[Hbond]

The question I have has to do with hydrogen bonding. I know it is an electrostatic/ionic type bond. What I was wondering does the hydrogen carry the net burden of potential within a hydrogen bonding molecule?

Here is my logic. If we react O2 and H2 we get an extremely exothermic reaction that produces water. The exothermic aspect, if I am correct is due to the oxygen gaining electron density to form a stable octet. The hydrogen loses electron density to become slightly positive which should be endothermic since molecular hydrogen was zero charged. If this was physics, this would be considered an anomoly; the exothermic formation of a stable charge dipole. In chemistry the orbital stability of oxygen allows the oxygen to stabilize its anion state (extra electrons) while passing on the burden of potential onto the hydrogen. This should make the positve side of water the more potentiated side of the molecule.

When a hydrogen bond forms in water, the hydrogen is lowering its potential, while the oxygen, by sharing its unbonded electrons, is losing some stability in the octet of electrons. As such, although charges may cancel for both the oxygen and hydrogen, the hydrogen  gains orbital stability within its 1S orbital, while the oxygen loses some stability within its octet. The net result should be that the hydrogen lowers potentials in two ways (electrostatic and orbital), while the oxygen lowers electrostatic potential but gains orbital potential.

Another way to do math is that the hydrogen lowers both magnetic and charge potential while the oxygen lowers charge potential but will gain magnetic potential. The lowering of charge potential is exothermic for both. While the hydrogen will exothermically lower magnetic potential while the oxygen will endothermically gain magnetic potential. The three exothermics and one endothermic gives off about 2-10 kcal/moles of h-bonds.

[Mitch]

The exothermic aspect, if I am correct is due to the oxygen gaining electron density to form a stable octet.

The oxygen's electrons are already in a stable octet, there is no antibonding character involved with the valence electrons. Don't confuse reactivity with stability.

[Hbond]

The question I am still asking is whether the hydrogen within hydrogen bonding materials is the business end of the molecule with respect to hydrogen bonding. Within water both hydrogen and oxygen participate in the hydrogen bond. Is the exothermic of the hydrogen bond formation mostly due to the hydrogen lowering a larger potential than oxygen, since oxygen, in part, loses some orbitial stability when it allows a neighboring hydrogen to form an hydrogen bond. The question should be, if a hydrogen bond forms but the distance and/or angle is not optimized does the hydrogen bond retain a slight electrophilic potential (due to the hydrogen)?

[Mitch]

Hmmm.... You mention that oxygen looses orbital stability by forming a bond. But if you say orbital than we are refering to Molecular Orbital theory. When you mention Hydrogen Bond, a hydrogen bond is best thought of as a very strong Van der Waals attraction and not participating in covalent bonding.

That being said, both hydrogen bonds and O-H bonds will have small components of the 2 above concepts mixed with them. But, once we start equating covalent bonding with van der waals forces in the same sentence we are bound to spiral into circular logic. I don't think that is what you proposed in the above, but its a very slippery slope. Maybe others can comment on this fruitful discussion.

[Hbond]

I am knit picking here because the possible electrophilic potential of hydrogen bonding hydrogen should play a very important role within the living cell. All the major molecules including DNA, RNA and proteins all are dependant on H-bonds. If the theory is true than every H-bond that is not optimized or does not form will bestow some electrophilic value to that biomaterial via its hydrogen bonding hydrogen.  Theoretically this would allow each biomaterial to define a specific electrophilic identity. The logical extrapolation is that the cell is organized as a electrophilic gradient from the cell membrane (low) to the DNA (high).

