EXAM 2 (EXP 13, 24, 22, 35, 58)

Question 1

IR frequency 3200-3600 (broad)

Answer 1

O-H stretch

Alcohol and phenol

Question 2

IR frequency 2500-3000 (broad)

Answer 2

O-H stretch

Carboxylic acid

Question 3

IR frequency 2800-3000

Answer 3

C-H stretch

alkane (sp3)

Question 4

IR frequency 3000-3100

Answer 4

C-H stretch

alkene (sp2)

Question 5

IR frequency 2100-2260

Answer 5

C-C (triple bond) stretch

alkyne

Question 6

IR frequency 1680-1750

Answer 6

C=O stretch

Ketones/aldehydes

Question 7

IR frequency 1730-1750

Answer 7

C=O stretch

esters

Question 8

IR frequency 1710-1780

Answer 8

C=O stretch

carboxylic acid

Question 9

IR frequency 1620-1680

Answer 9

C=C stretch

alkene

Question 10

IR frequency 1450, 1550, 1650

Answer 10

C=C stretch

Aromatic

Question 11

IR frequency 1050-1150

Answer 11

C-O stretch

Alcohol, ester, ether

Question 12

How to determine % yield?

Answer 12

(grams starting material * molecular weight of product) / molecular weight of starting material
THEN
(grams of starting material / grams calculated above ) * 100%

Question 13

IR frequency 1465-1440 or 1390-1365

Answer 13

CH3 bend

Question 14

why was reduced pressure used during the caffeine sublimation step?

Answer 14

a reduced pressure allows for sublimation at a lower temperature. (PV=nRT) Caffeine would melt if sublimation was done at atm pressure

Question 15

will the following sublime or melt?

a solid substance has a vapor pressure of 800 mmHg at its melting point of 80 degrees C

Answer 15

the substance will sublime

Question 16

will the following sublime or melt?

a solid substance has a vapor pressure of 100 mmHg at its melting point of 100 degrees C

Answer 16

the substance will melt

Question 17

What is the purpose of using anhydrous sodium sulfate in a solution?

Answer 17

to “dry” the solution - to remove any remaining H20 from the solution

Question 18

Which is more polarizable? Br- or Cl-?

Answer 18

Br- is more polarizable

Question 19

Which is a better nucleophile in H2O? Br- or Cl-?

Answer 19

Br-

Question 20

What is the rate determining step in an SN2 reaction?

Answer 20

The nucleophile attacking the R group

very good Nuc needed!

Question 21

What is the rate determining step in an SN1 reaction?

Answer 21

formation of the carbocation

Question 22

Will a tertiary (3) substrate undergo SN2, SN1 or both?

Answer 22

only SN1

Question 23

Will a secondary (2) substrate undergo SN2, SN1 or both?

Answer 23

both

Question 24

Will a primary (1) substrate undergo SN2, SN1 or both?

Answer 24

only SN2

Question 25

IR frequency 1480-1440

Answer 25

CH2 bend

Question 26

When extracting a solute, it it better to do 1 extraction with a large amount of solvent or multiple extractions with a small amount of solvent? Why?

Answer 26

Multiple extractions - you can extract a greater amount of the compound from the aqueous phase

Question 27

Why would you choose one solvent over another for extraction using a centrifuge?

Answer 27

It is easier to extract the lower layer from a centrifuge tube, so you want the solvent to be on the bottom layer. You choose a solvent based on density in this case. (Solvent (organic layer) density should be greater than aqueous layer density)

Question 28

When can you do distillation? (or when can you not?)

Answer 28

boiling point of products must be lower than the boiling point of reactants to perform a successful distillation (can not distill if product bp is higher than reactant bp)

Question 29

How can you drive a reaction toward products?

Answer 29

1. a large excess of starting material 2. distill as you form product 3. use a dehydrating agent to remove H20 (if H20 is a product of the rxn)

Question 30

Define extraction

Answer 30

Removing one or more (desired) components from a solution by transferring that solute into a different solvent that is immiscible with the original solution

Question 31

What does washing do?

Answer 31

remove undesired components

Question 32

Explain sublimation

Answer 32

At particular pressures, certain substances may transition directly from the solid phase to the gas phase.

Question 33

What is the purpose of an unsaturation test?

Answer 33

Unsaturation tests provide a confirmation of the presence of the C=C double bond

Question 34

what is the KEY to a Grignard Reaction? (ie. what can NOT be present?)

Answer 34

No Water

Question 35

when will a solid sublime?

Answer 35

if its vapor pressure is greater than atm pressure at its melting point