Chem 8LC

Pre-labs and procedures for labs 1-8

The solids obtained by vacuum filtration is mostly pure. Which of the following statements is false?

• the product is a solid that can be isolated by filtration

• most unreacted indene should pass through the filter because it is a liquid

• acetonitrile and indene are possible impurities contaminating the product

• formation of a diastereomeric product is possible, which can contaminate the major product

• vacuum filtration is capable of removing impurities because it is similar column chromatography

vacuum filtration is capable of removing impurities because it is similar column chromatography

You will be "rotovapping" a 1:1 mixture of acetonitrile/water. It is unlikely that all of the solvent will evaporate. Which solvent will remain and why?

• acetonitrile will remain because it has a higher boiling point

• acetonitrile will remain because it has a lower boiling point

• acetonitrile will remain because it is organic and organic solvents are harder to evaporate

• water will remain because it was a higher boiling point

• water will remain because it has a lower boiling point

water will remain because it has a higher boiling point

What is Oxone?

• O2

• O3

• KHSO5

• KHSO4

• a 2:1:1 mixture of KHSO₅/KHSO₄/K₂SO₄

a 2:1:1 mixture of KHSO₅/KHSO₄/K₂SO₄

How many mL of indene should you measure out if 2.15 mmol is required for the experiment? The density, ρ, of indene 0.997 g/mL.

• 0.233mL

• 2.33mL

• 0.025mL

• 0.25mL

• 2.5mL

0.25 mL

Oxone consists of a 2:1:1 molar mixture of KHSO₅ (152.20 g/mol), KHSO₄ (136.17 g/mol), and K₂SO₄ (174.26 g/mol). KHSO₄ and K₂SO₄ act to stabilize the active oxidant. Based on their molecular weights, approximately 49.5% of the Oxone reagent measured out will correspond to the active oxidant. How many mmol of KHSO₅ is present in 1 gram of Oxone? 

3.29 mmol 

Which of the following is not a vicinal halohydrin?

• A

• B

• C

• D

• E

D

Which of the following atoms or groups are arranged in a vicinal relationship?

• OH and CH3

• Cl and H

• OH and Ph

• OH and F

• Cl and CH3

OH and CH3

Will this reaction be successful in producing an iodonium ion? 

• Yes: NaI is a good source of iodine

• Yes: NaI is a good electrophile

• No: the alkene is a poor nucleophile

• No: iodonium ions are unstable

• No: NaI is not an electrophilic iodine source

No: NaI is not an electrophilic iodine source

Which is the correct chloronium ion formed in the following reaction? 

• A

• B

• C

• D

• E

B

Why does the nucleophile attack the halonium ion? [select multiple]

• the halonium ion is electron-rich and likes electrons

• the halogen is electronegative and renders the adjacent carbon atoms electrophilic

• attacking the halonium ion opens the 3-membered ring to produce a molecule with less strain

• the nucleophile is electron-poor and therefore interacts with the electron-rich halonium ion

• the halogen is electropositive and renders the adjacent carbon atoms nucleophilic

• the halogen is electronegative and renders the adjacent carbon atoms electrophilic 

• attacking the halonium ion opens the 3-membered ring to produce a molecule with less strain 

Which of the following are true regarding alkenes?

• alkenes contain a triple bond

• alkenes and olefins refer to different functional groups

• alkenes are C=N bonds

• alkenes are C=O bonds

• alkenes are C=C bonds

alkenes are C=C bonds

How many alkenes are in palbociclib?

• 2

• 3

• 4

• 5

• 6

• 7

4

Which of the following statements are FALSE regarding carbonyl compounds?

• aldehydes and ketones are carbonyl compounds

• carbonyl compounds have C=O bonds

• carbonyl compounds have triple bonds

• amides and esters are carbonyl compounds

• none of the above

carbonyl compounds have triple bonds

Is the product of this reaction a stabilized or unstabilized ylide?

• stabilized ylide

• unstabilized ylide

• neither stabilized nor unstabilized

• not enough information to determine

unstabilized ylide

Which of the product is correct for this reaction?

• Z-alkene

• E-alkene

• both are correct

• both are incorrect

Z-alkene

How many hydrogens are on each of the indicated carbons?

• a=2 b=2

• a=1 b=2

• a=1 b=1

• a=2 b=0

• a=2 b=1

a=2 b=1

Select all that is true regarding Nafion resin 417.

