CHEM 237 LAB EXAM QUESTIONS AND ANSWERS
ELABORATIONS!!
Is acetanilide polar or nonpolar
Answers:polar
Should crystals form quickly or slowly?
Answers:slowly -- get better yield
base add or remove proton
Answers:will remove proton
acid add or remove proton
Answers:will add proton
What does the y axis on IR spectrum represent?
Answers:intensity of the dipole moment -- more electronegative atoms have larger
peaks
What does the x axis on IR spectrum represent?
Answers:Represents the speed of vibration of the atom-- larger atoms will have
longer bonds and vibrate slower. They will be farther right on x-axis
(T/F) in a recrystallization, molecules in a mixture form a better lattice structure
Answers:False- this is why we are purifying the crystals of the product
Distillation is a good technique for
, Answers:2 miscible liquids with different boiling points
How did we get the benzoic acid from the aqueous layer into the organic layer in
the extraction lab?
Answers:Added NaOH to deprotonated the acid and make it charged. Charged
compounds will move into aqueous layer
*note* the acid was reprotonated by adding HCl after the extraction
How did we move the benzocaine from the organic to aqueous layer
Answers:Added HCl to add proton to the NH2 group at end of the benzocaine to
make it charged. Charged compound will move into aqueous layer to be extracted.
*note* had to remove the extra proton using NaOH to make the pure benzocain
What must happen for a bond movement to show up on IR?
Answers:There must be a change in dipole moments (net dipole moment cannot =
0)
what is the fingerprint region on IR
Answers:1500-400 (cm-1)
O-H stretch on IR
Answers:- will have a peak at 3300
- broad and large peak
Amine (NH2) on IR
Answers:- peak at 3300
- not as large/broad as O-H
ELABORATIONS!!
Is acetanilide polar or nonpolar
Answers:polar
Should crystals form quickly or slowly?
Answers:slowly -- get better yield
base add or remove proton
Answers:will remove proton
acid add or remove proton
Answers:will add proton
What does the y axis on IR spectrum represent?
Answers:intensity of the dipole moment -- more electronegative atoms have larger
peaks
What does the x axis on IR spectrum represent?
Answers:Represents the speed of vibration of the atom-- larger atoms will have
longer bonds and vibrate slower. They will be farther right on x-axis
(T/F) in a recrystallization, molecules in a mixture form a better lattice structure
Answers:False- this is why we are purifying the crystals of the product
Distillation is a good technique for
, Answers:2 miscible liquids with different boiling points
How did we get the benzoic acid from the aqueous layer into the organic layer in
the extraction lab?
Answers:Added NaOH to deprotonated the acid and make it charged. Charged
compounds will move into aqueous layer
*note* the acid was reprotonated by adding HCl after the extraction
How did we move the benzocaine from the organic to aqueous layer
Answers:Added HCl to add proton to the NH2 group at end of the benzocaine to
make it charged. Charged compound will move into aqueous layer to be extracted.
*note* had to remove the extra proton using NaOH to make the pure benzocain
What must happen for a bond movement to show up on IR?
Answers:There must be a change in dipole moments (net dipole moment cannot =
0)
what is the fingerprint region on IR
Answers:1500-400 (cm-1)
O-H stretch on IR
Answers:- will have a peak at 3300
- broad and large peak
Amine (NH2) on IR
Answers:- peak at 3300
- not as large/broad as O-H
