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Date	November 2020	Marks available	1	Reference code	20N.2.hl.TZ0.2
Level	HL	Paper	2	Time zone	TZ0
Command term	Justify and Deduce	Question number	2	Adapted from	N/A

Question

Compound A is in equilibrium with compound B.

Predict the electron domain and molecular geometries around the oxygen atom of molecule A using VSEPR

[2]

State the type of hybridization shown by the central carbon atom in molecule B.

[1]

State the number of sigma ( $σ$ ) and pi ( $π$ ) bonds around the central carbon atom in molecule B.

[1]

The IR spectrum of one of the compounds is shown:

Deduce, giving a reason, the compound producing this spectrum.

[1]

Compound A and B are isomers. Draw two other structural isomers with the formula $C_{3} H_{6} O$ .

[2]

The equilibrium constant, $K_{c}$ , for the conversion of A to B is $1.0 \times 10^{8}$ in water at $298 K$ .

Deduce, giving a reason, which compound, A or B, is present in greater concentration when equilibrium is reached.

[1]

f(i).

Calculate the standard Gibbs free energy change, $∆ G^{⦵}$ , in $kJ {mol}^{- 1}$ , for the reaction (A to B) at $298 K$ . Use sections 1 and 2 of the data booklet.

[1]

f(ii).

Propanone can be synthesized in two steps from propene. Suggest the synthetic route including all the necessary reactants and steps.

[3]

g(i).

Propanone can be synthesized in two steps from propene.

Suggest why propanal is a minor product obtained from the synthetic route in (g)(i).

[2]

g(ii).

Markscheme

Electron domain geometry: tetrahedral ✔

Molecular geometry: bent/V-shaped ✔

${sp}^{2}$ ✔

$σ$ -bonds: $3$
AND
$π$ -bonds: $1$ ✔

B AND $C = O$ absorption/ $1750 « {cm}^{- 1} »$
OR
B AND absence of $O - H / 3200 - 3600 « {cm}^{- 1} absorption »$ ✔

Accept any value between $1700 - 1750 c m^{- 1}$ .

Accept any two $C_{3} H_{6} O$ isomers except for propanone and propen-2-ol:

✔✔

Penalize missing hydrogens in displayed structural formulas once only.

$B$ AND $K_{c}$ is greater than $1$ /large ✔

f(i).

$« Δ G^{Θ} = - R T \ln K = 0.00831 kJ {mol}^{- 1} K^{- 1} (298 K) (\ln 1.0 \times 10^{8}) = »$
$- 46 « kJ {mol}^{- 1} »$ ✔

f(ii).

$H_{2} O$ /water «and $H^{+}$ » ✔

${CH}_{3} CH (OH) {CH}_{3}$ /propan-2-ol ✔

$K_{2} {Cr}_{2} O_{7}$ /«potassium» dichromate(VI) AND $H^{+}$
OR
${KMnO}_{4}$ /«acidified potassium» manganate(VII) ✔

Accept $H_{3} O^{+}$ .

g(i).

primary carbocation «intermediate forms»
OR
minor product «of the water addition would be» propan-1-ol
OR
anti-Markovnikov addition of water ✔

primary alcohol/propan-1-ol oxidizes to an aldehyde/propanal ✔

g(ii).

Examiners report

The majority of students got at least one of electron domain geometry or molecular geometry correct.

The vast majority of students could identify the hybridization around a central carbon atom.

The vast majority of students could identify BOTH sigma and pi bonds in a molecule.

Many candidates identified B having C = O and a peak at 1750.

A surprising number of candidates drew propanone here as an option, either failing to read the question or perhaps finding the structural formulae provided difficult to understand.

Most candidates identified B, the product, as being in greater concentration at equilibrium however some lost the mark because they did not include a reason.

f(i).

Most candidates could apply the formula for Gibbs free energy change, ΔG^Θ, correctly however some did not get the units correct.

f(ii).

The mean mark was ⅔ for the required synthetic route. Some candidates failed to identify water as a reagent in the hydration reaction, or note that dichromate ion oxidation requires acidic conditions. This was also the question with most No Response.

g(i).

