nss chemistry part 11 chemistry of carbon compounds

7/23/2019 NSS Chemistry Part 11 Chemistry of Carbon Compounds

1/47

H

P

N

1.

2.

a.

KAL Pas

rt 11 Ch

ming an

HKAL 199

Consider

#(i) G

(ii) D

ca

HKAL 199

Alcohol

(i) D

(ii)

t Paper

emistry

d Isomer

II Q5a

the followin

ive the hybr

raw allposs

rbon atoms

I Q4

has the stru

raw a three-

hat type of i

uestions

f Carbo

isms

compound

dization sta

ible three-d

a, b, c and d

cture CH3C

imensional

somerism c

:

Compo

F.

es of the car

mensional s

in one of th

(OH)C2H5.

representati

n be exhibit

1

nds

bon atoms a

tructures fo

structures.

n of E

ed by E?

, b, c and d.

F, indicati g the expected bond an

gles around

(5 ma

(2 ma

the

ks)

ks)


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b. (i) Draw the structure of threestructural isomers of E, all of which are alcohols.

#(ii) Describe how the reagent Zn/concentrated HCl can be used to distinguish E from the three structural

isomers.

(3 marks)

c. On treatment with dilute H2SO4(aq), E gives mainly two isomeric compounds, F and G, both of which have

the formula C4H8. On treatment with bromine, both F and G give a product H with formula C4H8Br2.(i) Draw structures for F, G and H.

(ii) What is the isomeric relationship between F and G?

(4 marks)


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3. HKAL 2008 II Q7a

Deduce the structure of isomeric compounds F and G, with formula 126HC , that have the following

characteristics:

Compound Characteristics

F It has a pair of enantiomers.

It loses its chiral centre after hydrogenation over Pt.

G It reacts with 2Br to give a single compound.

It reacts with HBr to give a single achiral compound.

(6 marks)


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4. HKAL 2009 II Q4a

The Table below lists the melting points and boiling points of cis-1,2-dichloroethene and

trans-1,2-dichloroethene:

(i) Explain why, in 1,2-dichloroethene, the carbon-carbon double bond cannot rotate freely.

(ii) Explain why

(I) cis-1,2-dichloroethene has a higher boiling point, and

(II) trans-1,2-dichloroethene has a higher melting point.

(6 marks)


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5. HKAL 2010 I Q4

Dimethyl fumarate can be found in most leather products since it is commonly used as a mould inhibitor.

However, it was banned in Europe for all kinds of consumer goods in March 2009 because it was found to

cause skin allergies. Compound A is an isomer of dimethyl fumarate. The structures and melting points of

these two compounds are given below:

(a) (i) Name the type of isomerism involved.

(ii) Explain why the melting point of Ais lower than that of dimethyl fumarate.

(3 marks)

(b) Both dimethyl fumarate and Acan be hydrolysed to their corresponding dicarboxylic acids, B and D.

(i) Explain why the melting point of Dis lower than that of B.

(ii) Explain why the

fH of Bis more negative than that of D.

(4 marks)


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6.

7.

HKAL 200

Consider

c. D

d.

HKAL 200

The three

(i) C

(ii)

I Q5a

the reaction:

raw the stru

ould the pr

II Q7b

-dimensiona

omment on t

ill P and Q

tures of all

duct rotate

l structures

he differenc

xhibit the s

possible ster

beam of pl

f two 2-chl

e, if any, in

me chemic

6

eoisomers o

ne polarize

robutanes (

hysical pro

l properties

the produc

light? Expl

andQ) are

erties betw

Explain yo

.

ain your ans

shown belo

en Pand Q

ur answer.

wer.

w:

.

(3 ma

ks)


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8. HKAL 1992 I Q1a

There are several isomers of benzenedicarboxylic acid.

(i) Draw the structures of all possible isomers of benzenedicarboxylic acid.

(ii) One of these isomers is used to make terylene. Outline the reaction involved.

(iii) On heating, one of the isomers gives a compound W, with formula C8H4O3. Give the structure of W.

