Chemistry Unit 4 Goodie bag

UNIT 4.8 ORGANIC REVISION QUESTIONS

1. Draw all the possible structural isomers of C5H11Br (there are 8 in total). Label the isomers A – H and name them.

a) Identify two molecules which are positional isomers.b) Identify two molecules which are chain isomers.c) Identify two molecules which are chiral and draw the two optical isomers

of each. Explain briefly how they could be distinguished.

2. Draw all the possible structural isomers of C5H10 which contain a double bond (there are five in total). Label the isomers A – E and name them.

a) Identify two molecules which are positional isomers.b) Identify two molecules which are chain isomers.c) Identify one molecule which shows stereoisomerism, state the type of

stereoisomerism shown and draw and name the two stereoisomers.d) Draw the structure of a molecule which is a functional isomer of all the

molecules A to E.

3.a) Draw the two possible structures of a molecule with molecular formula

C4H8O2 and containing a carboxylic acid group. Name both of the isomers.

b) Draw four possible structures of molecules with the same molecular formula but containing a different functional group. Name the functional group and the molecules containing it. What is the type of isomerism shown between these molecules and the molecules drawn in 3 (a)?

4. a) Draw the structure of pentan-2-one b) Draw a positional isomer of pentan-2-onec) Draw a chain isomer of pentan-2-oned) Draw a functional isomer of pentan-2-one (not an aldehyde)

5. State whether the following preparations will produce a racemate or a single enantiomer:

a) butan-2-ol from but-2-eneb) butan-2-ol from 2-bromobutanec) 2-hydroxybutanenitrile from propanal

6. Name and draw the structures of the organic products obtained by the following reactions. If there is no reaction, state “no reaction”.

a) propanal with acidified potassium dichromateb) propanal with NaBH4

c) propanone with acidified potassium dichromated) propanone with NaBH4

e) propanone with HCNf) butanal with Fehling’s solutiong) methylpropanal with Tollen’s reagenth) butanone with Fehling’s solutioni) butanone with HCN

7. Write equations and give the mechanism for the reaction of butanone with

a) NaBH4

b) HCN

8. Suggest starting materials for the production of the following hydroxynitriles:

a) 2-hydroxybutanenitrileb) 2-methyl, 2-hydroxybutanenitrilec) 3-methyl, 2-hydroxybutanenitrile

9. Write equations for the following reactions:

a) propanoic acid with sodium hydroxideb) butanoic acid with sodium carbonatec) sodium methanoate with hydrochloric acidd) sodium ethanoate with sulphuric acide) 2-methylpropanoic acid with sodium carbonate

10. Write equations for the following reactions and name any organic products:

a) propanoic acid with methanolb) ethanoic acid with propan-2-olc) methanoic acid with propan-1-old) butanoic acid with butan-1-ol

11. Write equations, using displayed formulae, for the following reactions:

a) ethyl methanoate with conc. H2SO4

b) methyl propanoate with NaOHc) methylethyl ethanoate with H2SO4

d) propyl methanoate with NaOH

12. Write equations for the reaction of the following oil with sodium hydroxide:

13. Write equations for the following reactions and name any organic products:

a) propanoyl chloride with ammoniab) butanoic anhydride with propan-2-olc) methanoyl chloride with aminoethaned) ethanoic anhydride with 2-aminopropanee) 2-methylpropanoyl chloride with water

14. Draw the structures for two possible starting materials for the following products:

a) ethyl ethanoateb) N-methyl propanamidec) methylethyl propanoated) N-ethyl methanamide

15. (a) Consider the following pair of isomers.

H C H O CO C H C H

O O

C H C H C H C H2 22 23 3

C D

(i) Name compound C.

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

(ii) Identify a reagent which could be used in a test-tube reaction to distinguish between C and D. In each case, state what you would observe.

Reagent ..............................................................................................

Observation with C .........................................................................................

Observation with D..........................................................................................

(4)

(b) Consider the following pair of isomers.

H C C H CC H C H

O O

C H C H C H C H C H2 22 2 23

3

3

E F

(i) Name compound E.

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

(ii) Identify a reagent which could be used in a test-tube reaction to distinguish between E and F. In each case, state what you would observe.

Reagent ..............................................................................................

Observation with E ........................................................................................

