In this video, we're going to focus on drawing structures within organic chemistry. Now, there's a few things that you need to know. So, let's go over elements like carbon, nitrogen, oxygen, and fluorine.
Carbon has four valence electrons, and as a result, it needs four more to get to eight, so carbon likes to form four bonds. Nitrogen has five valence electrons. It's in group 5A. of the periodic table, and so it needs 3 more electrons to get to 8, so nitrogen typically likes to form 3 bonds.
Oxygen has 6 valence electrons, it needs 2 more to get to 8, so it likes to form 2 bonds. Fluorine has 7 valence electrons, and it likes to form 1 bond. So the other halogens, like chlorine, bromine, iodine, they like to form 1 bond, typically. Elements like sulfur, selenium, usually like to form two bonds.
So you're going to see that trend throughout organic chemistry. Now carbon, it likes to form four bonds, so typically it looks like this. Nitrogen, which likes to form three bonds, usually has one lone pair, because it still needs eight electrons.
Oxygen, which likes to form two bonds, usually has two lone pairs. And fluorine, which likes to form one bond, Typically has three lump pairs now. Let's say if we want to draw the Lewis structure for Ch3 ch3 this is a condensed structure This is the same as ethane which can be written as C2 h6 C2 h6 is the molecular formula of f thing now we can see that the carbon atoms are connected to each other And hydrogen, hydrogen is in the first group of the periodic table, and it's also in the first row.
It has one valence electron, and because it's in the first row, it can only have up to two, which means that hydrogen only needs one bond to get the two electrons that it needs. So hydrogen will always form one bond. So we have three hydrogens on the first carbon, so we can put it around it, and we have three hydrogens on the second carbon, because it's a CH stream, and so this is how you can draw the Lewis structure for ething. As you can see, every carbon atom has four bonds, which is the usual case for carbon. Now, what about this one, CH2CH2?
How can you draw the Lewis structure for this particular compound? Feel free to pause the video and try it yourself. So, this is C2H4, which is an alkene. Alkenes have the general formula CnH2n, if it contains one...
One alkene functional group. So, we have the two carbon atoms in the middle, and there's two hydrogens. The first carbon atom has two hydrogens, and the second carbon atom also has two. But we know that carbon likes to form two bonds.
So what kind of bond do we have in the middle? Is it a single bond, double bond, or triple bond? We know it has to be a double bond because each carbon has two bonds, they need two more to get to eight. I mean... Two more to have four bonds, which equates to eight electrons.
Each bond represents two electrons. So this is ethene. It's an alkene that has one double bond. Alkenes are said to be unsaturated, because you can add hydrogen to it. Alkanes are saturated.
Now, what if you have the formula H-C-C-H? How would you draw the Lewis structure? So we have our two carbon atoms.
It is a hydrogen on each side. Now, so far each carbon atom has one bond. To get to four, it needs three more, which means that we need to put a triple bond in the middle. And that's how you can draw the structure.
This is an alkyne. Alkynes have triple bonds. Specifically, this is called ethine. When you think of ethane, ethane has two carbons.
Methane is 1, ethane is 2, propane has 3 carbons, butane has 4, pentane has 5, hexane has 6, heptane has 7, octane has 8, non-ethane has 9, decane has 10. So this is ethane. Now, the common name of this structure is called acetylene. It's very common in alkyne reactions.
Now what about this one? CH3CH2CH3. How can you draw the Lewis structure for this compound?
This is called propane because it has three carbons and it's an alkane. Now the first three carbons are attached to each other. The first carbon has three hydrogens.
The one in the middle is a CH2, it has two hydrogens. And the one at the end has three hydrogens. So that's the Lewis structure for propane. Now what about this one? CH3CHCH3CH2CH3.
So before we draw the Lewis structure, let's expand it. What this really means is that you have a CH3 and attached to the CH, there's a CH3 that comes off it. CH3 is always at the end.
It's never in the middle. CH2s, however, are in the middle. So notice that we have a CH3 at the end. So anytime you see a CH3, it's coming off something.
And the CH2 is always in the middle. And whenever you see a CH, it splits off into three directions. So now what we could do, we could expand it. Into a Lewis structure so we have a carbon carbon carbon carbon and another carbon and Just fill each carbon with hydrogens until every carbon has four bonds So that's how you can draw the Lewis structure For that compound Now what about converting it to a line structure?
