Quiz 1

Question 1

The solvent used for submitting 1H NMR samples in the 2311 course is:

Answer 1

deuterated chloroform

Question 2

A student weighed out a gram too much CaCl2 drying agent. Which is the correct way to manage this chemical?

a. Dissolve in water and flush down the drain or transfer to the nonhazardous solid waste stream
b. Dissolve it in acetone and add it to the nonhazardous solid waste stream
c. Return it to the reagent bottle
d. Neutralize it with baking soda and flush it down the drain

Answer 2

a. Dissolve in water and flush down the drain or transfer to the nonhazardous solid waste stream

Question 3

Simple Distillation is the method of choice:

a. when a liquid boils over 200 degrees Celsius
b. as the last step in the purification of a liquid
c. to determine the melting point of a pure liquid
d. when separating a mixture of two liquids whose boiling points differ by 50 degrees Celsius

Answer 3

b. as the last step in the purification of a liquid

Question 4

In a reaction of Acetic acid and Isopentyl Alcohol, why is the sulfuric acid indicated as a “catalyst” for the reaction? Explain.

Answer 4

It is regenerated in the reaction (not consumed) and thus not required in stoichiometric amounts.

Question 5

What is an appropriate size to use for a reaction flask in a 1 hour long reflux of 26.5 mL of acetic acid and isopentyl alcohol?

Answer 5

At least a 50 mL flask, but 100 mL would be okay too.

Question 6

What are all of the essential pieces of glassware and clamping necessary for a reflux?

Answer 6

• Ring stand
• Condenser
• Tubes & plastic funnel for water in and out
• 50/100 mL round bottomed flask
• Metal clamp
• Heating mantle
• Wood block to raise heating mantle

Question 7

While performing a reflux, describe how the reaction will be heated safely without bumping and describe the appropriate temperatures (outlet to use)

Answer 7

• Use boiling stones or a stir bar to prevent bumping.
• Be sure to plug the heating mantle into the Variac.
• Heating mantle should be raised on a wooden block or ring stand so it can be safely removed from the reflux apparatus.

Question 8

After a reflux, the product mixture is transferred to a separatory funnel and washed first with 2 x 20 mL of water, followed by 3 x 20 mL of aqueous saturated NaHCO3 (Sodium bicarbonate), then aqueous saturated NaCl. What is the purpose of each wash?

Answer 8

• Water: to remove excess acid, which is water soluble.
• Sodium bicarbonate: to neutralize the remaining acid left in the organic phase.
• Aqueous NaCl (brine wash): to “dry” the organic phase (helps to separate water)

Question 9

The product of the reflux was then dried over anhydrous MgSO4. Indicate whether each statement is T (true) or F (false) with respect to the use of the drying agent.

• The purpose of the drying agent is to bind with the product to purify it.
• The drying agent should be chemically inert to the product.
• Clumping indicates the product is dry.
• When an organic liquid is dry, it will be clear.

Answer 9

• The purpose of the drying agent is to bind with the product to purify it: FALSE
• The drying agent should be chemically inert to the product: TRUE
• Clumping indicates the product is dry: FALSE
• When an organic liquid is dry, it will be clear: TRUE

Question 10

Green Chemistry Principles - List three fundamental principles of green chemistry that guide how a
chemist may choose to design a reaction.

Answer 10

If possible…

• Choose a renewable starting material
• Use a catalyst
• Use minimal solvent

Question 11

Describe what a reflux apparatus includes and when it would it be appropriate to use.

Answer 11

For a reflux, a cooled vertical condenser is used so that even with heating to boiling, all reactants of a reaction condense back into the reaction flask (no solvent or products are lost)

Question 12

What is the expected by-product of a dehydration reaction using sulfuric acid as a catalyst?

Answer 12

water

Question 13

During a separatory funnel workup of a reaction, the student used “brine” in the last step. What is “brine”
and why was it used?

Answer 13

Brine is a saturated solution of sodium chloride. It is used to help “dry” the organic layer during extraction (by common ion affect.)

Question 14

The student decided to dry an alkene mixture using anhydrous MgSO4 and started with 40 mg per 1 mL of
solution.
- How will the student decide if more drying agent is required or if enough was added?
-What negative consequence could result from adding TOO MUCH drying agent?

Answer 14

If all of the MgSO4 if clumped, visible water is present or the solution is cloudy after sitting for 10 minutes,
more should be added.

If too much drying agent is added the liquid will absorb onto it and decrease the yield of product isolated.

