Hydrogen Bonding and Common Mistakes


Hydrogen bonding can be so confusing, so I
want to talk about some common mistakes people make so you won’t ever make them. Okay, so
hydrogen bonds are a type of intermolecular bond. Intermolecular bonds form between molecules,
that’s why we call them intermolecular. Now this “between” part is super important. Between
two different molecules, I’m underlining it twice in red. Okay, let’s look at hydrogen
bonds in some ethanol molecules. So, ethanol’s an alcohol and if we could take a drop of
ethanol and zoom in zillions and zillions of times in it this is what we’d see. We’d
see a bunch of different molecules all twisting around to different orientations and here
they are. So, where are the hydrogen bonds in these molecules? Well as I said earlier,
intermolecular bonds, hydrogen bonds, form between molecules, okay? So this can’t be
a hydrogen bond because it’s not between molecules, okay? The CH, that can’t be a hydrogen bond
either because it’s in the same molecule. It’s not between molecules. In the CC, it
can’t be a hydrogen bond either because it’s in the same molecule, not between different
molecules. So that’s the first important thing to keep in mind; if a bond is in just one
molecule it’s not an intermolecular bond and it’s certainly not a hydrogen bond. Okay,
so that means that the hydrogen bond has to be between different molecules. Here’s how
it works. In hydrogen bonding, in this case, an H connected to an O is bonded to an O on
another molecule. Okay, so this H is attached to an O and so it will form a hydrogen bond
with this O over here. I’ll indicate this hydrogen bond with a couple red dots so there
is a hydrogen bond here. This H connected to the O here can form a hydrogen bond with
this O over here on this molecule. So again, a hydrogen bond I’ll indicate with a couple
of these red dots here. So there’s a hydrogen bond here. Okay now, a common mistake that
some people make is they think anytime there is an H, it can form a hydrogen bond between
molecules. They say there’s an H here connected to the C, there’s an H here connected to the
C, so this can form a hydrogen bond. Right? No. It can’t. It has to be an H connected
to an O bonding with another O in this case. So it can’t be this H with the C and this
H with the C, that’s not a hydrogen bond. Another mistake is taking a H that’s connected
with the C and connecting it with an O. That’s kind of half right because in this case O’s
are forming hydrogen bonds but if the H is connected with a C it cannot form a hydrogen
bond either. It has to be an H connected with an O making a bond with an O on another molecule.
This is wrong, this is wrong, but these two hydrogen bonds between the molecules is the
way to go. Okay, so now that you know how to find and draw hydrogen bonds,
let’s talk about how hydrogen bonds form in the first place. Here I have two ethanol molecules;
they’re going to form a hydrogen bond between them. In this case, it’s all about the O and
the H. So the O and the H in this molecule are connected to each other with this line
which indicates that it’s a covalent bond that’s holding them together. They’re sharing
electrons to form this covalent bond so they’re stuck together because they’re sharing electrons.
Here’s the thing though with the sharing, they are not sharing those electrons equally,
okay? The oxygen has what we call a higher electronegativity. All that means is that
when it shares with hydrogen, it hogs the electrons. So it’s maybe supposed to be sharing
equally but instead it’s hogging the electrons. Because it has all these extra electrons that
it’s hogging, it has a little bit of a minus charge because of those electrons that are
spending more time with it. So we can write this minus sign here in this squiggle that’s
actual a lower case Greek Delta letter D. We have this lower case Greek Delta with a
negative sign meaning the O is a little bit negative because it’s hogging those electrons.
On the other hand, hydrogen here is getting the electrons hogged away from it. So it’s
missing those electrons so it has lower case Delta plus, it’s a little bit positive. Now
the same thing is happening over on this molecule. The oxygen is hogging an electron so it has
a Delta minus sign because it has a little bit of a negative charge; those extra electrons
that it’s hogging away. An H that is getting thieved away from here, it has a little bit
of a positive charge. So now you can see what’s going on here. The positive hydrogen here
is going to be attracted to the negative oxygen here. So this attraction, it’s sort of like
magnets. You know how magnets attract together? It’s like this attractive force between the
positive hydrogen and the negative oxygen. So we can say that the hydrogen bonds formed
because O is hogging electrons from H. It’s making O a little bit negative, it makes H
a little positive so this positive H is going to be attracted to a negative O on another
molecule. Now here’s the thing, earlier I said that if an H is bonded to a C it will
not form a hydrogen bond. Here’s why. It’s because C and H share their electrons evenly
in this spot. Because they’re sharing them evenly, it’s not possible for the C to become
negative and the H to become positive because the electrons spend equal time with both of
them. So you don’t get these negative and positive charges when H is bonded to a C since
there are no charges. H’s bonded to C’s can’t form hydrogen bonds. So it turns out that
O and H aren’t the only atoms that can form hydrogen bonds. We saw just a minute ago that
O when it’s bonded to H, O hogs those electrons away from H. It’s not the only atom that can
do that. Fluorine also has a high electron negativity which means it likes to hog so
fluorine when it’s bonded to an H also has a little bit of a negative charge making the
hydrogen get a little bit of a positive charge. Nitrogen(II) is able to hog electrons away
from hydrogen so it gets a negative charge getting hydrogen a positive charge. So there
are three atoms that can participate in hydrogen bonding besides hydrogen and they are F, O,
and N. If a hydrogen is bonded to a F, O, or an N that hydrogen can form a hydrogen
bond. You can think about it because it spells FON, not correctly, but F-O-N. So here’s the
thing, these guys all have to attach, they have to be attracted to an atom on another
molecule, okay? So for example, this positive H here can be attracted to an O on another
molecule because that O will be a little bit negative. But this O could also bind with
an H attached to an F. Or an O because it’s a little bit negative could bond to an H if
it’s attached to an N. Okay? So that’s possible. Or you can have an F, a fluorine, bonding
with any of these H’s if H is attached to it. F or an O or an N this slightly negative
fluorine will be able to hydrogen bond with a positive hydrogen. Similarly, nitrogen(II)
when it’s on another molecule can form a hydrogen bond with any of these three combinations;
the H to the N, the H connected to the O, or the H connected to the F. So whenever you
see a hydrogen connected to a fluorine, oxygen, or nitrogen that means that it can form a
hydrogen bond. Any of the hydrogens can form a hydrogen bond with a nitrogen, fluorine,
or oxygen on another molecule. So that is hydrogen bonding.

