>> Hello and welcome to the Penguin Prof channel.
Today's episode is by popular demand decoding basic chemical
structures, feel the power.
So if you're a biology student chances are you have a textbook
with pages that look like this where they give you these images
that they think are helpful to you
but most biology books don't actually explain what these
little hexagons mean so it leaves students very confused
and wondering what the heck is that supposed to be and how is
that supposed to help me.
By the end of this video believe it or not you are going
to be able to write the chemical formula for the structure.
Don't panic, I'm going to bring out the hula penguin.
So you need to recall bonding rules
and if you don't recall them or you've never been exposed
to them please check out my video on atomic bonds,
my chemistry basics part two video.
I will post that link in the description bar below.
In that video you're going to see this slide
which is really key and it shows you
that the column number tells you how many valence electrons any
given element has and that's going to be the key
to understanding how many bonds any element wants
in order to be stable.
So the bonding rules are really simple because if you look
at the column numbers you'll see that for hydrogen,
hydrogen has one valence electron but would
like to have two so hydrogen is going to want
to form one covalent bond.
Carbon on the other hand has four valence electrons,
would like to have eight, so carbon is going to be stable
with four covalent bonds going to it.
That's going to make carbon happy.
Nitrogen right next door has five valence electrons,
would like to have eight, so nitrogen needs three more bonds
in order to be stable and oxygen has six valence electrons,
would like to have eight, so oxygen who ran
out of room is going to want to look like this in order
to be happy so you've got to remember those bonding rules
in order to be able to correctly draw and name structures.
Now organic chemistry has a lot of rules about naming things
but these rules actually help you
as you try and name structures.
There's codes for how many carbons are in a given chain.
There's codes for whether or not there are single or double bonds
and this video really isn't going
to go through all of those.
This video is more about how
to understand what the basic structures mean but just
so you know things like butane,
the name itself tells you what it is, that but means
for carbons and that ane at the end tells you
that there are no double bonds but something
like propane tells you there are three carbons in the chain
with one double bond so once you learn the rules it's actually
really cool and very powerful to be able to draw these things
but you're going to see stuff like this and look at this
and go well what the heck is this thing.
Okay, there's two rules in addition to the bonding rules
that you need to know.
Rule number one carbon lives on ends and bends.
Rule number two hydrogens bring carbon happiness.
So let's look at this again.
This is actually ethanol.
Some of you may have some experience with ethanol.
Okay so the rule number one carbon lives on ends
and bends what I mean by that is any bend
in a chain means there is a carbon there.
That is code for carbon.
The end also implies a carbon so that's rule number one.
Hydrogens bring carbon happiness so if you recall carbon needs
to have four bonds going to it in order to be stable.
That's carbons happy place so when you look
at these carbons you can count the number of lines going
to them and fill in the missing ones with hydrogens
so this carbon has only one covalent bond going to it
which means that it needs three hydrogens in order to be stable.
This carbon already has two covalent bonds going to it
so it needs two and now you're done.
Now you can count up all the atoms so sort of do a tally,
two carbons, six hydrogens and one oxygen so if you write
that out in a linear fashion C2H6O that is the formula
for ethanol and by the way the name ethanol actually tells you
exactly what's in it, how convenient.
Okay let's look at another molecule,
something a little bit more interesting.
We're going to look at caffeine and caffeine is a molecule
that many people especially students absolutely cannot live
without, the most popular stimulant on the planet.
You might be curious to know what the heck does it look like.
Well this is exactly what it looks like and we are going
to come up with the chemical formula
for this thing following the bonding rules
and the two additional rules about carbon.
Okay, you ready?
So first of all carbon is going to be at the ends and bends
so let's do all of the ends first so here's the end
of the line that's a carbon, here's another end
of a line that's a carbon and here's another end
of a line that's also our carbon and now we're going to fill
in all the bends, the ones that don't have any nitrogens
in them, we're going to fill those in with carbons too
so there's a carbon here, here there's a nitrogen
so you don't fill that in.
Here's another bend there's a carbon,
here's another bend there's a carbon, here's another bend
and finally another bend
so you see everywhere the line bends you put a carbon
and finally now we get to fill in all of the empty spaces.
Remember carbon needs to have those four bonds going
to it in order to be happy.
We're going to fill those empty spots in with hydrogens
so this carbon only has one covalent bond going to it
so it's going to need three more hydrogens in order to be happy.
These are all happy on the interior.
They all have four lines going to them.
This one doesn't so we're going to need three hydrogens here.
This one also is missing one because it's only got three,
now he's got four, now he's happy
and this one needs three as well.
So now let's do a tally of atoms and come
up with the chemical formula for caffeine so if you count it all
up for the carbons I've got eight,
for the hydrogens I've got ten, for nitrogens I've got four
and oxygens I've got two and if you write that out
in a linear fashion you've got the chemical formula
for caffeine.
See it's not so bad.
Okay ready for one more?
Let's do one more.
Let's do something else that students rely
on a lot let's look at the structure of aspirin.
Here is aspirin.
We're going to write the chemical formula for aspirin.
This is the one I showed you at the very beginning of the video
and a promised you you would be able to do
and now hopefully you can see how easy this is, let's do it.
Okay, so we're going to start with carbon at the ends
and the bends so here we've got carbons at every bend.
This is called an aromatic ring.
Isn't it absolutely fabulous?
And there's one bend right there.
The only other spots we've got there's a bend
and this is an end so those are all the carbons
and now we're going to go back and fill in all the empty spaces
around carbon with hydrogens so this carbon is good.
It has four bonds going to it as does this one.
This one has three, needs one more.
This one has three and needs one more.
This one has three.
He needs one more.
Do you see a pattern?
This carbon here has four bonds going to it
so it is already happy.
So does this carbon and this one is terminal and needs three.
All right so now we've got all the carbons, all the hydrogens.
We've got everybody and now we can write the chemical formula
for aspirin.
If you do the tally you've got nine carbons, eight hydrogens
and four oxygens and there you have it the chemical formula
for aspirin as promised and not even very painful.
So now I hope you find that these structures mean something.
That was really the goal of this video.
It's not that complicated once you learn the basic rules.
I don't even think we needed the hula penguin but I'm just going
to throw it in just in case you're a little bit overwhelmed.
If you keep at it these structures actually get a little
bit charming, that's dopamine.
Dopamine makes you feel good.
It's the molecule of love and happiness
and I hope you find some love and happiness
in your studies of chemistry.
Sometimes you got to look hard though.
As always I hope that was helpful.
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Good luck.