5.1 Separations

Question 1

What is an extraction?

Answer 1

separation of one substance from a mixture of substances by adding a solvent in which the compound of interest is highly soluble

Question 2

What is a liquid-liquid extraction?

Answer 2

when a compound of interest is shaken with a second solvent and allowed to separate into two distinct phases; the compound of interest will distribute itself based on its solubilities in the individual solvents

Question 3

What two things does solubility depend on?

Answer 3

polarity of the solute
polarity of the solvent

Question 4

How can you extract organic amines?

Answer 4

basic organic compounds can be extracted upon treatment with a dilute acid causing the base to protonate, become positively charge, and solvate in an aqueous solution

Question 5

How can you extract carboxylic acids?

Answer 5

using a weak base which will convert carboxylic acid into anionic salt, negatively charged species will solvate in aqueous solution

Question 6

How can you extract phenols?

Answer 6

using dilute solution of sodium hydroxide converting phenol into anionic salt

Question 7

What device is used to carry out liquid-liquid extractions?

Answer 7

separatory funnel

Question 8

What is thin-layer chromatography?

Answer 8

compounds are separated based on differing polarities

Question 9

What is an Rf value?

Answer 9

ratio to front: distance traveled by an individual component divided by the distance traveled by the solvent front

Question 10

What is column chromatography?

Answer 10

used to isolate bulk compound based on differing polarities

Question 11

In column chromatography, which type of substance will be collected first?

Answer 11

less polar compounds come out first, more polar come out last

Question 12

What is ion-exchange chromatography?

Answer 12

separation of materials based on varying charge states

Question 13

If the stationary phase of ion-exchange chromatography is packed with positively charged ions, which will travel faster?

Answer 13

negative will travel faster

Question 14

What is high performance liquid chromatography?

Answer 14

uses the differing affinities of various compounds for a stationary or mobile phase; mobile phase is forced through stationary phase at very high pressures

Question 15

What is size exclusion chromatography?

Answer 15

technique that is used to separate bulk materials based on molecular size

Question 16

Which size molecules will elute first in size exclusion chromatography?

Answer 16

large will elute first

Question 17

What is gas chromatography?

Answer 17

form of column chromatography in which the partitioning of the components to be separated takes place between a mobile gas phase and a stationary liquid phase

Question 18

How does branching effect melting and boiling points?

Answer 18

more branching will lower the melting and boiling point

Question 19

How does molecular weight effect melting and boiling points?

Answer 19

the greater the molecular weight the higher the melting and boiling points

Question 20

How does hydrogen bonding effect melting and boiling points?

Answer 20

the more hydrogen bonding the greater the melting and boiling point