Observation with F..........................................................................................

(4)

(c) Draw the structure of the chain isomer of F which shows optical isomerism.

(1)(Total 9 marks)

16. Butenedioic acid has the formula HOOC-CH=CH-COOH

(a) Describe a simple test in each case to show that butenedioic acid is

an acid;

Test ……………………………………………………………….

Result …………………………………………………………..

(i) unsaturated.

Test ………………….………………………………………….

Result …………………………………………………………..

(4)

(b) Draw the structure of the cis-isomer of butenedioic acid and give two

reasons which together explain why butenedioic acid shows geometrical

isomerism

Structure

Reason 1 ………………………………………………………………….

Reason 2 ………………………………………………………………….

(3)

(c) Draw the structure of the organic product formed when butenedioic acid

is warmed with an excess of ethanol in the presence of a small amount of

concentrated sulphuric acid

(2)

(d) Outline a mechanism for the reaction of butenedioic acid with hydrogen

bromide.

TOTAL 13 marks

17. (a) Outline a mechanism for the reaction of CH3CH2CH2CHO with HCN and name the product.

Mechanism

Name of product ......................................................................................................

(5)

(b) Outline a mechanism for the reaction of CH3OH with CH3CH2COCl and name the organic product.

Mechanism

Name of organic product .........................................................................................

(5) (Total 10 marks)

18. (a) (i) Write an equation for the reduction of pentan-2-one by aqueous NaBH4

to form pentan-2-ol

Use [H] to represent the reductant.

…………………………………………………………………………….

(ii) Name and outline the mechanism for this reaction.

Name of mechanism ……………………………………………………

Mechanism

(i) State why the pentan-2-ol produced in this reaction is not optically active

…………………………………………………………………………….

(7)

(TOTAL 7 marks)

19. Esters can be hydrolysed by heating with dilute hydrochloric acid to form an alcohol and a carboxylic acid.

(a) (i) Name the ester CH3COOCH3

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

(ii) Write an equation for the hydrolysis of this ester.

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

(iii) Suggest the role of hydrochloric acid in this hydrolysis.

...................................................................................................................(3)

(c) State one use of esters other than as a flavouring in foods.

..............................................................................................................................(1)

(d) (i) State how you would find the relative molecular mass of an ester from its mass spectrum.

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

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

(ii) An ester formed by a reaction with butanol has a relative molecular mass of 116. Deduce the molecular formula of this ester.

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

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

...................................................................................................................(3)

(Total 12 marks)

20. The molecular formulae of some compounds that can be prepared trom ethanoic acid are given in the scheme below.

e th an o ic ac id

C H O2 24

P C l 5

C H O N2 5C H O 24 8 C H O N a2 23 C H O C l2 3

e th an o l/co n c H S O /h ea t2 4

P Q R S

(a) (i) Give the name and displayed formula of P.

Name..........................................................................................................

Displayed formula

(2)

(ii) Give the name of the type of reaction which occurs when P is formed from ethanoic acid.

...................................................................................................................(1)

(b) Ethanoic acid can be obtained from P.

(i) Give the name of the reagent(s) and state the conditions required.

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

...................................................................................................................(2)

(ii) Write a balanced equation for the reaction

...................................................................................................................(1)

(c) State the reagent and reaction conditions that could be used for converting ethanoic acid into Q.

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

...................................................................................................................(2)

(d) Give the name and Displayed formula of the amide S.

Name........................................................................................................

Displayed formula...................................................................................

(2)

(Total 10 marks)21. (a) Name and outline a mechanism for the reaction between propanone and

hydrogen cyanide.

Name ...................................................................................................................

Mechanism

(5)

(b) Carbonyl compounds can be reduced to alcohols.

Write an equation for the reduction of propanone to the corresponding alcohol and identify a suitable reducing agent. In the equation you may use the symbol [H] for the reducing agent.

Equation .........................................................................................................

Reducing agent .................................................................................................

(2)(Total 7 marks)

22. (a) P, Q and R have the molecular formula C6H12

All three are branched-chain molecules and none is cyclic.P can represent a pair of optical isomers.Q can represent a pair of geometrical isomers.R can represent another pair of geometrical isomers different from Q.

Draw one possible structure for one of the isomers of each of P, Q and R.

