ORGANIC SEM 3 REVISION

The structural formula of a compound X is shown

below. X undergoes oxidation,

producing a white solid which

reacts with ethanol in the

presence of a catalyst to form a

sweet smelling product. Write

the chemical equations involved

and state the catalyst used.

Draw the geometrical isomers of

X. [6m]

BY LALITHA/ktesi

❑ GEOMETRICAL ISOMERS 2 marks
Drawing structure with label cis & trans

❑ 2 EQUATIONS

1st equation: oxidation of X
2 marks – reagent on arrow & reactant with product

2nd equation: esterification BY LALITHA/ktesi
3marks – conc H2SO4

- ester
- ethanol + heat



STPM 2017 / NO 18

(a)Benzene reacts with 2-bromopropane in the presence of
aluminium bromide to form compound S. Chlorination of
compound S in the presence of light produces compound T as
the major product and compound U. When compound S is
treated with hot acidified potassium manganate(VIl) solution,
compound V is formed. Hydrolysis of compound T produces
compound W.

(i) Draw the structural formulae of compound S, T, U, V and W.
[5 marks]

(ii) Name the reaction for the formation of compound S and
write the reaction mechanism.
[5 marks]

BY LALITHA/ktesi

OBSERVATION •• DEDUCTION

Benzene + Eq 1 Friedel-Crafts alkylation
S is isopropylbenzene
2-bromopropane with

aluminium bromide gives S

S + Cl2 in UV gives T • Free radical substitution
• Cl atom is substituted at alkyl chain
Eq 2 • T is (2-chloroisopropyl)benzene
• Bcoz T forms more stable tertiary free
S + KMnO4/H+ gives V Eq 3
radical as intermediate compound
Hydrolysis T gives W Eq 4 • U is (2-chloroisopropyl)benzene
BY LALITHA/ktesi
• Oxidation occurs at side chain to
produce V ; benzoic acid

• Nucleophilic substitution forms
alcohol

• T is 2-phenyl-2-propanol

b) 2-bromopropane, 1 -bromopropane and

2-bromo-2-methylpropane are alkyl bromides.

(i) Arrange the alkyl bromides in descending

order of reactivity towards SN1 reaction.
Explain your answer. Write the chemical eq

methanol & most reactive alkyl bromide in

SN1reaction. [5m]

BY LALITHA/ktesi

• Most reactive towards least reactive: ……. M1
• 2-bromo-2-methylpropane is 3ο haloalkane …… M2
• most reactive bcoz forms most stable 3ο
M3
carbocation as intermediate compound …..

(CH3)3CBr + CH3OH (CH3)3COCH3 + HBr

BY LALITHA/ktesi

STPM 2017 / NO 19

Compound A, C4H10O, is heated with copper to produce compound B.
A greyish solid is formed when compound B is warmed with Tollens' reagent.

Treatment of compound A with hot concentrated sulphuric acid produces

compound C. Hydration of compound C forms compound D, C4H10O, which
does not decolourises acidified potassium manganate(VIl) solution.

Compound B react with hydrogen cyanide to produce compound E.

(a) Draw the structural formulae of compounds A, B, C, D and E. [5 marks]

(b) Write the chemical equations for all the reactions involved. [4 marks]

(c) Explain why compound D does not decolourises acidified potassium

manganate(VII) solution. [2 marks]

(d) Write the reaction mechanism that produces compound E. [4 marks]

BY LALITHA/ktesi

OBSERVATION DEDUCTION
Eq 1 • Oxidation of 1ο alcohol to B an aldehyde
A + heated Cu

B with Tollens’ gives • B is confirm an aldehyde
grey

A + hot con H2SO4 • Dehydration of alcohol
gives C Eq 2 produces unsaturated HC; C

is an alkene

C + H2O gives D Eq 3 • Hydration C forms alcohol D
which is negative with which is 3ο alcohol bcoz 3ο
KMnO4 alcohol resist oxidation.

B + HCN gives E Eq 4 • Nucleophilic addition

STPM 2017 / NO 20

An organic compound P, C8H11N, has a fishy-ammoniacal smell. Compound P
reacts with aqueous solution of HC1 to produce compound Q, C8H12NC1.
Compound P also dissolves in a newly prepared solution of aqueous HC1 and

NaNO2 at 0°C to form compound R, C8H9N2C1. When compound R is diluted with
water and heated to 70°C, effervescence occurs and compound S, C8H10O, is
formed. When compound R is added to alkaline phenol, a bright colour solid,

compound T, C14H13ON2Na, is precipitated.
(a) Draw the structural formulae of compounds P, Q, R, S and T. [5 marks]

(b) Write the chemical equations for all the reactions involved. [4 marks]

(c) Which base is stronger, compound P or aniline? Explain your answer. [2 marks]

(d) Suggest a chemical test to differentiate between compound P and compound S.

[2 marks]

(e) Name the reaction to produce compound T and state one industrial use of

compound T. BY LALITHA/ktesi [2 marks]

OBSERVATION DEDUCTION

P, C8H11N, has a fishy- • P is an aromatic amine or aniline; C6H5NH2
ammoniacal smell with alkyl group attach to ring

P + HC1 gives Q, • P is a base reacts with acid via neutralization
Eq 1
C8H12NC1 to form salt; Q
P + HC1 and NaN02 at •
0°C gives R, C8H9N2C1 P reacts with nitrous acid produces R is a

diazonium salt (N+ = NCl-) Eq 2

R + water and heated to • Diazonium salt forms phenol; S Eq 3
70°C, effervescence • N2 gas released

occurs gives S, C8H10O

R + alkaline phenol, a • Neutralisation of phenol Eq 4

bright colour solid, • Coupling reaction (N=N) Eq 5

compound T, • Electrophilic aromatic substitution

C14H13ON2Na, is • Azo dye; T BY LALITHA/ktesi

STPM 2016 / NO 18

Bromination of ethylbenzene in the presence of ultraviolet light
yields monobrominated products, P and Q. P rotates plane-polarised
light but Q does not. When P and Q are refluxed separately with an
aqueous solution of sodium hydroxide, R and S are formed
respectively.
(a) Determine the structural formulae of P, Q, R and S. [4 marks]
(b) Describe the mechanism for the formations of P and Q. [6marks]
(c) Determine the major product of the reaction. [3 marks]
(d) Suggest a chemical test to differentiate between R and S.

