Edexcel A-Level Chemistry AS 10 Organic Chemistry Halogenoalkanes Alcohols and Spectra Questions

Identify structures and reaction class first, then supply precise reagents, conditions, curly arrows or diagnostic spectral peaks required by the pathway or evidence.

Exam points

Draw nucleophilic substitution and elimination mechanisms with correct curly arrows.
Plan halogenoalkane or alcohol conversions using named reagents, conditions and products.
Interpret hydrolysis experiments, infrared absorptions and mass-spectral fragments.

Covered syllabus points

10.1—Classify reactions (including those in Unit 1) as addition, elimination, substitution, oxidation, reduction, hydrolysis or 10.2—The concept of a reaction mechanism 10.3—Heterolytic bond breaking results in species that are electrophiles or nucleophiles 10.4—The definition of the term ‘nucleophile’10.5—The link between bond polarity and the type of reaction mechanism a compound will undergo 10B: Halogenoalkanes Students will 10.6—The nomenclature of halogenoalkanes 10.7—The distinction between primary, secondary and tertiary halogenoalkanes 10.8—The reactions of halogenoalkanes with: i aqueous alkali 10.9—The mechanisms of the nucleophilic substitution reactions between primary halogenoalkanes and: i aqueous potassium hydroxide 10.10—Experimental observations and data can be used to compare the relative rates of hydrolysis of: i primary, secondary 10.11—CORE PRACTICAL 5 Investigation of the rates of hydrolysis of some halogenoalkanes 10.12—The trend in reactivity of primary, secondary and tertiary halogenoalkanes 10.13—Understand, in terms of bond enthalpy, the trend in reactivity of chloro-, bromo- and iodoalkanes 10.14—CORE PRACTICAL 6 Chlorination of 2-methylpropan-2-ol with concentrated hydrochloric acid 10.15—The nomenclature of alcohols 10.16—The distinction between primary, secondary and tertiary alcohols 10.17—The reactions of alcohols with: i oxygen in air (combustion) ii halogenating agents • PCl5 to produce chloroalkanes 10.18—Potassium dichromate(VI) in dilute sulfuric acid can oxidise: i primary alcohols to produce aldehydes (which give a positive 10.19—Understand, the following techniques in the preparation and purification of a liquid organic compound: i heating under 10.20—CORE PRACTICAL 7 The oxidation of propan-1-ol to produce propanal and propanoic acid 10.21—Interpret data from mass spectra to suggest possible structures of simple organic compounds using the m/z of the molecular 10.22—Infrared spectra, or data from infrared spectra, to deduce functional groups present in organic compounds, and predict 10.23—CORE PRACTICAL 8 Analysis of some inorganic and organic unknowns

[Maximum number: 2]

Propan-1-ol may be converted into propene.

\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH} \rightarrow \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}+\mathrm{H}_{2} \mathrm{O}

(a)

Which reagent is used for this reaction?

50% sulfuric acid

ethanolic potassium hydroxide

phosphoric(V) acid

red phosphorus

[ 1 ]

(b)

The reaction is best classified as

elimination

hydrolysis

reduction

substitution

[ 1 ]

[Maximum number: 1]

Figure for Question 2 — Edexcel A-Level Chemistry AS

[Maximum number: 10]

Some reactions of a halogenoalkane are summarised in the diagram. All the reactions are of the same type and mechanism.

Figure for Question 3 — Edexcel A-Level Chemistry AS

(a)

Name the type and mechanism of these reactions.

[ 1 ]

(b)

Give the IUPAC name and the structure of compound M.

[ 2 ]

(c)

State the reagent and conditions required for Reaction 1.

[ 2 ]

(d)

An incomplete mechanism for Reaction 2 is shown.

