hello everyone Victor is here and in this video I want to talk about the enantiomers and diastereomers an important thing to remember is that a nine tumors and diastereomers are the only stereochemical relationships between the stereoisomers if two molecules have the same molecular formula and the same connectivity between the atoms they are either and nine tumors diastereomers or they are the same molecule so don't say that the relationship is trans it's not a relationship neither is RS or easy those are the descriptions or properties of individual molecules the relationship is either enantiomers or diastereomers so without any further Ado enantiomers by definition the enantiomers are the two molecules that are mere reflections of each other and are non-superimposable in space so if I have two molecules like let's say molecule A and B over here those two molecules are are both mirror images of each other and their non-superimposable in space which means that no matter how much I rotate one of the molecules in space I will never be able to make it look exactly like the other one on the other hand the diastereomers they're going to be neither mere reflections of each other nor they're going to be superimposable in space which means that if I look at my molecules let's say C and D over here those two molecules they are not mere images of each other and they are not superimposable in space again no matter how many times I rotate one of those molecules I will never be able to make one into another one via simple rotations in space and one other thing that I want to point out is that when you have a pair of anonymous and you have the chiral atoms on those so all R and S stereo descriptors they will change between the molecules so like in my molecule a I have the stereo descriptors s and or for the corresponding atoms they become R and S for the mere reflection in the case of the diastereomers I have S and R for my molecule on the left as well however in the case of the diastereomers only sum of the r and asteroid descriptors are going to change so in this case the stereo descriptor by the oh group the s Theory descriptor State as is however my stereo descriptor at the carbon next to bromine did change so you can use that as a useful trick when you are determining whether your molecules are enantiomers or diastereomers by looking at the stereo configuration of the chiral atoms and assigning the stereo descriptors if all of your descriptors flipped that most likely you're going to have a pair of enantiomers if only some of those flipped then most likely you are going to have a pair of diastereomers so I've been talking about the mirror images over and over again here but what exactly are the mirror images and how we are going to make those mirror images so let's say I have a molecule that looks like this I have a five-membered ring and I have a bromine atom sitting on one of my carbons if I'm going to make a mirror image of this molecule there are three different ways how I can do that so one way is going to be by making a plane of mirror my vertical line if I reflect the molecule over that line I'm going to reflect it exactly like a wings of a butterfly or like an ink blood between the two pieces of paper so what that means that my green reflection over here is going to look like this now bromine is still on the watch but now bromine is on the left side I can also have a mirror plane being the horizontal line if I have that as my mirror plane then what I'm going to end up with as a mere reflection is again flipping the molecule over that line so I will have the double bond on top then the rest of my molecule and bromine is still on the right side like this on top of that I can also have the paper itself being my mirror so if paper itself is a mirror then essentially it will look like two molecules are standing in front of each other so in this case I will end up with a molecule where my wedged Line is now a dashed line like that so you can use that as a very quick trick by essentially taking all of your dashes making them into wedges taking all the wedges and making them into dashes or you can use one of the other mirroring techniques that I have just demonstrated let's do one more example I now have a molecule an open chain molecule and I have a bromine atom over here and I have an oh group in the middle like this so again if my plane of mirror is the vertical line like this then what I'm going to see in my mirror is now bromine is going to be on the left side the oh is still going to be in the middle if my plane of mirror is the horizontal line then what I'm going to see is the folding the bromine is now looking down and it is still on the wedge the oh is looking kind of up and it is still on the dash and if my plane of mirror is the page itself then I'm essentially going to be drawing the same skeleton but all of my dashes and wedges are going to be flipped so bromine is now looking away from me and oh is looking at me like that we can also confirm that we did the correct me Reflection by taking the RNA stereo descriptor and assigning those are unnecessary descriptors to our atoms so the chiral atom that I have in my first molecule that one is going to have the r stereo configuration while the chiral carbon in my green mirror reflection that one is going to have the s Theory configuration the blue molecule will have the s Theory configuration and the light purple molecule that one is also going to have the S stereo configuration and we remember that whenever we make a mirror image all of our RNs stereo configurations flip same deal I'm going to have in my other example the carbon with bromine in my original molecule has the s Theory configuration however in my green reflection that one is r in my blue reflection that is also R and in my purple reflection that is also R the oxygen or the carbon next to oxygen in my original molecule is going to be R in my green reflection that's now going to be s in my blue reflection that is going to be S and in my purple reflection that is also going to be S and of course I do employ you to check that work on your own and copy those molecules assign your RNs Theory descriptors just like we've talked about in one of my previous videos and check that for yourself don't just trust my word on that now what is the difference between the reflections and rotations in space when I'm doing the rotations in space I am not actually creating a new molecule I am just taking the old molecule and I'm rotating it at space let me demonstrate so I'm going to use exactly the same molecule as I had in the previous example so I will redraw it on my right side so you can see all the differences between my Reflections and rotations so I have my bromine atom and the stereo configuration of my Carol Autumn is still R over here so just like with Reflections there are three different rotations that we can do rotation number one is going to be taking my molecule and rotating it in the plane of paper so essentially as if you just took your screen and rotated it in space like a steering wheel of a car well in this case I'm going to end up with a molecule that looks like this and I have my bromine now over here on the left side to double check that I accidentally didn't make any reflection I can