• it is a solvent for Fischer esterification

• it protonates the carboxylic acid

• it is a superacid

• it is a catalyst

• it is a superbase

• it protonates the carboxylic acid

• it is a superacid

• it is a catalyst

The molecular ion, M+, is

• an ionized fragment of the molecule that is smaller than the molecular weight

• a positively charged molybdenum ion

• the ionized form of the molecule with a mass that corresponds to the molecular weight of the molecule

• the largest peak in the NMR spectrum

• always the tallest signal in the mass spectrum

the ionized form of the molecule with a mass that corresponds to the molecular weight of the molecule

The molecular ion for an unknown carboxylic acid has m/z = 122. Using the Rule of 13, determine a possible molecular formula. Hint: consider how many oxygen atoms a carboxylic acid should have.

• C₉H₁₄

• C₉H₅

• C₈H₁₀O

• C₇H₆O₂

• C₆H₂O₃

C₇H₆O₂

Which of the following molecules has 2 degrees of unsaturations?

• cyclohexane

• cyclohexene

• cyclopentane

• benzene

• cyclohexadiene

cyclohexene

How many degrees of unsaturation does the compound with molecular formula C₆H₁₂O₆ have?

• 0

• 1

• 2

• 3

• 4

1

Which signal in the above ¹³C NMR spectrum is characteristic of the ester carbonyl carbon?

• δ14

• δ19

• δ22

• δ31

• δ65

• δ171

δ171

Which is true of the signal at δ1.4?

• triplet representing 2 hydrogens

• singlet; hydrogens have 2 hydrogen neighbors

• triplet representing 3 hydrogens

• quintet; hydrogens have 4 hydrogen neighbors

• sextet; hydrogens have 5 hydrogen neighbors

sextet; hydrogens have 5 hydrogen neighbors

What is glacial acetic acid?

• acetic acid that contains minimal water

• regular vinegar

• acetic acid extracted from glaciers

• acetic acid with ice

• a specific brand of acetic acid

acetic acid that contains minimal water

When extracting water with diethyl ether, which of the follow statement(s) are correct?

• Diethyl ether is more dense than water

• Water is more dense than diethyl ether

• Water is the bottom layer

• Diethyl ether is the bottom layer

• The organic and aqueous layers are completely miscible

• Water is more dense than diethyl ether

• Water is the bottom layer

What important information can be derived from IR spectroscopy?

• the total number of carbons in the molecule

• the total number of hydrogens in the molecule

• the shape of the molecule

• the melting and boiling points of the sample

• key functional groups present in the sample

key functional groups present in the sample

What is a heterocycle?

• a molecule that contains two different rings

• any cyclic ring structure

• a cyclic ring structure that contains only carbons and hydrogens

• a cyclic ring structure that contains any element(s) outside of carbons and hydrogens

• a non-cyclic molecule that becomes a cyclic molecule

a cyclic ring structure that contains any element(s) outside of carbons and hydrogens

Which of the follow molecules represent an unsubstituted amine(s)?

• A

• B

• C

• D

• E

• A, C, and E

A

Which of the following molecules represent a disubstituted amine?

• A

• B

• C

• D

• E

C

In Figure 2 above, why is the S_N2 reaction a poor choice for synthesizing substituted amines?

• only 1 product can be formed from an SN2 reaction

• amines do not participate in SN2 reactions

• the primary amine is too nucleophilic

• amines' nucleophilicities increase with increasing substitution, which leads to multiple products

• the quaternary ammonium salt is not nucleophilic enough to react further

amines' nucleophilicities increase with increasing substitution, which leads to multiple products

Which of the following are true regarding the mechanism of imine formation? [select multiple]

• The aldehyde attacks the amine

• the amine attacks the carbonyl

• formation of the hemiaminal is reversible

• formation of the imine is reversible

• the hemiaminal is more stable than the starting aldehyde and amine

• the amine attacks the carbonyl

• formation of the hemiaminal is reversible

• formation of the imine is reversible

Predict the product of the following reaction. [free response]

C

Predict the product for the following reaction:

• A

• B

• C

• D

• C and D

D

The synthesis of compound X requires 2 steps. The first step was accomplished in 80% yield and the second step in 90% yield. What is the overall yield of the 2-step synthesis?

• 80%

• 90%

• 81%

• 64%

• 72%

72%

What is the purpose of mixing the 2 solids with a stirring rod?

• to prepare the substances to react at a later stage

• to purify the two solids

• to recrystallize the two solids

• to induce a chemical reaction between the two solids

• it doesn't accomplish anything

to induce a chemical reaction between the two solids

What can happen if too much hexanes is used in the recrystallization?

• the recrystallization yield can be low or even no crystals may form

• hexanes is a non-polar solvent so there is no consequence for using too much

• hexanes is a polar solvent so it can absorb water and complicate the recrystallization process

• the yield will be >100%

• the product may decompose

the recrystallization yield can be low or even no crystals may form

What is the most important piece of information that we can obtain from the IR spectrum at this step?