Figure for Question (d) — Edexcel A-Level Chemistry AS

intermediate J

[ 4 ]

(i)

Complete the mechanism by adding curly arrows, and relevant dipoles and lone pairs.
(2)

[ 2 ]

An answer that shows the following

- dipole on C-Br

- curly arrow from C-Br bond to Br atom or just beyond

- lone pair on oxygen of $\mathrm{OH}^{-}$

- curly arrow from oxygen to positively charged carbon atom

All four points correct scores (2)

Any two or three points correct scores (1)

Do not award second curly arrow from negative charge

Penalise use of half-arrows once only

Ignore an extra $\mathrm{OH}^{-}$ attacking the 2-bromo-2-methylpropane molecule.

Ignore lone pair on this extra species

Ignore extra curly arrows and lone pairs

Example of mechanism

Figure for Answer to Question (i) — Edexcel A-Level Chemistry AS

(ii)

Describe how intermediate J is formed in the first step, naming the process that occurs.
(2)

[ 2 ]

(e)

The reaction of halogenoalkanes with hydroxide ions is often carried out using sodium hydroxide or potassium hydroxide.

An alternative is ‘moist silver(I) oxide’, which is prepared by adding a few drops of water to solid silver(I) oxide.

Silver(I) oxide is insoluble in water but produces sufficient hydroxide ions for the reaction.

[ 1 ]

(i)

Suggest one advantage of using silver(I) oxide rather than sodium hydroxide or potassium hydroxide.

[ 1 ]

An answer that makes reference to one of the following

- because silver(I) oxide is insoluble, it can easily be separated from the reaction mixture when reaction is complete

- because silver(I) oxide is insoluble, it can be reused

- $\ce{NaOH}$ / $\ce{KOH}$ are caustic/corrosive, or $\ce{Ag2O}$ is less corrosive than $\ce{NaOH}$ .

[Maximum number: 1]

Propan-1-ol may be converted into propene.

\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH} \rightarrow \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}+\mathrm{H}_{2} \mathrm{O}

The reaction is best classified as

elimination

hydrolysis

reduction

substitution

[Maximum number: 2]

Some reactions of a halogenoalkane are summarised in the diagram. All the reactions are of the same type and mechanism.

Figure for Question 5 — Edexcel A-Level Chemistry AS

An incomplete mechanism for Reaction 2 is shown.

intermediate J

Describe how intermediate J is formed in the first step, naming the process that occurs.
(2)

[Maximum number: 1]

Which of these species is not a nucleophile?

$\mathrm{NH}_{4}^{+}$

$\mathrm{CN}^{-}$

$\mathrm{H}_{2} \mathrm{O}$

$\mathrm{CH}_{3} \mathrm{NH}_{2}$

[Maximum number: 1]

An alcohol can be attacked by a nucleophile because

the C-O bond is weak

the C-O bond is polar

the O-H bond can form hydrogen bonds

the O-H bond is polar

[Maximum number: 2]

This question is about bromoalkanes with the molecular formula $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ .

(a)

Give the IUPAC name of the only $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ tertiary bromoalkane.

[ 1 ]

(b)

Draw the displayed formula of the only $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ secondary bromoalkane.

[ 1 ]

An answer that makes reference to the following point:

- displayed formula of 2-bromobutane

Example of displayed formula:

Figure for Answer to Question (b) — Edexcel A-Level Chemistry AS

Ignore any other type of formula Ignore bond lengths and bond angles Ignore any name even if incorrect

Do not award non-displayed $\mathrm{CH}_{3}$ groups Do not award any missing hydrogens / bonds

[Maximum number: 1]

This question is about bromoalkanes with the molecular formula $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ .

Draw the skeletal formula of the only branched-chain $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ primary bromoalkane.

[Maximum number: 2]

This question is about sodium hydroxide.

Aqueous sodium hydroxide reacts with 1-bromopropane to produce propan-1-ol.

Under different conditions, sodium hydroxide reacts with 1-bromopropane to form propene.

Name the type of reaction and a suitable solvent.

Type of reaction

Suitable solvent

[Maximum number: 4]

This question is about sodium hydroxide.

(a)

Aqueous sodium hydroxide reacts with 1-bromopropane to produce propan-1-ol.

[ 4 ]

(i)

State the type and mechanism of this reaction.