What I am trying to do is use logic to develop the fundamental electrophilic premise of H-bonding hydrogen. The way I see it oxygen often exists as oxide; O-2. This shows the stability of oxygen with respect to holding extra electrons. The EM force is both magnetic and electrostatic. Within oxide the number of oxygen electrons is two more than the number of its nuclear protons, implying electrostatic alone can not explain this. What is also required is subtantial magnetic additon of orbtial electrons to overcome negative charge repulsion. Within water the oxygen is still not all the way to oxide and therefore can theoretically hold more electron density to maximize magnetic addition relative to the oxide state. It can only take so much from the hydrogen, because hydrogen has its own EM force needs. This creates a potential in the H. If there is a residual potential in the oxygen, it should be slightly electropilic for better magnetic addition leading to oxide. The formation of a H-bond, pulls the oxygen further from its magnetic addition or oxide stability. While the hydrogen gets to lower its EM potential to some extent. The affected oxygen will then take it out on its own hydrogen, which will have a slightly higher potential,  etc..

The observed higher density of liquid water relative to ice seems to indicate this also. Within ice the crystal structure finds the perfect compromise between the electrophilic needs of oxygen and hydrogen. Within liquid water the hydrogen gets closer by say 10%. This could be due to the oxygen trying to twist away. This alters the average liner bonding angle of an optimized h-bond. The off angle requires closer approach for the hydrogen to lower potential. A pure electrostatic bond only needs distance. If one places say metallic iron or almost any metal in the water, the oxidation reflects the net elelctrophilic potential within the water catalizing the reaction.

[alkemist]

In your first post, you mentioned that in formation of H-O bond, H loses an electron and therefore it should be endothermic.  This statement/assumption is incorrect.  First of all, the O-H bond energy is slightly greater than H-H bond energy, so if we are just talking about H-O bond formation, it is still exothermic.  Now, about hydrogen bonds ...  As Mitch said, hydrogen bonds are due to Van der Waals forces that increase the overall stability.  You are thinking of electrons as localized charges when you say H loses or O gains an electron.  This is not true since they share an electron and that just means that electron can be found somewhere between the two.  We don't know where it is, just the relative probabilities of its being at a particular place.  Therefore, we can look at it as particle in a box problem.  The solution to Schrodinger's particle in a box problem is
E = (h^2*n^2)/(8*m*L^2), where h is the plank's constant, n is the energy level, m is the mass of the particle and L is the length of the box.  As you see from this equation, increasing L, or the size of the box, decreases energy.  Therefore extanding the space available for an electron to move in, will decrease it's energy and stabilize it.  Through formation of H bonds we have this kind of stabilization going on - we are slightly extending available space for the electrons to move in.  I hope this answers your question.

[Hbond]

I agree that the O-H bond energy is greater than the H-H, but this is more due to oxygen gaining stability than the H. Instead of looking at bonds I am looking at atoms. The H contains only a slight potential as H-H (van der Waals), but as O-H it now has  much higher potential that has its own classification, hydrogen bond energy. You are correct also about delocalization of electron density more than transfer of electrons. What I am saying is the stability of the oxygen shifts the shared distribution more toward itself when a O-H bond forms compared to a O-O bond. While the hydrogen is better off as H-H compared to O-H, since the O-H bonds leaves rmore esidual potential in the H. The O-H bond energetics is the sum of two atoms with the O atom more exothermic and the H atom more endothermic.

When a hydrogen bond forms, if we look again at atoms, the hydrogen lowers potential by delocalizing electron density from the unbonded electrons of O. But O loses electron density which was helping to maximize its orbital stability, via the an outer octet. It loses some negative charge repulsion, which is exothemic but also loses magnetic addition for the rest of its remaining electrons. This may or may not be a wash. But it is a win win situation for the hydrogen.

[Juan R.]

I may confess that read your post several times and still do not understand exactly what you are asking or some parts of your post. However, I will add some data if it is of interest here.

The question I have has to do with hydrogen bonding. I know it is an electrostatic/ionic type bond.

In rigor, that is not true. The electrostatic component is a small contribution (order of 1/4 total energy) to total bond.

Here is my logic. If we react O2 and H2 we get an extremely exothermic reaction that produces water. The exothermic aspect, if I am correct is due to the oxygen gaining electron density to form a stable octet. The hydrogen loses electron density to become slightly positive which should be endothermic since molecular hydrogen was zero charged. If this was physics, this would be considered an anomoly; the exothermic formation of a stable charge dipole.

