2.4 Effects of intermolecular forces Flashcards
what are intermolecular forces
they are attractive forces between parts of two molecules
having or not having attraction between molecules affects physical properties…
-boiling/melting point
-solubility
-hydrophililicity/phobicity
how does intramolecular forces effect boiling point
when things boil/melt molecs get further apart
more intermolecular forces (attraction) means more energy (heat) is needed to move them apart
if dispersion forces are week how come some things with dispersion forces take more energy to boil
because the more you have the stronger the forces meaning the more heat required
how do substituents (branced off c) effect the boiling point
having substituents decreases how close two molecules can get, so it decreases the about of dispersion interactions leading to a lower BP
how do cyclic rings influence boiling point
they increase how close two molecules can get so it increase the amount of dispersion interactions. so it increases BP
what forces have highest to lowest boiling points (usally)
electrostatic, hydrogen bomding, dipole-dipole, dispersion
what can effect solubility
attractive forces from a molecule to molecules of solvent can affect solubility
what is the easies way to remember the solubility trend
like dissolves like
(molecs prefer solvents with similar intermolecular forces)
do all forces effect solubility equally
no
solvents are generally classes using two parameters:
polar + non-polar
protic + aprotic
what is polar/non-polar
wether or not it has a permanent dipole
what is protic/aprotic
whether it can or cannot donate a hydrogen bond
what is the best kind of solvent for a molecule
the solvent that does the same thing for it
e.g. hexane is nonpolar and aprotic and its best solvent would be hexane which is non-polar and aprotic
anything that increases electrostatic and dipole-dipole (H bonding) interactions increases…
hydrophilicity
