Chem 43A final

what is recrystallization

purification technique based on solubility and thermodynamically favorable process of crystal lattice formation.

what are the main steps of recrystallization

1. dissolution of solvent —> purified in hot solvent

2. filtration of mixture to remove insoluble impurities

3. allowing for crystal formation

4. isolation of the purified crystallin compound

what happens if too much solvent is added during crystallization?

compound will not form crystals

What is liquid-liquid extraction

separation method based upon differential solubility of components of a mizture in two immiscible solvent

partition coefficient

K - g/mL of a compound in organic solvent (mtBe) / g/mL of compound in water

quick steps for liquid-liquid extraction

1. dissolution of a mix in a suitable solvent followed by addining immiscible solvent

2. mixing layers

3. seperation of layers

4. drying organic solvent

5. isolation of seperarted components

solvents not miscible with water

ethanol and methanol

what is on top of seperation and bottom

lower density is on top and the more dense is on the bottom

(water is more dense than the organic)

what brine is used for MtBe

sodium chloride

what drying agent did we use in this lab

magnesium sulfate - high water absorption

what method is used for seperation

liquid -liquid, chromatography

what methods can be used for purification

recrystallization, distillation, and sublimation or chromatogrpahy.

what do we have to seperate caffeien from

cellulose, proteins, pigments, tannins

in caffeine what is water soluble and what is not

cellulose - not water solulble

proteins and pigment - water soluble

caffeine and tannin - water soluble but also both soluble in methylene chloride

how doe we seperate cafeinne from tannin

Hydrolysis of tannin with the base sodium carbonate - turn it into gluocse and gallic acid

what is sublimation

going from solid to vapor and condense back to solid without passing through liwuid

PURIFICATION

what are acid organic compound functional groups

carboxylic acid and phenol groups

what are basic organic compound func groups

amine group

waht is use to turn carb acid compound into a salt. what about phenol group and amine group

carb acid (strong a) + NaHCo3 (strong b)

phenol (weak a) + NaOh (weak b)

amine + HCl

what is chromatography

seperation and purification based on difference in the way compounds partition between a stationary and mobile phase

how does the stationary control the flow of compounds

more slowly - strong interaction

faster - weaker interaction

gradient starts with a nonpolar and ends with polar

waht is melting point

temp at which melting and solidifying are at equilibrium

what is eulectic point

30% A and 70% B

is slow formation of crystals thermodynamic or kinetic? what about quickly

slow = thermo = enthalpy favored entropy unfavored

quick = kinetic

why is it important that we vent

volatile solvents that have Co2 release = pressure build up