That is not true. It was already pointed by Mitch that oxigen already verifies the octet rule. Moreover, there is not physical anomaly. It is all rather normal. A molecule is not formed by electrostaic forces -i believe this is the error on all your logic- therefore the formation of a stable dipole is not anomalous. Formation of water is a very stable configuration and explained by quantum theory. Next, i will use minimal basis approximation on MO SFC method (without relativistic corrections).

We begin from AO

H1s
O1s O2s O2p_z O2p_y O2p_x

then we combine them for forming the MO (Energy ordered)

1a₁ 2a₁ 1b₂ 3a₁ 1b₁ 4a₁ 2b₂

There is a total of 10 electrons. Filling the MO, we find a great ratio (enlazant/antienlazant), which is the cause of the strong character of H-O bond on water and of great stability of molecule. Only last OMs 1b₁ 4a₁ 2b₂ are antienlazant and only 1b₁ is filled

The dipolar character is mainly due that the fundamental 1a₁ is practically the original O1s whereas hidrogen electrons are 'diluted' into several OMs.

In my opinion, the computation of energies from EV method would be more complex, but explanation of geometry is more accesible.

In chemistry the orbital stability of oxygen allows the oxygen to stabilize its anion state (extra electrons) while passing on the burden of potential onto the hydrogen. This should make the positve side of water the more potentiated side of the molecule.

I do not understand this part. Above discussion was quantum chemical one.

When a hydrogen bond forms in water, the hydrogen is lowering its potential, while the oxygen, by sharing its unbonded electrons, is losing some stability in the octet of electrons. As such, although charges may cancel for both the oxygen and hydrogen, the hydrogen  gains orbital stability within its 1S orbital, while the oxygen loses some stability within its octet. The net result should be that the hydrogen lowers potentials in two ways (electrostatic and orbital), while the oxygen lowers electrostatic potential but gains orbital potential.

Another way to do math is that the hydrogen lowers both magnetic and charge potential while the oxygen lowers charge potential but will gain magnetic potential. The lowering of charge potential is exothermic for both. While the hydrogen will exothermically lower magnetic potential while the oxygen will endothermically gain magnetic potential. The three exothermics and one endothermic gives off about 2-10 kcal/moles of h-bonds.

i do not understand this part, specially the appeal to magnetic potential. In fact i do not know what is a 'magnetic potential'. I only know scalar A₀ and vector potentials A.

The H bond is explained in a similar form as water molecule. Now we take the OM of water and combine them with a single OA O2p. Then it can be shown that an stable interaction is formed, because the atomic-molecular system H-O-H···O is more stable than H-O-H + O.

From an fundamental (but approximate because the real bond is not with an isolated O, it is with an O into other water molecule) point of view, the hidrogen bond is a new kind of bond. EV method is more useful now. We have main contributions to EV wavefunction:

O : H : O           pure covalent
O_: H₊ :O          Pure ionic without charge transfer
O₊ :H_ :O          Pure ionic without charge transfer
O_: H : O₊          Covalent with charge transfer
O. H_: .O           Covalent with charge transfer

From an energetic point of view one has four contributions (Kcal/mol):

Electrostatic:    -6.0
Delocalitation:  -8.0
Dispersion:      -3.0
Repulsion:        8.4
Others:            2.5

Other contributions may be considered but computations are very difficult. Due to compensation between repulsion, others, delocalitation, and dispersion the energetic value of total bond is very well aproximated taking only the electrostatic interaction. I think that this is reason many textbooks claim that H···O is mainly a electrostatic interaction between and H(delta+) and an O(delta_) due to polar character of H-O bond.

However one can easily understand that H···O bond is not due to electrostatic, WDW, etc. The H···O bond is spatially directed (and has specific distance), which cannot be explained from an electrostatic contribution, which is spherically simetric. If H···O bond was due to simetric forces, one would find an entire family of different molecular structures (angle and distance).

