Class 2

Question 1

What are the 2 phases of chromatography?

Answer 1

Stationary phase
Mobile phase
-mix mobile into stationary

Question 2

What is the Rf?

Answer 2

Retention time

• how long. it takes to pass on the paper
• greater the affinity with the stationary phase the more its retained on the medium

Question 3

What is size exclusion chromatography?

Answer 3

Separates based on molecular size

Question 4

What is TLC?

Answer 4

Thin layer chromatography separates based ono polarity of molecules
-things that h bond with the surface will be hard to move up the plate

Question 5

For TLC what is the gel?

Answer 5

polar stationary phase

-non polar moves further up the gel

Question 6

What is the relationship between Rf and polarity?

Answer 6

Nonpolar (alkenes, alkyl halides) = High Rf

Polar (ester, ketone, alkyl halide) = medium Rf

High polarity (OH, amines, carboxylic acids) = Low Rf

Question 7

What is column chromatography?

Answer 7

Same as TLC but difference is based on Polarity and separates large amounts of solids or high BP
-nonpolar would elute first, polar last

Question 8

What is HPLC?

Answer 8

High performance liquid chromatography separates based on polarity
-better than TLC

Question 9

What are the 2 phases of HPLC?

Answer 9

Normal phase: Most non polar is further away (polar stationary phase)

Reverse phase: non polar stationary phase assume this if not told otherwise

Question 10

What is ion exchange chromatography?

Answer 10

Separates based on charge

Question 11

What are the 2 phases of ion exchange?

Answer 11

Stationary: resin containing anionic/cationic groups with counter ions

Mobile phase: Buffer solution, specific pH

Question 12

What is the difference between cation exchange resin and anion exchange resin?

Answer 12

Cation retains cations

Anion retains anions

Question 13

What is gas chromatography?

Answer 13

Separates based on differences in volatility/BP

Used to separate small amounts of low BP compounds

Question 14

In gas chromatography which compounds exists first?

Answer 14

Lowest BP exits first (most volatile)

Question 15

What is distillation?

Answer 15

Separation based on BP

Question 16

What effects of molecules influence their distillation?

Answer 16

IMF between liquid molecules (hbond, dipole dipole, LDF)

Molecular weight: heavier=higher BP

Branching: More branching= Lower BP

Question 17

What are the 2 kinds of distillation?

Answer 17

Simple Distillation

Fractional distillation

Question 18

What is simple distillation?

Answer 18

When compound BP differences are greater than 30C

-Used to remove impurities from a relatively pure liquid

Question 19

What is fractional distillation?

Answer 19

When compound BP differences are less than 30C
Very good and efficient
Useful for diasteriomer

Question 20

What is solvent extraction?

Answer 20

Separation based on differences in solubility in polar and non polar solvents

Question 21

What are the rules for solvent extraction to determine what is soluble in what?

Answer 21

1. Like dissolves like
2. Compounds with less the 5C+polar is water soluble
3. Charged functional group are more water soluble than in organic compounds

Question 22

What are the acidic functional groups?

Answer 22

Carbonyl compounds< Alkyl alcohols< Phenols< Carboxylic acids

Question 23

What are the basic functional groups?

Answer 23

Amines

-they react with Phenols and carboxylic acids to pull them into the organic layer

Question 24

How is an extraction run done?

Answer 24

Weak base only deprotonates carboxylic acid
Strong base can deprotonate phenols and alcohols cause they aren’t acidic enough
Hal protonates amines

Question 25

What cant enantiomers be separated by?

Answer 25

Physical and chemical properties because R and S have the same BP polarity and solubility

Question 26

What are the steps in resolution of enantiomers?

Answer 26

1. Convert enantiomers into diasteriomers 2. Separate salts using conventional means 3. Revert salts to original enantiomers

Question 27

What is Mass spectroscopy?

Answer 27

Determining the molecular weight of a compound

Question 28

What is UV/Vis Spectroscopy?

Answer 28

Determining the presence of a conjugated pi system

Question 29

What is IR spectroscopy?

Answer 29

Different IR ranges causes different kinds of bonds to vibrate at distinct frequencies -indicates which functional groups present

Question 30

what are the limitations to IR?

Answer 30

Doesn't indicate whether a functional group is or how many in a molecules -good coffee constitutional isomers but not stereoisomers

Question 31

What are the IR wavelengths for O--H, C=O, C=C, CN or CC triple?

Answer 31

O--H: 3200-3600 C=O: 1700 C=C: 1650 CN or CC triple: 2100-2260

Question 32

What is HNMR?

Answer 32

Radio waves determine inför about H atoms on a molecule

Question 33

What are the 4 things regarding H atoms used in HNMR?

Answer 33

1. NUmber off signals: number of non equivalent Hs 2. Splitting pattern (n+1): number of nonequivalent neighbouring Hs 3. Area under signal: Number of Hs represented by each signal 4. Chemical shift: Chemical environment of that H (3Ds)