EXAM 2 (EXP 13, 24, 22, 35, 58) Flashcards
IR frequency 3200-3600 (broad)
O-H stretch
Alcohol and phenol
IR frequency 2500-3000 (broad)
O-H stretch
Carboxylic acid
IR frequency 2800-3000
C-H stretch
alkane (sp3)
IR frequency 3000-3100
C-H stretch
alkene (sp2)
IR frequency 2100-2260
C-C (triple bond) stretch
alkyne
IR frequency 1680-1750
C=O stretch
Ketones/aldehydes
IR frequency 1730-1750
C=O stretch
esters
IR frequency 1710-1780
C=O stretch
carboxylic acid
IR frequency 1620-1680
C=C stretch
alkene
IR frequency 1450, 1550, 1650
C=C stretch
Aromatic
IR frequency 1050-1150
C-O stretch
Alcohol, ester, ether
How to determine % yield?
(grams starting material * molecular weight of product) / molecular weight of starting material
THEN
(grams of starting material / grams calculated above ) * 100%
IR frequency 1465-1440 or 1390-1365
CH3 bend
why was reduced pressure used during the caffeine sublimation step?
a reduced pressure allows for sublimation at a lower temperature. (PV=nRT) Caffeine would melt if sublimation was done at atm pressure
will the following sublime or melt?
a solid substance has a vapor pressure of 800 mmHg at its melting point of 80 degrees C
the substance will sublime
will the following sublime or melt?
a solid substance has a vapor pressure of 100 mmHg at its melting point of 100 degrees C
the substance will melt
What is the purpose of using anhydrous sodium sulfate in a solution?
to “dry” the solution - to remove any remaining H20 from the solution
Which is more polarizable? Br- or Cl-?
Br- is more polarizable
Which is a better nucleophile in H2O? Br- or Cl-?
Br-
What is the rate determining step in an SN2 reaction?
The nucleophile attacking the R group
very good Nuc needed!
What is the rate determining step in an SN1 reaction?
formation of the carbocation
Will a tertiary (3) substrate undergo SN2, SN1 or both?
only SN1
Will a secondary (2) substrate undergo SN2, SN1 or both?
both
Will a primary (1) substrate undergo SN2, SN1 or both?
only SN2
IR frequency 1480-1440
CH2 bend
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?
Multiple extractions - you can extract a greater amount of the compound from the aqueous phase
Why would you choose one solvent over another for extraction using a centrifuge?
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)
When can you do distillation? (or when can you not?)
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)
How can you drive a reaction toward products?
- a large excess of starting material
- distill as you form product
- use a dehydrating agent to remove H20 (if H20 is a product of the rxn)
Define extraction
Removing one or more (desired) components from a solution by transferring that solute into a different solvent that is immiscible with the original solution
What does washing do?
remove undesired components
Explain sublimation
At particular pressures, certain substances may transition directly from the solid phase to the gas phase.
What is the purpose of an unsaturation test?
Unsaturation tests provide a confirmation of the presence of the C=C double bond
what is the KEY to a Grignard Reaction? (ie. what can NOT be present?)
No Water
when will a solid sublime?
if its vapor pressure is greater than atm pressure at its melting point