(5 marks)


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9. HKAL 1992 II Q7

A carboxylic acid P, with a relative molecular mass less than 100, contains C, 55.8%; H,7.0%; and O, 37.2%

by mass. An attempt to convert P to its methyl ester Q by prolonged refluxing of P with methanol in the

presence of aqueous H2SO4gave the desired ester Q but with much of the starting material P unchanged.

a. Determine the molecular formula of P.

b. Give the structures of four carboxylic acids having the molecular formula you determined in (a). Give

the systematic names for any one of the carboxylic acids and its methyl ester.

c. Suggest, with explanations, two ways which would make the esterification go towards completion.

d. Which has a higher boiling point, the carboxylic acid or its methyl ester? Explain your answer.

e. Show, using equations, how you would convert Q to P.

(17 marks)


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10. HKAL 1994 II Q7a

What do you understand by the terms structural isomerism and stereoisomerism?

(3 marks)

11. HKAL 1994 II Q8c

Give a systemic name to each of the following compounds.

a.

b.

c.

(3 marks)

CH3CH CH

CH3

CH2

CH3

CH=CH2

CH3CH2CH2-O-C-CH2CH2CH3

O

CH3CH2-C-CHCH2CH3

O

OH


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13

. HKAL 19

The follo

(i) butene

(ii) 2-ami

In each c

. HKAL 19State the

6 II Q8b

ing compo

dioic acid, a

opropanoic

se, state the

9 II Q6celationship

nds can exi

d

acid.

type of iso

etween eac

st in isomeri

erism and d

pair of str

10

c forms:

raw suitable

ctures show

representati

n below:

ons for the i

somers.

(4 ma

(3 ma

ks)

ks)


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14. HKAL 2002 II Q7b

For each of the following pairs of molecules, identify their relationship as identical, enantiomeric, geometrical

isomeric or structural isomeric.

(5 marks)


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Compound A (C6H6O6) is an acyclic tribasic acid isolated from the leaves and tubers of Aconitum napellus.

Hydration of A gives two isomeric compounds, B and D. B is achiral, but D is chiral. Deduce the structures of

A, B and D.

(5 marks)

16. HKAL 2006 I Q6c

Answer the following multiple-choice question:

(i) Which of the following compounds has a pair of enantiomers??

Ans: B


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Deduce the structure of compound Don the basis of the information given below:

(1) Elemental analysis data show that Dhas the following composition by mass: C 40.0%, H 6.7%

and O 53.3%.

(2) The relative molecular mass of Dis estimated to be in the range of 172 to 182.

#(3) The infra-red spectrum of D shows, apart from the absorption of CH stretching near 2900 cm-1, a

strong and broad absorption around 3400 cm-1, and no appreciable absorption around 1700 cm-1.

(4) All carbon atoms of Dhave the same bonding environment.

(5) Dis highly soluble in water, and the solution does not decolorise bromine water.

(8 marks)


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Compound Bis a strong stimulant. Its structural formula is as follows:

(i) Give the systematic name of B.

(ii) In fact, the above structural formula can represent two stereoisomers.

(I) Draw three-dimensional structures of the two stereoisomers.

(II) State a physical property which is different for the two stereoisomers.

(iii) It is known that among the two stereoisomers, only B has stimulant activity while the other onedoes not. Why?

(iv) A person is suspected to have taken stimulant B. A urine sample of the person is sent for analysis.

Suggest a method to establish whether Bis present in the urine sample.

(7 marks)


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Alkanes and Alkenes

19. HKAL 1999 I Q5a

Under certain conditions, methane reacts with chlorine to give chloromethane as the major product.

(i) State the conditions for the reaction

(ii) Outline the mechanism and name the mechanistic steps of the reaction.

(iii) Is the reaction of methane with chlorine an appropriate method for the preparation of dichloromethane?

Explain.

(5 marks)

(i)

(ii)

(iii)


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20. HKAL 2001 I Q5a

Consider the reaction:

(D is deuterium, as isotope of hydrogen)

(i) Draw the structure of the major product.

(iii) Is the product optically active? Explain your answer.

(3 marks)

21. HKAL 2001 I Q6b

After some lessons in organic chemistry, a student remarked, Alkanes are more stable than alkenes, therefore

alkanes do not react with chlorine but alkenes do.

Do you agree with the student? Explain.

