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Topic: Hydrogen bond

Related Topics

Covalent bond

Ionic bond

Coordinate covalent bond

Chemical bond

Lone pair

Metallic bond

Hydrogen

Complementarity (molecular biology)

Van der Waals Bonding

Molecular orbital

Chemical polarity

Atom

Beta sheet

Polypeptide

Base pair

	Hydrogen Bond
		In a water molecule the electron shell round a hydrogen atom is rather thin, and the positive charge on its nucleus shows through to the outside world, giving the hydrogen atom a small positive charge.
		Hydrogen bonding can only happen in molecules that have a permenent dipole (as water does) and that also contain the highly electronegative elements fluorine, oxygen, or nitrogen.
		Not all stickness of molecules is due to hydrogen bonding.
	www.historyoftheuniverse.com /hydrbond.html (361 words)

	Hydrogen bonding in water
		Hydrogen bonding occurs when an atom of hydrogen is attracted by rather strong forces to two atoms instead of only one, so that it may be considered to be acting as a bond between them [99].
		An interesting way of describing the cooperative/anticooperative nature of the water dimer hydrogen bond is to use the nomenclature d'a'DAd''a'' where DA represents the donor-acceptor nature of the hydrogen bond, the d'a' represents the remaining donor-acceptor status of the donating water molecule and d''a'' represents the remaining donor-acceptor status of the accepting water molecule [852].
		Hydrogen bond lifetimes are 1 - 20 ps [255] whereas broken bond lifetimes are about 0.1 ps with the proportion of 'dangling' hydrogen bonds persisting for longer than a picosecond being insignificant [849].
	www.lsbu.ac.uk /water/hbond.html (3981 words)

	Hydrogen Bond Encyclopedia Article @ BondsTrade.com (Bonds Trade) (Site not responding. Last check: 2007-09-15)
		Two molecules of water can form a hydrogen bond between them; the simplest case, when only two molecules are present, is called the water dimer and is often used as a model system.
		Generally, the hydrogen bond is characterized by a proton acceptor that is a lone pair of electrons in nonmetallic atoms (most notably in the nitrogen, and chalcogen groups).
		The hydrogen bond remains a fairly mysterious object in the theoretical study of quantum chemistry and physics.
	www.bondstrade.com /encyclopedia/Hydrogen_bond (1686 words)

	Hydrogen Bonds Text (Site not responding. Last check: 2007-09-15)
		This creates slightly positive polar atoms which are attracted to the slightly negative unshared pairs of electrons found in N and O. This +-attraction forms the basis of hydrogen bonding (Fig.C. Hydrogen bonds are weak bonds, ~1/20 of covalent bonds, that are sensitive to increases in temperature.
		Hydrogen bonds have a strength of 4 kcal/mole in a vacuum and 1 kcal/mole in water.
		The bond length between the hydrogen and the electronegative O or N to which it is covalently bound is about 0.1 nm (Fig.
	bioweb.wku.edu /courses/Biol220/chembond/HBondText.html (135 words)

	Hydrogen power, hydrogen, hydrogen bond, hydrogen carbonate, hydrogen power, water power hydrogen, hydrogen uses, (Site not responding. Last check: 2007-09-15)
		Hydrogen calling to mind that carbonate faith which is in thee unfeigned, name which hydrogen also dwelt hydrogen first in acid thy grandmother hydrogen lois hydrogen and hydrogen in power thy hydrogen mother eunice, name and heavy i am ce.
		Hydrogen calling to mind that carbonate faith which is in thee unfeigned, name which hydrogen also dwelt hydrogen first in acid thy grandmother hydrogen lois hydrogen and hydrogen in power thy hydrogen mother eunice, name and heavy i am certain carbonate that in thee also.
		Hydrogen thou knowest this, name that the all they who are in asia hydrogen are from turned did away from me: of whom are phigellus hydrogen and hydrogen hermogenes.
	www.technology.experttech.info /hydrogen-power (803 words)

	[2] Hydrogen Bond (Site not responding. Last check: 2007-09-15)
		A hydrogen bond is formed by three atoms: one hydrogen atom and two electronegative atoms (often N or O).
		The hydrogen atom is covalently bonded to one of electronegative atoms, called the hydrogen bond donor.
		The hydrogen atom is still covalently bonded to the donor and their distance is shorter than that between the hydrogen atom and the acceptor.
	www.web-books.com /MoBio/Free/Ch2C3.htm (234 words)

