I want you Out is it of the regional no because the rift rose so OK so good question and this is why we're going through this
with some care so here if I now go ahead and make this analysis this is the Indian India murder of what's that supposed to be an elder the Hyde so we're going to make that CHO so this is the inanity Amara all the rift throws and so this is you with that's another question so
this is the various center right now 1 thing that's interesting and we'll get to this when we talk about the fisher proof stereo chemistry is entails many years after the relatives chemistry the dire
streamers of observers were determined people couldn't tell which in India murder was which and so arbitrarily was chosen eventually it was discovered what was real but all of these relatives carry chemical relationships in the terms of D & L apply regardless of whether the all are as we saw it was or whether he is other questions at this so we
would say that L-3 is the Indian humor and be free of L 3 is a Kyocera more L a red rose and health Rios is a diocese area Mayor of the arrest of selective that's sort of a basic basic introduction or reintroduction to stereo chemistry and shows us how we can use these Fischer projections very nicely and quickly so I wonder why I wanna take us through a few other forms of few other ideas and
sugars and then we're going to come back to To some reactions of sugars so again there are there are 2
different diets serial murders of there Red Rose low-tech processes and then Rivaldo panto season of Aledo system were not going to learn think about every
sugar but I'll give you a few is an example here so I I think in terms of the Aldo on Pinto's since Albright Aldo Pinto carbon sugars those Leonard's gotta be the most important is right below us In Rainbows happens that have all of the all age groups on the same side in the Fisher projection will write the right post while
his rivals important it's in it's an RNA deoxyribonucleic is in the idea that the
oxygenated at the the 2 position and well this is a tremendous slave tremendously important sugar now we've learned to go
ahead and think about the ahead of today's US forward here we've learned to recognize that sugars have a site Foreman
generally even tho I've been drawing them predominantly urban drawing them as the free held up remember we talked about how the site like formed him I as a talent and the elder hide form rapidly Inter convert recent glucose for example is only . 0 0 3 per cent of the open form did for IPOs in water right post is predominantly the closed form at the time difference structures to different Samaras that exist 1 of them is 80 6 members ruling by summer and is and we're not going to focus remember I said the squiggly lines means mixture of alpha and beta leaders up Halfords down were not going to focus on that exterior 10 mystery that mixture of alpha and beta Panama's will exist in equilibrium 1 the DOH up the the data and the other with DOH down that's serious injuries and fixed its like buyout but we will focus on the
others and if you just imagine picking up the molecule of laying it down European city
in our worth projection here that are all wages are going to go down and maybe the only 1 that strictly in
one's mind allied to convert this Fisher projection to the hot worth projection may be the only position that's strictly is that next to the bottom 1 and so just imagine in your mind's eyes were
going to rotate rotate and rotate like that and now you say OK so we bring the sewage down here
the CH 2 comes here and that hydrogen comes here and so if you can do that rotation in your mind's eye you pick it up and you say OK
actually were granted of sorry for this 1 threat will do that next for the the furor knows
form for the period rose form were just fine because we just cycle eyes on this oxygen so we bring this oxygen around to that hydroxy group and so we have 3 wages pointing down time is getting ahead of myself OK so here's the haul worth projection for the pure
knows forms In solution right boasts exists in water it exists is 76 per cent of the pure knows form is a mixture of alpha and beta Panama's but the other formatted insists it is the
furor form the furor knows form is the five-member bring it's the 1 that when you see and a during the
chapter on your biochemistry courses using DNA and RNA I guess more specifically so we're going to draw the Peronists forms of the parent knows form is going to be
cycle icing onto this oxygen to make a six-member directing but onto this oxygen to make a five-member doing some now I guess I'll raise the supplemental bill to give the
rule so now will draw the hall with the projection of the Peronists warm so if
we look at that we're gonna site lies on this oxygen while it's still going to as we picked this up see my fingers here they're pointing out I'm just picking that up these 2
oxygen is there going down again I'm going to leave as Cereal chemistry unspecified had the Pan-American station because will have a mixture of alpha and
