Title: Organic section

Q: What would you expect for the melting point of your recrystallised benzoic acid compared to the benzoic acid-fructose mixture?
- The recrystallised benzoic acid has a higher melting point than the mixture.
- The recrystallised benzoic acid has a lower melting point than the mixture.
- The recrystallised benzoic acid has the same melting point as the mixture.
A: The recrystallised benzoic acid has a higher melting point than the mixture.

Q: In a solvent extraction using water and an organic solvent, which property will determine whether the organic phase will be the top layer or the bottom layer?
- Density
- Molecular weight
- Mass
- Viscosity
- Boiling point
A: Density

Q: The suitability of a TLC solvent to separate spotted samples mainly depends on which property?
- Polarity
- Molecular weight
- Boiling point
- Colour
- Viscosity
A: Polarity

Three of the techniques you will be using in this lab exercise are recrystallisation, thin-layer chromatography (TLC) and solvent extraction. You can remind yourself of the procedure and principles of these techniques at the Interactive Lab Primers web page (Royal Society of Chemistry, UK):

Recrystallisation (http://www.chem-ilp.net/labTechniques/Recrystallisation.htm)

TLC (http://www.chem-ilp.net/labTechniques/TLC.htm)

Solvent extraction (http://www.chem-ilp.net/labTechniques/SolventExtraction.htm)

Each of these links includes an animation and video, as well as other resources. Use these materials to answer the questions in this quiz.

Q: Water is formed as a by-product in the Biginelli reaction.  Where does the oxygen in the water come from?
- from ethyl acetoacetate
- from ethanol
- from benzaldehyde
- from air
- from urea
A: from ethyl acetoacetate; from benzaldehyde

Q: What is the boiling point of the lowest-boiling compound in the reagent mixture?
A: 78 (± 5)

Q: As a rule, when eluting the silica column with ethyl acetate-hexane (15:85), which molecules are going to elute (i.e., exit the column) first?
- The most polar molecules
- The most non-polar molecules
- the smallest molecules
- the largest molecules
A: The most non-polar molecules

Q: What is the boiling point of cyclohexane?
A: 81 (± 5)

Q: What happens to a sample of bromine when its temperature increases from 50 to 60 degrees Celsius?
- Nothing
- It melts.
- It evaporates.
- It sublimes.
A: It evaporates.

Q: Which of the following solvent combinations (for thin-layer chromatography) is the most polar one?
- acetone:hexane 50:50
- acetone:hexane 75:25
- chloroform:hexane 50:50
A: acetone:hexane 75:25

Q: What is the concentration of sodium hydroxide in the reaction in part A?
A: 2.5 (± 0.25)

Q: What is the correct formula to calculate the activation energy (E_A) in this energy diagram?

[Image: B1 energy diagram]
- EA=E2-E1
- EA=E2-E3
- EA=E1-E3
A: EA=E2-E1

Q: What is the molar concentration (in mol/L) of a 100 mL^ solution containing 20 g of sucrose (molecular formula C_12H_22O_11)?
A: 0.58 (± 0.1)

Q: What rotation angle would you expect to observe for a sucrose solution of concentration 0.2 g/cm3 in a polarimeter tube of 20 centimetres pathlength (specific rotation of sucrose: 66 cm3/dm g)
A: 26.4 (± 2)

Q: Methanol is a classed as dangerous good and hazardous substance. What hazards are associated with it?
- highly flammable
- toxic
- teratogenic
- corrosive
A: highly flammable; toxic

Q: A solution containing 1 mmol/L each of compounds 1 and 2 is analysed by UV/vis spectroscopy at a wavelength of 510 nm.  The absorbances of the individual compounds at 1 mmol/L are A1 and A2 (at 510 nm).  What is the absorbance of the mixture?
- A1 x A2
- A1 + A2
- A1 - A2
- A1 or A2, whichever is greater
A: A1 + A2

Q: The TLC in experiment B5 is run with an eluent containing acetic acid.  The R_f value for aspirin under these conditions is approximately 0.8.  How would the R_f value change if the acid were omitted from the eluent?
- Rf would increase
- Rf would decrease
- Rf would remain unchanged
A: Rf would decrease

Q: In the hydrolysis of sucrose in experiment Ins3, what is the role of the hydrochloric acid?
- it is a pH buffer
- it is a catalyst
- it is a reagent
- it is both reagent and catalyst
A: it is a catalyst

Q: What is the molecular formula of the gas that is formed when semicarbazide hydrochloride is combined with sodium hydrogen carbonate?
A: CO2

Q: What is the formal oxidation state of the chlorine atom in pool chlorine (=calcium hypochlorite)?
A: 1
Feedback: See tutorial handout (on LMS) for rules and links for the determination of oxidation states.

