A-LEVEL CHEMISTRY

AS ORGANIC CHEMISTRY GRAND TEST Duration 2 hours 15 minutes Prepared by: Kashif Khan

INSTRUCTIONS

1- Read the questions very carefully before answering.2- Answer the questions within the space given. Anything written outside the specified lines will not be given

credit.3- Marks for Conditions for the reaction will only be awarded if the reagent is correct. 4- Carefully read the instructions in every question and follow them.

MARKS DISTRIBUTION

Q.1Q.2Q.3Q.4Q.5Q.6Q.7Q.8Q.9

1 Crude oil is a naturally occurring flammable liquid which consists of a complex mixture of hydrocarbons. In order to separate the hydrocarbons the crude oil is subjected to fractional distillation.

(a) Explain what is meant by the following terms.

[1]

(i) hydrocarbon

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(ii) fractional distillation

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(b) Undecane, C11H24, is a long chain hydrocarbon which is present in crude oil. Such long chain hydrocarbons are ‘cracked’ to produce alkanes and alkenes which have smaller molecules.

(i) Give the conditions for two different processes by which long chain molecules may be cracked.

process 1..........................................................................................................................................................................

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process 2 .........................................................................................................................................................................

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Used car engine oil can be recycled for use as a fuel by the processes of distillation and cracking.

(ii) Assuming a typical molecule of engine oil has the formula C40H82, suggest an equation for a cracking reaction that could produce diesel fuel with the formula C16H34 and other hydrocarbons only.

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c) Briefly explain why cracking is done.

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[Total 10]2 The African weaver ant aggressively defends its territory by giving off alarm pheromones when threatened. Four organic compounds have been identified in the mandibular glands of these ants, and are related to this behaviour.

The structures of these molecules are as follows.

CH3CH2CH2CH2CH2CH2OH CH3(CH2)7COCH2CH3

[2]

A B CH3(CH2)4 (CH2)3CH3

H C=C H CH3CH2CH2CH2CH2C H C O O

C D

Outline a series of chemical tests, with the observations, to distinguish each compound from the others.Positive identification is required for each compound, and this may require the use of more than one test.

A………………………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………………………..

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B………………………………………………………………………………………………………………………………………

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C………………………………………………………………………………………………………………………………………

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D………………………………………………………………………………………………………………………………………

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[Total 8]

3 Fuels are very important in our life. A large majority of our energy demand is addressed by crude oil. Besides crude oil, natural gas and coal are the two other mass-scale provider of energy around the globe.

Petrol and diesel are both complex mixtures of hydrocarbons used as fuels in transport.

(a)(i) Petrol contains mixture of alkanes such as C7H16 and C8H18. Suggest the formula of a radical likely to be produced when petrol burns in an internal combustion engine.

………………………………………………………………………………………………………………………………………...

(ii) Give an equation for the combustion of petrol in an internal combustion engine.

[3]

………………………………………………………………………………………………………………………………………

(iii)The combustion of petrol produces different products. In the table below give the formula of the carbon-containing products and other products emerging from the combustion of petrol.

Carbon-containing products Other products

[5]The engines of modern motor cars have exhaust systems which are fitted with catalytic converters in order to reduce atmospheric pollution caused by the products mentioned in the table.

b)(i) What is the active material present in the catalytic converter?

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(ii) Select one pollutant from each column which are greenhouse gases.

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(iii) Which pollutants from the above table are not treated by catalytic converter and released in the atmosphere.

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iv) By choosing one pollutant from each column give the balanced chemical equation to show how it is converted into harmless products.

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[5]

c) Suggest two reasons why the exhaust fumes from a car fitted with a catalytic converter are still hazardous to human health to some degree.

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There is a growing concern about the enhanced greenhouse effect in the society these days.

(d)(i) What do you understand by the term enhanced greenhouse effect?

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[4]

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(ii) Name one greenhouse, other than those mentioned in the table, which is a major contributor to greenhouse effect.

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The three sources of energy i.e crude oil, natural gas and coal are non-renewable. Scientists are constantly working ways to find the alternate sources of energy. Renewable energy sources such as bio-fuels, bio-diesel has emerged as a possible substitute for non-renewable energy resources. Ethanol is a renewable fuel and is thought to be environmentally friendly.

(e) Explain why ethanol is renewable?

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(f) Suggest why ethanol will be environmental friendly.

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[Total 16]

4 Alkane is the simplest homologous series of hydrocarbons represented by the general formula of CnH2n+2. They are mainly used as fuels.

Heptane (C7H16) is an alkane. Each of the following skeletal formula represents heptane.

(a)(i) What is the empirical formula of heptane?