beta Panama's now as I said to get over there we're gonna cycle I send this oxygen so we'll just bring this oxygen down rotate SCH to opt to rotate that hydrogen over were just rotating about a bond as a mental operations so when you do that at that
puts the CH 2 always H R and the hydrogen down so that's the Kirino's form of rival those the Theranos form where can talk today so let me let me right here those form and fear knows form and this is a 24 % as equilibrium and you
should be a proficient enough and of course this is at equilibrium in water and you should favor efficiently enough To do these operations in your head that I've just don't know the best way to train yourself is to begin by working with models
plastic models are great way to go big amount from 51 a computer models are a great way to go and I've given you those tools to start with a little bit of imagination member I gave you glucose just a little bit of imagination in rotating and primal that structure I gave you for glucose will allow you to see this relationship or of course you can just entered it and put in the hydroxy groups in the right place and deleted but I think you that when you're form which is representing our official projections I've given you any a site quick form that represents the whole worth projection of the Peronist form so as you work through these you will become better
and better at seeing the relationship in your head on the floor of the sugars that drawing thus far all of the miners sector writes that drawn thus far Our Aldo show DeSalvo tech processes Aldo Pinto Ronaldo hack cells
let me show you a Quito sugar so remember based on the tone so we call them Cheetos seasonal show you a Cheadle cells in my philosophy has been to teach you some important
ones were not going to become sugar chemists were not going to master all the diocese theory emerged the Aldo Sosa's and then all of the various possible you
services that might be give you 1 of them that you will know longer buying Nadia it was but the "quotation mark but it again and going to draw drawing as Fisher projection and so this looks very much like glucose except remembered glucose had now the hideout on top and had a hydroxy group walked to the right at the position number 2 here we have a key town group we don't have a theory of chemistry at this position but I have to draw the Carbondale somewhere so we have 3 serious centers this show there is fruit or more specifically from tells you've of course heard of fruit dose
right you've heard of it into the fruit sugar tea and fruit you've heard of it all last in Haifa goes corn syrup which is produced by hydrolysis of starch goes corn starch from corn corn is very starchy starches finish polymer of glucose and upon a acid treatment through toast at glucose can I
summarized to fruit dose may be on that use mechanism at some point in the good example of what our anyway so coming down to us to fruit so case of proposed a key ally Samarra and fruit those exists in appearing knows four-minute 16 per cent in the Peronist form that again all of this is that equilibrium in water that would be site lies the on this hydroxy this hydroxy going the former Knesset Talwar that carbon yield and it's it's 40 per cent of the nose form that would be with this hydroxy cyclist onto their continual annual now remember
we've had this theme that Aldo hides or more reactive less stable than key towns and we see this in the sugars very nicely so glucose there is very very very little of the free held heightened solution . 0 0 . 3 per cent from knows there's still not a whole lot of the free tone in solution
but there's a good bit more there is about .period 25 per cent of the Clintonian solution also opened former hope I open form of course I mean the key all of this is a real solutions all right in water and to many in my
mind's eye that kind of kind of gives me this feeling about stability we saw this without the hides in Quito acetone and water is stable enough that you have very little of the German all asked about the height has about 50 per cent as the Germinal by all in water the elder height is much less stable because you don't have to electron withdrawing
electron donating alkyl groups and we see this year as well that you have about a hundred times more of the Quito form of the Open form of the carbon your form fruit goes than you
do in glucose and sodium Saudi says yeah how the hides a lot less stable a lot less happy than he tells me our write this this introduction to sugars indeed this whole chapter is only going to be an introduction this really sets us up to introduce some chemistry of sugars and the 1st chemistry I think I want to introduce is the hydrolysis and quite besides
before we started we look then blacked out
as a sugar your body if it does break down sugars breaks it down into the mine sack arrived units some people end up not being able to digest melt meaning they don't have the