So we had four carbons, and we had a methyl that came out. So this is the CH3, this is another CH3, and here's the CH3. In the middle, where it splits off into three directions, that's a CH.
And when it splits off into two directions, one, two, that's a CH2. let's try this example let's say if we have a ch3 ch2 times 4 and then a carbon with three CH trees so let's expand the condensed structure so what this means is that we have a CH3 and it's four CH2s and then we have a carbon which is connected to three CH3s. So I'm pretty sure you know how to draw the Lewis structure. So we're going to convert it to a line structure.
So the longest chain has seven carbon atoms. So this is 2, 3, 4, 5, 6, 7. Now this carbon is 2 CH3s. We have a methyl on top and a methyl on the bottom. So that's how you can convert it into a line structure.
Now, how can you draw the Lewis structure for CH3OCH3? This is called an ether. An ether has the general formula R-O-R.
So, let's start with the oxygen. The oxygen is attached to two carbons, and oxygen has two lone pairs on it. And then each carbon has three hydrogens. So that's how you draw the Lewis structure for dimethyl ether.
The reason why it's called dimethyl is because there's a methyl on both sides. There's two methyls. Di means two, tri means three, tetra means four.
So this is dimethyl ether. Now what about this one? CH3COCH3. How can we draw the Lewis structure for that compound? So this is a ketone.
ketones have a carbonyl functional group which looks like this is a double bond between a carbon and oxygen so the carbon in the middle has the carbonyl functional group and whenever oxygen has two bonds it's going to have two lump pairs and we have a CH3 on the right side and on the left side so there's three carbons instead of calling it propane it's called propanone the O and E this suffix is for ketone How about this one, CH3OH? So here we have an alcohol functional group. One carbon is methane, but this is called methanol. So we have the suffix"-ol", for an alcohol. So we have a carbon attached to an oxygen that is attached to a hydrogen.
The carbon has three hydrogens, it's a CH3, and the oxygen has two lumpers. So that's how you can draw the Lewis structure of an alcohol. Now what about this structure? Instead of seeing OH, what if you see HO?
How is it different? So this functional group is an aldehyde. Whenever you see CHO, it's an aldehyde. And it contains a carbonyl functional group, like the ketone. But the only difference is, the carbonyl group is at the end, as opposed to the middle of the structure.
So how can we draw the Lewis structure for this aldehyde? So we have two carbons. We know the last carbon has the carbonyl functional group. And the hydrogen is not at the end.
attached to the oxygen but it's attached to the carbon and then the other carbon has three hydrogens so to name it this is called ethanol with a suffix of a L for an aldehyde the common name is acetaldehyde Now what about this structure? CH3COOH. How can you draw the Lewis structure for this? So here we have a carboxylic acid functional group. To name the structure, there's two carbons, so instead of calling it ethane, it's going to be ethanoic acid.
That's the IUPAC name. The common name is acetic acid, which is found in vinegar. Now to draw it, there's two functional groups here. We have the carbonyl group, and we have the hydroxyl group, which is an OH group, which we can draw like this.
Both oxygens contain two lone pairs. And of course we have the CH3 on the left side. So that's how you can draw the Lewis structure for acetic acid.
What about this one? CH3COOCH3. So this is called an ester. So we have two carbons. The first carbon is a CH3.
The second carbon is attached to two oxygen atoms. And then the second oxygen has a CH3. So it looks like this. And each oxygen has two lone pairs.
So this is an ester. So this portion right here is the ester functional group. So how can we name this ester? So the left side, which includes the two carbons and the two oxygens, that is the acetate group. Also, it can be called the ethanoate part.
and this side here that's just metal so this is called when you combine it methyl ethanolate that's how you can name an ester Now what about CH3CH2NH2? How can we draw the Lewis structure? And what type of functional group do we have? So this is called an amine.
Whenever you see the functional group RNH2, this is an amine. So you can call it ethyl amine. Because on the left side, we have an ethyl group, which is two carbons.
