Chapter 12 - Separations and Purifications

extraction

combines 2 immiscible liquids, one of which easily dissolves compound of interest

polar layer of extraction

aqueous phase and dissolves the compound with H bonding or polarity

nonpolar layer of extraction

organic phase and dissolves nonpolar compounds

extraction is carried out in

a sep funnel

a wash is

the reverse of extraction where a small amount of solvent that dissolves impurities is run over the compound of interest

filtration isolates

a solid from liquid

gravity filtration

used when product is in the filtrate, hot solvent is used to maintain solubility

vacuum filatration

used when the product is the solid

recrystallization

product is dissolved in a minimum amount of hot solvent

distillation

separates liquids according to differences in bps

imple distillation

used if the bp are under 150 and are at least 25 apart

vacuum distillation

used if the bp are over 150 to prevent degredation

fractional distillation

used if bp are less than 25 apart

all forms of chromatogrpahy

uses 2 phases to separate

stationary phase

usually a polar solid

mobile phase

runs through the stationary phase and usually a liquid or gas, elutes the sample through the stationary phase

compounds with higher affinity for the stationary phase

have smaller retardation factors and take longer to pass through

thin layer and paper chromatography

used to identify a sample, stationary phase is a polar material like silica and the mobile phase is a nonpolar solvent which climbs the card through capillary action

thin layer and paper chromatography analysis

the card is potted and developed, Rf values can be calculated

reverse-phase chromatography

uses a nonpolar card with polar solvent

column chromatography

utilizes polarity, size, or affinity to separate, stationary phase is a solum containing silica or alumina beads, mobile phase is a nonpolar solvent traveling through gravity

ion-exchange chromatography

beads are coated with charged substances to bind compounds with opposite charges

size exclusion chromatography

beads have small pores which trap smaller compounds

affinity chromatography

column is made to have high affinity for a compound by coating the beads with a receptor

gas chromatography

separates vaporizable compounds according to how well they adhere to the absorbent in the column, stationary phase is a coil of crushed metal or polymer, mobile phase is a nonreactive gas

gas chromatography may be combined with

mass spec which ionized and fragments molecules

high performance liquid chromatography

HPLC is similar to column but uses computer mediate solvent and temp gradients, used it sample is small