Question 15

Waste Handling - Answer True or False to the statement below concerning handling waste in the 2311.

• A broken kerosene thermometer should be disposed of in the Liquid Organic Hazardous Waste.

Answer 15

FALSE - No, taken to the stockroom window

Question 16

Waste Handling - Answer True or False to the statement below concerning handling waste in the 2311.

• A waste container is considered full when the liquid level reaches the neck of the flask.

Answer 16

FALSE - according to the contract you signed “a waste container that is ¾ full at the “one gallon” line should be consider full and placed under the hood

Question 17

Waste Handling - Answer True or False to the statement below concerning handling waste in the 2311.

• Drying Agents are considered non-hazardous solid waste if free of organic materials.

Answer 17

TRUE

Question 18

Waste Handling - Answer True or False to the statement below concerning handling waste in the 2311.

• An aqueous 10% NaOH solution should be neutralized with sodium bicarbonate and flushed down the drain with excess water

Answer 18

FALSE - Basic waste should be neutralized with aqueous HCl.

Question 19

Waste Handling - Answer True or False to the statement below concerning handling waste in the 2311.

• Paper towels can be placed in either the blue or green trash cans in lab.

Answer 19

FALSE - Not in the blue glass trash because of the safety issues with covering up glass which could cut
custodial staff

Question 20

A change in chemical shift from 2.5 ppm to 4.0 ppm is described as:

Downfield or Upfield?

Answer 20

Downfield

Question 21

Simple Distillation: Why should the distilling flask never be more than ½ to ¾ full?

Answer 21

Bumping can occur and cause impure material to come over to the receiving flask

Question 22

Simple Distillation: Why should a distilling flask never be heated to dryness?

Answer 22

Mohrig, p. 152. Can overheat flask and break it OR make cleaning difficult OR peroxides can form and
cause explosion.

Question 23

Safety and Waste Handling - Explain why each statement below is FALSE and provide a few words that
would make the statement correct and demonstrate your knowledge of what action IS appropriate.

False: Drying agents that are wet with organic materials should be quickly placed in the organic hazardous waste
bottle.

True:

Answer 23

True: should be .. spread out to dry (or rinsed with acetone) then either placed in nonhazardous solid waste or
dissolved in water and flushed down the drain

Question 24

Safety and Waste Handling - Explain why each statement below is FALSE and provide a few words that
would make the statement correct and demonstrate your knowledge of what action IS appropriate.

False: A broken kerosene thermometer should be placed directly into the blue glass trash can.

True:

Answer 24

True: A broken thermometer (all fragments and any towels used to absorb the liquids) should be taken to the
stockroom window for disposal.

Question 25

Safety and Waste Handling - Explain why each statement below is FALSE and provide a few words that
would make the statement correct and demonstrate your knowledge of what action IS appropriate.

False: Excess organic reagents, such as isopentyl alcohol, should be dissolved in acetone before transferring to the
organic hazardous waste solvent stream and then the flask rinsed with additional acetone to clean.

True:

Answer 25

True: Excess organic reagents should be directly poured into the organic hazardous waste then the flask rinsed
with a minimal amount of acetone.

Question 26

Safety and Waste Handling - Explain why each statement below is FALSE and provide a few words that
would make the statement correct and demonstrate your knowledge of what action IS appropriate.

False: The caps should be left off of the organic solvent hazardous waste bottles so that pressure does not develop.

True:

Answer 26

True: Caps should be covering the organic solvent hazardous waste bottle whenever not in use to prevent
vapors from entering the environment.

Question 27

Safety and Waste Handling - Explain why each statement below is FALSE and provide a few words that
would make the statement correct and demonstrate your knowledge of what action IS appropriate.

False: It is safe to use a hot plate to heat organic liquids out on the open bench top because no flames are present.
.
True:

Answer 27

True: Hot plates can ignite volatile organic liquids so heating should always be done in the hood

Question 28

Match the description of the area of the IR spectrum with the type of bond vibration given:

O-H stretch

Answer 28

3200-3400 cm-1

Question 29

Match the description of the area of the IR spectrum with the type of bond vibration given:

C-O stretch

Answer 29

Fingerprint region

Question 30

Match the description of the area of the IR spectrum with the type of bond vibration given:

=C-H stretch

Answer 30

just above 3000 cm-1

Question 31

Match the description of the area of the IR spectrum with the type of bond vibration given:

C=O of carboxylic acid

Answer 31

1800-1680 cm -1

Question 32

Match the description of the area of the IR spectrum with the type of bond vibration given:

overtone band of C=O

Answer 32

3200-3400 cm-1

Question 33

Propose a reason that the acetic acid would be used in large excess in a Fischer Esterification reaction (such as in the formation of isopentyl acetate).

