Draw the structures of (a) ethylamine and (b) trimethylamine. Use dashed lines to show how they would form hydrogen bonds to water molecules.

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Hello, everyone. Welcome back. Our next problem says, provide the structures of Roman numeral one, butyl amine and Roman numeral two truty amine and show how each would form hydrogen bonds with water. Use dashed lines to represent hydrogen bonds. So let's start with our two structures here. Balamine, we have an NH two with a four carbon. We got beutel as our prefix. So a four carbon chain on it. So let's draw 1234 carbons and then a bond to NH two. We're going to be looking at hydrogen bonding. So I'm going to draw the lines to my hydrogen atoms so that I can separate them and see where they'd be in space. And then of course, don't forget that nitrogen having five valence electrons has a lone pair on it. Then our other structure is tribunal. I mean, well, when we have this try tells us there's three beetle chains, 34 carbon chains, there's, that means there's three bonds to the nitrogen. So no hydrogens at all. We just have a nitrogen with the A 123, four carbon chain and we've got three of them. But again, nitrogen has three carbon chains, but will still have that lone pair. So let's look at our one balamine and see how it would form hydrogen bonds with water. Well, we see our hydrogens right away and they're bound to an electron atom. So the hydrogens bonded to the carbons, of course, wouldn't participate in hydrogen bonding. But nitrogen, especially with a lone pair is quite electron. It has its partial negative charge while our hydrogens have partial positive charges. So I'm just putting a little delta plus by the hydrogens delta minus by the ni nitrogen. And so we can draw some water molecules surrounding this, the hydrogens on the water molecule with their partial positive charge will bond with the lone pair on the nitrogen. While the lone pairs on the oxygen atom of water, we'll make hydrogen bonds with the hydrogens on our nitrogen. So I've drawn little red dotted lines between the one of the hydrogens on a water molecule to the nitrogen. And for two different water molecules from the oxygen on the water molecule to the two hydrogens on our nitrogen. So it's pretty easy to tell on our primary amine here, which is what the one beetle amine is, how it will hydrogen bond. But what about the tri beetle amine? What about our tertiary amine? We have no hydrogen atoms bonded to the nitrogen here. So we might be tempted to think that there's no hydrogen bonding possible, but we do have a lone pair on an electron atom. In this case, we have that low pair on the nitrogen. So this is still capable of hydrogen bonding with water because the lone pair on that nitrogen can form hydrogen bonds with the hydrogens on the water molecule. So as you can see, it won't form as many hydrogen bonds, but it will still hydrogen bond due to the lone pair on the nitrogen. See you in the next video.

Draw the structures of (a) ethylamine and (b) trimethylamine. Use dashed lines to show how they would form hydrogen bonds to water molecules.

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Key Concepts

Hydrogen Bonding

Molecular Structure

Polarity