enzymes that help break that that bug like acidic linkage to break it down and then you have bacteria do it for for you in the wrong place in your body and give you a gas alright so I don't want us to start with the big sugar but I want us to see another sugar and show you another guy sack arrived here so remember I mentioned starts with the 1 that we can break down as well but also you a simple lines and will use of 1 glucose unit and 1 fruit those unit this is of course the 1 with 1 glucose unit and wants to when 1 group goes unit is still grows so when another very very important shotgun in many of the glycoside you have an alpha linkage between the sugars so starch has Alpha linkages and cellulose has the more stable Badaling did so alpha means down so here we have a glucose unit and national I'm going to connect 2 another ring and that ring is going to be a fruit those unit and so we have
a period of up your nose ring of five-member grinning and I'm going to go ahead and put all my parts of fruit those years I have a C H 2 0 age-group peers are an American position and I have in all age groups this position going down remember people often dual broken lines the show in back and then I have the 2 always age group going up there so that's a that's a glucose unit linked by an hour ago like acidic linkage we call this oxygenated
like acidic linkage but glucose linked by white
acidic .period feeds to food processing now acid catalyzed is the breakdown of like Pacifica linkages and so if we treat soon process
with in water all right this is the real class that would of course be a
strong acid dissolved in water HCL is widely used over sulfuric acid in water could be used as well remember and sulfuric acid dehydrate sugars but but in water you don't have that and if we
go ahead and we treat our To froze with strong acid for example boiling it up in 6 smaller we HCL which is popular as a good way to hide relies on a variety of different from the ones we hide realize the glide Hasidic leakage and get herself 1 glucose unit like so everyone from various you know like self but but because of the books and I have dropped hopes I have the fact that pool and structure year In the end the correct this race now held itself this position this position we have a hydroxy group at this position we have associates to all age groups adjusts to correlate this with the structure on the other blackboards starting from the top of our 1 position are to a position that was the key tone it's now an acid Tal are 3 position that's the hydroxy in the middle for position our 5 position that's that oxygen off on the bottom right next year know the disposition of over here and the last 1 is CHT 208 Our rights so that finished correcting the structure and so here's the structure of the group now
I've drawn this initially as the Bader and here and I've drawn this initially as 1 on America eventually both of them equilibrated to a mixture of alpha and
beta or at 1 of the
things about these molecules 1 of the things about organic chemistry in general is that molecules behave as their functional groups and if you look at the molecule of sucrose you will see embedded in the structure 2 acid talent cages so you will see
acetaldehyde over a year and in areas that our group over here and we know what has the talent to in a we
assassin they and we know the mechanism for that the molecules that but the
chemistry is the same and so the
mechanism for this is going to
involve an allergist at this hour of grief lay the mechanism is going to involve protons going on to oxygen pursuing apart and Oxo Tower being a mile final leaving group leaving and then it's going to involve attacked by waters so let me summarize that here's our fruit those molecule and so were
in a real solutions and so we can imagine protons spilled on
protons go and a
with solution and so the proton all the different oxygen but since we're breaking the on America link were breaking the glide
Pacific linkage the point at which were set up to break that linkage is 1 a proton goes on To the go like this civic linkages oxygen and so I'm going to walk you down that productive pathway like so I know other words oxygen is protons can go on and off on the oxygen is but this particular pathway happens to lead us somewhere and so I will show you that 1 of the Soviet program made this oxygen like so now that's very good
because that sets for
this oxygen leave and for us to form an axis her might inside you got in your head In other words we question With that lone pair of electrons it pushes out pushes electrons onto the oxygen and
now because they're sucrose molecule please call what is the day I'm going to have to take us across to the other black and so I just let it let me it continue here to get us to the other black word I will show and equilibrium Maryland and then we'll just sweating over here and they use your