Answer 33

To help push the equilibrium to the right/products

Question 34

After reflux of isopentyl alcohol and acetic acid, the product was separated from the excess starting materials using separatory funnel manipulations. Explain how excess acetic acid could be removed from the product.

Answer 34

Reaction placed in separatory funnel and rinsed with water to remove the majority of the acetic acid, then the organic layer repeatedly washed with aq NaHCO3 to neutralize the remaining acid and remove.

Question 35

Though esters, such as benzyl acetate, are pleasant smelling, why are they not used in perfumes and body
lotions?

Answer 35

They will hydrolyzed back to the starting smelly carboxylic acids with perspiration.

Question 36

What types of structures are represented by the “R” groups in a triglyceride? Propose two.

Answer 36

Long chain hydrocarbon (fatty acid) chains with - some are saturated and some can have unsaturation

Question 37

Why is only a catalytic amount of NaOH required in the reaction for the synthesis of biodiesel?

Answer 37

The mechanism regenerates the ethoxide group (students need simply say “it is regenerated”)

Question 38

REFLUX: A reaction was refluxed for 1.5 hours in order increase the rate of the reaction.

• How does a reflux apparatus differ from a simple distillation apparatus in terms of what is being accomplished and assembly?
• List three key safety features required to perform a SAFE reflux?

Answer 38

• A reflux reaction as the cooled condenser vertical so that all vapors return to the heated flask. In contrast, the cooled condenser leads to a receiving flask so that vapors are separated from the heated flask.
• Any three: boiling stone or stir bar, raised of the benchtop, clamp at neck of the reaction flask, water going
  in and out of the condenser bottom to top, out hose anchored in the hood, heating mantle in variac with
  temperature control so that the reflux is not vigorous (reflux ring 1/3 up condenser), etc..

Question 39

What strategies could be taken to push the equilibrium of a Fischer Esterification reaction (using isopentyl alcohol and acetic acid) towards product considering the cost and physical properties of the reagents and product? Provide 2.

Answer 39

Use of excess acetic acid

Question 40

Following a separatory workup of the isopentyl acetate reaction involving washing with water, saturated NaHCO3, and for the last step brine, a student drained the bottom layer into an Erlenmeyer flask and added anhydrous magnesium sulfate to dry. A cloudy solution resulted with no free flowing drying agent observed. Adding additional drying agent resulted in the same observation. Explain what happened.

Answer 40

The student was trying to dry the WATER layer not the organic layer so the drying agent just dissolved.

Question 41

In an H NMR, there was a singlet at 7.26 ppm. What would this signal correspond to in the sample?

Should this peak be considered when doing a purity calculation? Why or why not?

Answer 41

CHCl3 from the CDCl3

Not part of the purity calculation since the CDCl3 was the solvent used for the NMR and NOT part of the
sample analyzed

Question 42

TRUE OR FALSE: As long as a waste stream is aqueous, it can be poured down the drain

Answer 42

FALSE

Question 43

TRUE OR FALSE: Using a reaction scheme in your laboratory report that is copied from the internet is not permitted and will be considered an act of scholastic dishonesty

Answer 43

TRUE

Question 44

TRUE OR FALSE: As long as a student’s shoes cover his or her toes they are acceptable footwear in lab

Answer 44

FALSE

Question 45

TRUE OR FALSE: Goggles must be worn by all students even if only one student is using chemicals

Answer 45

TRUE

Question 46

TRUE OR FALSE: A waste bottle that is full should be carried to the stockroom for replacement

Answer 46

FALSE

Question 47

CLEANING GLASSWARE: A reaction was worked up in the separatory funnel by washing the organic layer with
aqueous sodium bicarbonate, water, and brine (aqueous sodium chloride). At the end of lab a student rinsed the
separatory funnel with acetone to clean it and noticed a white residue formed on the walls of the glass. What is
the residue and how should it be cleaned out?

Answer 47

The residue is most likely inorganic salts that are NOT soluble in acetone. Washing with water in the sink will clean the glassware.

Question 48

Upon distillation of a product, what would indicate isolation of either compound in pure form versus a mixture of products? (assuming proper thermometer position)?

Answer 48

If the boiling point was constant at either temperature it would indicate a pure compound. If there was a continual progression of boiling point from one temperature to the other, it would indicate a mixture.