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Topic: HYDROGEN BONDING  (Read 13235 times)

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samrow

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HYDROGEN BONDING
« on: October 17, 2004, 06:12:15 AM »
Any help would be great!!

um..where do i start..
can nyone explain y hydrogen doesnt form hydrogen bonds with chlorine, but it does with ammonia?? even though ammonia and chlorine have exactly the same electonegativity values!?!?

what is the origin of the hydrogen  bonds in methanol??

And why in some samples of hydrogen fluoride vapour, have moelcules been detected with a relative molecular mass of 100?

And finally, how does waters ability to form 2 hydrogen bonds per molecule, explain the structure of ice?

any input, on any of these would be greatly appreciated, and i would be a much less confused person!!

thankz

ssssss

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Re:HYDROGEN BONDING
« Reply #1 on: October 17, 2004, 10:10:06 AM »
Any help would be great!!

um..where do i start..
can nyone explain y hydrogen doesnt form hydrogen bonds with chlorine, but it does with ammonia?? even though ammonia and chlorine have exactly the same electonegativity values!?!?

what is the origin of the hydrogen  bonds in methanol??

And why in some samples of hydrogen fluoride vapour, have moelcules been detected with a relative molecular mass of 100?

And finally, how does waters ability to form 2 hydrogen bonds per molecule, explain the structure of ice?

any input, on any of these would be greatly appreciated, and i would be a much less confused person!!

thankz

Cant give you the best approach in all the questions but i am trying:

1st of all about the structure of ice.You need not to search here and there it is given in your Book.A cage like structure.This converges and Diverges with the temperature.And the this sructure is so that it gives the maximum Density of water at 4ocelsius.

About HF flouride its vapour Exist as a Diamer

Demotivator

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Re:HYDROGEN BONDING
« Reply #2 on: October 17, 2004, 04:39:50 PM »
1) The size effect of Cl spoils the ability to hydrogen bond (the electrons are too "diffuse"). High electronegativity plus small size is the right combination.

2) The H (specifically the one bonded to O) of one methanol hydrogen bonds to the O of another.

3) HF not only exists as a dimer in the gas phase, but can also exist as H4F4 and even H6F6.
« Last Edit: October 18, 2004, 09:17:42 AM by Demotivator »

Offline Donaldson Tan

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Re:HYDROGEN BONDING
« Reply #3 on: October 23, 2004, 05:34:21 AM »
1) The size effect of Cl spoils the ability to hydrogen bond (the electrons are too "diffuse"). High electronegativity plus small size is the right combination.

H bonding is confined to F,O,N atoms.

Quote
how does waters ability to form 2 hydrogen bonds per molecule, explain the structure of ice?
The oxygen in each water molecule has 2 lone pair available for hydrogen bonding. Hydrogen from adjacent water molecule therefore can H Bond with water at these two sites.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Demotivator

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Re:HYDROGEN BONDING
« Reply #4 on: October 23, 2004, 03:51:48 PM »
1. Yeah, we already know about N,O and F. The question was why?

2. Therefore, a tetrahedral structure is formed.
« Last Edit: October 23, 2004, 04:17:04 PM by Demotivator »

pizza1512

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Re:HYDROGEN BONDING
« Reply #5 on: January 22, 2005, 09:50:12 AM »
Doesn't it depend on their reactivity?

 :P

dexangeles

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Re:HYDROGEN BONDING
« Reply #6 on: January 22, 2005, 01:02:03 PM »
look at the periodic table and look at the trends that follow it like: size, eletronegativity, e- affiliation, and stuff --- this will give you a clue as to why its only N, O, F bonded to H that forms hydrogen bonds


Offline Mitch

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Re:HYDROGEN BONDING
« Reply #7 on: January 22, 2005, 02:30:35 PM »
Hydrogen Bonding can be such a complicated question, I don't even try to answer them anymore. We have to be very specific on how we define a "bond".
Most Common Suggestions I Make on the Forums.
1. Start by writing a balanced chemical equation.
2. Don't confuse thermodynamic stability with chemical reactivity.
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Offline Donaldson Tan

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Re:HYDROGEN BONDING
« Reply #8 on: January 22, 2005, 04:59:21 PM »
why F,O,N?

I think intermolecular bonding due to H atom attached to F, O or N exhibits signficantly stronger intermolecular bonding than the ongoing trend with other molecules.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

dexangeles

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Re:HYDROGEN BONDING
« Reply #9 on: January 22, 2005, 05:25:03 PM »
oh i meant.. they should check what is it with the intramolecular forces (periodic trend) between N, O, F bonded to H that makes it different from others; thus, realizing an intermolecular force of H-bonding between molecules that possess these.

yipster

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Re:HYDROGEN BONDING
« Reply #10 on: January 25, 2005, 08:23:56 AM »
Quote
Hydrogen Bonding can be such a complicated question,
I don't even try to answer them anymore.
We have to be very specific on how we define a "bond".

keep me posted on this topic anyway please.
i might even come up with some dumb questions...

found some bonding info at http://www.chemtutor.com/compoun.htm

Quote
BONDING FORCES IN WATER

The alchemists of old had several other objectives aside from making gold. The though of a fluid material that could dissolve anything, the universal solvent, was another alchemical project. No alchemist would say, though, what material would hold such a fluid. Surprisingly, the closest thing we have to a universal solvent is water. Water is not only a common material, but the range of materials it dissolves is enormous. The guiding principle for predicting which materials dissolve in which solvent is that 'like dissolves like.' Fluids in which the atoms are attached with covalent bonds will dissolve covalent molecules. Fluids with a separation of charge in the bonds will dissolve ionic materials.

The bonds that hold hydrogen atoms to oxygen atoms are closer to covalent than ionic, but the bond does have a great deal of ionic character. Oxygen atoms are more electronegative than hydrogen atoms, so the electron pair is held closer to the oxygen atom. Another way to look at it is that there are only a very small number of water molecules ionized. The ionization of water, H2O  H+ + (OH)-, into hydrogen ions and hydroxide ions happens in only a very small number of the water molecules, but the effect is quite important as the reason for the existence of acids and bases. Materials of a mildly covalent nature, such as small alcohols and sugars, are soluble in water due to the mostly covalent nature of the bonds in water.

The shape of the water molecule is bent at about a 105 degree angle due to the electron structure of oxygen. The two pairs of electrons that force the attached hydrogens into something close to a tetrahedral angle give the water molecule an unbalanced shape like a boomerang, with oxygen at the angle and the hydrogen atoms at the ends. We can think of the molecule has having an ‘oxygen side’ and a ‘hydrogen side’. Since the oxygen atom pulls the electrons closer to it, the oxygen side of the molecule has a slight negative charge. Cations (positive ions) are attracted to the partial positive charge on the oxygen side of water molecules. Likewise, the hydrogen side of the molecule has a slight positive charge, attracting anions. Polar materials such as salts, materials that have a separation of charge, dissolve in water due to the charge separation of water. The origin of the separation is called a dipole moment and the molecule itself can be called a dipole.

More about water later.

 
« Last Edit: January 25, 2005, 02:03:59 PM by yipster »

pizza1512

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Re:HYDROGEN BONDING
« Reply #11 on: January 27, 2005, 08:53:22 AM »
What's that to do with Hydrogen bonding?...



 ;D

yipster

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Re:HYDROGEN BONDING
« Reply #12 on: January 28, 2005, 06:08:18 PM »
actually your half rite, it was a multiple question from samrow though and the site mentioned does popular explain a few things on H bonding i couldnt easely find elsewhere.
 :1eye:

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