assign my stereo descriptor to my chiral atom and here if I do all the steps and I do it correctly I'm going to end up with the r stereo configuration as well alright well that was one rotation in space how about I do rotation in space along the horizontal plane like that so essentially it's as if I'm piercing my molecule with the long stick and rotating it along this long stick like I'm barbecuing my molecule in this case I'm going to end up with the molecule that looks like this bromine is still on the right side it is on the dash now and again if I were to assign my stereo descriptor to this atom it is going to be the r stereo descriptor as well and lastly one other type of rotation that we can have is when we are taking our molecule and we are rotating it along the vertical axis like that I like to call this rotation Single Ladies you know just like the dance so if I do the Single Ladies then what I'm going to end up with is a molecule that looks like this with my bromine on the left side and it's also going to be on the dash if I were to assign this Theory descriptor to this chiral atom again that is going to be the r stereo descriptor so these are going to be my rotations in space so these two operations Reflections and rotations are going to be probably the two most important type of operations that you are going to be doing with your molecules especially when you are trying to compare those molecules and you are trying to distinguish between the nine tumors there are stereomers same molecules Etc so practice your Reflections and rotations and use the RNs Theory descriptor as a useful trick to double check your work and here is a very common misconception and the misconception is that N9 tumors and diastereomers they need to have chiral atoms no that is not true the definition of a non-tumerism diastereomers only specifies the three-dimensional relationship between the molecules and it does not specify any of those molecules having chiral atoms the definition of anonymous is that they need to be non superimposable mirror images while the definition of diastereomers they are non-superimposable non-mirror images so anything that fits that definition will be the corresponding pair let me give you an example so let's say I have two cyclohexanes and those are substituted at the top position with for instance a bromine and the oh position with let's say an oh group so this is going to be my first molecule I'm going to call it molecule a the other one is going to have the substituents also at the top with Brahmin looking at me and oh at the bottom looking at me as well I'm going to call that molecule B so when it comes to the relationship between our molecules A and B well they are not mirror images are they superimposable in space upon close inspection we can see that they are not superimposable in space either so by definition that means that these two molecules are diastereomers however do we have any chiral carbons here absolutely not if you think that this carbon with the bromine might be chiral well it is not because the right and the left side of my molecules are the same same thing with the carbon within oh that carbon has the left and the right side of the molecule the same so it doesn't have four different substitutions that means that we do not have any chiral atoms in these molecules yet they are non-superimposable non-mirror images which by definition makes them diastereomers likewise people think that while an iron tumors they gotta be chiral so if the molecular spiral It's gotta have the chiral atoms in it right well actually no here is a classic example of aleins molecules with two double bonds coming from the same carbon in this case these two molecules they are mirror images and their non-superimposable in space so by definition they are enantiomers but do they have chiral carbons no they do not in order to be a chiral carbon needs to have four different substitutions and we do not have a single carbon in this molecule with four different groups around that so remember molecules don't need to have chiral atoms in order to be chiral likewise molecules don't have to have chiral atoms to have enantiomers or diastereomers the definition is the key here always go with the definition rather than the shortcut or the common example that you might have seen in your class because those common examples don't necessarily describe every single possibility that you are going to have within the scope of your course and by now you are probably rolling your eyes at me and thinking and non-tumerous diastereomers who cares well nature does so here is the deal and nine tumors are physically and chemically indistinguishable in a non-chiral environment and non-carolina environment is such an environment in which all other molecules are a chiral or non-chiral so for instance if you have an aqueous solution let's say just a glass of water that would be a non-chiral environment so in this non-charallel environment and nine tumors have same physical properties like melting point and boiling point and same reactivity however as soon as you put an enantiomerically pure molecule into a chiral environment like let's say your body our bodies are perfect example of chiral environment everything in our body cares very much about the stereochemistry so inside of our bodies different and tumors can have very different chemical properties and can have very different reactivity so if you want a good bad time Horror Story look up the history of thalidamide one in nine tumor of thalidamide is a drug that will alleviate the nausea headaches and a whole bunch of other very unpleasant Sensations while the other a non tumor is actually a very powerful mutagen and causes horrific birth defects just don't look it up while you're eating now when it comes to diastereomers they have different physical and often chemical properties regardless of the environment they're in this means that diastereomers can be easily separated using physical separation techniques such as chromatography distillation or crystallization technique the only physical property that will distinguish two and non-tumors is their Optical activity Optical activity is the property of the chiral molecule to twist the plane of polarized light either through the right or to the left so this is how we can experimentally study those molecules but other than that in a chiral environments and non tumors are the same diastereomers are pretty much always going to be different also many reactions in chemistry either going to produce stereochemistry or destroy stereochemistry so we always need to keep a very keen eye on what's going to happen with our molecule and if the molecule all of a sudden obtains stereochemistry if it does we'll have to pay attention to that and indicated in our products as well well that's about it I have about the enantiomers and diastereomers thank you for watching this video till the very end if you want practice questions on the stereochemical relationships to determine whether things are enantiomers or diastereomers or want to learn about any other topics in organic chemistry go check out organicchemistry tutor.com hit the like button if you found this video helpful drop your questions and feedback in the comments below and I'll see you next time