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Three-dimensional bond-line structures

Video transcript

and the video on bond line structures we start with this Lewis dot structure on the left and I showed you how to turn this Lewis dot structure into a bond line structure so here's the bond line structure that we drew in that video bond line structures contain the same information as a Lewis dot structure but it's obviously much easier much faster to draw the bond line structure on the right than the full Lewis dot structure on the Left what about three dimensional bond line structures so how could you represent this molecule in three dimensions using a flat sheet of paper well on the left here is a picture where I made a model of this molecule and this is going to help us draw this molecule in three dimensions so we have a flat sheet of paper how could we represent this picture on our flat sheet of paper let's start with the carbon in the center so that's our carbon in magenta so that's this one on our Lewis dot structure this one on our bond line structure well the carbon in magenta is sp3 hybridized right this is sp3 hybridized so we would expect tetrahedral geometry around that carbon and if you look at that carbon on the picture here you can see that this bond and this bond are in the same plane so if you had a flat sheet of paper you could say those bonds are in the same plane so a line a line represents a bond in the plane of the paper let me go ahead and draw that so this is the carbon in magenta and then we have these two bonds here and the the those bonds are in the plane of the paper next let's look at what else is connected to the carbon in magenta well obviously there is an OHA let me go ahead and circle that so there's an O H we can see there's an O H here and then the O H the o H on our picture is coming out at us in space so hopefully you can visualize that this bond in here is coming towards you in space which is why this oxygen this red oxygen atom looks so big so this is coming towards you we would represent that with a wedge so let me go ahead and draw a wedge in here and a wedge means that the bond is in front of your paper so this means the O H is coming out at you and so let me draw in the O H like that now let's look at what else is connected to that carbon in magenta we know there's a hydrogen right we didn't draw it over here but we know there's a hydrogen connected to that carbon and we can see that this hydrogen this hydrogen right here let me go in switch colors this hydrogen is going away from us in space right so this bond is going away from us in space or into or into the paper or the bond is behind the paper and we represent that with a dash so I'm going to draw a dash here showing that this hydrogen is going away from us so we're imagining we're imagining our flat sheet of paper and the O H coming out at us and that hydrogen going away from us alright next let's look at the carbon on the left here so this carbon in blue so that's this carbon and I'll say that's this carbon over here on the left so we know that this carbon we can see that this bond and this bond are in the same plane alright so let's go ahead and draw in let's go ahead and draw in the carbon so the carbon that I just put in is the carbon in blue and this hydrogen over here on the Left right this bond is in the same planes I'm going to draw a line right representing the bond is in the plane of the paper and so we have a hydrogen right here what about the other two hydrogen's well let me highlight those so this hydrogen hopefully you can see that this is coming out at us in space so we represent that with a wedge so we draw a wedge right here and then we draw in the hydrogen so the bond is in front of the paper the bond is coming towards us in space and then there's another hydrogen bonded to the carbon in blue and my thumb here is blocking a little bit but hopefully you can see that's going away from us in space all right so this hydrogen is going away from us in space so the carbon in blue it is also sp3 hybridized right this carbon is sp3 hybrids would expect tetrahedral geometry around that carbon and then finally let's look at the the last carbon so this carbon right here in red so that's this one right here and this one right here this carbon is also sp3 hybridized so we expect tetrahedral geometry and if we look at this carbon use let me use yellow again this bond and this bond are in the same plane so let's draw in the carbon in red and we can draw in the hydrogen right here in the same plane and then let's let's visualize the other two hydrogen's all right so this hydrogen is coming out at us in space so we represent that with a wedge like that so we have a hydrogen coming out at us in space and this other hydrogen here is going away from us in space it looks a little bit smaller so that's a dash right here all right so we've drawn everything out and notice when you have a tetrahedral carbon sp3 hybridized carbon you have this pattern you have this pattern of two bonds in the plane of the paper and one wedge and one dash so that's how we're representing our tetrahedral geometry around those carbons around those sp3 hybridized carbons alright it's it's usually usually you don't see the hydrogen's drawn in on one of these so we could simplify our three dimensional bond line structure even more we could just say we're going to say we have an OHA out at us in space so I draw a wedge right here alright and you could draw it