[ 1 ]

An answer that makes reference to the following points:

nucleophilic and substitution

Allow nucleophile

Ignore $\mathrm{S}_{\mathrm{N}} 2$

Do not award $\mathrm{S}_{\mathrm{N}} 1$ , halogenation, nuclear

(1)

(ii)

Complete the mechanism for this reaction.

Include curly arrows, and relevant lone pairs and dipoles.

Figure for Question (ii) — Edexcel A-Level Chemistry AS

[ 3 ]

An answer that makes reference to the following points:

- dipole on C-Br bond

- lone pair on O of $\mathrm{OH}^{-}$

- curly arrow from lone pair to C of C - B r. If no lone pair shown, allow curly arrow from O

- arrow from C-Br to Br or just beyond

- organic product

- $\mathrm{Br}^{-}$

Figure for Answer to Question (ii) — Edexcel A-Level Chemistry AS

Example of mechanism

Allow product as structural formula rather than displayed

Allow NaBr

Ignore $\mathrm{Na}^{+}$

Do not award HBr 6 points correct scores (3)

4 / 5 points correct scores ( 2 )

2 / 3 points correct scores (1) Ignore intermediate/ transition state if shown

[Maximum number: 1]

This question is about halogenoalkanes.

The rates of hydrolysis of 1-chloropropane, 1-bromopropane and 1-iodopropane in reactions with aqueous silver nitrate solution were compared.

State what would be measured in the experiment to compare the rates of hydrolysis.

[Maximum number: 1]

This question is about bromoalkanes with the molecular formula $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ .

Give the structure of the $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ bromoalkane that would react fastest with aqueous silver nitrate in ethanol.

The fastest reacting bromoalkane is the tertiary bromoalkane with structure $\ce{(CH3)3CBr}$ , i.e. 2-bromo-2-methylpropane.

[Maximum number: 2]

This question is about halogenoalkanes.

The rates of hydrolysis of 1-chloropropane, 1-bromopropane and 1-iodopropane in reactions with aqueous silver nitrate solution were compared.

State which of these halogenoalkanes would hydrolyse the fastest. Justify your answer.

[Maximum number: 1]

This question is about alcohols with the molecular formula $\mathrm{C}_{6} \mathrm{H}_{14} \mathrm{O}$ .

Two primary $\mathrm{C}_{6} \mathrm{H}_{14} \mathrm{O}$ alcohols, A and B, are shown.

alcohol A

Figure for Question 15 — Edexcel A-Level Chemistry AS

Give the IUPAC name of alcohol A.

[Maximum number: 3]

This question is about alcohols with the molecular formula $\mathrm{C}_{6} \mathrm{H}_{14} \mathrm{O}$ .

Draw the skeletal formula of each of the three tertiary alcohols with the formula $\mathrm{C}_{6} \mathrm{H}_{14} \mathrm{O}$ .
tertiary alcohol 1
tertiary alcohol 2
tertiary alcohol 3

[Maximum number: 2]

This is a question about alcohols.

(a)

Alcohols can be converted into halogenoalkanes.

[ 2 ]

(i)

Write the equation for the reaction between methanol, $\mathrm{CH}_{3} \mathrm{OH}$ , and phosphorus(V) chloride, $\mathrm{PCl}_{5}$ .

[ 1 ]

correct equation

Example of equation
$\mathrm{CH}_{3} \mathrm{OH}+\mathrm{PCl}_{5} \rightarrow \mathrm{CH}_{3} \mathrm{Cl}+\mathrm{POCl}_{3}+\mathrm{HCl}$

Allow multiples

Allow $\mathrm{PCl}_{3} \mathrm{O}$

Ignore state symbols even if incorrect

(1)

(ii)

State the observation that would be made from this reaction.

[ 1 ]

An answer that makes reference to the following point:

- steamy fumes / misty fumes / white fumes

Ignore effervescence / bubbles / gets hot / $\mathrm{PCl}_{5}$ dissolves

Do not award white smoke / additional incorrect observations

(1)

[Maximum number: 8]

Propan-1-ol, propan-2-ol and 2-methylpropan-2-ol are all alcohols commonly used in school laboratories.