Q: Ibuprofen (A) is a weak acid (pK_a=4.4). What would be the ratio of unprotonated (A^-) to protonated (A) ibuprofen in a solution at pH 4.4?
A: 1
Feedback ("1"): Such ratios can be calculated using the Henderson-Hasselbalch equation.

Q: What is the boiling point of hexane?
A: 69 (± 5)

Q: What is the time-weighted average exposure limit for furfural (in mg/m^3)?
A: 7.9 (± 1)

Q: What is the boiling point of 2-furaldehyde (furfural) at atmospheric pressure (in degrees Celsius)?
A: 162 (± 5)

Q: In experiment F3, you will prepare a solution of your product in methanol (with a final concentration of approximately 5 x 10^-5 M) in two steps:
(1) A small amount of the cinnamate is dissolved in 50 mL of methanol.
(2) 5 mL of that initial solution are further diluted to 50 mL.

If you wanted to prepare the solution in a single step, how many millilitres of methanol would you need (using the same amount of cinnamate as above)?
A: 500

Q: At least how many moles of potassium hydroxide are needed to convert 1 mol of benzaldehyde into benzoic acid and benzyl alcohol?
A: 0.5
Feedback: In the actual experiment, KOH is supplied in excess of the stoichiometric amount because the H^+ ions formed in the reaction will neutralise some of the hydroxide.

Q: What is the upper explosion limit of diethyl ether (in % v/v)?
A: 48 (± 2)

Q: What is the lower explosion limit of diethyl ether (in % v/v)?
A: 1.8 (± 1)

Q: What is the boiling point of diethyl ether?
A: 35 (± 5)
Feedback: Mixing ether with water (or other chemicals) during an extraction will cause a slight increase in temperature and, given the low boiling point of ether, increase the pressure in the separation funnel. Let your demonstrator show you how to release that pressure in a safe way. Ether should always be used in the fumehood!

Q: What is the boiling point of dichloromethane?
A: 40 (± 5)

Q: What is the molar concentration (in mol/L) of a 5 % sodium hydrogen carbonate solution (i.e., 5 g of NaHCO_3 in 100 g of solution - assume that the solution has the same density as water)?
A: 0.6 (± 0.1)

Q: What is the molar concentration (in mol/L) of a 5 % sodium sulfite solution (i.e., 5 g of Na_2SO_3 in 100 g of solution - assume that the solution has the same density as water)?
A: 0.4 (± 0.1)

Q: What is the dangerous goods class of benzoyl chloride (provide the number of the class)?
A: 8
Feedback: You can find the dangerous goods classes in section 14 of the MSDS.

Q: What is the function of boiling chips?
- Their rough, porous surface enables vapours to form bubbles.
- They move when the solution is heated and thereby help to stir the mixture.
- Their acidic surface catalyses the reaction.
- They indicate traces of moisture in the solution by changing colour in the presence of water.
A: Their rough, porous surface enables vapours to form bubbles.
Feedback: For more information see http://orgchem.colorado.edu/hndbksupport/dist/boilchip.html .

Q: In experiment B3, you will prepare a solution of your product in methanol (with a final concentration of approximately 4 x 10^-5 M) in two steps:
(1) A small amount of the chalcone is dissolved in 50 mL of methanol.
(2) 5 mL of that initial solution are further diluted to 50 mL.

If you wanted to prepare the solution in a single step, how many millilitres of methanol would you need (using the same amount of chalcone as above)?
A: 500

Q: What is the boiling point of acetic anhydride?
A: 139 (± 10)

Q: What is the flash point of 2-butanol (in degrees Celsius)?
A: 27 (± 3)
Feedback: You can find such data in chemical handbooks or material safety data sheets.

Q: What is  the boiling point of 2-butanol (in degrees Celsius)?
A: 98 (± 3)
Feedback: You can find such data in chemical handbooks or material safety data sheets.

Q: When leaving an experiment unattended, you must leave a note with what information on it?
- your experiment number
- your name
- estimated time of your return
- your criminal record
- the structure of the expected product
- the amount of starting material (in g or mL)
A: your experiment number; your name; estimated time of your return

Q: It is suspected that toluene may be a teratogen. What does this mean?
- It may possibly cause harm to the unborn child.
- It may possibly cause cancer of the thyroid.
- It may possibly cause damage to cell membranes.
A: It may possibly cause harm to the unborn child.