like that and which is implied that there's a hydrogen going away from you so if you draw an OHA out at you that implies that there is a hydrogen going away from you in space so three dimensional bond line structures are an important skill to be able to visualize for this molecule it's not so important that the O H is coming out at us it's just that's just how I drew it here because that's what it looks like in the picture but later in organic chemistry it's very important to understand what's coming out at you in space what's going away from you what's what does the molecule look like in three dimensions and bond line structures three dimensional bond line structures allow us to visualize that model sets help so you should definitely purchase a model set I'm at this point in your study of organic chemistry because it's going to help you a lot later in the course on the left is the Lewis dot structure for acetone and we could turn that into a bond line structure really quickly so here is the bond line structure for acetone I could put in lone pairs of electrons on the genore I could leave them off I'll just go ahead and put those lone pairs in there like that what would be a three dimensional bond line structure for acetone well on the left here is a model of the acetone molecule and hopefully you can see that these atoms right here these atoms are all in the same plane of the page and so is oxygen actually so so is this oxygen here that's a little bit easier to see in the picture on the right so in the picture on the right so these are the atoms that we were just talking about so these are all in the same plane so if you can hopefully you can visualize like a sheet of paper so let me see if I can sketch in a sheet of paper right here like this and so all of those atoms all those atoms are in the same plane of that paper so we could draw that in like this we could have our carbons over here like that are three carbons and according to this picture these two hydrogen's here so if we're trying to copy this picture those two hydrogen's are in the plane of the page and so is this oxygen so this oxygen right here is in the plane of the page so we'll draw it in there like that I'll go ahead and put in lone pairs of electrons on the oxygen all right let's focus in on the carbon in the center for right now I'm not done with my three dimensional bond line structure I just want to point something out right here so this carbon right here in magenta right is this carbon which is this one just it's hiding it's hiding back here but we know that carbon is sp2 hybridized so we would expect trigonal planar geometry around that carbon so trigonal planar right we would expect everything to be planar so the atoms connected to the carbon in magenta we would expect those to have be in the same plane and a little bit easier to see that on the right here so these carbons and these carbons in this oxygen alright those are all in the same plane we have sp2 hybridization alright let's now look at the other carbons so let's do let's do blue here so carbon on the Left right here I'm saying that's this one this carbon is sp3 hybridized right sp3 hybridized which means tetrahedral geometry we would expect tetrahedral geometry around that carbon and so we have these two bonds in the plane of the page right and then this hydrogen is coming out at us in space and then this other hydrogen back here is going away from us in space so on our three dimensional bond line structure we could draw we could draw a hydrogen coming out at us in space right so that's a wedge and then hydrogen going away from us in space so that would be a dash and then the carbon on the right which I'll make I'll make red this is also sp3 hybridized so we would expect tetrahedral geometry and we can see this bond is in the plane this bond is in the plane of the page and this hydrogen is coming out at us and then this one's going away from us so we could complete our three dimensional bond line structure over here on the right by showing a hydrogen coming out at us and a hydrogen going away from us in space all right if we look at this picture on the right again and we have we've already visualize our flat sheet of paper imagine your eye is right here imagine your eye is looking down on your flat sheet of paper so your eye would see I would see let me use dark blue for this these these two hydrogen's coming out at you in space right so that's these two hydrogen's coming out at you so hopefully this just helps you visualize it a little bit better and then your eye would see these two hydrogen's these be behind the plane of the paper right so it's going away from you in space so the hydrogen's in green would be going away from you so we represent that with a dash so hopefully that helps you visualize it a little bit better here now for acetone you normally wouldn't draw out a three dimensional bond line structure and there's not much of a point to drawing the structure on the right I just did it to help you visualize things a little bit better and to contrast an sp2 hybridized carbon with an sp3 hybridized carbon to think about what it looks like in three dimensions so pretty much for something like acetone you're going to stick with the the bond line structure right here and not make it three-dimensional but I think it is important to think about these things and to make these molecules build them yourself visualize it and understand this concept before you move on to other parts of organic chemistry