Chem 242 Final Exam Questions With Complete Solutions
_____ is being used in excess in this lab in order to _____
Correct Answers acetic acid, push the equilibrium to favor more
product
_____ will have a higher Rf on the TLC plate, because
__________ Correct Answers benzil, benzoin is more polar
than benzil - the OH group can do H-bonding
"Explain why in solid IR, the KBr had to be pressed into a
pellet, rather than Correct Answers
"You will carry out a series of extractions to purify your
product. Correct Answers
According to either the lab manual or other material posted on
Canvas, which compound has the shortest retention time?
(isoborneol, camphor, borneol) Correct Answers Camphor
Based on WebMO data, which is more stable, borneol or
camphor? Correct Answers We cannot tell, because the
molecules don't have the exact same molecular weight
Borneol and isoborneol are _____ of each other. Borneol and
camphor are _____ of each other. Correct Answers
diastereomers, not isomers
Camphor has ___ chiral centers and borneol has ___ chiral
centers Correct Answers 2, 3
, Consider the transformation of pentanol into pentyl acetate. An
argument in favor of pentanol having the higher boiling point /
GC retention time is _____. An argument in favor of pentyl
acetate having the higher boiling point / GC retention time is
_____. Based purely on these arguments, _____. Correct
Answers it can do H-bonding ; it has higher MW, it's not clear
which compound will have the higher BP and the only way to
know for sure is to measure it
Explain why the NMR solvent you used for the esters and
unknown labs was deuterated chloroform, CDCl3, and not
regular chloroform, CHCl3 or even methylene chloride,
CH2Cl2. Correct Answers The concentration of solvent
molecules is much larger than the concentration of your sample.
If you use a proton solvent like CHCl3 or CH2Cl2, you would
only see a massive peak due to that solvent, and your
compound's signals would barely be visible above the baseline.
How do WebMO results compare with what is predicted of
esterification reactions? Correct Answers Results don't match,
because esterification reactions are nonspontaneous and require
a strong acid to proceed
How does the molecular ion peak give us the number of Br
atoms? Correct Answers Look for M+2 peak of equal height to
the M peak
How does the molecular ion peak give us the number of C atoms
in a molecule? Correct Answers Compare the height of the M,
M+1 peaks. Then, divide (M+1) / (M + M+1) divided by 1.1%
to get the number of C atoms
_____ is being used in excess in this lab in order to _____
Correct Answers acetic acid, push the equilibrium to favor more
product
_____ will have a higher Rf on the TLC plate, because
__________ Correct Answers benzil, benzoin is more polar
than benzil - the OH group can do H-bonding
"Explain why in solid IR, the KBr had to be pressed into a
pellet, rather than Correct Answers
"You will carry out a series of extractions to purify your
product. Correct Answers
According to either the lab manual or other material posted on
Canvas, which compound has the shortest retention time?
(isoborneol, camphor, borneol) Correct Answers Camphor
Based on WebMO data, which is more stable, borneol or
camphor? Correct Answers We cannot tell, because the
molecules don't have the exact same molecular weight
Borneol and isoborneol are _____ of each other. Borneol and
camphor are _____ of each other. Correct Answers
diastereomers, not isomers
Camphor has ___ chiral centers and borneol has ___ chiral
centers Correct Answers 2, 3
, Consider the transformation of pentanol into pentyl acetate. An
argument in favor of pentanol having the higher boiling point /
GC retention time is _____. An argument in favor of pentyl
acetate having the higher boiling point / GC retention time is
_____. Based purely on these arguments, _____. Correct
Answers it can do H-bonding ; it has higher MW, it's not clear
which compound will have the higher BP and the only way to
know for sure is to measure it
Explain why the NMR solvent you used for the esters and
unknown labs was deuterated chloroform, CDCl3, and not
regular chloroform, CHCl3 or even methylene chloride,
CH2Cl2. Correct Answers The concentration of solvent
molecules is much larger than the concentration of your sample.
If you use a proton solvent like CHCl3 or CH2Cl2, you would
only see a massive peak due to that solvent, and your
compound's signals would barely be visible above the baseline.
How do WebMO results compare with what is predicted of
esterification reactions? Correct Answers Results don't match,
because esterification reactions are nonspontaneous and require
a strong acid to proceed
How does the molecular ion peak give us the number of Br
atoms? Correct Answers Look for M+2 peak of equal height to
the M peak
How does the molecular ion peak give us the number of C atoms
in a molecule? Correct Answers Compare the height of the M,
M+1 peaks. Then, divide (M+1) / (M + M+1) divided by 1.1%
to get the number of C atoms