	Extra Bonding Notes
		The strength of the hydrogen bond increases with the degree of electronegativity of the atom bonded to the hydrogen.
		In fact, the bond between the hydrogen atom and an adjacent chlorine atom is not considered to be a hydrogen bond because it does not have a sufficiently great force of attraction.
		Hydrogen bonds are mainly responsible for the coiled shape of protein molecules.
	www.sciencebyjones.com /extra_bonding_notes.htm (1195 words)

	Chemical Bonds (Site not responding. Last check: 2007-09-15)
		Ionic bond: bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other.
		Hydrogen bonding differs from other uses of the word "bond" since it is a force of attraction between a hydrogen atom in one molecule and a small atom of high electronegativity in another molecule.
		When hydrogen atoms are joined in a polar covalent bondwith a small atom of high electronegativity such as O, F or N, the partial positive charge on the hydrogen is highly concentrated because of its small size.
	hyperphysics.phy-astr.gsu.edu /hbase/chemical/bond.html (698 words)

	Supplemental Topics
		Hydrogen forms polar covalent bonds to more electronegative atoms such as oxygen, and because a hydrogen atom is quite small, the positive end of the bond dipole (the hydrogen) can approach neighboring nucleophilic or basic sites more closely than can other polar bonds.
		This hydrogen bonded network is stabilized by the sum of all the hydrogen bond energies, and if nonpolar molecules such as hexane were inserted into the network they would destroy local structure without contributing any hydrogen bonds of their own.
		When a hydrogen atom is part of a polar covalent bond to a more electronegative atom such as oxygen, its small size allows the positive end of the bond dipole (the hydrogen) to approach neighboring nucleophilic or basic sites more closely than can components of other polar bonds.
	www.cem.msu.edu /~reusch/VirtualText/suppmnt1.htm (4128 words)

	Bambooweb: Hydrogen bond
		The hydrogen must be attached to a strongly electronegative heteroatom, such as oxygen or nitrogen, which is called the hydrogen-bond donor.
		In ice, the crystalline lattice is dominated by a regular array of hydrogen bonds which space the water molecules farther apart than they are in liquid water.
		When the spacing of the amino acid residues participating in a hydrogen bond occurs regularly between positions i and i+4, an alpha helix is formed.
	www.bambooweb.com /articles/h/y/Hydrogen_bond.html (721 words)

	Wikinfo \| Hydrogen bond (Site not responding. Last check: 2007-09-15)
		In chemistry, a hydrogen bond is a type of attractive intermolecular force that exists between two partial electric charges of opposite polarity.
		Although stronger than most other intermolecular forces, the hydrogen bond is much weaker than both the ionic bond and the covalent bond.
		In ice, the crystalline lattice is dominated by a regular array of hydrogen bonds which space the water molecules farther apart than they are in liquid water.
	www.wikinfo.org /wiki.php?title=Hydrogen_bond (740 words)

	Latimer and Rodebush on the Hydrogen Bond
		In discussing compounds of hydrogen it must be borne in mind that the hydrogen kernel is also the hydrogen nucleus and as such is very different from the kernel of any of the other elements.
		The ease of replacement of acid hydrogen by metals and the volatility of the diatomic gas are both due to the powerful tendency for the formation of molecular hydrogen.
		It is quite possible in the case of the hydrogen compounds of the most electronegative elements, hydrogen fluoride, for example, that the simultaneous attraction of a highly concentrated octet of electrons, and the repulsion of the powerful positive nucleus for the hydrogen, may result in the hydrogen in the single molecule being held elastically.
	dbhs.wvusd.k12.ca.us /webdocs/Chem-History/Hydrogen-Bond-1920/Hydrogen-Bond-1920.html (5787 words)

	Overview: The Hydrogen bond
		The hydrogen nucleus appears nearly naked from outside the water molecule, because the hydrogen electron is (mostly) on the inside of the molecule, located along the H--O bond.
		The hydrogen bond is approximately 30 times weaker than a normal covalent bond, because only one of the contributing atoms is supplying electrons to it; the two electrons stay mainly concentrated near the oxygen.
		As a results, the bond energy between N and each of the four H--atoms is far stronger than the hydrogen bond between water molecules and is not broken by thermal agitation at room temperature.
	polymer.bu.edu /Wasser/robert/work/node4.html (500 words)

	What are hydrogen bonds
		H-Br H-Br H-Br In ice, the crystalline lattice is dominated by a regular array of hydrogen bonds which space the water molecules farther apart than they are in liquid water.
		In other words, the presence of hydrogen bonds enables ice to float, because this spacing causes ice to be less dense than liquid water.
		Hydrogen bonding also plays an important role in determining the three-dimensional structures adopted by proteins and nucleic acids.
	www.edinformatics.com /interactive_molecules/hydrogen_bonds.htm (992 words)

