CLF108 Organic Chemistry (Revision Week 1-8)
SHORT ANSWER QUESTIONS
Question 1
An experiment was conducted to determine bond unsaturation of an unknown organic
compound with the condensed formula of CH3CHCHCH2CH2CH3. Two drops of the
organic compound in 0.5mL of dichloromethane in a test tube before adding saturated
bromine water.
(a) Draw the skeletal structure of the organic compound given the condensed
formula.
(
2 marks
)
(b) Based on your answer from part (a), state what will be the expected observation?
(
2 marks
)
(c) Write the reaction mechanism for the observation described in part (b).
(
4 marks
)
Question 2
CH3
CH 2Cl
+
Cl 2
u.v.
+
HCl
Construct reaction mechanisms for the THREE-STAGE free-radical substitution of
methylbenzene to form chloromethylbenzene.
( 10 marks )
Question 3
Hex-3-ene occurs in two isomeric forms, known as geometric isomers.
(a) Draw and label the TWO (2) isomeric forms of hex-3-ene. Hence, indicate which
isomer is more stable. Briefly explain your answer.
( 6 marks )
(b) Hex-3-ene is the mid-product from hex-3-yne when 2 moles of hydrogen gas
are passed through hex-3-yne. Draw the reaction mechanism when hex-3-yne
reacts with 2 moles of hydrogen gas. Show the FINAL product from the reaction.
( 4 marks )
Question 4
Using the following structure below to answer the following question;
(a) Identify the type of hybridization for the oxygen atoms.
( 1 mark )
(b) Draw the orbital diagram to illustrate the hybridization of the oxygen atoms from
ground state to hybridized state.
( 3 marks )
(c) Explain, with the aid of diagrams, inclusive of all hybridizations, the formation
of sigma and pi bonding for ALL bonds in this molecule.
Hence, state how many sigma and pi bonds are present in this molecule?
( 6 marks )
Question 5
The reaction pathway involving the formation of Compound X from benzene is as
follows;
Step 1
CH3
Step 2
Reagent A
conc. HNO3
Condition 1
conc. H2SO4
CH3
NO 2
Compound X
(a) The following equation above shows the electrophilic substitution of benzene.
Briefly explain why benzene does not undergo addition reaction.
( 2 marks )
(b) State “Reagent A” and “Condition 1” that is required to yield methylbenzene in
step 1.
( 2 marks )
(c) By means of an equation, explain the role of the concentrated sulfuric acid used
in step 2.
( 2 marks )
(d) Describe the mechanism for the formation of Compound X from methylbenzene,
including curly arrows showing the movement of electrons, and all charges.
Hence, name Compound X according to IUPAC nomenclature.
( 4 marks )
Question 6
Using Fischer Projection, draw ALL the stereoisomers for 2,3-dihydroxybutanedoic
acid. Identify the
(a) Meso compound
(b) Pairs of enantiomers
(c) Pairs of diastereomers
( 10 marks )
Question 7
Different concentrations of 2-chloro-2-ethylpentane are mixed with sodium hydroxide
and measures the rate of the reaction and concentration of the sodium hydroxide and
2-chloro-2-ethylpentane.
The experiment was repeated times and a rate equation was concluded below;
Rate = k[2-chloro-2-ethylpentane]
(a) Construct the reaction mechanism to show how 2-chloro-2-ethylpentane reacts
with sodium hydroxide. Show the organic product formed using the relevant
stereochemistry, step(s), arrow pushing and the structure of the intermediate (if
any).
(
8 marks
)
(b) How will the rate of reaction be affected if the same experiment was repeated
using the same sodium hydroxide to react with 2-bromo-2-ethylpentane?
(
2 marks
)