Imagination's nation and we have a molecule of glucose told you going to see a lot of glucose vanish we have the axle tarbey near my God From through heroes installed draw that here but because the group of and now to complete operation the acts of opprobrium I've isn't isn't sustainable and sold to complete our equation water can attack and shorthand things and we can lose a proton and I will simply say Here's our through their structure
the included U.S. OK and so it has been very aptly pointed out that you can do it by using this oxygen to push out there now here's why I did it the way I did it my way is a little more write a little more real just as the elder height is less stable than the key told the IOC said Kirby Ireland from an elder height is less stable than the Oxo Kirby a from a key because of that electron donation of the alkyl groups
and so I promised to give the better Oxo ,comma near my arm but it you're stages and that you're learning yes absolutely we could go either way Our so that gives us a kind of kind of an introduction and we can see lots and
lots of other chemistry for example and I'm not going to take you through the details of the mechanism because I expect at this point you should be able to go ahead and do this mechanistic letting you know had both this will review a boxer opprobrium on and chemistry as as well as as well as all the acid talkin mystery but I want to show you a fundamental reaction if you take acid and sugar so here in the previous example we saw a hydrolysis of a guy like acidic linkage now I want to show you of formation of a blank disintegrated quality formation of glides inside if we'd taken hostage and use an alcohol as solvent so you've got lots and lots of Alcohol CH 3 major ethanol will do this with methanol and again of course you can go to him sacrament by the each plus that means you do this with HCl or H 2 S L 4 In methanol now held by the exact same type of chemistry we can form a mixture of these data and help but like silence but but but but but but but but but but but but but but but but but but so on the right guy on the left I have debated Mathilde lighter side of glucose is on the right I have the alpha methyl quite a side of glucose and of
course both of these former by program aiding the hydroxy group you take out the gives the so can't being in
like so and then methanol can attack from either the data base To give the
debate Adam attack and loss of proton nor from
the health of faces and give the elephant and tomorrow but the but so in your
mind's eye protons go on protons all different positions of the molecule but if we progress made on this side rack we can push it out with the lone pair together the Oxo Kirby near my honor and now where
in alcohol we have a huge access of alcohol and alcohol can attack from 1 face or the other the methanol is also attacking at the carbon deal so I was only showing it from 1 side or the other so methanol attacks the carbon we form a new carbon-oxygen
bonds at that point you have protonated methanol you lose a proton were in this vast sea of methanol protons skill on protons come along so what the mines engaging with this right you're figuring
the mechanism in your head and this is good this is good because ultimately what you're doing is working through and wrestling with the motion of electrons and the formation of on we reported by the media can we reform the glycans citic linkage with the right life on the the life of only the
Act in other words can we go back to can I admit 2 molecules of glucose for example or molecule of glucose and a
molecule of fruit nose and go back in the are a great question really important and a contemporary super super important problems in Sugar said persists now the problem with going back is we're always dealing with an equilibrium we took how we added water in the hydrolysis direction you want to take water out and the problem is the things that taking water out also react with the other hydroxy group should pure sulfuric acid is great at taking water out however appear sulfuric acid also ends up reacting and hide realizing the sugar so yes when people want to reform like
acidic linkages they do this by something very special it's the same idea rather than having a hydroxy group had been an Americanization they make that hydroxy group into a good leaving groups something that won't go back and then the reaction goes they can use chloride
at that position they can use various derivatives of of sulfur that often get used it goes beyond the scope of this course but there's a beautiful and rich sugary chemistry and we're just getting pardon my horrible upon a tiny little taste of sugars here foreign so I wanted continue with our taste of sugars talking about some reaction so in these 2 examples the hydrolysis of grows and the formation of a methyl glycoside we saw that all we're getting is the behavior of Aldo hides answered towels and tells even the atomization was just as the Taliban behavior shoppers also will have lots and lots of alcohol groups and we learned lots of chemistry of alcohols you text but chose to give you a few examples and I'm going to take you through those there's also some nice examples in the homework problems but there's plenty more rich chemistry of sugars are the way way back the 51 day and you learned the Williamson the sense that you learn that if you talk and all and as suitable date there deliberately being dicey here because there are lots of bases and lots of conditions and I'll give you 1 4 shooters in this in this sector and an alkyl halide call are prime Max suitable for acid into no wonder suitable for well methyl is
