Solubility & Chromatography - Chemistry

Boiling Point

energy required to pull 2 molecules away from each other (not breaking bonds); stronger IMF means higher bp

(involves one type of molecule)

Solubility

generally: the ability of a substance (solute) to dissolve in a solvent

at the molecular level: a solvents ability to solvate (surround) the solute

(involves 2 types of molecules)

is water a polar or nonpolar solvent?

polar

Polar means…

the molecule has a permanent dipole

Chromatography

generally: the separation of molecules based on their interactions with a stationary and mobile phase

at the molecular level: a molecule will interact with the stationary and/or mobile phase to different degrees based on its ability to make the strongest possible IMF with each other

(involves at least 3 molecules interacting)

all chromatography will consist of…

a stationary phase and a mobile phase

Rf value

spot distance/solvent distance (the solvent front)

The closer the rf value is to 1, the farther the molecule moved (should never be greater than 1)

if a molecule can make stronger IMF’s with a polar stationary phase …

it is more soluble and has a lower Rf value

double bonds are..

more polarizable because when 2 double bonds come close to each other, the electrons in one double bond induces a dipole on the other.

What’s the most important structural feature of a molecule having a high solubility in water?

high polarity (more permanent dipoles/stronger IMF)

Water will always want to…

hydrogen bond, either with itself or another molecule