Structure of P

Structure of Q

Structure of R

(3)

(b) Butanone reacts with reagent S to form compound T which exists as a racemic mixture. Dehydration of T forms U, C5H7N, which can represent a pair of

geometrical isomers.

(i) State the meaning of the term racemic mixture and suggest why such a mixture is formed in this reaction.

Racemic mixture

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

Explanation................................................................................................

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

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

(ii) Identify reagent S, and draw a displayed formula for each of T and U.

Reagent S .....................................................................................................

Compound T

Compound U

(6)(Total 9 marks)

23. (a) “Terylene” is a condensation polymer that can be formed from benzene-1,4-dicarboxylic acid and ethane-1,2-diol. Draw displayed formulae to represent:

(i) benzene-1,4-dicarboxylic acid;

(1)

(ii) ethane-1,2-diol;

(1)

(iii) the polymer “Terylene”.

(2)

(b) Give the name of the type of condensation polymer of which “Terylene” is an example.

.............................................................................................................................(1)

(c) Outline the difference between the formation of an addition polymer and a condensation polymer.

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

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

..............................................................................................................................(2)

(d) Give the name of one addition polymer.

..............................................................................................................................(1)

(Total 8 marks)

24. (a) Draw the structure of each of the three ketones which have the molecular formula C5H10O.

(3)

(b) Draw the structure of each of the four aldehydes which also have the molecular formula C5H10O. Label with the letter Z the compound which

shows optical isomerism. (5)

(c) When carbonyl compounds react with HCN, racemic mixtures are often produced. Name the type of mechanism involved and explain what is meant by the term racemic mixture. Choose any carbonyl compound which does not form a racemic mixture when it reacts with HCN and draw the structure of the product formed by the reaction of this carbonyl compound with HCN.

(4)

(d) Explain why aldehydes react with Tollen’s (or Fehling’s) reagent but ketones do not.

(3)(Total 20 marks)

25. Simple organic compounds, including structural isomers, can be distinguished from each other by chemical tests, or by spectroscopic methods, or by a combination of both. This question concerns the four compounds whose structural formulae are shown below.

CH3(CH2)2CHO (CH3)2CHCHO CH3COC2H5 CH3COOC2H5

A B C D

(a) Draw displayed formulae for A, B, C and D, clearly indicating which is which. Give the names of A, B, C and D.

(8)

(b) Compound D can be made by a reaction called esterification. State the names of two compounds needed for the reaction and give a condition used in the reaction.

(3)

(c) Give the name and draw the graphical formula of an isomer of compound D that is not an ester.

(2)

(d) Describe one chemical test that would distinguish between B and C, and state what you would observe in each case.

(3)

(e) Compound C reacts with HCN. Give the name of the type of mechanism, and an outline of the mechanism for this reaction.

(5)(Total 21 marks)

ANSWERS TO UNIT 4.8 ORGANIC REVISION QUESTIONS

1.

1-bromopentane 2-bromopentaneA B

3-bromopentane 1-bromo,2-methylbutaneC D

2-bromo,2-methylbutane 2-bromo,3-methylbutaneE F

1-bromo,3-methylbutane bromodimethylpropaneG H

a) any two from A, B, C or any two from C, D, E, Fb) two from A, D or G, H or B and E or F

c) B, D and F are chiralB:

and D:

and

F:

and

The isomers could be distinguished because they rotate the plane of plane-polarised light in opposite directions.

2.

A: pent-2-ene B: pent-1-ene C: 3-methylbut-1-ene

D: 2-methylbut-2-ene E: 2-methylbut-1-ene

a) A and B or two from C, D, Eb) A and D or B and C or Ec) A shows geometrical isomerism

cis pent-2-ene trans pent-2-ene

d)

