Intermolecular Interactions Flashcards
What is electronegativity?
describes the ability of an atom to pull e- towards itself
what is a polar bond?
when the bond is officially covalent but there is a difference in e- density between the two
polar covalent bond
permanent dipole
same element forming covalent bond
distribution of e- in molecular orbitals is symmetrical
different atoms form covalent bond
asymmetric distribution of e-
different electronegativities
different abilities to attract e-
extent relies on atoms electronegativities
what is a permanent dipole?
small charge difference across a molecule
from different electronegativities
overall dipole reinforced depending on orientation of the bonds
what’s the difference between reinforcing and opposing dipoles?
reinforcing dipoles are on the same side
opposing dipoles on either side of double bond
transform is not a polar molecule
what is an intermolecular interaction?
occur between molecules
strong = high melting/boiling point
all occur because of:
- difference in electronegativity
- polarity of molecules
dipole-dipole interactions
permanent dipole attract each other
due to electronegativity difference
weak interaction
dispersion interactions
interaction between molecules that don’t have permanent dipole
a result of induced dipoles
van der Waals
e- never stationary
can lead to small temporary dipole
can then induce another in another molecule
these attract one another
between molecules with induced dipoles
increase with increasing chain length
decrease with increased branching
weakest intermolecular interaction
strength of vdW
weaker than dipole-dipole
still play major biological roles
hydrogen bonding
when H attracted to another electronegative atom
this is also attracted to another electronegative atom
occur in molecules with h bonded to o or n
strongest intermolecular interaction
e.g. water
water
simplest example H bonding
Solubility
2 compounds mixing together
when will 2 substances mix completely?
sum of intermolecular attractions between molecules after mixing is >= Sumer of intermolecular attraction between molecules before mixing
like dissolves like
compounds that show extensive H bonding will dissolve in water