(3 marks)

(i)

(iii)


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Hydrocarbons G reacts with HBr to give J as the major product.

(i) Give the structure of J and its systematic name.

(iii) A student commented that J obtained from the above reaction is optically active. Do you agree with

the student? Explain.

(5 marks)

23. HKAL 2005 I Q6b (iii)

Which of the following statements concerning the hydrogenation of ethene is INCORRECT?

A. The hydrogenation is an exothermic process.

B. The hydrogenation occurs in the presence of a catalyst at room temperature.

C. The H-H bond is weak to allow the hydrogenation to occur.

D. Ethane is less energy rich than the starting materials.

Ans: C

(i)

(iii)


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24. HKAL 2007 I Q5a (ii)

Give the structure of the major organic product E in the following reaction. Indicate the stereochemistry of the

products as appropriate.

(1 mark)


Consider the following reaction:

(i) Give the structure of the major organic product L.

(1 mark)


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Neoprene, a synthetics rubber, can be obtained from buta-1,3-diene via the following route:

#(i) The reactant for Step 1is Br2. Propose a mechanism for the formation of Afrom buta-1,3-diene.

(ii) Suggest reactant(s) and conditions for each of Steps 2,3and 4.

#(iii) Explain why the strength of neoprene can be improved after heating it with sulphur.

(8 marks)


Identify the following unknown structure.

CH2=CHCO2CH3M CH3CH2CO2CH3

(1 mark)

M: Pd or Ni or Pt / H2


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State with explanations, what you would observe in each of the following experiments, and write equations for

the reactions.

(i) A mixture of pentane and bromine in tetrachloromethane is exposed to sunlight.

(ii) Propene is bubbled into aqueous alkaline potassium manganate(VII).

29. HKAL 1998 II Q5cGive the structures of the major organic products, G and H, in (i) and (ii) below.

#Outline a mechanism for the formation of the major product in each of the three reactions.

(i)

(ii)

(2 marks)

G: C

CH3

CH3

Br

CH2CH

3(i)

(ii) H: CH3CH2CH2OH

(i) The reddish brown bromine turns colourless (1)

The reaction is a free-radical substitution reaction (0.5)

Depending on the amount of bromine, various substitution products are obtained.

CH3CH2CH2CH2CH3+ Br2CH3CH2CH2CH2CH2Br or CH3CH2CH2CH2CHBr2etc (1)

(ii) The purple colour of KMnO4turns to colourless. (1)

KMnO4is reduced and the alkene is oxidized. (0.5)

CH3CH=CH2 C

OH

C

OH

CH3

H

H

H

KMnO4(1)


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Alkanols, Ketones/Aldehydes and Carboxylic acids

30. Show how you carry out the following conversions in the laboratory, giving the structures of intermediate

compounds and the reagents for each step.

a. HKAL 1995 II Q8b(ii)

CH3CH2CH2OH C

OH

CH3CH3

H (3 marks)

b. HKAL 1996 II Q9a(iv)

OH OH

OH

(3 marks)


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31. Outline chemical tests which would allow you to distinguish between the compounds in the following pairs.

Describe what you would observe in each case.

a. HKAL 1991 II Q9a (ii)

(2 marks)

b. HKAL 1991 II Q9a (iv)

C

H

CH2OHCH

3CH

2CH

2

CH3

CCH3CH

2CH

2

CH3

CH3

OH

(2 marks)

c. HKAL 1993 II Q8a(iv)

(3 marks)

Warm the compounds with acidified K2Cr2O7.

The primary alcohol will turn the solution from orange to green while the tertiary alcohol will not.


The primary alcohol will turn the solution from orange to green while the tertiary alcohol will not.

Add solution of NaHCO3to the compound, C6H5COOH will react to give CO2while the phenol C6H5OH will not.

COOH

OH

OH

CH3

CH2OH


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d. HKAL 1995 II Q7a(iii)

(4 marks)

e. HKAL 1993 II Q8a(ii)

CH3CH2CH2CH2CHO CH3CH2COCH2CH3

(3 marks)

f. HKAL 1996 II Q7c

C

O

H

O

(2 marks)


The aldehyde will turn the solution from orange to green while the ketone will not.