3.a)

methylpropanoic acid butanoic acid

b) they are esters

ethyl ethanoate methyl propanoate

propyl methanoate methylethyl methanoate

They are functional isomers of the carboxylic acids

4.a) pentan-2-one: b) positional isomer:

c) chain isomer: d) functional isomer

5. a) racemate b) single enantiomer c) racemate

6.a) propanoic acid b) propan-1-ol c) no reaction

d) propan-2-ol e) 2-hydroxymethylpropanenitrile

f) butanoic acid g) methylpropanoic acid h) no reaction

i) 2-hydroxy,2-methylbutanenitrile

7. a) CH3CH2COCH3 + 2[H] CH3CH2CH(OH)CH3

b) CH3CH2COCH3 + HCN CH3CH2CH(CH3)CN

8. a) propanal and HCN b) butanone and HCN c) methylpropanal and HCN

9. a) CH3CH2COOH + NaOH CH3CH2COO-Na+ + H2Ob) 2CH3CH2CH2COOH + Na2CO3 2CH3CH2CH2COO-Na+ + CO2 + H2Oc) HCOO-Na+ + HCl HCOOH + NaCl

d) 2CH3COO-Na+ + H2SO4 2CH3COOH + Na2SO4

e) 2CH3CH(CH3)COOH + Na2CO3 2CH3CH(CH3)COO-Na+ + CO2 + H2O

10. a) CH3CH2COOH + CH3OH == CH3CH2COOCH3 + H2O organic product = methyl propanoateb) CH3COOH + CH3CH(OH)CH3 == CH3COOCH(CH3)CH3 + H2O

organic product = methylethyl ethanoatec) HCOOH + CH3CH2CH2OH == HCOOCH2CH2CH3 + H2O

organic product = propyl methanoated) CH3CH2CH2COOH + CH3CH2CH2CH2OH == CH3CH2CH2COOCH2CH2CH2CH3 + H2O

organic product = butyl butanoate

11. a)

b)

c)

d)

12.

13. a) CH3CH2COCl + NH3 CH3CH2CONH2 + HClorganic product: propanamide

b) (CH3CH2CH2CO)2O + CH3CH(OH)CH3 CH3CH2CH2COOCH(CH3)CH3 + CH3CH2CH2COOH

organic products: methylethyl butanoate and butanoic acidc) HCOCl + CHCHNH HCONHCHCH + HCl

organic product: N-ethyl methanamided) (CH3CO)2O + CH3CH(NH2)CH3 CH3CONHCH(CH3)CH3 + CH3COOH

organic products: N-methylethylethanamide and ethanoic acide) CH3CH(CH3)COCl + H2O CH3CH(CH)COOH + HCl

organic products: methylpropanoic acid

14. a)

b)

c)

d)

15. (a) (i) propyl methanoate (1)not propanyl

A wrong reagent or no reagent scores zero

An incomplete reagent such as silver nitrate for Tollens, or potassium dichromate loses the reagent mark, but can get both observation marks

penalise observations which just say colour change occurs or only state starting colour

(ii) Reagent: NaHCO3 (1)Observation with C: no reaction (1)Observation with D: effervescence (1) 4

for C and D NOT Tollens

Test an identified (hydrogen) carbonate

acidified K2Cr2O7

acidified KMnO4

correct metal

UI or stated indicator

PCl5

Observation with C

no reaction goes green goes colourless

no reaction

no change no reaction

observation with D

bubbles or CO2

no change no change bubbles or H2

red or correct colourpH 3 – 6.9

(misty) fumes

(b) (i) Reagent: pentan-2-one (1)or 2-pentanone

but not pent-2-one or pentyl

(ii) Reagent: Tollen’s or Fehling’s (1)

Observation with E: no reaction (1)

Observation with F: silver mirror or red ppt (1) 4

for E and F

Test Tollens Fehlings or Benedicts

iodoform or I2/NaOH

acidified K2Cr2O7

Schiff’s

observation with E

no reaction no reaction yellow (ppt) no change no reaction

observation with F

silver or mirror or grey or ppt

red or pptnot red solution

no reaction goes green goes pink

(c) C H C H C C H O

C H

H

3

3

2 (1) 1

must be aldehyde. Allow C2H5 for CH3CH2 otherwise this is the only answer

16(a) (i)

Test

Result

p H /u n ive rsa l in d ica to r p H m ete r o r N aH C O M g (1 )

n am ed ca rbo n a teN a C O2

2

2

3

3

red /p in k /o ran g e /y e llo w v a lu e < 7 C O e ffe rv escen c eo r H o r

e ffe rv esce n ce (1 )

(ii)

Test

Result

2 4B r

d eco lo u rize d

K M n O

co lo u rless or b ro w n

(1 )

