ORGANIC SEM 3 REVISION

TEKNIK
JAWAB

ORGANIC

STPM

2018

BY LALITHA
S.BALAKRISHNAN

KEY NAME
WORDS: DRAW / DETERMINE / DEDUCE
STATE / SUGGEST/DESCRIBE
BY LALITHA/ktesi WRITE
SHOW
DEFINE
EXPLAIN
COMPARE
ARRANGE

NAMING

Must be spelling
no formula

CLASS OF COMPOUND NAME OF HOMOLOGOUS SERIES FUNCTIONAL GROUP

HYDROCARBON ALKANE CARBON SINGLE BOND CARBON
ALKENE CARBON DOUBLE BOND CARBON
HALOALKANE ALKYNE CARBON TRIPLE BOND CARBON
HYDROXY AROMATIC / ARENE PHENYL GROUP (AROMATIC COMPOUND)
COMPOUNDS HALOALKANE CHLORO, BROMO, IODO
CARBONYL ALCOHOL HYDROXYL
COMPOUNDS PHENOL PHENOLIC
CARBOXYLIC ACID ALDEHYDE CARBONYL GROUP
KETONE CARBONYL GROUP
CARBOXYLIC ACID CARBOXYLIC ACID CARBOXYL GROUP
DERIVATIVES ESTER CARBOALKOXY
ACYL CHLORIDE ACYL GROUP
AMMONIA DERIVATIVES AMIDE CARBOXAMIDE
AMINE AMINO GROUP
AMINO ACID AMINO & CARBOXYL
PROTEIN PEPTIDE LINGKAGE
NITRILE NITRILE
ETHER ETHER

COMMON NAMES

❑ ACETONE ❑ d4-TERT-BUTYLPHENOL
❑ BENZYLCHLORIDE ❑ ACETYLENE
❑ BENZOYL CHLORIDE ❑ BENZONITRILE
❑ BENZALDEHYDE ❑ ACETOPHENONE
❑ CUMENE ❑ FORMIC ACID
❑ ISOPROPYLBENZENE ❑ ACETALDEHYDE
❑ ANILINE ❑ ACETIC ACID
❑ TOLUENE ❑ ETHYLENE
❑ BENZOIC ACID ❑ BENZYL ALCOHOL
❑ FORMALDEHYDE
BY LALITHA/ktesi

NAME TYPE OF REACTION/

MECHANISM

1. FREE RADICAL SUBSTITUTION
2. ELECTROPHILIC ADDITION
3. ELECTROPHILIC AROMATIC SUBSTITUTION (BENZENE & COUPLING)
4. UNIMOLECULAR NUCLEOPHILIC SUBSTITUTION SN1 not accepted
5. BIMOLECULAR NUCLEOPHILIC SUBSTITUTION SN2 not accepted
6. NUCLEOPHILIC ADDITION
7. ELIMINATION

BY LALITHA/ktesi

NAME THE REACTION

1. CHLORINATION / BROMINATION (not halogenation)

2. HYDROGENATION

3. FRIEDEL-CRAFTS ALKYLATION

4. FRIEDEL-CRAFTS ACYLATION

5. HYDRATION

6. ESTERIFICATION

7. CONDENSATION

8. HYDROLYSIS

9. OXIDATION

10.REDUCTION BY LALITHA/ktesi
11.COUPLING

DRAW
DETREMINE

DEDUCE

DRAWING STRUCTURES

O MUST SHOW THE
C-OH Functional group

F. G CANNOT BE
CONDENSED

+

BY LALITHA/ktesi

STPM 2020 / no.17




STATE/SUGGEST
REAGENT
&

OBSERVATIONS

COMMON REAGENTS

❑Fehling’s solution // alkaline solution of copper(II) complex

❑Iodoform test // warm with iodine in NaOH solution (or aqNaOH)

❑2,4-dinitrophenyhydrazine // Brady’s reagent

❑Tollens’ reagent with warm

❑NaNO2 with HCl, rtp
❑NaNO2 with HCl, (0-5)℃ followed by water with heat(70℃)
❑Hot Acidified potassium manganate(VII)
❑Hot Acidified potassium dichromate(VI)