This question regarding the formation of a minor product was not well answered. Many candidates struggled to explain the formation of propan-1-ol and to then oxidize it to propanal.

g(ii).

Syllabus sections

Core » Topic 10: Organic chemistry » 10.1 Fundamentals of organic chemistry

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17M.2.hl.TZ2.6b:
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Calculate the standard enthalpy change for the reaction, ΔH ^θ, using section 12 of the data booklet.
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Draw the structure of the dipeptide Asp–Phe using section 33 of the data booklet.
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Deduce the structural formulas of the two possible isomers.
17M.3.sl.TZ1.10b.ii:
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18M.2.hl.TZ1.7c.iii:
Deduce the name of the class of compound formed when the product of (c)(i) reacts with butanoic acid.
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18N.2.hl.TZ0.2d:
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Deduce the structural formula of the compound.
18N.2.sl.TZ0.2c: Classify propan-2-ol as a primary, secondary or tertiary alcohol, giving a reason.
18N.2.sl.TZ0.2a:
Draw the structural formula of propan-2-ol.
18N.2.hl.TZ0.8b.i:
Draw two structural isomers of methyloxirane.
17M.1.sl.TZ1.26: What is the name of the compound with this molecular structure applying IUPAC rules? A. ...
16N.1.sl.TZ0.24:
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A. I and II only

B. I and III only

C. II and III only

D. I, II and III
19N.3.sl.TZ0.10c: Explain why maltose, C12H22O11, is soluble in water.
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19N.2.sl.TZ0.3d(ii):
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19M.1.hl.TZ2.34: What is the name of this compound using IUPAC rules? A. 2,3-diethylbutane B....
17M.1.hl.TZ2.37:
In which order should the reagents be used to convert benzene into phenylamine (aniline)?
19M.2.hl.TZ1.2c:
Outline one piece of physical evidence for the structure of the benzene ring.
19M.2.sl.TZ1.1b:
Draw the structure of one other isomer of xylene which retains the benzene ring.
19M.3.sl.TZ1.5a:
State the name of the functional group which allows the molecule to be responsive to applied electric fields.
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16N.3.sl.TZ0.20a:
Compare and contrast the functional groups present in methadone and diamorphine (heroin), giving their names. Use section 37 of the data booklet.
19M.1.sl.TZ2.24:
Which compound has the lowest boiling point?

A. CH₃CH₂CH₂CH₂CH₂CH₃

B. CH₃CH₂CH₂CH₂CH₃

C. CH₃CH(CH₃)CH₂CH₃

D. CH₃C(CH₃)₂CH₃
19M.1.hl.TZ2.32:
Which compound has the lowest boiling point?

A. CH₃CH₂CH₂CH₂CH₂CH₃

B. CH₃CH₂CH₂CH₂CH₃

C. CH₃CH(CH₃)CH₂CH₃

D. CH₃C(CH₃)₂CH₃
22M.1.sl.TZ1.25: Which compounds are members of the same homologous series? A. propanal, propanone,...
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17M.3.sl.TZ1.15b:
Deduce the formula of the biodiesel formed when the vegetable oil shown is reacted with the reagents in (a).
17M.2.hl.TZ2.7c.i:
State the reagents and the name of the mechanism for the nitration of benzene.
17M.1.sl.TZ2.27:
Which compound contains a secondary carbon atom?