[Mitch]

Here is a nice chem review. Just read the introduction on hydrogen bonding, the rest gets to technical on blue-shifting H-bonds.

http://pubs.acs.org/cgi-bin/archive.cgi/chreay/2000/100/i11/pdf/cr990050q.pdf

[Hbond]

Thanks everyone that was excellent. My explanation is more intuitive than logical because I am having a hard time putting my gut instincts into words. The understanding I am trying to achieve is, that going into a hydrogen bond does the hydrogen bonding hydrogen carry the primary burden of potential? The partially directed nature of the hydrogen bond should stem from the potential within the H instead of the O. This hydrogen potential adds something more than a electrostatic attraction between the two. The oxygen electrons should be reacting to the hydrogen rather than directly inducing the directed nature of the bond.

Maybe an easier example to see is HCl in water. The choride is a very weak base because of the orbital stability and the high electronegativity of the chloride. The hydrogen of HCl is proportionally higher with respect to its electrophilic potential compared to chlorides nucleophilic potential. Molecular water should be proportionally higher in the electrophilic potential of the hydrogen compared to the nucleophilic potential of the oxygen due to the higher electronegativity of the oxygen.

I simplified my conceptual analysis by looking at the EM force that binds electrons to protons and allows electrons and negative charge to share close space within orbtials as electrostatic and magnetic interactions of electrons. It is not rigorous but it should add to the same thing.

[tutanka]

Hello,
here you can found the first  HBE=HYDROGEN BOND ENERGY REACTOR in action.. https://www.youtube.com/watch?v=NwyTNO5llBo .When hydrogen bonds are broken you obtain an exothermic lightIng reaction.. The video is in italian language but the video is very comprensible.. If you need additional information you can contact me.. Cheers

[orgopete]

Hello,
here you can found the first  HBE=HYDROGEN BOND ENERGY REACTOR in action.. https://www.youtube.com/watch?v=NwyTNO5llBo .When hydrogen bonds are broken you obtain an exothermic lightIng reaction.. The video is in italian language but the video is very comprensible.. If you need additional information you can contact me.. Cheers

Can someone explain this experiment to me?

[orgopete]

First off, I am an organic chemist so I really don't belong here. For example,

... does the hydrogen bonding hydrogen carry the primary burden of potential?

I don't even know what that means. I think I have an idea about hydrogen bonds, but I cannot follow this discussion. I also see a discussion of interactions that do not match my own thinking. Is the universe limited to four fundamental forces, strong, weak, gravity, and electromagnetic, or are there additional forces for bonding, like van der Waals and covalent?

If not, then all bonding types are dependent on an electromagnetic interaction. In some ways this could be simple (except for electron-electron interactions). A favorite example might be a F:H:F^- bond. In this case, the distances have been reported to be about equal. These seems plausible and leads to a question of structure. What are the bonding distances of HO:H:OH^- or H₂O:H:OH₂⁺? In the two examples I am citing, the hydrogen bonds are symmetrical and I think may be fundamentally different from the examples I think the poster is asking about.

The partially directed nature of the hydrogen bond should stem from the potential within the H instead of the O. This hydrogen potential adds something more than a electrostatic attraction between the two. The oxygen electrons should be reacting to the hydrogen rather than directly inducing the directed nature of the bond.

??

Maybe an easier example to see is HCl in water. The choride is a very weak base because of the orbital stability and the high electronegativity of the chloride. The hydrogen of HCl is proportionally higher with respect to its electrophilic potential compared to chlorides nucleophilic potential. Molecular water should be proportionally higher in the electrophilic potential of the hydrogen compared to the nucleophilic potential of the oxygen due to the higher electronegativity of the oxygen.

I'm hoping this is a long version of HCl donates a proton in water or water is more basic than a chloride ion.

[Arkcon]

I really wouldn't worry about a decade old thread.  Seems to be quite a bit of ... I dunno...here in this thread.  Mitch did his best to help people make sense.

[orgopete]

No, I just didn't take note of the date. I'll let it rest.