L4 - Covalent And Non-covalent Bonding

The electrostatic interaction of the differently charged species

• in order to reach stability of a filled shell, it can gain an e- from a suitable source • when salt in solid form, ions are arranged in regular arrays • energy of the electrostatic interactions is partly why it’s stable

The chemical bond that involved the sharing of pairs of electrons between atoms

Bring two atoms close together, the 2 atomic orbitals now merge into a single bond orbital that contains both electrons

• electrons must have opposite spins, must be paired • each electron is able to exist in any part of the bond orbital, belongs to both atomic nuclei

The energy needed to break the bond that was formed A measure of how strong the bond is

A partially electrostatic attraction between a H which is bound to a more electronegative atom such as N,O,F and another adjacent atom bearing a lone pair of electrons

The donor and acceptor atoms and their environments and geometries

Increase in melting point, boiling point, solubility and viscosity

Relatively weak forces that attract neutral molecules to one another

• electrically neutral molecules may exhibit permanent electric dipoles • these dipoles have tendency to align = net attractive force • permanent dipoles may temporarily distort the electric charge in a neraby molecule • molecules with no permanent dipole temporarily dipoles from the random electron motion = london forces

Attractive, non covalent interactions between aromatic rings

• sandwhich • t shaped • parallel; displaced

• gas phase and low temp benzene forms a dimer, binding energy • x-ray crystallography gives perpendicular and offset paraller configuartions in many simple aromatic compounds

Describes the segregation of water and non-polar substances

• strong network of hydrogen bonds = non polar molecules cannot form hydrogen bonds

Molecules both hydrophobic and hydrophilic domains

The hydrophilic head is found on the outside and the hydrophobic tails reside inside

Macromolecules • glycine • alanine • valine • leucine • phenylalanine • tryptophan • methionine

They can intereact with the surrounding water molecules • minimises the number of hydrophobic side chains exposed to the water solvation sphere = the principle driving force behind the folding process

• primary • secondary • tertiary • quaternary

Sequence of amino acids in the polypeptide chain - held together by peptide bonds - formed from the acid group of one and the amine group of another

Highly regular sub-structures on the polypeptide backbone chain (alpha helix, beta pleated sheets) - pattern defined by hydrogen bonds - between the main-chain peptide groups

Overall 3D shape of the protein molecules, 2nd structure folded into a compact globular structure - driven by the non-specific hydrophobic interactions - interactions such as salt bridges, hydrogen bonds, tight packing of side chains and disulphide bonds