Acidified potassium dichromate(VI) is used to oxidise alcohols.

(a)

State the colour change seen when an alcohol is oxidised with acidified potassium dichromate(VI).

[ 2 ]

(b)

An electric heater may be used to heat a sample of an alcohol with acidified potassium dichromate(VI).

[ 6 ]

(i)

State why there is no reaction when 2-methylpropan-2-ol is heated with acidified potassium dichromate(VI).

[ 1 ]

(ii)

Identify, by name or formula, all the possible oxidation products of propan-1-ol and propan-2-ol.

[ 1 ]

(iii)

Give a further chemical test and the positive result for each of the oxidation
products of propan-1-ol.

[ 4 ]

A description that makes reference to the following points:

- test for propanal/aldehyde: Benedict's or Fehling's solution, or ammoniacal silver nitrate / Tollens' reagent (1)
- result for propanal: red precipitate, or silver mirror with Tollens' reagent (1)
- test for propanoic acid: addition of carbonate / hydrogencarbonate solution, reactive metal, or a named alcohol and acid catalyst (1)
- result for propanoic acid: effervescence/fizz of carbon dioxide which turns limewater cloudy;
or hydrogen that pops with a lighted splint;
or a sweet/fruity-smelling ester (1)

Additional guidance:
- Do not award acidified potassium dichromate(VI) for propanal
- Ignore addition of $\ce{PCl5}$ gives misty fumes
- Ignore reference to indicators
- If candidates omit names of compounds, assume the tests are for the correct compounds

Figure for Answer to Question (iii) — Edexcel A-Level Chemistry AS

[Maximum number: 8]

Cyclohexene may be prepared from cyclohexanol using 85% phosphoric(V) acid.

Figure for Question 19 — Edexcel A-Level Chemistry AS

A simplified procedure for this preparation is shown.
Step 1 Accurately weigh about 4 g of cyclohexanol into a pear-shaped flask.
Step 2 Add about $0.5 \mathrm{~cm}^{3}$ of 85% phosphoric(V) acid and a few anti-bumping granules to the flask.

Step 3 Set up the apparatus for fractional distillation.
Step 4 Heat the flask and collect the distillate that contains impure cyclohexene and water.

Step 5 Separate the impure cyclohexene and water, using a separating funnel.
Step 6 Add a few granules of anhydrous calcium chloride to the impure cyclohexene and allow the mixture to stand.

Step 7 Decant the impure cyclohexene into a clean pear-shaped flask. Distil the cyclohexene and weigh the distillate.

Data

Table for Question 19 — Edexcel A-Level Chemistry AS

(a)

State how anti-bumping granules make liquids boil more smoothly.

[ 1 ]

(b)

The diagram shows the apparatus used for fractional distillation in Step 4.

Figure for Question (b) — Edexcel A-Level Chemistry AS

Suggest two reasons why fractional distillation is used rather than simple distillation.

[ 2 ]

(c)

Draw a diagram of the separating funnel and its contents in Step 5, labelling each layer.

[ 2 ]

(d)

Explain the change in appearance of the liquid when it is allowed to stand with anhydrous calcium chloride in Step 6.

[ 2 ]

(e)

State a suitable temperature range for collecting the distillate in Step 7.

[ 1 ]

An answer that makes reference to the following point:

- lower temperature within a suitable range and upper temperature within a suitable range

$79-82\left({ }^{\circ} \mathrm{C}\right)$ $84-88\left({ }^{\circ} \mathrm{C}\right)$

Do not award a range which starts or ends with $83\left({ }^{\circ} \mathrm{C}\right)$

[Maximum number: 4]

Propan-1-ol, propan-2-ol and 2-methylpropan-2-ol are all alcohols commonly used in school laboratories.

Acidified potassium dichromate(VI) is used to oxidise alcohols.

Draw a labelled diagram of the apparatus that is required to prepare and collect a sample of propanal by heating propan-1-ol with acidified potassium dichromate(VI).

