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Current time:0:00Total duration:9:30

Video transcript

we've already seen in an earlier video that enantiomers are stereoisomers that are non-superimposable mirror images of each other so let's say we want to draw the enantiomer of this compound on the left one way to do it would be to reflect this compound in the mirror and if you look at this carbon skeleton here we have our carbon skeleton with our OAH group coming out at us in space that's this model on the left there's our carbon skeleton with our OAH coming out at us in space if we reflect this compound in the mirror we'll see the enantiomer in the mirror our mirror image on the right is non superimposable upon our model on the left so let's just draw what we see we see our carbon skeleton like this all right so let's draw that so there is our carbon skeleton and our O H group is coming out at us in space so we could represent that with a wedge so let's fill in our wedge here and let's draw our OAH and so this drawing on the right is the enantiomer to the drawing on the left there's another way to represent the enantiomer on the right and to do that let's check out the video so in the video I imagined an axis going through this carbon and then I rotate about this axis to give us another viewpoint of our and other enantiomer so here's a model of our enantiomer and you can see our carbon skeleton with our Oh H coming out at us attached to this carbon and then a hydrogen going away from us in space if we imagine rotating about an axis through this carbon so let's go ahead and do that we'll see another way to look at the enantiomer so now we have for our carbon skeleton you can see our carbon skeleton looks like this now and then at this carbon we have the O H going away from us in space and the hydrogen's coming out at us so here we have some pictures from the video to help us with our drawings we can see that this picture is this compound if you look at that carbon skeleton and you can see the O H coming out at us in space so in the video we took this compound and we rotated it to give us this image on the right so these are just two images of the same compound and this gives us another way to draw our enantiomer this time our carbon skeleton is going like that so let me go ahead and draw in our carbon skeleton and our Oh H group is going away from us in space so we have to put in the O H group with a dash like that so these two drawings represent the same compound the enantiomer that we were trying to draw so there are two main ways to draw enantiomers at least two ways that I like to use the first way is to reflect the compound in a mirror that's we did first we took we took this compound and we reflected it in the mirror and we drew what we saw and that gave us this drawing of the enantiomer we've seen that this drawing on the right is the same thing as this drawing on the left here and notice the difference between this drawing and our original compound the carbon skeletons are the same if you look at these two the only difference is we change the wedge to a dash so that's another very convenient way to draw an enantiomer if you're starting with a wedge change it to a dash if you're starting with a dash change it to a wedge now let's draw the enantiomer of this compound and the first method will use is the mirror method so here's a simplified representation of our compound so ignoring things like confirmations of our ring at this carbon our bromine is going down in space so that's this carbon so you can see the bromine is going down and then at this carbon bromine is going up in space that's this carbon with our bromine going up in the mirror we can see the mirror image or the enantiomer so let's go ahead and draw our enantiomer here so we draw our cyclohexane ring and then at this carbon we have our bromine going it down in space so let's go ahead and put in our bromine going down and then at this carbon we have our bromine going up in space so that's a wedge so we draw in our bromine here let me fill in this wedge and let's put in the bromine so this on the right is the enantiomer and sometimes you don't have model sets or a mirror but you can draw the mirror image by just using this drawing on the left you can imagine a mirror right here and just as you see up here this bromine is reflected in the mirror this bromine is reflected in the mirror right so these two these bro means are reflecting each other and then this carbon is opposite of this carbon so that's this carbon and this one and then this carbon is as opposite of this one so this carbon is opposite of that one so just a few tricks to help you draw the mirror image so there's another way to represent our enantiomer on the right and let's go to the video to see the other way so here we have our two enantiomers so you can see there are mirror images of each other I rotate the enantiomer on the right you can see it from a different viewpoint notice that both chiral centers have been inverted and just to prove that these are enantiomers of each other let's try to superimpose one on top of the other notice how you can't do it so these are non-superimposable mirror images of each other so this picture on the right in the video shows you the relationship between our two and nanti immers so thinking about reflecting the molecule on the left and the mirror we can see the enantiomer on the right but we took this molecule on the right this enantiomer and I rotated it into this position so now let's draw the enantiomer from this perspective we start out with our cyclohexane ring and you can see if this carbon our bromine is going down in space so that must be a - so there's my bromine and then at this carbon our bromine is coming up in space coming out at us so that's a wedge so let me go ahead and draw in our wedge and we'll put in our bromine so this is just another way to represent our enantiomer so on the right so this drawing and this drawing are two different ways to represent the same molecule so this is the enantiomer to the compound on the left so let's look at our original compound and compare this drawing on the right notice that this carbon your bromine is coming out at you in space whereas it this carbon your bromine is going away from you in space at this carbon your bromine is going away from you in space and at this carbon your bromine is coming out at you in space so to draw our enantiomer we just invert all chirality centers so if you have a wedge change it to a - if you - change it to a wedge so this way is often easier so just make sure to invert all your chiral centers to draw the enantiomer for by cyclic compounds it's easiest to use the mirror method so if our goal is to draw the enantiomer of this compound we can imagine a mirror right here and we can use this picture above as a guide you can see that the hydrogen is reflected in the mirror and the chlorine is reflected in the mirror so let's go ahead and draw those in so we draw our hydrogen here and then our bond going down to this carbon and then a chlorine going straight down from here so notice how this hydrogen is reflected in this chlorine is reflected next let's think about let's think about reflecting this carbon so we need to draw a line in this way right here so now this carbon is reflected with that one let me highlight those carbons so right here I'm going to extend this line out a little bit so we can see we can see where the horizontal is approximately like that so that's this carbon in this carbon right so that carbon is reflected in our mirror next let's draw a line up in space relative to that horizontal like that and that takes us to this carbon which is reflecting this one in our mirror now let's worry about this one so this should go up in space so let me draw a horizontal line down here just to help us with our drawing so approximately horizontal at this point we know we want to go up in space from this point so let's do that so that's this line so this carbon is reflecting this carbon next let's go ahead and reflect our top carbon here so let's draw this line over to here so you could think about this top carbon alright reflecting that one so let's draw let's draw our lines over here so from here and then back down to here so this is more of a drawing exercise really and then we're going to go down a little bit we'll leave leave that line broken so we can see that one's going behind and then we'll draw this to the carbon in the back and then we know with the draw down from this line to the carbon in the and then we can connect those lines so finally we've drawn our enantiomer so on the right is the enantiomer to the compound on the left and just to prove that this on the right is the enantiomer let's look at a video where I try to superimpose the mirror image on the original compound here we have our two enantiomers so the mirror images of each other that are non-superimposable just to prove they're non superimposable I'll rotate the enantiomer on the right and try to superimpose it on the one on the left and you can see that they don't match up so these are enantiomers