organic chemistry — bonds and forces

intramolecular bonding

forces that hold atoms within a molecule or ionic compound together

Intramolecular forces are often strong, as the bond energies are very strong. When they break, they form different molecules or atoms, as the chemical composition changes

intermolecular forces

Intermolecular forces are forces between molecules or atoms in different molecules. They are responsible for state properties — solid, liquid and gas. Types include: London Dispersion, dipole-dipole and hydrogen bonds. Intermolecular forces are weaker than intramolecular forces, and hence are easier to break. When such bonds are disrupted, molecules may change state (i.e. become a liquid from a gas etc). When intermolecular bonds are broken, the chemical composition is not broken.

How does a temporary dipole form?

As electrons are always moving and are not necessarily evenly distributed, an asymmetrical distribution of electrons can occur, causing a temporary dipole. Temporary dipoles are the weakest intermolecular forces, and occur between all molecules, regardless if they’re polar or not.

london dispersion forces

When molecules are close to one another, a temporary dipole can induce temporary dipoles in surrounding molecules.

Although this is only at an instant, it can impact the properties of non-polar molecules.

effects of london dispersion forces

Longer and heavier molecules have stronger dispersion forces. The shape and length of a molecule affect dispersion forces.

Larger carbon chains have stronger dispersion forces.

Higher order bonding can disrupt the forces

saturated bonds

• single-bonded carbon chains

• slow reactions

• substitution reactions

unsaturated bonds

• contains a double or triple carbon bond

• fast reaction

• addition reaction

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