(1 )

(a c id )

(b ro m id e C E = 0 )

4

(b)[1 ]

H O O C

C C

CC O O H

H O

H H C

pe n alize

o r C O O H

cannot rotate double bond (1)

2 different groups on each C (1) 3

(c) C2H5 C2H5CH3CH2OOC – CH CH – COOCH2CH3 (2)

monoester scores 1

wrong alcohol 0

penalise C (sticks) once per paper 2

(d)

H O O C C H C H C O O H H O O C C H C H C O O H+

(1 )(1 )

(1 )

(1 )

. . H

B r

B r –H

penalize first mark : if wrong acid (unless if same error as in (b)) or if Br2 4[13]

17. (a) Mechanism

(1 )

(1 ) (1 )

(1 )O

(H )

M 1 M 3

M 2

M 4

(C H C H C H ) C C H C H C H C H C H C H C H C H3 3 32 2 22 22

N C :

O : O H

C N C N

H–

–

+

Allow C3H7 if structure shown elsewhere

penalise HCN splitting if wrong

Name of product: 2-hydroxypenta(ne/o)nitrile (1) 5or 1-cyanobutan-1-ol

(b) Mechanism

(1 )

(1 )

O

O O

O :O

O C H

M 1

M 2

(C H C H ) C C l C H C H C C l C H C H C3 3 3

3

2

3 3

2 2

(C H ) C H H H

..

..

+

–

( )C l–

stru c tu re M 33 a rro w s M 4

(1 )(1 )

Name of organic product: methylpropanoate (1) 5

[10]

18. (i)C H C C H C H C H

O

3 32 2 + 2 [H] CH3CH(OH)CH2CH2CH3 (1)

or C5H10O or C5H11OH

(ii) Name of mechanism: nucleophilic addition (1)QoL

Mechanism:

C C

(C H ) C H H

H(C H C H C H ) C H C H C H O :

O3 3

–

3 3

3 7

2 22 2– +

(1 )(1 )

(1 ) (1 ):H

[C O a lo n e lo ses th is m ark]o r C Hif s tru c tu re sho w n in (i)

(iii) racemic (racemate) mixture formed (1)

OR explained e.g. 2 enantiomers in equal amounts 7

[7]

16. (a) (i) methyl ethanoate (1)

(ii) CH3COOCH3 + H2O CH3COOH + CH3OH (1)

(iii) Catalyst (1) 3

(b) solvents/plasticizers (1)

(c) (i) Line with the highest m/z (1) 1

(ii)R C

O

O C H4 9

1 0 1

R = 116 – 101 = 15CH3COOC4H9 (1)

Molecular formula = C6H12O2 (1) 3[7]

19. (a) (i) methyl ethanoate (1)

(ii) CH3COOCH3 + H2O CH3COOH + CH3OH (1)

(iii) Catalyst (1) 3

(b) solvents/plasticizers (1)

(c) (i) Line with the highest m/z (1) 1

(ii)R C

O

O C H4 9

1 0 1

R = 116 – 101 = 15CH3COOC4H9 (1)

Molecular formula = C6H12O2 (1) 3[7]

20. (a) (i) ethyl ethanoate

H

C

H

H

H

C

O

O

H

C

H

H

C

H

(1) 2

(ii) esterification / condensation / addition - elimination (1) 1

(b) (i) aqueous / dilute sulphuric / hydrochloric acid (allow HCl(aq); H2SO4(aq)

not water) (1)

temp. < 100° / warm / heat / reflux (this mark dependent on sensible reagent) (1)

2

(ii) CH3COOC2H5 + H2O CH3COOH + C2H5OH

(allow C4H8O2, C2H4O2 but must have C2H5OH) (1) 1

(c) sodium hydroxide / sodium carbonate / sodium hydrogen carbonate

(allow formula) (1)

room temperature / aqueous (2nd mark dependent on correct reagent) (1) 2

(d) ethanamide not ethylamide.

