{"id":1020,"date":"2019-10-22T13:16:36","date_gmt":"2019-10-22T13:16:36","guid":{"rendered":"http:\/\/chemdictionary.org\/?p=1020"},"modified":"2019-10-22T13:16:42","modified_gmt":"2019-10-22T13:16:42","slug":"hydrogen-bonding-in-hydrogen-flouride-hf","status":"publish","type":"post","link":"https:\/\/chemdictionary.org\/hydrogen-bonding-in-hydrogen-flouride-hf\/","title":{"rendered":"Hydrogen Bonding in Hydrogen Flouride (HF)"},"content":{"rendered":"\n

Definition\n<\/strong><\/h3>\n\n\n\n

Hydrogen bonding is a weak type of force which forms a dipole-dipole interaction between two molecules within the same molecule. Depending upon different contexts, its definition has been changing. According to earlier definitions “Hydrogen bonds is an interaction between the covalent pair A—H (donor) to a nearby electronegative atom B or X (acceptor). And \u201cA\u201d is more electronegative [1] [2].<\/strong><\/p>\n\n\n\n

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Fig 1: Basic Structure of intermolecular hydrogen bonding.<\/strong><\/p>\n\n\n\n

<\/p>\n\n\n\n

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            Fig\n2: Hydrogen bond donor and hydrogen bond acceptor molecule.<\/strong><\/p>\n\n\n\n

            With\nthe context of van der wals interactions “Hydrogen bond exists between the\nfunctional group A-H and atom or group of atoms X in same or different\nmolecules when below mentioned conditions are fulfilled i.e.<\/p>\n\n\n\n

a)<\/strong> Evidence of bond formation. <\/p>\n\n\n\n

b)<\/strong> Hydrogen already making a bond to\nsome atom and this linkage will be an additional one [3].<\/strong><\/p>\n\n\n\n

Primary Features\nof hydrogen bonding<\/strong><\/p>\n\n\n\n

Due to the\nfollowing main reasons, hydrogen bonding is originated between molecules. Firstly,\nHydrogen is attached to one of most electronegative elements and this bonding\ncauses hydrogen to acquire a positive charge. Secondly, all atoms, to which\nhydrogen is attached, are not only negative but that each element should have\none active lone pair present in the outermost shell.<\/p>\n\n\n\n

Types of hydrogen bonds<\/strong><\/p>\n\n\n\n

The Following two types of hydrogen bonds exist depending\nupon the position of elements that are bonding together by these bonds.<\/p>\n\n\n\n

  1. Intramolecular\nhydrogen bonding:<\/strong><\/li><\/ol>\n\n\n\n

    Intramolecular hydrogen bonds are those which occur within one molecule. This is mainly due to the presence of two functional groups of a molecule that are capable of forming hydrogen bonds with each other. For this to happen, both a hydrogen donor an acceptor must be present within one molecule, and they must be within proximity of each other in the molecule. For example, Intramolecular hydrogen bonding occurs in ethylene glycol between its two hydroxyl groups and nitrophenol.<\/p>\n\n\n\n

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    <\/figcaption><\/figure><\/div>\n\n\n\n

    Figure 3: Examples of Intramolecular\nhydrogen bonding in Ethylene glycol (left) and O-nitro phenol (Right)<\/strong><\/p>\n\n\n\n

    • Intermolecular hydrogen bonding:<\/strong><\/li><\/ul>\n\n\n\n

      Hydrogen bonds can also occur between separate molecules of the same substance. They can occur between any numbers of molecules as long as hydrogen donors and acceptors are present in positions in which they can interact. For example, intermolecular hydrogen bonds can occur between NH3 molecules, between H2O molecules alone, or between NH3NH3 and H2OH2O molecules. HFHF is also another example of intermolecular hydrogen bonding. And this bonding gives a unique set of physical properties to these molecules in bonded form [4]<\/b>.<\/p>\n\n\n\n

      <\/p>\n\n\n\n

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      Figure 4: Intermolecular hydrogen bonding:\n(a) NH3-H2O (b) H2O- H2O (c) H2O \u2013NH3 (d) HFHF<\/strong><\/p>\n\n\n\n

      Hydrogen Bonding in HF <\/strong><\/p>\n\n\n\n

      One important example of intermolecular\nhydrogen bonding is among HF molecules. Hydrogen bonding, in this case, is\noriginated in the following way:<\/strong><\/p>\n\n\n\n

      Hydrogen contains one electron, and fluorine requires one electron to become stable, so the bond forms readily when the two elements interact. As a result of this interaction; hydrogen fluoride is formed. These HF molecules further make chains with each other through hydrogen bonding interactions. When two hydrogen fluoride molecules interact with each other then, they form a zig-zag structure involving interaction between positively charged hydrogen of one molecule with negatively charged fluoride of another molecule [5].<\/strong><\/p>\n\n\n\n

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      \"\"<\/figure>\n\n\n\n

      Fig\n3: Linear structure showing hydrogen bonding between HF molecules and sigma\npositive and sigma negative charges,<\/strong><\/p>\n\n\n\n

      Physical\nProperties of hydrogen fluoride<\/strong><\/p>\n\n\n\n

      Hydrogen\nfluoride is a colorless gas that is corrosive in nature. When hydrogen fluoride\nis dissolved in water, hydrofluoric acid is formed. HF forms orthorhombic crystals below\n\u221283.6 \u00b0C (\u2212118.5 \u00b0F), consisting of zig-zag chains of HF molecules. The HF\nmolecules, with a 95 pm length H\u2013F bond, are linked to nearby molecules by\nintermolecular H\u2013F Hydrogen <\/p>\n\n\n\n

      bonding having a distance of 155 pm. Liquid HF also consists of chains of HF molecules, but the chains are shorter, consisting of an average of only five or six molecules [6].<\/strong><\/p>\n\n\n\n

      <\/p>\n\n\n\n

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      Figure 5: Bond length and Bond angle<\/strong><\/p>\n\n\n\n

      Bonding\nangle <\/strong><\/p>\n\n\n\n

      The bonding angle of HF hydrogen bonding is 115 degrees. This gives it an\northorhombic structure, as this angle is purely dependent on outermost\norbitals.<\/strong><\/p>\n\n\n\n

      Strength of HF molecule:<\/strong><\/p>\n\n\n\n

      Hydrogen fluoride,<\/em> HF, is the only halide that can form hydrogen bonds. Since fluorine is the most electronegative element, the difference in electronegativity between itself and hydrogen will be the biggest of the group. However, in the case of the other halides, the inability to form hydrogen bonds has another important reason behind it.<\/p>\n\n\n\n

      \"\"<\/figure><\/div>\n\n\n\n

      Fig 6: The presence of charge at molecules ends are well explained\nby orbitals in red color.<\/strong><\/p>\n\n\n\n

      Two\nreasons are the atomic size and electronegativity difference.<\/p>\n\n\n\n