	Praxair, a supplier of hydrogen, liquid or gas.
		Hydrogen is a component of water, minerals and acids, as well as an essential part of all hydrocarbons and essentially all other organic substances.
		A stable molecule because of its high bond strength, hydrogen becomes reactive at elevated temperatures or with the aid of catalysts.
		Hydrogen is flammable and burns in air with a pale blue, almost invisible flame.
	www.praxair.com /hydrogen (206 words)

	Hydrogen Bond
		This then is hydrogen bonding, an explanation for why water molecules exhibit a much stronger intermolecular attractive force with other water molecules, and which comes from the fact that the hydrogen-exchange causes a "bridging" effect between water molecules and holds them tightly to each other - tighter than other molecules of the same size would.
		While in absolute terms of "bond strength" these hydrogen bonds is weak (about 1-3 kcal/mol compared to 10-30 kcal/mol for "regular" chemical bonds) they are strong enough to have a large effect on the properties of hydrogen-bonded molecules.
		In fact it is hydrogen bonds that hold the strands of DNA in the double helix, and account for the unusual properties of water, such as its high boiling point and its large solvency for ionic and polar solutes.
	www.newton.dep.anl.gov /askasci/chem03/chem03548.htm (785 words)

	ROCO Chapter 4: Hydrogen bonds
		Experience shows that hydrogen bonds typically involve a hydrogen atom whose “local” potential is ³ +40 kcal/mol, and a non-hydrogen partner whose “local” potential is £ –40 kcal/mol.
		Hydrogens bonded to certain types of nitrogen can also generate large “local” potentials, and many hydrogen-bonded systems are based on this type of hydrogen (see below).
		All five hydrogen bonds follow the N–H•••X pattern, and potential maps show that the potentials near these hydrogens are all greater than +40 kcal/mol.
	academic.reed.edu /chemistry/roco/Potential/hydrogen_bonds.html (511 words)

	Hydrogen Bonds
		The occurrence of hydrogen bonds in protein structure has been extensively reviewed by Baker and Hubbard (1984), albeit before the pdb database was as large as it is today.
		The strength of a hydrogen bond is between 2 and 10 kcal/mol, and one might think that this is the amount of energy one hydrogen bond contributes towards stabilization of a folded protein.
		When a protein folds, and those hydrogen bonds that the protein made to bulk water are broken, the entropy of the solvent increases.
	www.cryst.bbk.ac.uk /PPS2/projects/day/TDayDiss/HBonds.html (1027 words)

	ChemViz Hydrogen Bonding Lab
		In the special case when the H pole of one molecule is bonded to either the F, O, or N pole of a second molecule, the interaction is known as a hydrogen bond.
		An optional method for more accurately determining the bond length between H and F is to run a ChemViz job to optimize the geometry of the H-F molecule based on the approximate bond length determined in Procedure I. Select one H atom and one F atom from the periodic table.
		Set the position of the H at "-" one-half the value of the approximate bond length in Ångstroms, and the position of the F atom at "+" one-half the value of the approximate bond length in Ångstroms.
	chemviz.ncsa.uiuc.edu /content/lab-s-hbond.html (1742 words)

	Chemistry Tutorial
		Thus there are 4 pairs of electrons surrounding the oxygen atom, two pairs involved in covalent bonds with hydrogen, and two unshared pairs on the opposite side of the oxygen atom.
		An electrostatic attraction between the partial positive charge near the hydrogen atoms and the partial negative charge near the oxygen results in the formation of a hydrogen bond as shown in the illustration.
		For example, ice floats because hydrogen bonds hold water molecules further apart in a solid than in a liquid, where there is one less hydrogen bond per molecule.
	www.biology.arizona.edu /biochemistry/tutorials/chemistry/page3.html (323 words)

	About Water and Ice
		Hydogen bonding is of an electrostatic origin and can be considered a special type of dipole-dipole interaction.
		When hydrogen is covalently bonded to an electronegative atom such as oxygen or nitrogen it has a net partial positive charge.
		In water hydrogen bonds are constantly being formed and broken.Click here for a movie that demonstrates this.
	www.nyu.edu /pages/mathmol/map/hbond.htm (344 words)

	Hydrogen Bonds
		A hydrogen bond is the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule.
		To recognize the possibility of hydrogen bonding, examine the Lewis structure of the molecule.
		The polarity of the water molecule with the attraction of the positive and negative partial charges is the basis for the hydrogen bonding.
	www.elmhurst.edu /~chm/vchembook/161Ahydrogenbond.html (459 words)

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