CHEM 233 Unit 4 Questions and
Answers
What type of distillation will you perform first? (1 pt) - answer fractional distillation
A fractional distillation involves the use of a fractionating column to provide multiple
condensation/evaporation cycles over a given distance. (1 pt) - answer true
A fractional distillation is less efficient (less capable of giving pure product) than a
simple distillation. (1 pt) - answer false
The distillate you collect from your final simple distillation should have a head
temperature (temperature at the thermocouple) of 80 °C to 85 °C. What does this
temperature correspond to? (1 pt) - answer roughly the boiling point of your desired
alkene product
For the Bayer test, you will add a solution of potassium permanganate to which of the
following items? Select all that apply. (1 pt) - answer a solution of your isolated
product
a solution of your starting alcohol
You consider starting material A. You know that A can undergo two reactions as shown
in the below reaction coordinate diagram with one reaction pathway labeled in red and
one reaction pathway labeled in blue. The red path leads to Product B, while the blue
path leads to Product C. Assuming both reaction pathways occur simultaneously in
competition with each other, what is the major product, and why? (2 pts) - answer
Product B, because the transition state leading to Product B is lower in energy than the
transition state leading to Product C.
Let's push a little further. We did not discuss this in the webcast, but imagine you have a
multi-step reaction, whose reaction coordinate diagram is shown below. Using what you
know about transition state energies, which step is the rate-determining step? (1 pt) -
answer B to C
Which of the following nucleophiles would perform well as a nucleophile, but poorly as a
base? (1 pts) - answer chloride ion
The alkyl halide shown below undergoes an elimination reaction. Select all possible
elimation products from the given structures provided below. (1 pts) - answer A
(Hofmann product)
, You are performing an elimination reaction using an alkyl halide and a non-bulky base.
The three products shown below are produced in the reaction. What product would be
created in the smallest amount? (2 pts) - answer A (Hofmann/terminal alkene)
You know the Bayer test is used to identify the presence of alkenes. You attempt to
perform an elimination reaction and test what you hope is the product using the Bayer
test. Adding KMnO4 to a solution of the starting material requires 2 drops to remain
purple, with no precipitate observed. A solution of your potential product requires 15
drops to remain purple, with no precitipate observed. Did you successfully perform an
elimination reaction? (1 pts) - answer Yes, because the solution of potential product
took more drops of KMnO 4 to remain purple.
A mixture of 0.9 mole fraction B is distilled by fractional distillation using a Vigreux
column having two theoretical plates. (Keep in mind that the initial boiling of mixture in
the distillation flask before the column adds an additional"plate".) According to the
phase diagram below, what is the composition of the distillate (liquid from condensed
vapor) you collect? Select the answer closest to the expected value. (2 pts) - answer
0.30 mole fraction B
The below phase diagram corresponds to what type of mixture? (1 pts) - answer
non-ideal solution with a negative deviation
If a liquid mixture containing 60 Mole Percent B was distilled using a simple distillation,
according to the below phase diagram, what temperature would the liquid mixture boil
at? (2 pts) - answer 68 degrees C
If a liquid mixture containing 60 Mole Percent B was distilled using an efficient fractional
distillation column, according to the below phase diagram, what temperature would be
read on the thermometer at the top of the fractionating column? Think back to what you
observed in the Elimination experiment! (1 pts)
An "efficient" fractional distillation column is efficient when it has at least the required
number of theoretical plates to distill a mixture to a desired purity. Assume that the
fractional distillation column can do as many distillations as you could need or has an
infinite number of theoretical plates. - answer 50 degrees C
If a liquid mixture containing 80 mole percent B were distilled using an efficient fractional
distillation column, what would be the composition of the liquid remaining in the
distillation pot? (2 pts) - answer 75 mole percent B
If a liquid mixture containing 80 mole percent B were distilled using an efficient fractional
distillation column, what would be the composition of the distillate collected? (2 pts) -
answer 75 mole percent A
Consider a situation where you were able to develop TLC conditions to analyze and
visualize a mixture of the starting alcohol and the alkene product in the Elimination
Answers
What type of distillation will you perform first? (1 pt) - answer fractional distillation
A fractional distillation involves the use of a fractionating column to provide multiple
condensation/evaporation cycles over a given distance. (1 pt) - answer true
A fractional distillation is less efficient (less capable of giving pure product) than a
simple distillation. (1 pt) - answer false
The distillate you collect from your final simple distillation should have a head
temperature (temperature at the thermocouple) of 80 °C to 85 °C. What does this
temperature correspond to? (1 pt) - answer roughly the boiling point of your desired
alkene product
For the Bayer test, you will add a solution of potassium permanganate to which of the
following items? Select all that apply. (1 pt) - answer a solution of your isolated
product
a solution of your starting alcohol
You consider starting material A. You know that A can undergo two reactions as shown
in the below reaction coordinate diagram with one reaction pathway labeled in red and
one reaction pathway labeled in blue. The red path leads to Product B, while the blue
path leads to Product C. Assuming both reaction pathways occur simultaneously in
competition with each other, what is the major product, and why? (2 pts) - answer
Product B, because the transition state leading to Product B is lower in energy than the
transition state leading to Product C.