[Maximum number: 2]

Terpenes and terpenoids are groups of chemicals found in plants.
They contribute to the smell and taste of the plant, and so are used in flavourings and perfumes.

Both terpenes and terpenoids have carbon skeletons based on one or more units of the compound isoprene.

Figure for Question 21 — Edexcel A-Level Chemistry AS

isoprene
Terpenes are made up of two or more isoprene units joined together, while terpenoids have additional functional groups, often containing oxygen.

Limonene and myrcene are both terpenes composed of two isoprene units.
Menthol, linalool and citronellol are terpenoids containing an - OH group.

The peaks with the highest intensity in the mass spectrum of isoprene are at m / z=68 and m / z=53.
Identify the species responsible for these two peaks.
m / z=68

m / z=53

An answer that makes reference to the following points:

- m / z=68 is $\left(\mathrm{CH}_{2}=\mathrm{C}\left(\mathrm{CH}_{3}\right)-\mathrm{CH}=\mathrm{CH}_{2}\right)^{+}$

(1)

- m / z=53 is $\left(\mathrm{CH}_{2}=\mathrm{C}-\mathrm{CH}=\mathrm{CH}_{2}\right)^{+}$

(1)

Penalise molecular formulae once only Penalise lack of positive charges or presence of negative charges once only

Allow displayed or skeletal formulae, with or without brackets around the outside Ignore absence of double bonds

Award $\left(\mathrm{CH}_{3}-\mathrm{C}\left(=\mathrm{CH}_{2}\right)-\mathrm{CH}=\mathrm{CH}_{2}\right)^{+}$

Award $\left(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{C}\left(\mathrm{CH}_{3}\right)=\mathrm{CH}_{2}\right)^{+}$

Award $\left(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{C}\left(=\mathrm{CH}_{2}\right)-\mathrm{CH}_{3}\right)^{+}$

Award $\left(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{C}=\mathrm{CH}_{2}\right)^{+}$

[Maximum number: 3]

This question is about alcohols and related compounds.

Propan-2-ol is a secondary alcohol. One of its uses is as a solvent to clean the surfaces of vinyl records.

Propan-2-ol can be oxidised to form the ketone, propanone, in a laboratory. However, most propanone produced in industry is made using the Cumene process, where hydrocarbons from oil are used to synthesise cumene.

cumene

Cumene is then oxidised directly to form phenol and propanone.

Figure for Question 22 — Edexcel A-Level Chemistry AS

Propan-1-ol is also a solvent, and can be used as a fuel. The fuel biopropanol, which is mainly propan-1-ol, is formed from glycerol, a waste product of biodiesel production from plant oils.

The reaction used is called hydrogenolysis, and requires catalysts containing nickel, tungsten and zirconium.

The oxidising agent used to oxidise propan-2-ol in a laboratory is an acidified solution containing $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}$ ions.

Describe how the IR spectrum of the reaction mixture would change during this reaction.
Your answer should consider only the organic reactant and product. Use information from the Data Booklet to support your answer.

A description that makes reference to the following points:

- peak at $3750-3200\left(\mathrm{~cm}^{-1} \mathrm{O}-\mathrm{H}\right)$ would diminish

(1)

- peak at $1720-1700\left(\mathrm{~cm}^{-1} \mathrm{C}=\mathrm{O}\right)$ would appear

(1)

- fingerprint region would change (shape) or peak due to C-O would diminish

(1)

For M1 and M2 allow any range or specific wavenumber within the given range

All question bank results loaded

Covered syllabus points

Question 1

Question (a)

Question (b)

Question 2

Question 3

Question (a)

Question (b)

Question (c)

Question (d)

Question (i)

Question (ii)

Question (e)

Question (i)

Question 4

Question 5

Question 6

Question 7

Question 8

Question (a)

Question (b)

Question 9

Question 10

Question 11

Question (a)

Question (i)

Question (ii)

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question (a)

Question (i)

Question (ii)

Question 18

Question (a)

Question (b)

Question (i)

Question (ii)

Question (iii)

Question 19

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)

Question 20

Question 21

Question 22