H

C

H

H

H

H

C

O

N

(1) 2 [10]

21. (a) Name nucleophilic addition (1)

Mechanism

C C

C N

O :

C H

C H

O

C H C H3

3

3 3

(1 )

(1 ) (1 )

(1 )N C :

–

H +

–

5

(b) Equation CH3COCH3 + 2[H] CH3CH(OH)CH3 (1)

Reducing agent NaBH4 (1) 2[7]

22. (a) Structure of P: CC H C H

H C H C H

C H

2

3 32

(1) 3

Structures of Q and R:

(1 ) (1 )

C CC CC H H

H HC H C H C H (C H )

C H C H

2 3 3

3 7

2

3 33an d

N O T C H

Q and R in any order

(b) (i) Racemic mixture: equal mixture of optical isomers / enantiomersOR in explanation

Explanation: planar ( >C=O) (1) attack from either side is equally likely (1)

(ii) Reagent S: HCN or (KCN / HCl or H2SO4) (1)

Compound T:

O H

C N

3 32C H C H C C H (1)

Compound U: C CC H

H C N

C H 3 3

23. (a) (i) C C

O

H O

O

O H (1) 1

(ii)

H H

H H

O HH O C C allow HOCH2CH2OH (1) 1

(iii)

H

H

H

H

CC

C C

O

O

O

O

n

ester linkage correct ie –COO–CH2– shown as fully graphical structure

(1)

rest of molecule correct including n

(1)

repeat unit may start and finish in different placeallow e.c.f. from (a)(ii) 2

(b) polyesters (1) 1

(c) addition: joining together (of monomers with double bond) one product only (1)

condensation: also involves the elimination of a small molecule (1)allow specific example e.g. H2O, HCl, CH3OH 2

(d) poly(ethene) / poly(propene)condone missing brackets (1) 1

[8]

24. (a) 3 Ketones:

C H C H C H C C H C H C H C C H C H3 33 33

3

32 22 2

O OO

(1 ) (1) (1 )C H

C H

C HC H C

3

(b) 4 aldehydes:

C H C H C H C H3 2 2 2

(1 )(1 )(1 )

(1 )

(1 )

(1 )

(1 )

C

CC

C

C

H

HH

H

O

OO

O3C H

3C H

3C H

3C H

3C H

3C H

2C HC H

C H3 2C H C H

Y Z X 5

(c) nucleophilic addition (1)

equal (1) mixture of optical isomers (1)

e.g (1 )C

3 2C H C H

3 2C H C H

O H

C N

4

(d) Reagents are oxidizing agents (1)

Aldehydes can be (easily) oxidized (1)

Ketones are not (easily) oxidized (1) 3[15]

25. (a)

CCH CC

H

H

H

H

O

H

H

H

CH HCCC

O H

H

H

H

H

H

CH HCCOC

O H

H

H

H

H

H

CCH C

H

H

O

H

H

C H 3

A

C

B

D

(1 )

(1 )

(1 )

(1 )

A = butanal

B = methylpropanal

C = butanone

D = ethyl ethanoate (1)

Ignore numbers in names unless they make them incorrectspellings must be correctaccept alternative trivial names correctly spelled 8

(b) ethanol / correct formula (1)

ethanoic acid / ethanoyl chloride / ethanoic anhydride / correct formula (1)

temperature less than 100 °C / reflux heat / concentrated sulphuric acid (1)

dilute sulphuric acid / acid conditions / H+

(this mark dependent on sensible answers for first two marks)

for ethanoyl chloride, room temperature / dry / anhydrous

for ethanoic anhydride, heat / up to 100 °C 3(c)

CCC CC HH

HH

CC

HH

HH

OO

OO

HHH

C H 3HH

(1 )

o r

(1)

butanoic acid methylpropanoic acid (1) 2

(d) heat with Fehling’s solution / ammoniacal silver nitrate / Tollen’s reagent /other suitable oxidising system eg acidified dichromate / Schiff’s reagent

B gives red, green or brown (precipitate) / silver (mirror) or black/grey (1)precipitate / other, dependent on reagent

C shows no change (1)

B and C can be referred to as ‘aldehyde’ and ‘ketone’ only if names correct in (a) or if there is some other valid identification 3

(e) nucleophilic addition (1)

C H 3 C H 3 C H 3

C C CO

O O H

C N C N C N

+

–

–

C H C H3 2 C H C H3 2 C H C H3 2

H

(1 )

(1) for intermediate (1) for product

allow –ve charge on Nbut curly arrow must come from C allow H from HCN or H2O 5

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