Q: Which of the following products are formed when sodium borohydride is exposed to water?
- hydrogen gas (H2)
- sodium hydroxide (NaOH)
- boric acid (B(OH)3)
- sodium boride (NaB)
- oxygen gas (O2)
- sodium hydride (NaH)
A: hydrogen gas (H2); sodium hydroxide (NaOH); boric acid (B(OH)3)

Q: What is silicosis?
- A respiratory disease caused by breathing in silica dust.
- A silicone-type polymer, which is extremely flexible.
- An allergy against silica powder.
A: A respiratory disease caused by breathing in silica dust.
Feedback: Always handle dry silica in a well-ventilated place - fume hoods are best.

Q: What is the main difference between a separatory funnel and a dropping funnel?
- None - these are just two names for the same thing.
- Separatory funnels have a curved shape, whereas a dropping funnel has straight walls.
- The dropping funnel has a side tube connecting the main funnel volume with the funnel outlet.
A: The dropping funnel has a side tube connecting the main funnel volume with the funnel outlet.
Feedback: The extra tube on the side has the function of allowing the pressure to equilibrate as liquid runs out of the funnel.

Q: Product purification in experiment D3 is achieved by recrystallisation from a hexane-dichloromethane (DCM) mixture, in which the triphenylcarbinol precipitates as one of the components evaporates faster than the other. Which of the following statements are correct?
- Dichloromethane evaporates more quickly than hexane.
- Hexane evaporates more quickly than dichloromethane.
- Triphenylcarbinol has a higher solubility in dichloromethane than in hexane.
- Triphenylcarbinol has a higher solubility in hexane than in dichloromethane.
A: Dichloromethane evaporates more quickly than hexane.; Triphenylcarbinol has a higher solubility in dichloromethane than in hexane.

Q: Which of the following compounds is the most polar?
- lycopene
- chlorophyll-b
- chlorophyll-a
- beta-carotene
A: chlorophyll-b

Q: What is the correct way to dispose of a broken thermometer containing mercury?
- Transfer the spilled mercury (including glass pieces containing mercury) into a special waste container (ask your demonstrator). ([Image: Mercury tongs (source: Carl Roth, Germany)] Correct. Fine droplets of mercury are best absorbed using, for example, zinc dust or sulfur powder. Larger drops can be picked up using mercury tongs (picture above). For more information, see: http://sydney.edu.au/ohs/ohs_manual/mercurys.shtml#small .)
- Wait until the mercury has evaporated, then sweep up the glass and dispose of it in the broken glass bin. (Mercury vapour is hazardous to health. Clean up mercury spills immediately.)
- Sweep up the glass and mercury with a dustpan and broom and dispose of in toxic waste bin. (Mercury must not be mixed with general laboratory waste.)
A: Transfer the spilled mercury (including glass pieces containing mercury) into a special waste container (ask your demonstrator).

Q: Which is the limiting reagent in this experiment?
- None - the reagents are added in stoichiometric proportions
- the aldehyde (Note that the conversion from grams into moles will include rounding errors: disregard the small differences (less than 1 mmol) arising from those.)
- acetone (Note that the conversion from grams into moles will include rounding errors: disregard the small differences (less than 1 mmol) arising from those.)
- sodium hydroxide (Note that the conversion from grams into moles will include rounding errors: disregard the small differences (less than 1 mmol) arising from those.)
A: None - the reagents are added in stoichiometric proportions

Q: The esterification reaction of benzoyl chloride with propanol (reaction A) proceeds much faster than that of benzoic acid with propanol (reaction B). Which of the following statements is correct?
- The activation energy in A is lower than the activation energy in B.
- The activation energy in A is higher than the activation energy in B.
- The product of reaction A is more stable than that of reaction B.
- The by-product of reaction A (HCl) is more stable than the by-product of reaction B (H2O).
A: The activation energy in A is lower than the activation energy in B.

Q: What would you expect the ratio of ibuprofen enantiomers (R and S) in the ibuprofen tablets to be?
- less than 25 % S-isomer
- less than 50 % S-isomer
- 50 % of the S-isomer
- more than 50 % S-isomer
- more than 75 % S-isomer
A: 50 % of the S-isomer

Q: What are the hazards posed by 2,4-dinitrophenylhydrazine?
- It is corrosive.
- It is explosive when dry.
- It is highly flammable.
- It is known to cause cancer.
- It is not a hazardous substance or dangerous good.
A: It is explosive when dry.; It is highly flammable.

