Lab Quiz 2 - Density, Recrystalization and TLC

density (p)

m/v

recrystalization is a chemical purification technique characterized by

the dissolving of an impure compount in a suitable solvent

recrystalization encourages the formation of

pure compound as crystals

recrystalization - dissolve ______ solid in ___ solvent, then let ____ to recrystalize

impure, hot, cool

most reactions go from starting material and reagant to

starting material, reagant, desired product, unwanted side product

acetanilide

water solubility of acetanilide at 0 degrees celcius

0.5g/100ml

water solubility of acetanilide at 100 degrees celcius

5.5g/100ml

skills used

dissolving sample in water, filtration with buchner funnel, weighing

heating and stirring makes solution

uniform, homogenous

vacuum filtration is for

separating the filtrate

mixed solvent recrystallization example

trans - cinnamic acid

all compounds of impure trans-cinnamic acid dissolve in ________. add drops of water to form _________.

methanol, crystals

techniques to purify a compound if it doesn’t crystalize

Column purification, thin layer chromatography

Column purification utilizes the ______ phase vs __________ phase

mobile, stationary

example of mobile vs stationary phase

hexanes could be in a mobile phase while silica gel could be in the stationary phase

example for chromatography separation

my column purification!!

two compounds A and B. A in the mobile phase is eluted through B in the stationary phase. A moves faster than B and therefore they are separated

column chromatography steps

packing the column, loading the sample, eluting, collect

after purifying

run on a gel to see density

how do we quantify mobility?

retention factor (Rf)

Rf for TLC=

distance traveled by sample / distance traveled by solvent

nonpolar solvents

hexane, dcm, methanol

Thin layer chromatography - on a cillica gel the most polar sample travels the

Least

Thin layer chromatography - on a cillica gel the least polar sample travels the

Furthest

the desired compound will be the ____ polar

most

the impurities will be the _____ polar

least