CH3

OH

CH2OH


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In an experiment, 25 g of (CH3)3COH react with 36 g of HCl to gives 28 g of (CH3)3CCl.

(i) Find the limiting reactant of the reaction,showing clearly your calculation.

(ii) Calculate the percentage yield of (CH3)CCl.

(3 marks)


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An acyclic compound, R(C7H12O) has a linear structure, R can be converted to S and then to T:

C7H12O C7H14O C7H16OLiAlH4 H2/Pd

R S T

Given that R exists as a mixture of geometrical isomers, S has a chiral carbon center, and T does not have any

chiral carbon center, deduce allpossible structures of R, S and T.

(8 marks)


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34. HKAL 2001 I Q8b

In an experiment to prepare propanal from propan-1-ol,

CH3CH2CH2OH CH3CH2CHOCr2O7

2-/ H+

heat

a side-product N (C6H12O2) was formed.

(i) What is N? Suggest how N is formed.

(ii) Suggest onemethod to separate propanal from a mixture of propanal and N.

(iii) Suggest twomethods to confirm the identity of propanal.

(3 marks)

(i)

(ii)

(iii)


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35. HKAL 2002 I Q5b

Suggest reagent(s) to accomplish each of the following single-step transformations:

(1 mark)


Formaldehyde (methanal) is one of the commonly found organic indoor air pollutants.

(i) Suggest a source of household formaldehyde.

#(ii) The indoor air quality (IAQ) standard for formaldehyde has been set at 0.10 ppm by volume.

Calculate the maximum allowable quantity of formaldehyde, in gram in a room of volume 200 m3at

298 K and 1.01 105N m

-2.

(You may assume that formaldehyde behaves as an ideal gas.)

(iii) Some indoor air purifiers remove formaldehyde by chemical means. Suggest one chemical for the

removal of formaldehyde with the formation of less harmful products.(iv) Name one other organic indoor air pollutant and suggest its source.

(7 marks)


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37. Identify the following unknown structure.

a. HKAL 1994 II Q7

CH3CH=CHCH2CH2COOHLiAlH4

(1 mark)

b. HKAL 1995 II Q9b(ii), (iv)

(ii)

CH3CH2CH2COOH CH3CH2CH2COClL

(1 mark)

(iv)

HOCH2CH2OH C

O

C

O

OCH2CH2On

N

(1 mark)

CH3CH=CHCH2CH2CH2OH


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38. HKAL 2002 II Q7d

Suggest a synthetic route, in not more than three steps, for the transformation of 3-methylbenzoic acid to

N,N-diethyl-3-methylbenzamide, a substance commonly used in mosquito repellant.

CO2H

CH3

CH3

CON(CH2CH

3)2

3-methylbenzoic acid N,N-diethyl-3-methylbenzamide

(2 marks)

39.Identify the following unknown structure.

a. HKAL 1993 II Q7a(iii)

(1 mark)

b. HKAL 1994 II Q7

(1 mark)

NH2CH3COCl

NH2CH3CH2COCl

N

O

N

H C

O

CH3


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. HKAL 19

The follo

which is

(i) N

(ii) G

(iii) S

7 II Q5b

ing equati

chiral comp

ame all func

ive one stru

ggest a met

n represents

und.

tional group

ture for E a

hod to separ

the acid hy

s in D.

d one for F.

ate E and F

30

rolysis of a

Draw a suit

rom the rea

dipeptide D

able represe

tion mixtur

to produce

ntation for t

.

compounds

e chiral pro

E and F, on

duct.

(5 ma

of

ks)


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41. HKAL 2007 I Q4a, b

(a) Consider the alkaline hydrolysis shown below:

Give the structure of product A.

(1 mark)

(b) Consider the acidic hydrolysis shown below:

(i) Give the structure of product B,

(ii) Suggest the amount of acid required for the hydrolysis of 1 mole of the ester. Explain

your answer.

(2 marks)

a.

b. (i)

(ii)


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(a)

(b

(c)

(d

(e)

(f)

. HKAL 20

3-Methyl

distinctiv

5.0 cm3o

L.