great methyl iodide methyl bromide or great Edison to reactions how very very good Howell is double bond
except for penal here live bands always uh benzene CH 2 allied those are all really good OK as well by the time you get to brands like isopropyl not so good and Williamson if you go ahead and get anything well short notice
can do the same chemistry and again with a suitable based some of the basic chemistry all special for sugar is undergoing
an example that actually is basically 1 of your textbook problems and he's very very close but 2 things that you've seen before in the Williamson affair synthesis suffice it to say there are many bases so let me take our good friend glucose here and I'll take it as a mixture of alpha and beta Panama's ever going to treat it with a strong basis sodium hydride and output in parenthesis access and I'll give us bands old bromide remains what they've been sold chloride as a allied again will use in excess of that normally unless I indicated otherwise even fighting right
excess I would mean that you use plenty of it basically use sodium
hydride can pull off all the different hydroxy protons making
them into Parkside sodium hydride is a very strong base and your Bensalem allied is a good alkylate engages in unison
alkylation so 1 can go ahead and cleaning lady and climbers abbreviate the H 2 than was in group has been added so you couldn't cleanly S alkaline all of the exposed hydroxy groups and this is a beautiful example not only
of the chemistry of sugars but also of the fact that basically all the stuff you learned in 51 and 51 still works even in much bigger and more complicated and biological molecules no again not trying to get to diverse not trying to show you too
many different reactions talking about the things that are 18 year chapter so another reaction you learned in fact that we learned just back in the quarter that earlier in the quarter what is that you can make an ester by reacting in acid chloride or said Anaheim hydride with an alcohol and so if I take some alcohol ROH and I take on writing down here acidic and hydride or S & T 0 chlorides and we take a suitable basis like period means that alcohol reacts to give an acetate ester and sugar have
lots and lots of alcohol and another reaction that worked very very well is to make gestures particularly acid teal
because Yukon hydride is small and it's highly reactive and so again I will take good friend glucose or you could do this with the galacticos if you wanted you could do this with commandos you can do this With right boasts but if I take our good friend will cost and I treated with acidic and hydride which I'll abbreviate as ABC to all that's just that
structure out there and purity in which I will abbreviate PAY are remember period being the is the
parasite base that's less basic and triathlon means because the lone pair of electrons is seen as key to work at all and held more tightly it's a very mild base albeit somewhat toxic now we begin the acetate will abbreviate that always see remember that's just an abbreviation for that and so we can make the acetate of
glucose Baron so seen chemistry of alcohols we've seen chemistry of upon
I answered tells and answered tells let's focus in on some chemistry of Al the hides so the elbow surgeries have an Aldo groups and if it's not tied up with its in and my acetaldehyde out of my group is available and so just to refresh we learned that al behind a very easy to reduce when we were talking about the tone set out the hides we learned for example that sodium Bora hydride for is a wonderful mild reducing agent now 1 of the things about sugars insolvencies you know like dissolves like generally
sugars like to dissolve in polar solvents from water methanol things like that they generally are not so soluble and things like Ted provider of fury and which is much less polar so methanol water great solvents for sugars also you reduction
of a generic Al the height with methanol or associations to all age we add hydride and and then program make the resulting Alcock side to give the alcohol and so it shouldn't surprise us that should have some similar chemistry and so I will take a sugar or get away from my friend group units here will come back to to him in a moment so I'll take a different show the 1 that you will have unbeknownst to you but probably had heard of that before was chewed
sugarless gum here a few look on the back of sugarless gum you will often see that it contains sorbet tall and managed to now sugar is called Manaus a more specifically