• product formation can be distinguished by looking at the C-H stretches between 2850-3150 cm^-1

• product formation can be distinguished by looking for a new C=O stretch at approximately 1700 cm^-1

• product formation can be distinguished by the presence of an O-H stretch between 3200-3400 cm^-1

• product formation can be distinguished by looking for new C=C stretches at approximately 1600-1650 cm^-1

• product formation can be distinguished by the disappearance of the C=O stretch at approximately 1700 cm-1

product formation can be distinguished by the disappearance of the C=O stretch at approximately 1700 cm-1

Is p-toluidine or o-vanillin expected to be more polar?

• they are both equally polar

• p-toluidine

• o-vanillin

• p-toluidine is more polar only in polar solvents

• it is impossible to distinguish

p-toluidine

Ethanol - Is the highlighted atom best described as a hydrogen, proton, or hydride?

• proton

• hydride

• hydrogen

• All of the above

• None of the above

proton

LiAlH₄ - Is the highlighted atom best described as a hydrogen, proton, or hydride?

• proton

• hydride

• hydrogen

• all of the above

• none of the above

hydride

Acetic acid - Is the highlighted atom best described as a hydrogen, proton, or hydride?

• proton

• hydride

• hydrogen

• all of the above

• none of the above

proton

Methyl acetate - Is the highlighted atom best described as a hydrogen, proton, or hydride?

• proton

• hydride

• hydrogen

• all of the above

• none of the above

proton

Benzene - Is the highlighted atom best described as a hydrogen, proton, or hydride?

• proton

• hydride

• hydrogen

• all of the above

• none of the above

hydrogen

Pyridinium - Is the highlighted atom best described as a hydrogen, proton, or hydride?

• proton

• hydride

• hydrogen

• all of the above

• none of the above

proton

Wilkinson's catalyst - Is the highlighted atom best described as a hydrogen, proton, or hydride?

• proton

• hydride

• hydrogen

• all of the above

• none of the above

hydride

Predict the product of the reaction below:

D

What is the purpose of saving some imine for TLC analysis? Select all that apply.

• to add to the reaction in case something goes wrong

• it helps the solvent elute faster during tlc analysis

• to decrease the melting point

• to determine reaction progress 

• to compare the R_f's of the starting material and product

• to prevent imine from decomposing

• to determine reaction progress 

• to compare the R_f's of the starting material and product

A gas is formed in this step from the quenching of any unreacted borohydride. What is this gas?

• hydrogen gas

• helium gas

• oxygen gas

• air

• steam

hydrogen gas

What should be in the organic layer?

• ethyl acetate only

• ethyl acetate and NaBH₄

• NaBH₄ and amine product

• ethyl acetate and amine product

• water and byproducts from NaBH₄

ethyl acetate and amine product

What is the purpose of washing the organic layer with brine?

• it removes NaCl from the organic layer

• it removes amine from the organic layer

• it removes water from the organic layer

• it purifies the organic layer

• it purifies both the organic and aqueous layers

it removes water from the organic layer

What structural feature of ethyl acetate will complicate the IR spectrum?

• the methyl C-H bonds

• the ethyl C-H bonds

• the C=O double bond of the ester

• the C-O single bond of the ester

• both A & B

the C=O double bond of the ester

A TLC analysis using 30% EtOAc in hexanes indicated an R_f = 0.63 for the product. What should you do from here?

• Record the R_f and proceed with the experiment according to the procedure

• Repeat the TLC analysis using a solvent mixture with greater polarity (50% EtOAc in hexanes) to increase the R_f further

• Repeat the TLC analysis using a solvent mixture with lower polarity (15% EtOAc in hexanes) to decrease the R_f to about 0.3

• Repeat the experiment entirely because something went wrong

• Ask TA for help because it is impossible to obtain an Rf = 0.63

Repeat the TLC analysis using a solvent mixture with lower polarity (15% EtOAc in hexanes) to decrease the R_f to about 0.3

Which of the following statements are true with respect to Figure 3?

• S_N2 reactions can proceed with iodobenzene

• S_N1 reaction can proceed with iodobenzene

• S_N2 reactions cannot proceed with iodobenzene

• Aniline can be synthesized through a reductive amination

• Aniline can neither be synthesized from S_N2 reactions nor reductive aminations

Aniline can neither be synthesized from S_N2 reactions nor reductive aminations

Which of the following statements are true for household bleach? (Select all that apply.)

• bleach contains 5.25%-5.75% sodium hypochlorite

• bleach is mainly chlorine gas

• bleach is mainly sodium hydroxide

• sodium hypochlorite is in equilibrium with chlorine gas and sodium hydroxide

• sodium hypochlorite is safe when dilute

• bleach contains 5.25%-5.75% sodium hypochlorite

• sodium hypochlorite is in equilibrium with chlorine gas and sodium hydroxide

• sodium hypochlorite is safe when dilute

What is the role of bleach in this experiment?