Suggest

Calculate

isoamyl a

Draw a la

What are

Outline t

cannot be

Suggest

9 I Q8

l-butyl etha

pleasant b

f isoamyl al

hat reagent

the mole ra

lcohol=0.81

belled diagr

the major co

e procedure

effectively

hy isoamyl

oate, com

nana odour

ohol is allo

Lmay be a

io of isoam

g cm-3; den

m of the as

mpounds pr

s to isolate i

eparated fr

alcohol is N

only known

and is used

wed to react

d give the r

yl alcohol t

ity of glacia

embly of ap

esent in the

soamyl acet

m the result

OT used in

32

as isoamyl

in food fla

with l5.0 c

action cond

glacial ace

l acetic acid

paratus use

esulting mi

te from the

ing mixture

xcess in thi

acetate, is a

ouring. In a

3of glacial

itions for thi

tic acid use

=1.05g cm-3

in this prep

ture at the e

resulting m

by fractiona

preparatio

naturally oc

n experime

acetic acid

s preparatio

in this pre

)

aration.

nd of this pr

xture. (It is

distillation.

.

curring com

t to prepare

in the prese

.

aration. (G

eparation?

known that

)

pound havi

the compo

ce of a rea

(l m

ven: densit

(2 m

(2 m

(l m

isoamyl ace

(3 ma

(l m

g a

nd,

ent

rk)

of

rk)

rk)

rk)

ate

ks)

rk)


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Suggest a possible structure for each of the compounds J, K and L below and explain briefly your deductions.

(i) J, C4H6O, on oxidation gives K, C4H6O2.

(2 marks)

(ii) L, C5H12O, can exist as a pair of enantiomers, and reacts with phosphorus pentachloride to give

hydrogen chloride.

(2 marks)

(i)

(ii)


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Important Organic Chemicals


A mixture of 2.8 g of butane-1,4-diol and 6.3 g of benzene-1,3-dicarbonyl chloride was heated at 215oC for 30

minutes to give 6.4 g of a polymer M.

HO(CH2)4OH

COCl

COCl

butane-1,4-diol benzene-1,3-dicarbonyl chloride

(i) Draw the repeating unit of M.

(ii) What type of polymerization is involved in the formation of M?

(iii) Calculate the percentage yield of M.

(5 marks)


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Saponification of 1 mol of fat G with NaOH(aq) produces 1 mol of a triol C3H8O3, 2 mol of

CH3(CH2)16CO2-Na

+and 1 mol of CH3(CH2)14CO2

-Na

+.

(i) If G is optically active, suggest its structure. Explain.

(ii) If G is optically inactive, suggest its structure.

(iii) What is the minimumnumber of moles of base required for the complete saponification of 1 mol of G?

(4 marks)


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46

(i)

(ii

(ii

. HKAL 19

Dacron is

shown be

Suggest t

Draw the

involved.

) How can

9 II Q5c

the most co

ow.

o types of

structures

Dacron be d

mon of th

aterial whi

f the two

egraded in t

group of p

ch can be m

onomers us

e environm

37

lymers kno

de from po

ed in manu

nt?

n as polyes

yesters.

acturing Da

ters. A seg

cron. Name

ent of the p

the type of

lymer chai

polymerizat

(5 ma

is

ion

ks)


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(i) Draw the structure, showing two repeating units, for each of the following polymeric materials:

(I) poly(chloroethene) and

(II) cellulose

(ii) Large quantities of poly(chloroethene) and cellulose used in daily life, Suggest, with explanation, an

appropriate waste disposal method for each material.

(5 marks)


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a.

b.

. HKAL 20

Sodium s

sodium h

(i) D

(ii)

(iii) E

ProductJ, fr

(i) D

(ii) St

(iii) St

0 II Q6

tearate CH3

droxide sol

raw the stru

ith the help

plain why

om the trans

raw the stru

ate oneadv

ate oneenvi

CH2)16CO2-

tion.

ture of the t

of equation(

ashing sod

formation b

ture ofJ.

ntage of usi

ronmental p

Na+, the m

riglyceride.

s), describe

, Na2CO3

elow, is co

ngJas a det

oblem asso

39

st common

he chemistr

10H2O, can

monly-used

ergent.

iated with t

soap, can

y when soap

help to redu

household d

e use ofJ.

e made by

is added to

ce the hardn

etergent.

heating a tr

hard water.

ess the wate

iglyceride

.