So to draw the Lewis structure, we have a carbon attached to another carbon attached to a nitrogen atom. Now the first carbon has three hydrogens. The second carbon is a CH2, so it has two hydrogens. And the nitrogen also has two hydrogens.
But it also has a lone pair. Typically, when you see nitrogen, it usually has three bonds. And a single lone pair. But this is how you draw the Lewis structure for ethyl amine. Now, what about CH3, CO, and H2?
Feel free to pause the video and draw the Lewis structure. Whenever you see CONH2, this is an amide functional group. So the amide functional group has a carbonyl group, and it also has an amino group. So we have a carbon attached to another carbon that has the carbonyl group next to an NH2 group or an amino group.
The nitrogen has two hydrogens and one lone pair. The carbon on the left has three hydrogens. and so that's how you can drop the Lewis structure now to name it there's two carbon so instead of calling it a thing it's replaced to eat in a thing with a my so at the name What about this one CH3CN? Whenever you see a CN group, this is the functional group for a nitrile. And a nitrile has a triple bond between the carbon and the nitrogen atom.
So to draw it, let's start with a triple bond. Now since the nitrogen already has three bonds, we only need to add one lone pair to it. So since there's two carbons, it's called ethane nitrile. The common name is acetonitrile.
When you hear the word aceto or acetic, think of two carbons. So this is acetonitrile. Now what about this one? CH3CH2F.
So if you see a fluorine, bromine, chlorine, or iodine atom attached to a carbon, this is called an alkyl. halide. Now, keep in mind, whenever you have a halogen, it usually has one bond and three lone pairs, which we discussed earlier in this video. So, we're going to have two carbons attached to a fluorine. first carbon atom has three hydrogens and the second has two hydrogens and the fluorine which has one bond has three lone pairs and that's how you can draw the Lewis structure for this aqua halide so the common name is ethyl fluoride the IUPAC name is fluoroethane we really can't say one fluorothane because it can only be on one of the carbon you can't draw two flow I think it's not possible whichever carbon the flooring is going to be on it's going to be carbon one so this is just floral ethane now let's say if we have the name three Ethel dash 24 dash dimethyl hexane.
How can we draw the line structure for this compound? So the first thing we should do is draw the parent name. Hexane means that we have six cartons. Two, three, four, On a carbon 3, we have an ethyl group which represents two carbons, and we have a methyl on 2 and another methyl on 4. So that's how we can draw the line structure of the carbon. three ethyl two four dimethyl hexane by the way how many primary hydrogens do we have and how many secondary hydrogens and tertiary hydrogens how can you figure that out so To answer a question like that, you need to be able to determine which carbon atoms are primary, which ones are secondary, and which ones are tertiary.
The carbons at the end, which are the CH3s, those are primary carbons because they're only attached to one other carbon atom. So these are all primary carbons. The carbon atoms that split off into three directions are tertiary carbons.
So this carbon is tertiary because it's attached to three other carbon atoms. So here we have another tertiary carbon and this one is tertiary. Now this carbon atom is secondary because it's attached to two other carbon atoms.
So this one is also secondary. So if you want to find out how many primary hydrogens there are, you can count it. A primary carbon has three hydrogens attached to it.
It's a CH3. So because we have five primary carbons, and each of them has three primary hydrogens, five times three is 15, so there's 15 primary hydrogens. Now, the secondary hydrogens, they're associated with the CH2s.
So as you can see, because the secondary carbons are attached to two other carbon atoms, for them to have four bonds, they must be attached to two hydrogen atoms. That's why it's a CH2. And since we have two secondary carbons, each with two hydrogens, we have four secondary hydrogens.
Now, a tertiary carbon, which already has three bonds to carbon atoms, it only has one hydrogen. So, since we have three tertiary carbons, we have three tertiary hydrogens. So, let's try another example. How would you draw the line structure of 2, 2, 3, 3? Tetramethyl.
pentane. So like the other one, this one is not bad. We can start with the parent chain which pentane has five carbons, two, three, four, five.
We have two methyls on carbon 2 and two methyls on carbon 3. So you can also draw it this way. So that's it for that example. Now let's say if we have three isopropyl dash for sec butyl octane so it's draw octane we have a carbons two three four five six seven eight now on three we have an isopropyl group and isopropyl group looks like this and on four we have a sec butyl group which looks like this And that's how you can draw it.
