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When we compare water and hydrogen peroxide's hydrogen bond strength, which one should have the greater one? I know that peroxide has more hydrogen bonds, but when we compare the strength of each hydrogen bond, which one would be greater?

Online values of the boiling points indicate a greater bond strength in $\ce{H2O2}$. But peroxide has a larger number of hydrogen bonds.

This was a question for comparing bond strength in a test paper.

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    $\begingroup$ Who said peroxide has more H bonds? $\endgroup$ – Ivan Neretin Oct 12 '17 at 5:25
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    $\begingroup$ Really interesting question. // It seems that hydrogen bonds are weaker in H2O2, but that there are more of them. researchgate.net/publication/… $\endgroup$ – MaxW Oct 12 '17 at 6:25
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Online values of the boiling points indicate a greater bond strength in $\ce{H2O2}$.

The boiling point of water is $\pu{100 ^\circ C}$ while that of hydrogen peroxide is about $\pu{150 ^\circ C}$. Here is a list of factors that might contribute to this difference (adapted from source)

  • Stronger dispersion forces in $\ce{H2O2}$ (larger molar mass)
  • Higher dipole moment in $\ce{H2O2}$
  • More hydrogen bond acceptors in $\ce{H2O2}$

As for the number of hydrogen bonds, if we look at the structure of ice, each hydrogen atom of water is involved in a hydrogen bond (each oxygen is involved in two). If we assume that each hydrogen can make one bond at maximum, we would not expect more hydrogen bonds per molecule for $\ce{H2O2}$. The crystal structure of solid $\ce{H2O2}$ confirms that.

But peroxide has a larger number of hydrogen bonds.

We can't infer that from the molecular structure alone. As stated above, in the solid state, the number of hydrogen bonds per molecule is the same. However, the density of solid $\ce{H2O2}$ (1.7 g/mL) is much higher than that of ice. This is true of the liquid forms as well (1.45 g/mL vs about 1 g/mL). This might allow for more dispersion forces (better contacts).

In liquid water, there are 3.4 hydrogen bonds per molecule on average (source). The higher density of $\ce{H2O2}$ compared to water suggests that atoms are closer in $\ce{H2O2}$, but you have to consider that the composition of the two substances are different. On a per-atom basis, the available volume is comparable.

Is the strength of hydrogen bonding greater in hydrogen peroxide or water?

The question is a bit vague. If you compare one $\ce{H2O2}$:$\ce{H2O2}$ hydrogen bond to one water:water hydrogen bond, the hydrogen bond length is very similar (at least in the solid phase - source). Because the bond partners are the same atoms and the geometry around the oxygen is not that different in the two molecules, this would suggest that the strength of the bond is similar as well.

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If I were to dissolve diatomic oxygen into water, the water would form only a negligible amount of hydrogen bonds with the oxygen molecules. This is because the oxygen atoms in an oxygen molecule share electrons evenly, and as such are neutral (ignoring the dipoles that may form for a few femptoseconds due to the electrons being temporarily closer to one nucleus than the other). On the other hand, water molecules form strong hydrogen bonds, as the oxygen in water has a -2 oxidation state, meaning that based on probabilistic sharing or electrons, one would expect 2 more electrons to be closest to the oxygen than it has protons in its nucleus. The combination of electronegativity relative to hydrogen (which gives the probability of the oxygen having a temporary negative charge at any given moment) and of oxidation state (which gives the expected strength of the temporary negative charge) results in hydrogen bonds that are analogous to (albeit weaker) than the ionic bonds formed by a +1 cation and a -2 anion.

By contrast, if we look at hydrogen peroxide, the two oxygens will share the electrons in their bond equally. As such, each oxygen has only a -1 oxidation state, and the resulting hydrogen bonds are more analogous to the ionic bonds formed by +1 cations and -1 anions. As the expected distance between the hydrogen and oxygen in the hydrogen bond is more or less the same, the factor that governs relative strength is the strength of the (temporary) ions involved in the bond, so water should form stronger hydrogen bonds. Similarly, I would expect stronger hydrogen bonds in ammonia than in hydrazine.

I would hazard a guess that the reason why hydrogen peroxide has more hydrogen bonds than water, as seen from the research quoted by maxW in a comment, is that the expected number of hydrogen bonds made by each hydrogen should increase along with the number of atoms to which the hydrogen bond can form.

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Well its an unexpected question and shows the interest of one's in Chemistry.

We can understand or can compare the strength of H. Bonding in water and Hydrogen peroxide by observing their stability in open air.

Take 10 ml of each liquid in an open jar and let them place in open for about 10 minutes and then see what happens? Measure the volume of both liquids after 10 minutes you will see that there will be more water then Hydrogen per oxide. this is because of the thermal stability of inter-molecular forces like Hydrogen Bonding.

Actually in Hydrogen peroxide polarity is not so prominent as in Water, So we can say that Strength of Hydrogen bond in Water is stronger than in Hydrogen Peroxide

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You are absolutely right, it has a higher boiling point because it has more hydrogen bonds. However the bonds are slightly weaker since the oxygen are closer to each other and repel slightly more.

" The hydrogen bonds are slightly weaker (12–15%) than those in water " See https://www.google.com/amp/s/www.researchgate.net/publication/230086767_Hydrogen_bonding_in_hydrogen_peroxide_and_water_A_Raman_study_of_the_liquid_state/amp#ampshare=https://www.researchgate.net/publication/230086767_Hydrogen_bonding_in_hydrogen_peroxide_and_water_A_Raman_study_of_the_liquid_state

Edit my appologies, maxW was earlier with approximate the same answer but I did not see his comment. Should I delete this awnser so you can get the credits you deserve? (Glad to know we are on the same page :)

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    $\begingroup$ You are free to do whatever you feel like. Note, however, this you answer may be considered a link-only (non-) answer. It is better to include the key points of the reference here (as a quote, if need be) and use the link as a source only. $\endgroup$ – Jan Oct 12 '17 at 12:32
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    $\begingroup$ MaxW has posted it as a comment, and while I think the answer could use some more context or explanation and much better formatting, it essentially is an answer. Posting the same information as an answer, which was given already in a comment, is not against the guidelines. (I personally think this should be encouraged.) $\endgroup$ – Martin - マーチン Oct 12 '17 at 19:21

protected by andselisk Jul 7 at 17:10

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