(4 ma

(3 ma

ith

ks)

ks)


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c. Dodecyl

(i) E

(ii) S

lucoside is

plain why

ggest how

new deterg

edocyl gluc

odecyl gluc

ent.

oside can be

oside can be

40

used in the

degraded i

cleansing of

the environ

oily dirts.

ment.

(4 ma ks)


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49

. HKAL 20

Aspartam

(i)

C

as

(ii)

(iii)

In

S

5 II Q5b

e is a comm

opy the stru

terisk.

ith referenc

a coffee sh

ggest a reas

nly used ar

cture of asp

to its struc

op, a packet

on for inclu

ificial swee

artame into

ure, explain

of sweeten

ing silicon

41

ener.

your answe

why asparta

er contains

ioxide in th

book, and

me is unsta

bout 5% of

e packet.

mark each

le in cookin

aspartame

chiral carbo

g.

nd 95% of

atom with

silicon diox

(4 ma

an

de.

ks)


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In the past, people chewed willow bark to ease their pain and to lower fever. Later on, chemists identified

salicin as the active ingredient in willow bark.

salicin

Salicin undergoes acid hydrolysis to give glucose and 2-hydroxybenzyl alcohol.

#(i) Suggest a chemical test to distinguish between salicin and glucose. Account for the difference in

results of your suggested test.

(ii) 2-Hydroxybenzyl alcohol can be converted in two steps to acetylsalicylic acid, which is the active

ingredient of aspirin.

2-hydroxybenzyl alcohol acetylsalicylic acid

(I) Give the reagents used in Step 1and in Step 2.

(II) In a typical experiment, 2.0 g of 2-hydroxybenzyl alcohol gives 2.0 g of acetylsalicylic acid.

Calculate the percentage yield of the conversion.

(7 marks)


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51

(i)

(ii

. HKAL 2

Polyethe

diagram

Give the

Polyethe

(I) D

(II)

007 II Q6d

e terephthal

elow shows

eagent(s) an

e naphthalat

raw the stru

hich polym

te (PET) is

a route for t

d condition

e (PEN) is a

ture of a re

r, PET or P

a polymer

he synthesis

for each of

polymer fo

eating unit

N, do you

43

sed in maki

of PET.

Steps 1, 2, 3

med from n

f PEN.

xpect to be

ng clothing

and 4.

phthalic aci

more rigid?

ibres and s

d and ethan

Explain.

ft drink bot

-1,2-diol.

les. The f

(6 ma

ow

ks)


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44

52. HKAL 2010 II Q4d

Polyethylene terephthalate (PET) is a polymer commonly used in making soft drink bottles.

(i) Suggest a synthetic route with no more than three stepsto convert benzene-1,4-dicarbaldehyde

to PET. (You are NOT allowed to use organic reagents with more than three carbon atoms.)

(ii) Suggest why PET as compared with polystyrene, is more readily degraded in the environment.

(4 marks)


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53

iscellane

. HKAL 20

Identify

ous

0 II Q6e

, M and N i the followi

ng reactions

45

:


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46


Consider the substances listed below:

butane benzoic acid dichlorodifluoromethane

ethanoic acid hexane polystyrene

propanone tetrachloromethane triethylamine

For each of the descriptions of physical properties from (a) to (h) below, choose from the above list, one

substance which best fits the description.

(i) a colourless, flammable gas

(ii) a colourless liquid with a sour odour

(iii) a colourless, water miscible, flammable liquid

(iv) a colourless, non-flammable liquid

(v) a colourless liquid with a fishy smell

(vi) a colourless, water immiscible, flammable liquid

(vii) a white solid which is insoluble in both cold and hot water

(viii) a white solid which is insoluble in cold water, but soluble in hot water

(8 marks)


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55. HKAL 2003 I Q6b

The weakest chemical bond in an organic compound always breaks first in a chemical reaction.

The above statement is not always true. Give one example for which the statement is true and one example for

which the statement is not true. Explain each case briefly.

(4 marks)

nss chemistry part 11 chemistry of carbon compounds

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