A. CH₃CH(Cl)CH(CH₃)₂

B. (CH₃)₂CHCH₂Cl

C. (CH₃)₃CCl

D. CH₃CH₂Cl
16N.3.sl.TZ0.10a: State the IUPAC name for leucine.
17M.1.sl.TZ1.27:
Which molecule has a tertiary nitrogen?

A. (CH₃)₂NH

B. (C₂H₅)₄N⁺I⁻

C. C₃H₇N(CH₃)₂

D. C₆H₅NH₂
17M.2.hl.TZ2.7a.iii:
Suggest the structural formula of this compound.
17M.2.hl.TZ1.7c:
State the reagents used to convert benzene to nitrobenzene and the formula of the electrophile formed.
19N.3.sl.TZ0.7a:
Draw the structure of the dipeptide Asp–Phe using section 33 of the data booklet.
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19N.3.hl.TZ0.12c: State one similarity and one difference in composition between phospholipids and...
19N.2.hl.TZ0.3d(iii):
Explain why the ¹H NMR spectrum of C₃H₆O, produced in (d)(i), shows only one signal.
17M.2.hl.TZ2.9b.i:
Hydrogenation of propene produces propane. Calculate the standard entropy change, ΔS^θ, for the hydrogenation of propene.
19N.2.hl.TZ0.3a(ii): State the IUPAC name of the major product.
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19N.3.hl.TZ0.24a:
Infrared (IR) spectroscopy is used to identify functional groups in organic compounds.

Deduce the wavenumber, in cm⁻¹, of an absorption peak found in the IR spectrum of testosterone but not in that of cholesterol.
17M.3.hl.TZ2.3c.iii:
Subsequent steps proceed under differing conditions, forming the dendrimer polymer with the following repeating unit.

State the name of one functional group in this repeating unit.
19N.2.hl.TZ0.3d(ii):
Explain why the compound C₃H₈O, produced in (a)(iv), has a higher boiling point than compound C₃H₆O, produced in d(i).
17M.2.sl.TZ1.6b:
State the typical reactions that benzene and cyclohexene undergo with bromine.
17M.1.sl.TZ1.25:
What are the functional groups in the aspirin molecule?

$\begin{gathered} \begin{array}{*{20}{l}} {{\text{I.}}}&{{\text{Ether}}} \\ {{\text{II.}}}&{{\text{Carboxyl}}} \\ {{\text{III.}}}&{{\text{Ester}}} \end{array} \hfill \\ \hfill \\ \end{gathered}$

A. I and II only

B. I and III only

C. II and III only

D. I, II and III
17M.2.sl.TZ1.6a:
Discuss the physical evidence for the structure of benzene.
21M.1.sl.TZ2.25: What is the IUPAC name of the molecule shown? A. 2,4-dimethylhexane B. ...
17M.2.hl.TZ2.7b.i:
Bromine was added to hexane, hex-1-ene and benzene. Identify the compound(s) which will react with bromine in a well-lit laboratory.
18N.1.sl.TZ0.25:
What is the order of increasing boiling point for the isomers of C₅H₁₂?

A. CH₃CH₂CH₂CH₂CH₃ < CH₃CH(CH₃)CH₂CH₃ < CH₃C(CH₃)₃

B. CH₃C(CH₃)₃ < CH₃CH(CH₃)CH₂CH₃ < CH₃CH₂CH₂CH₂CH₃

C. CH₃C(CH₃)₃ < CH₃CH₂CH₂CH₂CH₃ < CH₃CH(CH₃)CH₂CH₃

D. CH₃CH(CH₃)CH₂CH₃ < CH₃C(CH₃)₃ < CH₃CH₂CH₂CH₂CH₃
19M.2.sl.TZ2.1c(ii):
State the name of product B, applying IUPAC rules.
18M.2.hl.TZ1.3d:
One possible Lewis structure for benzene is shown.

State one piece of physical evidence that this structure is incorrect.
17M.2.sl.TZ1.5a:
Ethane, C₂H₆, reacts with chlorine in sunlight. State the type of this reaction and the name of the mechanism by which it occurs.
20N.1.hl.TZ0.40:
Which compound with the molecular formula $C_{4} H_{8} O$ has this high resolution ${}_{1}H NMR$ ?

From: libretexts.org. Courtesy of Chris Schaller, Professor (Chemistry)
at College of Saint Benedict/Saint John’s University.