100 Replies to “Hydrogen Bonding and Common Mistakes”

  1. Tyler, you're awesome! I'm 54 and learning chemistry for the first time with relation to becoming a nutritionist. If I need help I know I can rely on your videos. Thank you.

  2. I wish you were my Chemistry Professor instead! You make Chemistry so easy to understand 👍👍👍. I believe all your lectures will be helpful with my upcoming exam on Tuesday. Thanks

  3. Hydrogen bonds can occur within one single molecule, between two like molecules, or between two unlike molecules. Intramolecular hydrogen bonds: Intramolecular hydrogen bonds are those which occur within one single molecule. This occurs when two functional groups of a molecule can form hydrogen bonds with each other!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  4. I have a practicum tomorrow and skipped all the lessons about electronegativity and hydrogen bonds so you really just saved my mark

  5. In ethylene glycol the gauche form is most stable bcz of hydrogen bonding but the H is attached to C so why is it even a Hydrogen bond?

  6. Thank you for your videos actually I like the way you explain with .can you make a video explaining the Geometric shape for molecule that have more than one central atom like C2H4 or C2F4

  7. okay I never ever wrote a single comment on youtube, but this time I had to !!
    you are amazing!! the method that you are using, the way you speak, the sections of the screen !!! It's all perfect!!
    Thank you so much !!!!

  8. These are the kind of channels people should donate money to…
    Not the other nonsense that people watch and donate to

  9. Chemistry has always been such a terror for me. I am so glad my prof put these videos up, they are soo helpful. You are soo gifted with the ability to teach, I wish you could be my teacher for all subjects 🙂 Thank you..!!

  10. Thank you so much, this information was really helpful to my grade 12 learners to understand hydrogen bonding

  11. bruh the delta is written the otherway around δ like so moron , if you are going to teach someone something teach them the right thing

  12. @ 8:30. Does the N, O, F on the right side have to be attached to a hydrogen bond to give it a partial negative so that it can bond with the partial positive hydrogen on the left side? Or can it be attached to anything, like a carbon?

  13. Your videos are by far the best at explaining! I watch endless amount of chemistry videos and they all confuse me more. Thank you so much!! I just wish you made a video to help me understand how to draw Lewis structures correctly.

  14. I seen that you can create a hydrogen bond using FH, OH, AND NH they will bond to any F,O,N but do the F,O,N also need to connect to an H on their molecule or does it matter. example can O-H create a hydrogen bond with O2? or does it have to be O-H creates hydrogen bond with O2-H. Hope i worded this in a way you understand my question.

  15. You are phenomenal, I'm training to become a Chemistry teacher and your method of teaching is inspirational. Hydrogen bonding concepts never been this clear in my mind. Great job..keep up the good work

  16. The best chemistry teacher in the world ❤️❤️❤️❤️❤️❤️🙏🙏🙏 love from India

  17. Brother! I owe you one 👍 If this works in my formula and fixes the instability I will need a huge hug from you 🤞🤝👏 Thank you for sharing this!!!!

  18. Hey hey wait a minute H bonds are also made by sp hybridized C and they can be intra molecular as well like in the case of ortho nitro phenol. And that is the reason why o nitro phenol is more viscous than p nitro phenol. On the other hand p nitro phenol has has inter molecular H bond which increases its MP and BP as compared to o nitro phenol. Salicylaldehyde also forms intra molecular H bond there are numerous examples where intra molecular H bond increases the Vapour pressure as well.

  19. Im confused about one thing, you say here hydrogen bonds are between molecules, but other websites say they can be within molecules? im really confused about who is correct. Also can a hydrogen conneted to an oxygen attach to a O/F/N which isn't itself connected to a hydrgen, or does it have to be an O/F/N thats attached to a hydrogen that connects to the initial hydrogen combo? hope that makes sense!

  20. Great video. Please can someone explain to me why textbooks and professors say certain molecules ending in OH have hydrogen bonding. I thought that was intramolecular/covalent bonding. This is what keeps confusing me. Some are and some aren't.

  21. H-bonding can also occur intramolecularly…. I mean I stopped there LOL but keep trying to educate all these millenial fucks who can barely wipe their asses

  22. Amazing video!! You're explantations and pace of the lesson is phenomenal…you explain every step that is required and that is what I needed!!

  23. Unlike Metallic bond (Metals), Ionic bond (Salts, ionic compounds) and Covalent bonds (Pure Non metals), Hydrogen bond is intermolecular bond!

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