So you need to be familiar with certain substituents. So this might be a good time to review it. So this is a propyl group.
It has three carbons. An isopropyl group, it splits off into two directions. So you usually end with two CH3s.
That's an isopropyl group. We still have a total of three carbons outside of the parent chain. Isobutyl looks like this.
One, two, three, four. It splits off into two directions. Isopentyl looks like this.
One, two, three, and then four, five. Secbutyl, that's normal butyl is just four carbons. that's butyl.
The sec butyl, you're going to attach it to the secondary carbon. This carbon is secondary before you connect it. Once you connect it, it's now tertiary. But if you don't count this attachment, you're attaching it to the secondary carbon, so it's called sec butyl.
This is a tert-butyl group. Before you connect it, this carbon is tertiary. So this structure is the tert-butyl group. So make sure you're familiar with those common names now how would you draw the Lewis structure of two pentime so if you see why any it's an alkyne so tense that's five carbons and on a carbon two which really is between two and three you can have a triple bond so that's how you can draw two pentime now what about 2-bromo-3-chloro, let's say, heptane.
How can we draw the structure for this one? So, heptane has 7 carbons, 2, 3, 4, 5, 6, 7. We have a bromine on carbon 2, a chlorine on 3, and that's it for this one. Now what about 3-chloro-2-methyl-1-hexene? So feel free to pause the video and try this example.
So let's start with the hexene part. Hexane has six carbons, but hexene, we have an alkene, that means we have a double bond. And it's on a carbon one, which means it's between...
one and two on carbon-3 we have chlorine and on a carbon-2 we have a methyl and so this is the Lewis structure for three chloral two methyl one hexene so what if we wanted to draw trans 3-hexene and cis-3-hexene. How would you do it? So let's start with hexene, which has 6 carbons. The double bond is between 3 and 4. This is trans because the hydrogens are opposite to each other. To draw the cis version, you want to draw it like this.
So now the hydrogens are on the same side. So that's how you can draw cis and trans 3-hexene. Now, what if you want to draw cis and trans? Let's say 1,2-dimethylcyclohexane. How would you do it?
So, cyclohexane is a ring with six cards. So it looks like this. That's cyclohexane.
And the two methyl groups can be cis or trans with respect to each other. So for it to be cis, they need to be on the same side. On the wedge or on the dash.
So, because they're both on the wedge, this is the cis isomer. To draw the trans isomer, one is going to be on the wedge, and the other is going to be on the dash. So this is on the wedge, this is on the dash. If it's on the wedge, it means that it's coming out of the page towards you.
It's in the front. And if it's on a dash, it's going into the page, or it's behind the page. So it's moving away from you.
So this is the trans isomer. And this is the cis. now what about this one let's say if you have two amino dash three a foxy dash for hydroxy dash five methoxy dash 6 oxo and then have to know it acid how would you draw the structure now the reason why I wrote out this long name is so you can be familiar with the substituents amino ethoxy hydroxy methoxy and oxo so have to know gas it tells us that we have a carboxylic acid function group and heptane is associated with seven carbons so this is going to be two three four five six seven so on the first carbon which won't make it the carbon on the right this is the carbosilic acid. The carbosilic acid has the highest priority out of all the groups listed, so therefore that means that this is carbon 1. And so carbon 2 is the next carbon.
We have an amino group on carbon 2. An amino group is simply an NH2 group. On carbon 3 we have an ethoxy group, which is an ether but with an ethyl. So we're going to have an oxygen attached to an ethyl, so it's OCH2CH3. that's an ethoxy group. A hydroxy group is basically just an OH.
That's on carbon 4. And on carbon 5, we have a methoxy group. So instead of being OCH2CH3, it's simply OCH3, because CH3 is methyl, and CH2CH3 is ethyl. So ethoxy versus methoxy.
Hopefully, you see the difference there. And on 6, we have an oxo group, which is a ketone. It could be an aldehyde too. So that's an oxo group.
And so that's how you can draw the structure. So now you know what an oxo group is, what a hydroxy group is, an amino group, a methoxy group that's an O with a methyl, and ethoxy that's an O with an ethyl group. So that concludes this video.
Thanks for watching. watching and have a great day.