Q: What happens when diethyl ether is added to water?
- Two layers form, with ether as the top layer.
- Two layers form, with ether as the bottom layer.
- Ether reacts with water to form ethanol and hydroxide.
- The two liquids mix to form a single layer.
A: Two layers form, with ether as the top layer.

Q: What happens when dichloromethane (DCM) is added to water?
- Two layers form, with DCM as the top layer.
- Two layers form, with DCM as the bottom layer.
- DCM reacts with water to form methanol and hydrochloric acid.
- The two liquids mix to form a single layer.
A: Two layers form, with DCM as the bottom layer.

Q: What is the purpose of the drying tube on top of the reflux condenser in experiment D3?
- To prevent moisture from entering the reaction apparatus.
- To prevent ether fumes from leaving the reaction apparatus.
- To prevent gas exchange between the reaction apparatus and the laboratory air.
A: To prevent moisture from entering the reaction apparatus.
Feedback: The drying agent in the tube absorbs moisture, but it should not prevent gas flow - that could cause pressure to build up in the apparatus.

Q: Which work-up step in experiment D2 will separate triethylamine from the propenoic acid products?
- During extraction after adding 10 % HCl - triethylamine will remain in the aqueous phase.
- During extraction after adding 10 % Na2CO3 - triethylamine will remain in the organic phase.
- Triethylamine will evaporate during the reaction.
- Triethylamine will be removed during the recrystallisation step.
A: During extraction after adding 10 % HCl - triethylamine will remain in the aqueous phase.

Q: In the distillation set-up, how should the cooling water be connected to the Liebig condenser?
- The water inlet should be at the downstream (in respect to the distillate flow) end of the condenser.
- The water inlet should be at the upstream (in respect to the distillate flow) end of the condenser.
- Both ends of the condenser should have water flowing into them.
A: The water inlet should be at the downstream (in respect to the distillate flow) end of the condenser.

Q: Which of the three liquids below is the heaviest (assume that they all have the same volume)? Select the correct order (from heaviest to lightest).
- benzaldehyde > water > methanol
- benzaldehyde > methanol > water
- methanol > water > benzaldehyde
- methanol > benzaldehyde > water
- water > methanol > benzaldehyde
- water > benzaldehyde > methanol
A: benzaldehyde > water > methanol

Q: What is the correct way to dispose of the following solutions (or suspensions)? Match each compound with the appropriate waste container.
- 0.01 M hydrochloric acid in methanol | non-halogenated hydrocarbon waste
- 0.01 M hydrochloric acid in water | toxic aqueous waste
- 4-bromobenzaldehyde in methanol and water | halogenated hydrocarbon waste
- 3,4-dimethoxybenzaldehyde and sodium hydroxide in ethanol | non-halogenated hydrocarbon waste
- 2-nitrobenzaldehyde in acetone and water | non-halogenated hydrocarbon waste
- 4-bromobenzaldehyde in hexane | halogenated hydrocarbon waste

Q: What is the correct way to dispose of the following solutions (or suspensions)? Match each compound with the appropriate waste container.
- 0.01 M hydrochloric acid in methanol | non-halogenated hydrocarbon waste
- 0.01 M hydrochloric acid in water | toxic aqueous waste
- 4-chlorobenzaldehyde in methanol | halogenated hydrocarbon waste
- 3,4-dimethoxybenzaldehyde and sodium hydroxide in ethanol | non-halogenated hydrocarbon waste
- 4-methylbenzaldehyde in acetone and water | non-halogenated hydrocarbon waste
- 4-chlorobenzaldehyde in acetone and water | halogenated hydrocarbon waste

Q: Match the substituents attached to the chiral centre of phenylethylamine (pictured) with their priority in the Cahn-Ingold-Prelog (CIP) system (the system used to assign R/S stereochemistry).

1- highest, 4-lowest priority

[Image: phenylethylamine]
- What is the configuration of the chiral centre depicted above (R or S)? | R
- hydrogen | 4
- Phenyl group (C_6H_5) | 2
- methyl group (CH_3) | 3
- amino group (NH_2) | 1
Also offered: S
Feedback: The following website may help: http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/sterism3.htm

Q: Cinnamic acid is an ___________ carboxylic acid.
- Saturated
- Unsaturated
- Branched
A: Unsaturated

Q: Quenching means:
- accelerating a chemical reaction
- using bromine as a catalyst
- stopping a chemical reaction
A: stopping a chemical reaction