F.6 Chemistry ProjectDipole-dipole interaction and

its application

Fung Chun Yu (8)Kwok Chun Nga (9)Chan Wai Sum (5)

Introduction

• What is dipole-dipole interaction?– The difference in electronegativities between

elements in a covalent bond produces a certain degree of polarization

– The electron cloud is distorted, and a dipole is produced

Introduction

• What is dipole-dipole interaction?– example can be seen in hydrogen chloride (HCl)

– Cl, being more electronegative, pulls the electron cloud towards it Distortion of electron cloud

– The positive end attracts the negative end the molecules are packed regularly in a head-to-

tail fashion

Introduction

An illustration of the head-to-tail arrangement of molecules due to dipole-dipole interaction

Introduction

An extraordinarily simple animation showing the interaction between HCl molecules

Application of dipole-dipole interaction

–LCD

–Biological field

Liquid Crystal Display

• consists of two sheets of polarizing material with a liquid crystal solution in between• can be orientated into a a desired direction under current. • light will be polarized by this pattern

Why can the liquid crystal be arranged by electricity?

Liquid Crystal Display

• liquid crystal molecule used is introduced below• Methoxybenzilidene Butylanaline (MBBA)

• p-decyloxybenzylidene p'- amino 2-methylbutylcinnamate (DOBAMBC)

 

Liquid Crystal Display

• The molecules are dipoles • they twist the plane of polarization originally• They are aligned regularly

in a head-to-tail fashion asmentioned above when electric field is applied

formed a polaroid• light is then blocked

Biological Field• Molecular arrangement of

protein There are four levels of protein structurePrimary levelarrangement of amino acid Secondary structure helical coiling of the peptide

Biological Field

Tertiary structure spatial relationship of different secondary structures Quaternary structure

How can we stabilize the protein structure???

Biological Field

• Polypeptide is a long chain molecule

• Dipole is present in polypeptide• Interactions including Dipole –

dipole interaction stabilize the structure

Biological Field

• Example: HaemoglobinConsists of four protein

subunits + haem moleculeFormation of

haemoglobin involved dipole-dipole interaction

Dipole-dipole interaction allow the haemoglobin to take its final shape

Acknowledgement

• Wikipedia (http://en.wikipedia.org/• http://www.gullwinguk.com• http://bucarotechelp.com/computers/

anatomy/91060003.asp

The End