Deman Manaus is the same as glucose except its AP American attitude position if we take the Mattos and we reduce it should a more hydride their costs other option reducing agents including catalytic hydrogenation which is probably how this is going is just young so if we reduce our Deman knows we get DE Manitoba and the aid and I T O L it kind of makes
sense as a name Madeleine's goes manage tall doesn't make any sense why the common name for the alcohol you get when you reduce glucose is called sorbet but you will see that glue that there is a mixture of sorbet and manner told that is a mixture of Apple
murders at this position all right so all of this
chemistry we're seeing here really in is a very familiar and in the back of your mind sigh at the back of your head can be this little footnote glucose exists in equilibrium between the Peronists form and the open even know there's very little of the other side's form because of that equilibrium the album -dash form be reduced more out of life forms by by which evaluates principle it's reduce and eventually all of our glucose through all of our man knows reduced to sorbet told Vermont
at all however so the other chemistry and this will set the stage for talking about sugared structure determination so when we talk about how the hides we learned Minalga hides were very easily oxidized by mild oxidizing agents even for example silver oxide a G 2 In a Rios ammonia NH 4 a wager an age 3 however you like to write it ends up oxidizing the elder hired to carboxyl against it and you can do this selectively in the presence of alcohol so it shouldn't surprise us that you can go ahead and do this saying chemistry was shown around the sides of for example all come back to my friend glucose year I just needed to pick some examples for Ford today's classes salty glucose works with all the sugars in which you have a free out hide group and so applied take glucose and I sit expose it to these conditions or IDE who posts over here and we expose it to the same conditions and justice save on writing I'll write and did all mark now we get the corresponding carboxyl said but but but but but but but but but and this has a much more sensible nicknamed this is called Deep gloom ,comma said wouldn't expect it and all of all of these names but they're kind of fun to roll off the tongue alright then what does
this reaction in the laboratory and it's it's often done as a laboratory demonstration of this property what happens is the silver gets deposited on the flats because you're
going from silver oxide it's acting as an oxidizing agent you're going to to silver medal it's getting reduced the silver medal gets deposited on the last day in the states of beautiful mural silver the whole lasting about 10 minutes of shaking becomes a bright silver Mira well now nowadays there are lots and lots of good ways to tell Cedras apart but back in the 19th century people had only chemical reactions and only properties and so it was noted that some sugar like
glucose reacted with silver oxide silver nitrate pneumonia makes silver oxide reacted with silver nitrate ammonia to give a bright silver mirror and others like silk
rounds under the same conditions are just put it Golden no reaction you don't get a bright silver and so it really really stands out the sugars that reacted were called reducing sugars so cool coast is
reducing sugar sucrose is not a reducing sugar because it doesn't react in this reaction and this became a common classification if less sugar has what basically is a free out of my group in other words it's a purer notary furor
knows in equilibrium with an held high then it reacts if on the other hand likes to close all of the elder hide groups are tied up by a talented agency researchers just wondered how the growth that it doesn't react in that would be called not a reducing sugar and so this test this over Meritorious unit called the tolerance test after the inventor before reducing sugars
all right so 1 of the themes and will see this for for the rest of
today's lecture 1 of the themes of organic chemistry historically has been what this stuff of life made up what are the molecules that make up the food that you eat water the molecules that make up your skin your hair we now know starch in corn starch in wheat bread is only go SEC arrived we know that it's made up of glucose units and we know that the proteins in your hair and your skin and your arms are all made up of amino acids but at the end of the 19th century beginning of the the 20th century this
was when people discover that so the chemistry we're seeing now and some of these questions like categorizing is a sugar reducing sugar or not is part of that understand so I want to show you a couple more reactions and go
somewhere over there so cannot give you 1 more to more reactions of glucose not how the hides our very very easy to oxidize and so there are lots and lots of oxidizing agents that can oxidize or
reducing sugar and the and the other 1 is of bromine another 1 is fight is copper a couple