[2 marks]

BY LALITHA/ktesi

STPM 2016 / NO 19

An optically active haloalkane, X, which has a molecular formula,
C10H13C1 reacts with an aqueous solution of NaOH to form a compound,
Y. X reacts with Mg in dry ether followed with CH3COCH3 and is
hydrolysed to form Z.

(a) Deduce the structure of X. Write the chemical equations for all the

reactions involved. [7 marks]

(b) Write the reaction mechanism for the formation of Y. [3 marks]

(c) X also reacts with an ethanolic KOH solution. State the type of

reaction and draw the structures of all possible products.

Determine the major product of the reaction. [5 marks]

BY LALITHA/ktesi

STPM 2016 / NO 20

BY LALITHA/ktesi

STPM 2015(U)/ NO 18

18 (a) Compound P, C9H80, forms an orange precipitate with Brady's reagent.
Compound P does not produce silver mirror with Tollens' reagent. Deduce the

structure of compound P and write the reaction equation involved. [6 marks]

(b) Compound Q, C8H80, is formed when ethanoyl chloride reacts with benzene in
the presence of FeCl3 as a catalyst. Reaction of compound Q with LiAlH4 in dry
ether followed by acid hydrolysis yields compound R, C8H10O. Compounds Q and
R give a positive iodoform test. Draw the structures of compounds Q and R. Write

all the reaction equations involved. [6 marks]

(c) Suggest a simple chemical test, which can be used to distinguish between

compounds Q and R, apart from using the Brady's reagent. State the observation and

write the reaction equation involved. [3 marks]

BY LALITHA/ktesi

STPM 2015(U) / NO 19

(a) (i) Butanoic acid and ethyl ethanoate are structural isomers. Which

isomer has a higher boiling point? Explain your answer. [6 marks]

(ii) Show how N-ethylbutanamide can be prepared from butanoic acid.

[4 marks]

(b) Tristearin is a naturally occurring ester. Its structural formula is

shown below. Write the reaction equations of

the tristearin with the following

reagents and state reaction

condition involved.

(i) NaOH

(ii) LiAlH4 [5marks]

BY LALITHA/ktesi

STPM 2015 / NO 20 STPM 2015(U)/ NO 19

BY LALITHA/ktesi

(i) Give the IUPAC name of phenylalanine. [1 mark]

(ii) Draw the structures of the products formed when phenylalanine reacts with

1. propanol in the presence of mineral acid, [1 mark]

2. hydrochloric acid, [1 mark]

3. aqueous solution of sodium hydroxide. [1 mark]

(iii) Draw the dipolar ion of phenylalanine and write an equation for the formation of a dipeptide

from phenylalanine. Indicate the peptide linkage. [3 marks]

(b) Amphetamine, 2-amino-l-phenylpropane, is a strong stimulant which can be synthesised from

phenylalanine.

(i) Between amphetamine and phenylalanine, which compound has a higher melting point?

Explain your answer. [3 marks]

(ii) Show how amphetamine can be synthesised from phenylalanine. [5 marks]

STPM 2015/ NO 20

Compound P, C9H10O2, undergoes a reduction reaction at room temperature to form Q, C2H60,
and R, C7H80. Q reacts with PC15 to produce acidic fume while R does not. Q produces a yellow
precipitate when heated with iodine in aqueous solution of sodium hydroxide.

(i) Draw the structural formulae of P, Q and R. [3 marks]

(ii) Explain the observation for the reaction of Q with iodine in aqueous solution of sodium

hydroxide and write the equation involved. [2 marks]

(iii) Draw the structure of the product formed when Q reacts with PC15. [1 mark]

(b) Glucose, C6Hi206, is a reducing sugar. State the observation and write an equation to show its
reaction with Tollens’ reagent.
[3 marks]

(c) By using a reaction scheme, state the reagents and reaction conditions necessary to

convert benzene to

(d) A sample of aminoethanoic acid was found to be contaminated with glucose. A 0.350 g

sample of the impure aminoethanoic acid required 27.45 cm3 of a 0.150 mol dm-3 of hydrochloric

acidBtYo nLeAutLraIlTisHe Ait./Ckatlecusliate the percentage of purity of the sample. [3 marks]

STPM 2015/ NO.19

(a) Two organic compounds, P and Q, are formed when 2-pentene reacts

with hydrogen bromide. P is an optically active compound.

(i) Show how P and Q are formed and determine their structural

formulae. [7 marks]

(ii) Draw the three-dimensional formulae for the optical isomers of P.

[2 marks]

(b) 2-Chloro-2-methylpentane reacts with an aqueous solution of sodium

hydroxide to form W, and with an ethanolic solution of sodium hydroxide

to form X and Y.

(i) Name the type of reactions involved. [2 marks]

(ii) Draw the structural formulae of W, X and K [3 marks]

(iiBi)YNLaAmLIeTHthAe/mkteecshi anism involved in the formation of W. [1 mark]