Why we can't live without water?

Discussion in 'Chemistry' started by Plazma Inferno!, Jun 23, 2016.

  1. wellwisher Banned Banned

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    Hydrogen bonds get stronger and stronger, as more and more hydrogen bonds form a cooperative. Clusters form a rather unique form of resonance structure with both hydrogen and electron movement. The first bond in the cooperative is the hardest to break, no matter where you try to break it. This is similar to breaking the first bond of benzene. With each breaking of the bond the cooperative bonding gets uniformly weaker while all the bonds expanding slightly.

    The quote is from the link below. This topic is very interesting to me. It is about hydrogen bonding and information transfers in water. There are a wide range of energy levels, not only within hydrogen bonding; two components, but also between cooperative and anti-cooperative hydrogen bonding.

    The quote can be found with this link, after the largest graphic; water hydrogen bonding.

    http://www1.lsbu.ac.uk/water/hydrogen_bonding.html
     
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  3. exchemist Valued Senior Member

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    Thanks for the link. However the variation in H bond strength mentioned, due to cooperative versus anticooperative behaviour seems to be +/- 3kJ/mol. The strength of the H bond in water is in the range 20-25kJ/mol.

    That translates into a variation of 10-15% or so, i.e. fairly minor, not the factor of 2.5 that you mentioned. It was that much larger figure that did not look right to me.
     
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  5. wellwisher Banned Banned

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    I think the number of 3KJ/mole is how much each additional cooperative hydrogen bond, added to a cooperative, increases the bond strength of all the bonds. The 250% of hydrogen bond strength, relative to the dimer, in the cooperative would assume a cooperative of about 20 water added to the dimer.

    Using quantum chemical calculation of different clusters of water molecules has shown that the hydrogen bonding strength can vary for as much as 90% between extreme cases of cooperativity and anti-cooperativity with cooperativity increasing (~3 kJ mol-1) the bond strength and reducing (~0.03 Å) the hydrogen bond length per added molecule and anti-cooperativity reversing these effects by the same amounts. The hydrogen bond strength is computed to vary for as much as 90% between extreme cases of cooperatively and anti-cooperativity [1829].

    Anti-cooperatives are affects that weaken the average hydrogen bonding strength of the cluster. A cooperative cluster can compensate for other moieties that have an anti-cooperative affect on the cluster. The water can maintain a cluster even among organics since it has strength to spare. This can come in handy if we need the cluster to be weaker, in some places, so it can be disrupted a little easier.
     
    Last edited: Jul 11, 2016
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  7. exchemist Valued Senior Member

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    Yes I too read that passage but did not understand what was meant by variation by "as much as 90%". It seems a very odd and unclear way of describing the degree of variation.

    If the nominal bond energy is say 20kJ/mol, and the total variation gives a range with a width of "90%" , does that mean the range is from 14kJ/mol to 27kJ/mol, i.e. 14 + 90% of 14? Or are we expected to work out 90% of the midpoint of the range, i.e. 18kJ/mol and infer that the range is from 11kJ/mol up to 29kJ/mol? Or something else?

    I can find no other source on line that mentions anything like a range of this magnitude. I see this Chaplin guy appears in a number of rather suspicious contexts (homeopathy and commercial water filtration for example). I am starting to wonder if he knows what he is talking about, or whether he may be some kind of crank.
     
  8. wellwisher Banned Banned

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    The entire web site is called Water Structure and Science. It summarizes all the main things science know about water, with water the most researched material in all of science. It references about 2500 papers. It is not just about what Chaplin has done. He summarizes that in a few paragraphs in one of about 50 chapters.

    The quote above makes reference's number 1829, which is below;

    M. Huš and T. Urbic Strength of hydrogen bonds of water depends on local environment, J. Chem. Phys.136(2012) 144305; see also S. Iwata, Analysis of hydrogen bond energies and hydrogen bonded networks in water clusters (H2O)20 and (H2O)25 using the charge-transfer and dispersion terms, Phys.Chem.Chem.Phys.16 (2014) 11310-11317.

    Each time we add another hydrogen bond to a cooperative, the strength of all the bonds in the group get stronger and all bonds length in the cooperative shrink. It is very similar to resonance.

    Say we start with the dimer. We then add water molecules, until there are 20 water in the cluster. If you measure the hydrogen bond strength of the original two waters of the dimer, the hydrogen bond strength is now up to 250% stronger. The cluster hydrogen bonds strength begin to approach covalent bonding strength. It becomes unclear which molecule of water owns which hydrogen atoms; delocalization of hydrogen and elections in a resonance. This is not well known about water, which is why it seems so odd. But it comes in handy for life.

    Below are some of the water clusters; Clusters F and G have 20 water.

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  9. exchemist Valued Senior Member

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    I'm afraid I do not have £40 to spend to read these articles in full.

    I understand of course the general principle, it is the magnitude of the alleged effect that I am calling into question. I just find it very hard indeed to believe that H bonds can more than double in strength due to these cooperative effects. You get nothing like that with "resonance" phenomena.
     
  10. timojin Valued Senior Member

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    • Please post on-topic.
    SH2 Is a gas at standard condition , NH3 is a gas if you think NH2' NH4 they are to alkaline and to bulky and will react with phosphate in the nucleotide.. Silane SiH4 is to reactive with oxigen.
     
  11. exchemist Valued Senior Member

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    Actually I have now found I could access the Hus and Urbic paper without paying. This is a set of calculations using computer programs and predicts a linear increase in bond strength of ~3kJ/mol per additional molecule in the first solvation shell. Once that shell is full then you get a much weaker effect in subsequent shells.

    I do not see anywhere in this a variation in hydrogen bond strength by a factor of 2.5. I think that would be to misread the nature of the work they have done - which is only computer modelling anyway and has not been validated by comparison with experiment. The maximum calculated variation they predict with these models seems to be between 5 and 9kcal/mol, i.e. ~20-36kJ/mol.

    But nonetheless, this is all very interesting I agree, so thanks for drawing my attention to these papers.

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  12. wellwisher Banned Banned

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    In water, we have an affect called pH. With pH, hydrogen protons can freely move between water molecules. The average hydrogen proton, in water, changes partners about once every millisecond. How is this possible, if H2O is composed of two strong covalent bonds that should not break, that easily, at that pace? It has to do with hydrogen bonding, acting a bridge between electrostatic and covalent bonds.

    Although it is called hydrogen bonding, the oxygen of water plays an equally important role in hydrogen bonding in water. Oxygen is highly electronegative and can hold electron. This holding can be enhanced if the oxygen also has other molecules of water hydrogen bonded pulling away electron density. This can force one of its own hydrogen, to go from covalent to hydrogen bond attached somewhere else.

    The cooperatives by lowering the bond lengths are keeping the oxygen and hydrogen in the transition zone, where the hydrogen become mobile. This is not easy to measure, but it logically follows from the swapping of hydrogen protons. Going from a hydrogen bond to covalent bond, implies a center zone that is neither but is both at the same time.
     

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