Organic Chemistry Chapter 12: Separations and Purifications

Question 1

Extraction

Answer 1

combines two immiscible liquids, one of which easily dissolves the compound of interest.

Question 2

What are the two phases of extraction?

Answer 2

Polar (water) layer = aqueous phase

Nonpolar layer = organic phase

Question 3

Where is extraction carried out?

Answer 3

a separatory funnel. One phase is collected ant the solvent is then evaporated.

Question 4

Wash

Answer 4

the reverse of extraction, in which a small amount of solute that dissolves impurities is un over the compound of interest.

Question 5

Giltration

Answer 5

isolates a solid (residue) from a liquid (filtrate).

Question 6

Gravity filtration

Answer 6

Used with the product of interest is the solid.Hot solvent is used to maintain solubility

Question 7

Vacuum filtration

Answer 7

Used when the product of interest is the solid. A vacuum is connected to the flask to pull the solvent through more quickly.

Question 8

Recrystallization

Answer 8

the product is dissolved in a minimum amount of hot solvent. If the impurities are more soluble, the crystals will reform while the flask cools, excluding the impurities.

Question 9

Distillation

Answer 9

Separates liquids according to differences in their boiling points; the liquid with the lowest boiling point vaporizes first and is collects as the distillate.

Question 10

Simple distillation

Answer 10

can be used if the boiling points are over 150 degrees C. and are at least 25 degrees C apart.

Question 11

Vacuum distillation

Answer 11

should be used if the boiling points are over 150 degrees C to prevent degradation of the product.

Question 12

Fractional distillation

Answer 12

should be used if the boiling points are less than 25 degrees C apart because it allows more refined spearation of liquids by boiling point.

Question 13

Chromatography

Answer 13

used two phases to separate compounds based on physical or chemical properties.

Question 14

The stationary phase or adsorbent

Answer 14

usually a polar solid.

Question 15

Mobile phase

Answer 15

Runs through the stationary stage and is usually a lipid or gas. This elutes the sample through the stationary phase.

Question 16

Retardation factors

Answer 16

larger for compounds with higher affinity for the stationary phase & take longer to pass though, if at all. compounds with higher affinity for the mobile phase elute through more quickly.

Question 17

Partioning

Answer 17

Separation of compounds.

Question 18

Thin layer and paper chromatography

Answer 18

Used to identify a sample - stationary phase is a polar, material (silica, alumina, paper)
Mobile phase is a nonpolar solvent
Card is spotted and developed
Rf values calculated

Question 19

Reverse phase chromatography

Answer 19

uses a nonpolar card with a polar solvent

Question 20

Column chromatography

Answer 20

utilizes polarity, size or affinity to separate compounds based on their physical or chemical properties.
Stationary phase = column containing silica or alumina beads
Mobile phase = nonpolar solvent, which travels through the column by gravity

Question 21

Ion-exchange chromatography

Answer 21

the beads are coated with charged substances to bind compounds with opposite charge

Question 22

Size-exclusion chromatography

Answer 22

the beads have small pores which trap smaller compounds and allow larger compounds to travel through faster

Question 23

Affinity chromatography

Answer 23

made to have high affinity for a compound by coating beads with a receptor or antibody to the compoud

Question 24

Gas chromatography

Answer 24

separates vaporizable compounds according to how well they adhere to the adsorbent in the column.
Stationary = coil of crushed metal or a polymer
Mobile = nonreactive gas

Question 25

High performance liquid chromatography

Answer 25

similar to chromatography but uses computer-mediated solvent and temp gradients. It is used if the sample size is small or if forces such as capillary action will affect results. It was formally called high pressure liquid chromatography.