….……………………………………………………………………………………………………………………………………

E F GWrite the above compounds in order of boiling point, highest boiling point ………

[5]

………

lowest boiling point .……..

(ii) Suggest an explanation for your stated order.

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(iii) Identify another isomer of C7H16 that is likely to have a boiling point lower than the boiling points of E, F or G.

[4]It is an established fact now that organic reactions in which organic molecules have polarity proceed faster than those organic reactions in which organic molecules have no polarity or low polarity.

(b)What do you mean by the term polarity?

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(ii) Alkanes are generally considered to be unreactive compounds, showing an inertness to common reagents such as NaOH, H2SO4, and K2Cr2O7. Suggest a reason why these reagents do not attack an alkane such as C7H16.

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(iii) Apart from polarity what other feature must an organic molecule possess in order to react faster than non-polar organic molecules? ..................................................................................................................................................................................... [3]

Ethane reacts with chlorine as shown below.

C2H6 + Cl2 C2H5Cl + HCl

c)(i) What is the name of this type of reaction?

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(ii) Use equations to describe the mechanism of this reaction, naming the steps involved.

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[6]

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(iii) This reaction can produce organic by-products, in addition to C2H5Cl. Draw the structural formulae of three possible organic by-products. Two of your by-products should contain 4 carbon atoms per molecule. Briefly describe how each by-product could be formed.

structural formula of by-product formed by

[10]

(d) In the boxes below draw the skeletal formulae of four different structural isomers of C5H11Cl that could be obtained from the chlorination of 2-methylbutane. Indicate any chiral centres in your structures by an asterisk (*).

+ Cl2 C5H11Cl+ HCl

[5] [Total 22]

5 (a) Complete the reaction schemes A and B.

Scheme A

Esters of 2,3-dibromopropan-1-ol with phosphoric acid are useful flame retardants used in plastics and fibres.2,3-dibromopropan-1-ol can be made from propenal by the following two-stage process.

[7]

I IICH2 CH2OH

A Br

Draw the structure of the intermediate A in the box opposite.

(ii) Suggest reagents and conditions for

• reaction I,

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• reaction II.

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Scheme B KMnO4 and K2Cr2O7 are the reagents that can be used to carry out the following transformation.

CHO

I II OH

(i) Draw the structure of intermediate E in the box above.

(ii) Suggest reagents and conditions for the following.

reaction I ..........................................................................................................................................................................

reaction II .........................................................................................................................................................................

[6]

b) Compounds D and E are both ketones.

CH3CH2COCH2CH3 CH3CH2CH2COCH3

[8]

E

D E

The reduction of D with NaBH4 produces just one alcohol, but a similar reduction of E produces two isomers in equal amounts. Explain these observations, drawing structures where appropriate.

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[Total 8]

6 In today’s world, many traditional materials have been replaced by different sorts of polymers. This includes rigid polymers such as those used in car bodies to replace steel and flexible polymers like those used in textiles to replace cotton or wool.

(a)(i)To form a polymer, what is the minimum number of functional groups that the monomer must possess?

...........................................................

(ii) Illustrate your answer to (i) with the structure of a possible monomer.

A polymer has the following repeat unit.

O

n

(iii) Mention the names of functional groups present in this polymer.

………………………….. and ……………………….

[9]

(iv) Give the structural formulae of the monomers used to make this polymer.

Monomer 1 Monomer 2 Monomer 3 (iv) One of the monomers mentioned above shows stereoisomerism. Identify this polymer ……………………………

(v) From the above three monomers there are two monomers which give ethanoic acid when treated with different reagents. Mention these two monomers and also state the reagent and conditions required to convert these into ethanoic acid.

Monomer…………. Reagent and conditions………………………………………………….

Monomer…………. Reagent and conditions…………………………………………………. [9]

(b) Polyvinyl acetate, PVA, is a useful adhesive for gluing together articles made from wood, paper or cardboard. The monomer of PVA is ethenyl ethanoate, B.

CH3

PVA is formed from B by the process of addition polymerization.

(i) Draw a section of the PVA molecule containing at least 2 monomer molecules, and identify clearly the repeat unit.

B can be hydrolysed in the usual way, according to the following equation.

O

B + H2O H3C OH +

[10]

C (C2H4O)

(ii) Use this information to suggest a possible structure for C and draw it in the box above.

A student extracted C from the product mixture, it is found that it does not decolourise Br2(aq), but it does form an orange precipitate with 2,4-dinitrophenylhydrazine. The student did not carry out the Tollens’ reagent test.

(iii) Suggest a structure for C that fits this new information.

(iv) Explain why the student did not carry out the Tollens’ reagent test.