to work out 1 I forget now that's the spelling test for shivers but bromine is another 1 from your textbook insult to show you that bromine can also go take glucose to good tonic asset that so just as we did with the talents status now I want to show you another 1 and then we're going to go somewhere it again I'll take my friend but but but but but but but and now we're going to treat it with a different oxidizing agent as a really neat reaction we will talk about how this occurred hours we're gonna take this would 917 in water you text but doesn't mention he but usually you do this with boiling waters in boiling water situated 100 degrees tonight I guess it is a good oxidizing agent it's not surprising that the elder hide group ends up getting oxidized to the answers group and it's probably not surprising since we've seen lots and lots of conditions that don't touch alcohols but due to a general the lives of it's probably not surprising that the
remaining alcohol groups in the molecule remain intact with 1 exception and that is the primary alcohol group also gets oxidized should occur about select areas and so now we've transformed Globe glucose at the top end and the bottom and then again things have funny funny names this
compound here is called the group's apparently acid and again I wouldn't expect you to know notice these names justified to say what is flying what is interesting of course and what we wanted picked out and picking out the some of the forest for the trees here is that it is asset that is a molecule with 2 remarks would be answered said In
at so I wanted to take us back to the beginning of the lecturing now at the beginning of the lecture we started with the Aldo tech resources and I
drew out the structure of the 2 Aldo Tektronix but but but but but but but but but but but but but but but but but but but but but but but but but but but but but but but and I know
people say organic chemistry is about remembering it's not it's about thinking we've seen mechanisms approach but now I'm going to ask you to do something I'm going to ask you to forget something food yet which Aldo intact roses which but but but but but but but but but but
but but hoped and more get into the
way WayBackMachine when we didn't know which shall those is the 306 and which Alvarez is the
risk throws of the get
back into the WayBackMachine when we didn't have I R a spectrometers and NMR spectrometers
to look at things like functional groups and coupling constants people could burn molecules and measure how much carbon dioxide was produced and how much water was produced you could figure out the empirical formula that way and people the collective of properties of matter and good news too freezing Point depression and could figure out the more molecular weight that way but you couldn't directly ask questions of Styria chemistry like you can now within an Aymara spectrometer telling you assist sound former Trans-Am King and come back to the roots of organic chemistry where the question is what is the stuff of life made from and put yourself in the laboratory of Emil Fischer who won the Nobel Prize in 1902 for his work with sugars his name permeates not only the Fisher projection but the fisheries verification and also a synthesis of proteins and peptides that interested him after he tackled shows that he was
going after all of life he also got some of the nucleic acid bases and so now we look at what you could do that and you go go back to the time of Louis Pasteur Todd trade optical activity and will bear 1 understanding that carbon was territory he'd role in understanding the origins of optical activity and only being able to measure whether light is rotated plane polarized light is rotated and how much it's rotated and melting away in formulas and you ask What are the structures of all Of the 8 Aldo Hecht's reform I should say Dyess Air America how the heck services because of course spontaneity immersed the 16 the Dyess dairy American Aldo Pinto and to Dyess Air America out of
10 processes and will just ask a simple question for the elderly processes Fisher extended this all the way up so let's look at what you can do fight when you take 1 Aldo Tedros you treated with Knight Ridder said In water needed 100 degrees Celsius you get an optically active I asked the Diana not draw the structure in just the 2nd it's called part character as they digested in which you oxidize the upper and lower position when you take the other Aldo territories at the you subjected to the same you get and how you get a guy acid that doesn't rotate plane polarized light that's optically inactive current
so let me go ahead and draw drawing using Fischer projections at the same time doubt Cundinamarca the the conditions are so let me right 2 structures here
however to Diana since some of but but but but but but but but but but but but but but but but but but but but which of these
