Vander Waals Forces and Its Significance

By -: Lovnish Thakur(IBT-1ST SEM)Enrollment No. -: ASU2014010100099Presentation-:U4P1Course-: Chemistry for biologist(102)

Vander Waals force

• It is the sum of theattractive or repulsiveforces between molecules.

• These were named after -:

Johannes Diderik van der

Waals

Its main characteristics are:-

They are weaker than normal covalent ionic bonds.

Van der Waals forces are additive and cannot be saturated.

They have no directional characteristic.

They are all short - range forces and hence only interactions between nearest need to be considered instead of all the particles. The greater is the attraction if the molecules are closer due to Van der Waals forces.

Van der Waals forces are independent of temperature except dipole - dipole interactions.

• These includes-:

• force between two permanent dipoles (Keesomforce)

• force between a permanent dipole and a corresponding induced dipole (Debye force)

• force between two instantaneously induced dipoles (London dispersion force).

Dipole-Dipole

• Two polar molecules align so that d+ and

d- are matched (electrostatic attraction).

• Ex: ethane (C2H6) vs. fluromethane (CH3F)

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Dipole-Induced Dipole

A dipole can induce (cause) a temporary dipole to form in a non-polar molecule

The molecules then line up to match d+ and d-charges

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Dispersion Forces

A temporary dipole forms in a non-polarmolecule which leads to a temporary dipole toform in another non-polar molecule.

Dispersion is the only intermolecular attractionthat occur between non-polar molecules

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SIGNIFICANCE

In Protein folding

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Vander waals interaction isthe another importantbonding type that helpsstabilizing the proteinstructure. In the coiled-coilprotein, there is interactionbetween side chain in alphahelix. If these repeatingresidues are hydrophobic,such as leucine, van der waalsinteraction will be formed tostabilize this proteinstructure.

Graphenes Bonding Forces in Graphite

Weak forces betweengraphenes suggestthat they are the vander Waals Forces.

In polymer formation

• Many polymeric chain are cross linked by vanderwaals force and get stable.

www.m2polymer.com

Used by some animal

• Gecko lizard use these forces to climb on the walls.

• Some other animal use animal to walk on water.

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In modern technology

In May 2014, DARPA demonstrated the latestiteration of its Geckskin by having a 100kgresearcher (saddled with 20kg of recordinggear) scale an 8m tall glass wall using only twoclimbing paddles. Tests are ongoing, butDARPA hopes one day to make the technologyavailable for military use, giving soldiers SpiderMan-like abilities in urban combat

www.wired.com

References

http://en.wikibooks.org/wiki/Structural_Biochemistry/Chemical_Bonding/Van_der_Waals_interaction

antoine.frostburg.edu/chem/senese/.../h-bonding-vs-london-forces.shtml

en.wikipedia.org/wiki/Van_der_Waals_force

chemwiki.ucdavis.edu › ... › Intermolecular Forces

przyrbwn.icm.edu.pl/APP/PDF/112/a112z308.pdf