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[Total 14]

7 Alkenes are very important in making new organic compounds because of their reactivity towards certain reagents. Pentene exists in different isomeric forms. One of form is given below.

H-C=C-CH2CH3 H-CH=CH-CH3CH2CH3 H CH3

The above isomer does not show cis-trans isomerism.

Compounds J and K are isomers with the molecular formula C4H8O2, and they contain the same functional group.They may both be obtained from the following routes.

Hot alkaline MnO4-

Step I

A LiAlH4

Step III Step II CH3OH HCOOH Conc: H2SO4

Step iv

[11]

T

V W

X

Conc: H2SO4

(a) Apart from the two isomers given, T is another isomer of pentene which does not show cis-trans isomerism. Give the structural formula of T in the above box. (b) Follow the reaction scheme and appropriately give the structural formula of W, V, X, J, K.

(c) Name the functional group present in both J and K……………………………………………………………………….

(d) State the type of reaction occurring in each step:

II………………………………......... III…………………………………………..

(e) The reaction of ethanal with HCN in the presence of HCN is a nucleophilic addition reaction. The reaction produces yields cyanohydrins.

In 1853 Stanislao Cannizzaro performed a chemical reaction in which a strong base such as KOH or NaOH was reacted with benzaldehyde. The following reaction took place.

O C-H CH2OH COOH KOH + benzaldehyde

This was termed as Cannizaro’s reaction.

(i) What is unusual about this reaction?

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(ii) By using the information about this reaction deduce the identity of A from the above reaction scheme.

[Total 11]

[12]

J K

8 Use the information in the table below to deduce the structures of the compounds in the following scheme, and draw these structures in the boxes provided.

hot concentrated acidified KMnO4

C7H12O C3H6O + C4H6O3

D E F

Results of tests (✓ indicates a positive result; ✗ indicates a negative result)

Results of tests with each compound

Test reagent D E F

Br2(aq) ✓ ✗ ✗

2,4-dinitrophenyl hydrazine reagent ✓ ✓ ✓

Fehling’s solution ✓ ✗ ✗

Na2CO3(aq) ✗ ✗ ✓

(a) State the formulae of the functional groups which the above four reagents test for.

(i) Br2…………………………………………………………………………………………………………………….

(ii) 2,4-dinitrophenyl hydrazine reagent……………….…..…………………………………………………………

(iii) Fehling’s solution………………………….. …………..…………………………………………………………

(iv) Na2CO3 ……………………………………………………………………………………………………………[4]

(b) Structures

[13]

D (C7H12O)

E (C3H6O) F (C3H6O3)

[3]

c) Treatment of compound F with NaBH4 gives compound G, C4H8O3. Heating G with Al2O3 gives a mixture of two isomeric unsaturated carboxylic acids H, J(C4H6O2 ) both H and J are stereoisomers of each other.

Suggest structures for G, H, J, and K, and name the type of stereoisomerism shown.

Al2O3 +

type of stereoisomerism……………………………………………………………………………………………………[5]

(d) D does not show cis-trans isomerism. Suggest an structural isomer of D which exhibits cis-trans isomerism.

(e) Compound A (C7H14O) is another compound which also gives E and F when treated with hot concentrated acidified KMnO4. A does not react with Fehling’s solution but reacts with PCl5. Suggest the structural formula of A.

[Total 14]

[14]

G JH

9 Menthone, C10H18O, is a cyclic ketone that occurs in oil of peppermint O

menthone

(a) Use asterisks (*) on the formula above to identify any chiral centres in the molecule of menthone. [2](b) Menthone can be reduced to menthol, which can be dehydrated to a mixture of two alkenes, L and M.

O HO

step I

menthone menthol step II

+

(i) Suggest reagents for

step 1, ......................................................................................................................

step 2. .......................................................................................................................

(ii) Suggest structures for L and M and draw them in the boxes above. [4]

[15]

L M

When heated with concentrated, acidified KMnO4(aq), one of the two alkenes L or M produces the dicarboxylic acid N.

CO2H CO2H

(i) Give the letter of the alkene that produced N by this reaction.

..................................................................................................................................................................(ii) Suggest the structure of the product, P, of the reaction between the other alkene you have drawn and hot concentrated acidified KMnO4.

(iii) Suggest one chemical test that would enable you to distinguish between N and P.

reagent(s) …………………………….................................................................................................................

observation .....................................................................................................................................................

(d) Chlorocyclohexane can be prepared by bubbling HCl(g) through a solution of cyclohexene.

+ HCl Cl

Suggest the mechanism of this 2-stage reaction by means of a diagram. Include all whole or partial charges, and represent the movements of electron pairs by curly arrows.

[Total 12]

[16]

P