❑Bromine water / Bromine in CCl4
❑FeCl3 solution
❑Ethanolic silver nitrate BY LALITHA/ktesi

❑Mg in COMMON REAGENTS

dry ether, followed by acetone & hydrolysed

❑Ethanoyl chloride with FeCl3
❑LiAlH4 in dry ether followed by acidic hydrolysis
❑Lucas test // ZnCl2 with HCl
❑Na // K // metal
❑Sodium carbonate

❑Ethanolic NaOH with heat//ethanolic KOH with heat

[cannot ethanol in NaOH]

❑ ethanolic KCN with heat // ethanolic NaCN with heat

❑HCN with NaOH // KCN with HCl

❑ Aqueous NaOH BY LALITHA/ktesi
❑ hot concentrated H2SO4

COMMON OBSERVATIONS

EFFERVERSENCE OCCURRED
YELLOW PRECIPITATE
ORANGE PRECIPITATE
FRUITY SMELL // SWEET SMELL
FISHY AMMONIACAL SMELL //ROTTEN FISH SMELL (aniline)
SILVER MIRROR// GREYISH SOLID (2017no.19)
BRICK RED PRECIPITATE
BRIGHT COLOUR SOLID (AZO DYE)
PURPLE COLOUR OF KMnO4/H+ TURNS COLOURLESS
WHITE FUMES// ACIDIC FUMES
WHITE SOLID SOLUBLE IN WATER
WHITE PRECIPITATE WITH BROMINE WATER
DECOLOURISES BROWN COLOUR BROMINE WATER

BY LALITHA/ktesi

WRITE
CHEMICAL
EQUATIONS

WRITING EQUATION

✓REACTANTS ON LEFT SIDE
✓ORGANIC PRODUCTS ON RIGHT SIDE
✓BY-PRODUCTS SUCH AS GASES (N2/HCl/H2) & H2O

INCLUDED (insisted if mention in question)
✓REACTION CONDITION ON ARROW

(TEMPERATURE/ MEDIUM/ SOLVENT/ CATALYST)

✓REVERSIBLE ARROW FOR ESTERIFICATION

BETWEEN C/ACID & ALCOHOL

✓ No need balance equation

✓∆(heat) MUST BE BELOW ARROW BY LALITHA/ktesi

BY LALITHA/ktesi

BY LALITHA/ktesi

BY LALITHA/ktesi

SUGGEST/
DESCRIBE
CHEMICAL

TEST

M1 : REAGENTS & CONDITIONS
M2 : OBSERVATION FOR BOTH

POSITIVE &
NEGATIVE (no visible changes)
M3 : EQUATION for +ve

BY LALITHA/ktesi

STPM 2019

BY LALITHA/ktesi

CHEMICAL TEST
Homologous Series REAGENT OBSERVATION

ALDEHYDE ONLY Fehling’s solution ,warm Brick red precipitate

CARBONYL (METHYL Iodoform test // warm with aqueous alkaline Yellow precipitate
KETONE) & HYDROXYL iodine solution// I2 in aq NaOH
(METHYL ALCOHOL)

ALDEHYDE & KETONE 2,4-dinitrophenyhydrazine // Brady’s reagent Orange precipitate (yellow ppt Cannot)

ALDEHYDE & Tollens’ reagent , warm Silver mirror formed // greyish solid
BENZALDEHYDE (HEAT OR REFLUX) formed

1° AMINE NaNO2 with HCl, rtp Effervescence observed

PHENYLAMINE NaNO2 with HCl, (0-5)℃ followed by water with heat Effervescence observed

ALKENE Acidified potassium manganate(VII) with heat Purple decolourised
1° & 2° ALCOHOL Acidified potassium dichromate(VI) with heat Orange to green
ALDEHYDE

