CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 51 ANSWER a) i) Skeletal structure Expanded structure ii) Functional Group Homologous series Hydroxyl Alcohol Carboxyl Carboxylic acid b) i) Structural isomerism is when different compounds that have the same molecular formula but differ in their connectivity, that is, in the sequence in which their atoms are bonded together. ii) c) i) Class of carbocation: 3 o carbocation 1 o carbocation 2 o carbocation ii) Order of increasing stability: d) a) Substitution b) Elimination c) Addition e) Class Carbon Hydrogen 1 o 2 6 2 o 4 8 3 o 2 2
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 52 MCQ PRACTICES 1. Organic compounds basically consist of C and H. They can also consist of other common element atoms which may be A O B N C Br D All the above 2. Which of the following compounds has a quaternary carbon atom? A CH3CH2CH3 B CH3CH(OH)CH2OH C (CH3)3CCH2CH3 D C6H5COCH(CH3)2 3. Which of the following does not contain a secondary carbon atom? A (CH3)3CCH(CH3)2 B CH3CH2CH3 C C6H5CH2CH2CH3 D (CH3)2CHCH2CH3 4. The compound R has the structural formula shown below. R is classified as.. A Carboxylic acid B Aldehyde C Ester D Ketone 5. The functional groups present in the amino acid with the structural formula as shown below are. A alkoxy, carboxyl, amide and aromatic ring. B alkoxy, carboxyl, amino and aromatic ring. C hydroxyl, carboxyl, amino and aromatic ring. D hydroxyl, carbonyl, amino and aromatic ring. 6. The number of possible structural isomers for bromobutane, C4H9Br is A 2 B 3 C 4 D 5 7. Which of the following is NOT grouped in the same homologous series? A Propane, butane, hexane B Ethanol, methyl propanol, 1-butanol C Ethanoic acid, propanoic acid, nitric acid D Heptene, ethane, pentene. 8. What is the relationship between the two compounds shown below? 3 3 2 3 3 3 3 3 2 3 : ( ) ( ) : ( ) ( ) X CH C CH CH Y CH CCH CH CH CH A Both compounds have the same structural formula B Both compounds are constitutional isomers with each other C Both compounds have different molecular formula D Both compounds undergo different chemical reaction.
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 53 9. How many isomers are possible for an organic compound with a molecular formula of C3H6? A 5 B 4 C 3 D 2 10. The following structures have the same molecular formula except A CH3CH2CH2CH2(OH)CH3 B CH3CH2CH2CH2CH2OH C CH3CH2CH(OH)CH2CH3 D CH3CH2CH2CH2CHO 11. Which of the following molecular formula represent a carbonyl compound? A C4H10O B C4H8O C C4H8O2 D C4H8 12. The functional groups found in the following compound E are. A amine, alkoxy, carbonyl, carboxyl B amino, hydroxyl, ketone, alkoxy C amino, hydroxyl, carbonyl, carboalkoxy D amino, alkoxy, carbonyl, carboalkoxy 13. Based on the chemical equation, what is the type of reaction involve in the synthesis of compound A? A Elimination reaction B Substitution reaction C Addition reaction D Rearrangement reaction 14. A heterolytic cleavage occurs at the C-Cl bond of the following compounds. Which of the compounds will form the most stable carbocation? A CH3Cl B CH2(CH3)Cl C CH3CH(Cl)CH2CH3 D C(CH3)2ClCH2CH3 15. A free radical has…. A Unpaired electrons B Paired electrons C No electrons D Even number of electrons 16. Which statement is CORRECT about covalent bond cleavage? A Polar bond will be break symmetrically. B Carbocation is an intermediate formed from homolytic cleavage. C Heterolytic cleavage is a bond breaking of non-polar bond. D Free radicals are formed from homolytic cleavage. 17. All compounds consist of particular atoms in their molecules or group of atoms which is called as A Prominent group B Atom group C Functional group D Function group 18. Reaction in which replacement of one atom or group of atoms are involved is termed as A Addition B Elimination C Substitution D Oxidation
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 54 19. General formula for amine compounds is A RCH2 B R2CH C RNH2 D RCOOH 20. Uneven breaking of bond is? A Homolytic fission B Heterolytic fission C Binary fission D Multiple fission
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 55 CHAPTER 5 ALKANES
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 56 SUBJECTIVE PRACTICES 1. Draw the structure for each of the following compound: a) 3-ethyl-2,4-dimethylheptane b) 4-isobutyl-1,1-dimethylcyclohexane c) 1-ethyl-3-methylcyclopentane d) 3-cyclohexyl-2,2-dimethyloctane e) 5-sec-butyl-2,4-dimethylnonane f) 1-ethyl-3-iodocyclopentane ANSWER a) b) c) d) e) f)
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 57 2. Name the following compounds according to the IUPAC nomenclature. a) b) Answer: 3-methylhexane Answer: 3,3-diethylpentane c) d) Answer: 1,3-diethylcyclopentane Answer: 1-fluoro-2-iodo-4,5-dimethylcyclohexane e) f) Answer: 1-bromo-3-ethyl-1-methylcyclopentane Answer: 4-isopropyl-3,6-dimethyloctane 3. Draw all the structural formulae for alkanes with molecular formula C5H12 and give their IUPAC name. ANSWER