A. but-3-en-2-ol, ${CH}_{2} = CHCH (OH) {CH}_{3}$

B. butanal, ${CH}_{3} {CH}_{2} {CH}_{2} CHO$

C. butanone, ${CH}_{3} {COCH}_{2} {CH}_{3}$

D. but-3-en-1-ol, ${CH}_{2} = {CHCH}_{2} {CH}_{2} OH$
17M.2.sl.TZ2.6b:
Bromine was added to hexane, hex-1-ene and benzene. Identify the compound(s) which will react with bromine in a well-lit laboratory.
17M.3.sl.TZ1.10b.i:
Describe the difference in their structures.
19N.1.sl.TZ0.25: Which compound is not in the same homologous series as the others? A. C5H12 B. C6H12 C. ...
21N.1.sl.TZ0.26: Which pair of compounds are structural isomers? A. Propane and propene B. Propanal and...
21N.1.sl.TZ0.27: What is the general formula of alkynes? A. CnH2n+2 B. CnH2n C. CnH2n−2 D. CnHn
18M.3.sl.TZ2.2a:
Describe two differences, other than the number of atoms, between the models of ethane and ethene constructed from the kit shown.
19N.3.sl.TZ0.15a: State the names of two functional groups present in all three molecules, using section 37 of...
19N.3.sl.TZ0.9b: State one impact on health of the increase in LDL cholesterol concentration in blood.
20N.2.hl.TZ0.2e:
Compound A and B are isomers. Draw two other structural isomers with the formula $C_{3} H_{6} O$ .
20N.1.sl.TZ0.24: Which functional groups are present in this molecule? A. carbonyl, ether, nitrile B. ...
18M.3.sl.TZ2.2b.i:
The above ball and stick model is a substituted pyridine molecule (made of carbon, hydrogen, nitrogen, bromine and chlorine atoms). All atoms are shown and represented according to their relative atomic size.

Label each ball in the diagram, excluding hydrogens, as a carbon, C, nitrogen, N, bromine, Br, or chlorine, Cl.
17M.2.hl.TZ2.2a.v:
Identify one organic functional group that can react with acidified K₂Cr₂O₇(aq).
17M.2.hl.TZ2.7a.ii:
Identify the functional group that shows stretching at 1710 cm^–1 in the infrared spectrum of this compound using section 26 of the data booklet and the ¹H NMR.
17M.2.hl.TZ1.6c.i:
One possible product, X, of the reaction of ethane with chlorine has the following composition by mass:

carbon: 24.27%, hydrogen: 4.08%, chlorine: 71.65%

Determine the empirical formula of the product.
20N.3.sl.TZ0.9b: State a class of organic compounds found in gasoline.
19N.3.hl.TZ0.24b:
Describe a technique for the detection of steroids in blood and urine.
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22M.2.sl.TZ1.3c(i):
State the name of Compound A, applying International Union of Pure and Applied Chemistry (IUPAC) rules.
17M.3.hl.TZ2.20a.iii:
Suggest two absorbances, other than the absorbances due to the ring structure and C–H bonds, that would be present in the infrared (IR) spectrum of aspirin.
17M.2.sl.TZ1.5c.i:
One possible product, X, of the reaction of ethane with chlorine has the following composition by mass:

carbon: 24.27%, hydrogen: 4.08%, chlorine: 71.65%

Determine the empirical formula of the product.
20N.2.sl.TZ0.1d(v):
Ethoxyethane (diethyl ether) can be used as a solvent for this conversion. Draw the structural formula of ethoxyethane
19N.3.hl.TZ0.24c:
Explain how redox chemistry is used to measure the ethanol concentration in a breathalyser.
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18M.3.sl.TZ2.2b.iii:
Pyridine, like benzene, is an aromatic compound.

Outline what is meant by an aromatic compound.
20N.3.hl.TZ0.11b: State a class of organic compounds found in gasoline.
20N.3.hl.TZ0.11e(iii):
Suggest a wavenumber absorbed by methane gas.
21M.2.hl.TZ1.5a(ii): State the molecular formula of the next member of the homologous series to which ethene belongs.
21M.2.hl.TZ1.5a(i): State the class of compound to which ethene belongs.
21M.1.sl.TZ2.24: Which is in the same homologous series as CH3OCH3? A. CH3COCH3 B. CH3COOCH3 C. ...
21M.1.sl.TZ2.28:
Which spectra would show the difference between propan-2-ol, CH₃CH(OH)CH₃, and propanal, CH₃CH₂CHO?

