 Let's do this problem. It says Sean are three amino acids written in their condensed structures draw out the Lewis structures and identify if any are chiral Okay, so Remember what chiral means that means to rotate plane polarized light, but and When we're looking at structures What we're going to do to figure out if a molecule is chiral. We're going to be looking for specifically for you guys We're going to be looking for a carbon atom that has four different groups attached to it Okay, so if those groups are different in any way, then we'll say yes, they are different okay, so it's very difficult especially for Introductory organic students to look at these condensed structures and identify Whether a carbon has four different groups on so what I would recommend you do and just like the problem asks you to do is take These condensed structures and expand them to their Lewis structures. Okay, so let's do that first So this one we've got CH3 and that's bonded to C H and an NH2 Like that. Okay, you cool with doing that one. Okay, and remember this COOH That's a very common organic functional group. So get I'm used to how to draw it. It's C put the double bond oh Okay, and I'm just going to draw in the lone pairs just to remind you remind you all That that's where they go. Okay, is everybody are the two of you okay with this one? Okay, so let's try this one You see the COOH We'll start there. So now we're going to connect that remember Carbon has to make four bonds. Okay, so this carbon has two hydrogens attached to it It's attached to that COOH and has a that a mean group on it. Okay, so we've got C H H and and NH2 Like that. Okay Put the lone pair. So are you okay with that one? And again these condensed structures sometimes they look weird So you got to be kind of careful as to what you're drawing you want to remember like Carbon wants to make four bonds nitrogen wants to make three bonds Hydrogen wants to make one bond oxygen wants to make two bonds. Okay, and then let's draw this one out here So we'll start with that COOH again the carboxylic acid functionality that's attached to the CH Which is also attached to the NAH2 That CH Is attached to this CH2 here. Do you see that? Okay, so it is kind of weird for Introorganic students sometimes to do this so oh and then I'll just And if I wanted to I could expand these amine groups. In fact, let's do that since we've expanded everything else That really does show those Nitrogens making the three bonds if you were ever having any trouble seeing any more sense or does that look murky up the water Okay, so what did we say remember chiral means rotates plane polarized light but for when we're looking at the structures We're looking for carbons that have four different groups on them. Okay, so Here let's look at the carbon atoms. Well, there's only the two carbon atoms, right? The only one has four things bonded to it So the only one we really would be interested in looking at is this one and hopefully you can see right away That it's bonded to two hydrogen. So this molecule is not chiral. In fact, we would call it a chiral So let's go to this one over here Again the carboxylic acid carbon, you don't have to worry about okay We could look over here at this methyl carbon. Hopefully you see three hydrogens attached to it. Not we don't have to worry about it It's not a stereo center. Okay, but then we look at this middle carbon here, right? so in fact that is a stereo center and it makes this Molecule chiral. In fact, what we like to do is the label stereo centers with a little asterisk there This molecule is chiral, and I'm going to show you The four things that it's attached So This carbon is attached to a hydrogen. Okay, which of course is different than an NH2 right, is everybody okay with that and then both NH2 and Hydrogen are different than COOH Right, so that's three different groups and all three of those COOH H and NH2 are different than CH3 Okay, so it's the whole group. Okay, it doesn't matter that this is a carbon and this is a carbon Okay, so it's like a whole group. Yeah, I know that's what there was introductory students off Okay, so it's not just the next atom. It's attached to that whole thing. Okay, so let's try it here You tell me is this carbon stereo center? No, why not? Very good. Yes, it does have four bonds, but it has two hydrogens bonded to it, right? So it's not a stereo center. What about this carbon here? No, never. Carboxylic acid never. Okay, so whenever you got that double bond, you know It's not bonded to four different things, so it can't be. So the only one we'd be interested in is this one here, right? So is this this carbon bonded to the four different groups? Yeah, NH2 is different than H clearly which they're both different than COOH and All three of those are different than CH2OH. Is that okay? So we would label that as a stereo center there and we would say this is Any questions on this one? Who didn't make a difference like on that CH2OH if you put that one H on top and one at the bottom and the OH to the side? Doesn't matter. Yeah, it doesn't matter how you draw them as long as they're bonded To the same carbon, you know, then if there's two H's or something like that, you're never going to have a stereo center Okay, remember in those other problems when we were we built the Molecule and we showed we can rotate around the single bond so it doesn't matter which one of those hydrogen replace their equivalent Okay, any other questions on this one? Good job guys