• to disinfect glassware

• to kill bacteria that would interfere with the Hofmann rearrangement

• to be used as a clean source of water

• to be used as a convenient source of chlorine

• to be used as a source of strong acid

to be used as a convenient source of chlorine

How much sodium hypochlorite (in grams) is in 9.0 mL of 5.75% bleach solution?

• 5.2g

• 9.0g

• 52g

• 5.75g

• 0.52g

0.52g

What is the purpose of adding sodium bisulfite solution?

• it is a strong acid to react with sodium hydroxide

• it is a strong base to react with 3-nitrobenzamide

• it is a reducing agent to neutralize unreacted chlorine

• it helps to cool the reaction mixture

• it is an oxidant to neutralize unreacted chlorine

it is a reducing agent to neutralize unreacted chlorine

Predict the product of the following reaction.

C

Predict the product of the following reaction.

B

Predict the product of the following reaction.

D

How many acetal functional groups are in this molecule?

• 1

• 2

• 3

• 4

• 5

• None

2

What is the role of para-toluenesulfonic acid?

• it is the solvent

• it is the acid catalyst that reacts with benzaldehyde dimethylacetal

• it is the acid catalyst that reacts with acetonitrile

• it is the acid catalyst that reacts with the sugar

• it removes water from the reaction

it is the acid catalyst that reacts with benzaldehyde dimethylacetal

What is triethylamine reacting with?

• acetonitrile

• unreacted sugar starting material

• unreacted benzaldehyde dimethylacetal

• para-toluenesulfonic acid

• water

para-toluenesulfonic acid

Which of the following is/are true regarding the organic layer? (select all that applies)

• the organic layer is consists of ethyl acetate & acetonitrile & organic product

• the organic layer consists of ethyl acetate only

• the organic layer is beneath the aqueous layer

• the organic layer is above the aqueous layer

• the organic layer consists primarily of water

• the organic layer is consists of ethyl acetate & acetonitrile & organic product

• the organic layer is above the aqueous layer

What happens if one were to use too much DCM?

• the yield will increase because more solids will precipitate

• the yield will decrease because the product decomposes

• the product will revert back to starting material (i.e. deprotection)

• the solution will not be saturated and the product will not precipitate as easily or at all

• there should be no consequences

the solution will not be saturated and the product will not precipitate as easily or at all

The pKa's refer to the protons highlighted in blue. Select all of the correct statements.

• Butane is more acidic than acetone

• Acetone is more acidic than butane

• Butane can be deprotonated by NaOH (pKa = 15) or LDA (pKa = 35.7)

• Acetone can be deprotonated by NaOH (pKa = 15) or LDA (pKa = 35.7)

• Butane can deprotonate acetone

• Acetone is more acidic than butane

• Acetone can be deprotonated by NaOH (pKa = 15) or LDA (pKa = 35.7)

Which of the following statements is false?

• The higher the pKa, the harder it is to deprotonate the hydrogens

• The higher the pKa, the easier it is to deprotonate the hydrogens

• The pKa of a molecule is low when the molecule can form a stabilized carbanion after deprotonation

• Deprotonation of acetone forms a stabilized enolate carbanion

• Acetone is more acidic than pentane

The higher the pKa, the easier it is to deprotonate the hydrogens

Identify the main electrophile in the reaction depicted in Figure 3?

• aldehyde

• ketone

• β-Hydroxyketone

• HCl

• αβ-Unsaturated ketone

aldehyde

Which of the molecules drawn on the product side of the chemical reaction is incorrect?

• A

• B

• C

• D

B

What is the product of the aldol reaction?

• A

• B

• C

• D

• This reaction as drawn does not work

D

Why is a reflux condenser needed for this experiment?

• It is not really necessary

• To prevent dust and dirt in the air from entering the reaction apparatus

• It helps to heat the reaction mixture

• It prevents the solvent from boiling away by condensing the vapors

It prevents the solvent from boiling away by condensing the vapors

What is the purpose of adding 6 M HCl?

• To protonate the aldehyde

• To react with acetone

• To promote elimination of water in the aldol condensation

• To heat up the ice

To promote elimination of water in the aldol condensation

What is the solid precipitate that forms when the mixture is acidified with 6 M HCl?

• Hydrogen chloride

• The β-hydroxyketone

• Sodium chloride

• αβ-Unsaturated ketone

• Vanillin

αβ-Unsaturated ketone

Which of the following statement is false regarding TLC analysis?

• It provides an indication of the progress of the reaction.

• It provides information on the purity of the substance.

• Silica gel acts as the stationary phase.

• Ethyl acetate acts as the mobile phase.

• Hexanes acts as the stationary phase.

Hexanes acts as the stationary phase.