Hydrogen Bonds and Water

What type of bonding is Hydrogen bonding?

Hydrogen bonding is a special type of dipole-dipole

attraction between molecules.

What is dipole-dipole bonding?

A pair of equal and oppositely charged or

magnetized poles separated by a distance.

What are some characteristics of Hydrogen Bonds?

• Relatively weak bonding and can be broken easily

• Weak as singular bonds but are very strong if there are many

Why are hydrogen bonds important?

• Source of unique properties of water

• Structure and function of proteins

• Structure and function of DNA

• Structure and function of polysaccharides

• Binding of substrates to enzymes

• Binding of hormones to receptors

• Matching of mRNA and tRNA

What are Van der Waals forces?

The more electrons a molecule has, the stronger the

London dispersion forces (Van der Waals forces) are. This force exists between all types of molecules, ionic or covalent and polar or non-polar.

What are the characteristics of Van der Waals forces?

• Weak individually easily broken, reversible

• Universal occur between any 2 atoms that are near

each other

What are the properties of water?

• Liquid at room temperature

• Water molecules are cohesive (sticky)

• Water is a solvent for polar molecules “universal

solvent”

• Temperature of liquid water rises and falls

slowly.

• Water has a high heat of vaporisation

• Frozen water is less dense than liquid water.

What does a solution consist of?

• A solvent (the most abundant part) and

• A solute (less abundant part) that is dissolved in the solvent

Is water polar or non-polar?

Polar (O is slightly negative, H is slightly positive)

What compounds do and don’t dissolve in water?

• Polar compounds readily dissolve; hydrophilic

• Nonpolar compounds dissolve only slightly; hydrophobic

Do ionic compounds dissolve in water?

Yes

Why is water used for life?

• Chemical reactions occur in water

• Water is a critical determinant of the structure and function

of proteins, nucleic acids, and membranes.