I. mass
II. infrared
III. ¹H NMR

A. I and II only

B. I and III only

C. II and III only

D. I, II and III
18M.2.sl.TZ2.7a:
The Kekulé structure of benzene suggests it should readily undergo addition reactions.

Discuss two pieces of evidence, one physical and one chemical, which suggest this is not the structure of benzene.
21M.2.sl.TZ1.5a(i): State the class of compound to which ethene belongs.
21M.2.sl.TZ1.5a(ii): State the molecular formula of the next member of the homologous series to which ethene belongs.
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21M.2.sl.TZ2.4c:
Write the equation and name the organic product when ethanol reacts with methanoic acid.
20N.2.sl.TZ0.2c:
Compound A and B are isomers. Draw two other structural isomers with the formula $C_{3} H_{6} O$ .
17M.2.sl.TZ2.6a:
Using relevant equations, show the initiation and the propagation steps for this reaction.
20N.2.hl.TZ0.1d(iv):
Ethoxyethane (diethyl ether) can be used as a solvent for this conversion.
Draw the structural formula of ethoxyethane
19M.2.hl.TZ1.1b:
Draw the structure of one other isomer of xylene which retains the benzene ring.
20N.2.hl.TZ0.4c: Discuss, referring to intermolecular forces present, the relative volatility of propanone and...
20N.2.sl.TZ0.2b:
The IR spectrum of one of the compounds is shown:

COBLENTZ SOCIETY. Collection © 2018 copyright by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved.

Deduce, giving a reason, the compound producing this spectrum.
20N.3.sl.TZ0.9f(iii):
Suggest a wavenumber absorbed by methane gas.
20N.3.sl.TZ0.14a(i): Name two functional groups that both zanamivir and oseltamivir contain.
22M.2.hl.TZ2.8d(iv):
Suggest two differences in the ¹H NMR of but-2-ene and the organic product from (d)(ii).
22M.2.hl.TZ2.8e(ii):
Deduce the splitting pattern in the ¹H NMR spectrum for 1-bromopropane.
19M.2.hl.TZ2.1c(ii):
Determine the enthalpy change for the reaction, in kJ, to produce A using section 11 of the data booklet.
22M.2.sl.TZ2.4b: State two features showing that propane and butane are members of the same homologous series.
22M.2.sl.TZ2.4d(i): Draw the full structural formula of but-2-ene.
22M.2.sl.TZ2.4d(iv):
Suggest two differences in the ¹H NMR of but-2-ene and the organic product from (d)(ii).
17M.2.hl.TZ1.6c.ii:
The mass and ¹H NMR spectra of product X are shown below. Deduce, giving your reasons, its structural formula and hence the name of the compound.
18M.2.sl.TZ1.3c:
One possible Lewis structure for benzene is shown.

State one piece of physical evidence that this structure is incorrect.
17M.2.sl.TZ1.5c.ii:
The mass and ¹H $\,$ NMR spectra of product X are shown below. Deduce, giving your reasons, its structural formula and hence the name of the compound.
21M.1.sl.TZ1.24: Which series is in order of increasing boiling point? A. CH2CH2CH3OH CH3COCH3 ...
22M.1.sl.TZ2.26:
Which is a homologous series?

A. C₂H₄, C₃H₅, C₄H₆

B. C₂H₂, C₃H₄, C₄H₆

C. C₂H₂, C₂H₄, C₂H₆

D. C₂H₂, C₄H₄, C₆H₆
21N.1.sl.TZ0.25: What is the name of this substance using IUPAC rules? A. 2-ethyl-1-methylbutan-1-ol B. ...

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Core » Topic 11: Measurement and data processing » 11.3 Spectroscopic identification of organic compounds

Core » Topic 10: Organic chemistry

Core » Topic 11: Measurement and data processing

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