PHENOL & ANILINE Bromine water White precipitate

PHENOL FeCl3 solution Purple solution
HALOALKANE
Ethanolic silver nitrate, heat White/pale yellow/yellow ppt
Ethanolic silver nitrate at rtp Cloudiness within seconds//1min//few min

ALCOHOL/PHENOL/CA Na // K Effervescence observed
CARBOXYLIC ACID ONLY sodium carbonate Effervescence observed

Aliphatic ALCOHOL Lucas test // ZnCl with HCl don’t use PCl & Cloudiness within seconds//

CONVERSION
QUESTIONS

BY LALITHA/ktesi

• Write reaction scheme or synthetic
pathway or reagent & condition for
synthesis….

1 LINE answer - reagent/condition on arrow

• But if question as to write equations for
each stage : must write equations
separately

• Analyse class of compound before & after the check
num of C atoms before & after

STPM 2020
Reaction scheme for the preparation of X from ethylbenzene

BY LALITHA/ktesi x

DRAW/WRITE
MECHANISM

BY LALITHA
S.BALAKRISHNAN

BY LALITHA/ktesi

BY LALITHA/ktesi

ELECTROPHILIC AROMATIC SUBSTITUTION

BY LALITHA/ktesi

ELECTROPHILIC AROMATIC SUBSTITUTION

BY LALITHA/ktesi

slow

fast

BY LALITHA/ktesi

BY LALITHA/ktesi

NUCLEOPHILIC ADDITION

BY LALITHA/ktesi

NUCLEOPHILIC ADDITION

BY LALITHA/ktesi

EXPLAIN BY LALITHA
COMPARE S.BALAKRISHNAN
ARRANGE

EFFECT OF SUBSTITUENT GROUPS TO BENZENE RING
I) REACTIVITY: - increase / decrease rate of reaction
II) ORIENTATION:- position of substituent

ACTIVATING RING DEACTIVATING RING

Electron releasing group/donating group Electron accepting / withdrawing group

Positive Inductive effect (+I) Negative Inductive effect (-I)

Increases electron density of the ring Decreases electron density to the ring

Increases rate of reaction Decreases rate of reaction

Ortho & para directors meta directors

Eg: (with lone pair e or alkyl group) Eg: (group with multiple bond)

-- 2 > 3 > ≡ >
> > > > >
> 2 > >

HALOGENS ARE ORTHO & PARA BY LALITHA/ktesi
DIRECTORS EVENTHOUGH
DEACTIVATING GROUP

Q: EXPLAIN THE BONDING IN ORGANIC
COMPOUND….

1.IDENTIFY TYPE OF HYBRIDISATION FOR C ATOM
2.NUMBER OF HYBRID ORBITALS & UNHYBRIDISED

ORBITALS
3.HYBRID ORBITALS OVERLAPPING WITH ……(exp:1s of H)
4.NUMBER OF SIGMA & PI BONDS IN THE MOLECULE
5.SHAPE OF MOLECULE (LINEAR/TETRAHEDRAL/PLANAR)
6.BOND ANGLE (sp=180ο, sp2=120 ο,sp3=109.5 ο)

BY LALITHA/ktesi

Q: COMPARE….

1. Don’t use mathematical symbol > or <
2. List with , then draw arrow to indicate increasing or

decreasing.
E.g.: STPM 2020

amide , ester , acyl chloride , carboxylic acid

increasing reactivity

ORGANIC
ANALYSIS
QUESTION

STPM PAST
YEAR
QUESTIONS.

BY LALITHA/ktesi

TECHNIQUES TO ATTEMPT…
1. READ QUESTIONS THROUGHLY. BY LALITHA/ktesi

2. EXTRACT/ CIRCLE THE QUESTIONS ASKED.

3. UNDERLINE THE REACTANTS, REAGENTS &

GIVEN CONDITIONS.

4. DRAW A TABLE OF OBSEVATION & DEDUCTION//

DRAW REACTION SCHEME.

