McMurry (Kap 2,12) Flashcards
What is the difference between covalent interactions and noncovalent interactions/intermolecular forces/van der Waals forces?
Covalent interactions focus on bonds, and the covalent interactions between atoms within a molecule.
Intermolecular forces focus on the variety of interactions between molecules, that affect molecular properties. Important to understand for large biomolecules such as proteins and so on.
What are the three main types of van der Waals forces?
1) dipole-dipole forces
2) Dispersion forces
3) Hydrogen bonding
Describe the dipole dipole forces?
In polar molecules, they have a partial negative side and a partial positive side. These charges between molecules can affect each other.
The forces can either be attractive to each other or repulsive.
The attractive geometry is lower in energy and therefore dominates.
Describe the dispersion forces?
Occurs between all neighboring molecules. Because the electron distribution is constantly changing within a molecule, causing a temporary dipole. (even in nonpolar molecules)
This temporary dipole causes another neighbor molecule to have the temporary opposite dipole, and a tiny attraction is induced between the two.
The effect is often strong enough to hold molecules close together to hold liquid and solids rather then gas.
Describe the hydrogen bond?
An attractive interaction between a hydrogen bonded to an electronegative O or N atom, and an unshared electron pair on another O or N atom. In other words a very strong dipole-dipole interaction.
In water, the partial negative charge on O attracts the partial positive charge on H from another water molecule, resulting in an attractive force.
What does hydrophilic mean?
Water loving.
Example sugar. Usually have a number of OH groups in the structure, which allows (hydrogen bonds force) with water.
What does Hydrophobic mean?
water fearing
Example oil. Usually dont contain any OH groups or other groups that can form (hydrogen bond forces) with water.