Let's push a little further. We did not discuss this in the webcast, but imagine you have a
multi-step reaction, whose reaction coordinate diagram is shown below. Using what you
know about transition state energies, which step is the rate-determining step? (1 pt) -
answer B to C
Which of the following nucleophiles would perform well as a nucleophile, but poorly as a
base? (1 pts) - answer chloride ion
The alkyl halide shown below undergoes an elimination reaction. Select all possible
elimation products from the given structures provided below. (1 pts) - answer A
(Hofmann product)
, You are performing an elimination reaction using an alkyl halide and a non-bulky base.
The three products shown below are produced in the reaction. What product would be
created in the smallest amount? (2 pts) - answer A (Hofmann/terminal alkene)
You know the Bayer test is used to identify the presence of alkenes. You attempt to
perform an elimination reaction and test what you hope is the product using the Bayer
test. Adding KMnO4 to a solution of the starting material requires 2 drops to remain
purple, with no precipitate observed. A solution of your potential product requires 15
drops to remain purple, with no precitipate observed. Did you successfully perform an
elimination reaction? (1 pts) - answer Yes, because the solution of potential product
took more drops of KMnO 4 to remain purple.
A mixture of 0.9 mole fraction B is distilled by fractional distillation using a Vigreux
column having two theoretical plates. (Keep in mind that the initial boiling of mixture in
the distillation flask before the column adds an additional"plate".) According to the
phase diagram below, what is the composition of the distillate (liquid from condensed
vapor) you collect? Select the answer closest to the expected value. (2 pts) - answer
0.30 mole fraction B
The below phase diagram corresponds to what type of mixture? (1 pts) - answer
non-ideal solution with a negative deviation
If a liquid mixture containing 60 Mole Percent B was distilled using a simple distillation,
according to the below phase diagram, what temperature would the liquid mixture boil
at? (2 pts) - answer 68 degrees C
If a liquid mixture containing 60 Mole Percent B was distilled using an efficient fractional
distillation column, according to the below phase diagram, what temperature would be
read on the thermometer at the top of the fractionating column? Think back to what you
observed in the Elimination experiment! (1 pts)
An "efficient" fractional distillation column is efficient when it has at least the required
number of theoretical plates to distill a mixture to a desired purity. Assume that the
fractional distillation column can do as many distillations as you could need or has an
infinite number of theoretical plates. - answer 50 degrees C
If a liquid mixture containing 80 mole percent B were distilled using an efficient fractional
distillation column, what would be the composition of the liquid remaining in the
distillation pot? (2 pts) - answer 75 mole percent B
If a liquid mixture containing 80 mole percent B were distilled using an efficient fractional
distillation column, what would be the composition of the distillate collected? (2 pts) -
answer 75 mole percent A
Consider a situation where you were able to develop TLC conditions to analyze and
visualize a mixture of the starting alcohol and the alkene product in the Elimination