5. IDENTIFY THE COMPOUNDS SEPARATELY.

6. WRITE COMPLETE EQUATIONS FOR EACH REACTION.

7. SEPARATE ANSWERS ACCORDING TO EACH PART.

STPM 2018 / NO 19

Reaction between 2-methylpropene and hydrogen

chloride produces P. Reaction between P and

water produces Q while reaction between P and

ethanolic sodium hydroxide produces R. Draw

structure P, Q and R. Write all the equations

involved and name the type of reactions involved.

Explain why P is the only product in the reaction.

Name the functional group of Q. Write the

mechanism of Q formation. [15 marks]

BY LALITHA/ktesi

1. Draw(not name) structure P, Q and R (3)

2. Write all the equations …….(3)

3. Name the type of reactions …….(3)

4. Explain why P is the only product ……(1)

5. Name the functional group of Q ………(1)

6. Mechanism of Q formation ………(4)

[15 marks]

BY LALITHA/ktesi

OBSERVATION DEDUCTION

2-methylpropene + Electrophilic Addition reaction
HCl P is 2-chloro-2-methylpropane or

2-chloro-2-methylpropane

whereby major product follows Markovnikov’s rule
2-chloro-2-methylpropane forms more stable 3ο
carbocation

P + water Hydrolysis of 3ο haloalkane with water to produce
alcohol Q

Q is 2-hydroxy-2-methylpropane.

Functional group is hydroxyl group.
Unimolecular nucleophilic substitution

P+ ethanolic NaOH Elimination of HCl to form alkene
Major product is the more substituted alkene

BY LALITHA/ktesi

STPM 2018 / NO 20

The compound K, C8H16, is a hydrocarbon which decolourises
bromine water. Ozonolysis of K produces two compounds, L and
M Both L and M form an orange precipitate with
2,4-dinitrophenylhydrazine. L also forms yellow precipitate with
alkaline iodine solution. Oxidation of M with hot acidified
potassium manganate(VII) solution yields butanoic acid.(a)
Deduce the structures of K, L and M. (must explain)
Write all chemical equations involved. [13 marks]
(b) Suggest another chemical test to differentiate between L and
M. State your observation.

[2 m]

BY LALITHA/ktesi

OBSERVATION DEDUCTION

K decolourises Br2 • K is a unsaturated hydrocarbon
water Eq 1 • K has carbon double bond C; C=C

• K is alkene cos C8H16 is CnH2n

Ozonolysis K gives • Breaks between the C=C; cleavage of C=C

L&M Eq 2 • Forms 2 carbonyl compound

L & M forms • Confirm both M&L are carbonyl compound with
orange ppt with C=O
DNP Eq 3 + 4
=O
L forms yellow ppt • L has methyl ketone group CH3 C
with alkaline EI2q sol • L is a ketone

5

M oxidized with • M is an aldehyde coz ketone can’t oxidise

KMnO4/H+ form • M aldehyde with 4C

C4H8O2 Eq 6 • C=C is at 4th C BY LALITHA/ktesi

6 equations
Reagent : Tollens’ reagent& warm //

Fehling’s solution
Observation: Silver mirror formed for M but

no visible changes for L //

BY LALITHA/ktesi

STPM 2018 / NO 18

(a) Two compounds, S and T, are hydrocarbons with the
empirical formula of CH. S has two π bonds while T has
three delocalised π bonds. Draw the structural formulae of S
and T. Explain the bonding of S and T and their molecular
shapes.
[9 marks]

BY LALITHA/ktesi

COMPOUND S COMPOUND T

❑ S is an ethyne ❑ T is an BENZENE RING

❑ Each Carbon atom in S has 2 ❑Each Carbon atom in T has
sigma bond between 1s 3 sigma bond between 1 pi
orbitals of H atoms and 2 pi bonds between C atoms
bonds between C atoms
❑C atom uses sp2 hybridized
❑C atom uses sp hybridized orbitals
orbitals
❑ S is a planar / hexagonal
❑ S is a linear planar

❑BOTH S & T compounds ; (cannot trigonal planar)
H atoms USES 1s ORBITALS BY LALITHA/ktesi