molecules has a plane of symmetry the 1 on the right the plane of cemetery in Europe molecules that has stereo centers but has a plane of symmetry is a Musoke company optically and acid which you carbon sunny there and for
carbon diet acid into hydroxy is in the middle it's called Tariq dancers the structure on the right there is reason start tearing of the structure on the left is optically all right up there could be even give here for the 1 on the right the structure and the left lacks a plane of symmetry it's optically active right optically active for over a year and this particular molecule is called the Dieter Tarradellas said founding great the
structure that pastor was able to resolve a humorous from OK so now we have a logic problems gives you tons of logic problems I've tried to cut them back on the homework a little bit because I think the goal will not sign it this is the history of sugar chemistry they're giving you
all right so that means that the if the gives an optically active products the structure of the Arnaldo tapped Rose had to be there and so there is the 1 that was called the radio then in fisheries knew was this structure and the 1 that was called a red rose Fisher knew was this structure but but but but but but and that's pretty smart
are now I will show you the real world genius bootstrapping of Fisher will introduce 1 last reaction and that is the way that Fischer could bootstrap themselves to all of the Aldo heck Sosa's starting with very small molecule and so well introduced finally
is the Qiliania fishes sentences the textbook introduces the whole degradation the opposite now let you read about this but I want you to see the forest for the trees I'm so how do you bootstrap yourself about how you build up the sugars and events how do you go ahead and puzzle out all this area chemical questions of the Aldo Tetris is the Aldo penthouses and the although hacked Sosa's and ultimately how do you really answer was the stuff of life is made up so Fisher started with the glycerol the height and all the chemistry now you have factor of all a chemistry you need to get up all the way to the although Texas alone you won't be taken now the high nutrient with hydrogen cyanide we already learned what happened happens you former assign an overnight raid when you do so in a non stereo specific fashion no other words you get full-time area Mercer we form a carbon-carbon bond we've introduced a nite trail group now in large lots and lots of the chemistry of the nite trio group we learned that the nite trio group within the carboxyl like acid family we learned that under the right conditions you could with for example a quiz answers Hydro lies the nitro group To the carboxyl against group we also learn various conditions for reduction of nite trails and 1 of those conditions this catalytic hydrogenation itself on marriage and now that we go ahead and we carry out catalytic hydrogenation with hydrogen and palladium palladium was a catalyst but you can attenuate the reducing ability of palladium by poisoning it with a heavy metal you learn this in the reduction of Al kinds with little Laura catalysts palladium can be poisoned by metals like lead and barium heavy metals that reduce its ability to hydrogenated attenuated and so if we have palladium on barium sulfate and you do this in water you end up reducing the nite trail groups down
from the nite trails last carboxyl like acid oxidation state that was reactivation state to the AL the hideout oxidation state remember carboxyl like plus 3 it's the highest oxidation state you can go without getting to the carbon-dioxide oxidation state
so you reduce the triple bonds to a double bonds and you get come to your ?question mark here what will inherently Mbeya implicit question mark in the 2nd and so you go to stretch your way up 1 carbon to a restaurant and radios were 307 with roses and written on this black but but but but but but and so Fisher could start when 1 molecule at the time
he didn't know the absolute stereo chemistry but he could start with a molecule D glycerol the height and converted to a rift frozen 3 outs which he could then tell apart by by the optical rotation properties upon oxidation and he could bootstrap himself up to the Pinto's and so forth so the 1
question hear you probably have is wait a sec aware that nitrogen go well they primarily of the means and unstable and so in water under the conditions your text but shows acid that's fine too but I honestly in water they idolized the waters the Amin Hydro license to the elder hired and so but in so the sequence of sigh and a hybrid information followed by partial reduction through distracts you upper levels sorry but I think
this is where I would like to end up we have now had all of the basics of sugar chemistry of gets some more exposure through the homework will
finish off a final week talking about the chemistry of peptides and the chemistry of organic metallic reactions among just get a little taste of that chemistry from Chapter 28 inches 26


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