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 58 4. For each of the following pairs of compounds, select the substance which you expect to have a higher boiling point. Explain. a) hexane and decane b) pentane and octane c) pentane and 2-methylbutane d) hexane and 2,2-dimethylbutane ANSWER a) The molecular weight of decane is larger than hexane. The surface area in contact between decane molecules is larger than hexane. The van der Waals forces of attraction between decane molecules are stronger than hexane. More energy is needed to separate the decane molecules than hexane. Thus, decane has a higher boiling point than hexane. b) The molecular weight of octane is larger than pentane. The surface area in contact between octane molecules is larger than pentane. The van der Waals forces of attraction between octane molecules are stronger than pentane. More energy is needed to separate the octane molecules than pentane. Thus, octane has a higher boiling point than pentane. c) Pentane and 2-methylbutane have the same molecular weight. The branches in 2-methylbutane make the molecule more compact. The surface area in contact between 2-methylbutane molecules is smaller than pentane. The van der Waals forces of attraction between 2-methylbutane molecules is weaker than pentane. Less energy is needed to separate the 2-methylbutane molecules than pentane. Thus, pentane has a higher boiling point than 2-methylbutane. d) Hexane and 2,2-dimethylbutane have the same molecular weight. The branches in 2,2-dimethylbutane make the molecule more compact. The surface area in contact between 2,2-dimethylbutane molecules is smaller than hexane. The van der Waals forces of attraction between 2,2-dimethylbutane molecules is weaker than hexane. Less energy is needed to separate the 2,2-dimethylbutane molecules than hexane. Thus, hexane has a higher boiling point than 2,2-dimethylbutane. 5. Combustion of alkanes could occur at the condition of sufficient and insufficient oxygen. Write the chemical equation when 2-methylbutane reacts in d) excess oxygen e) limited oxygen ANSWER a) 5 12 2 2 2 C H O CO H O + → + 8 5 6 b) 5 12 2 2 5 12 2 2 11 5 6 2 11 10 12 2 C H O CO H O C H O CO H O + → + + → + @
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 59 6. 5 drops of chlorine in inert solvent was added to methane and the mixture was then exposed to sunlight. a) State the type of the reaction above. b) What is the function of sunlight in the reaction? c) Write the equation for the reaction. d) Write the mechanism for the reaction. ANSWER a) Free radical substitution reaction. b) Provide energy for the homolytic cleavage. c) d) Initiation step: Propagation step: Termination step:
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 60 7. Chlorination of alkanes is a very important process. Write the reaction mechanism of monochlorination of cyclohexane. ANSWER Initiation step: Propagation step: Termination step: 8. A mixture of propane and bromine is exposed to sunlight. a) State the type of reaction. b) What is the function of sunlight in the reaction? c) Give the observation of the reaction. d) What would happen if the mixture were kept in the dark at room temperature? ANSWER a) Free radical substitution reaction. b) To provide energy for the homolytic bond cleavage. c) Reddish brown colour of bromine decolourised. d) Reddish brown colour of bromine remains unchanged.
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 61 9. The structure of compounds I and II are shown below. CH3CH2CH(CH3)CH3 CH3C(CH3)2CH3 I II Which compounds have a lower boiling point. Explain. ANSWER Structure I and II have the same molecular weight. Structure II has more branches than I making the molecule more compact. The surface area in contact between structure II molecules is smaller than I. The van der Waals forces of attraction between structure II molecules is weaker than I. Less energy is needed to separate the structure II molecules than I. Thus, structure II has a lower boiling point than I. 10. The bromination of cyclobutane in the presence of ultraviolet light yields compound G. a) Give the structure and IUPAC name of compound G. b) State the type of reaction. c) Write the mechanism for the reaction. ANSWER a) Bromocyclobutane b) Free radical substitution reaction. c)
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 62 11. Monobromination of neopentane in the presence of light gives T. a) Write the balanced chemical equation for the complete combustion of neopentane. b) Write the chemical equation involved in forming T and suggest the structure. c) Show the mechanism for the formation of T. ANSWER a) 5 12 2 2 2 C H O CO H O + → + 8 5 6 b) c)
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 63 MCQ PRACTICES 1. Which of the following is a saturated hydrocarbon? A C2H4 B C6H11Cl C C5H8 D C4H10 2. How many structural isomers are possible for a substance having the molecular formula C4H10? A 1 B 2 C 3 D 4 3. Molecular formula of cyclopentane is A C5H8 B C5H10 C C5H12 D C5H5 4. The hydrocarbon, C5H12, contain a quaternary (4o ) carbon. What is the IUPAC name for this hydrocarbon? A pentane B 2-methylbutane C 2,2-dimethylpropane D 1,2-dimethylbutane 5. What is the reaction mechanism when cyclohexane reacts with Br2 in CCl4 under ultraviolet light present? A Electrophilic addition. B Electrophilic substitution. C Nucleophilic addition. D Free radical substitution. 6. Which of the following reagents can be used to distinguish between cyclohexane and cyclohexene? A Hydrogen B Chlorine water C Hydrogen bromide D Potassium permanganate (VII) in NaOH(aq) 7. A compound that is wrongly named 3,3,4- trimethylbutane should be correctly named as A 2-methylpentane B 3,3-dimethylpentane C 2-methylhexane D hexane 8. Which of the following is most probably a cyclic alkane? A C4H10 B C5H10 C C6H10 D C6H6 9. Which of the following reagents can be used to distinguish between an alkane and an alkene? I. Bromine water II. Liquid bromine III. Aqueous solution containing MnO4 - ions A I only B I and II only C II and III D I, II and III 10. In a free radical substitution reaction of alkanes, free radicals are formed at. A Initiation step. B Propagation step. C Termination step. D Hydrogenation step.
CHAPTER 5 ALKANES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 64 11. Arrange the following compounds in decreasing order of boiling point. 2-methylhexane, heptane, 2,2-dimethylpentane, 2,2,3-trimethylbutane A Heptane, 2-methylhexane, 2,2- dimethylpentane, 2,2,3-trimethylbutane B 2,2,3-trimethylbutane, 2,2- dimethylpentane, 2-methylhexane, heptane C 2,2-dimethylpentane, 2-methylhexane, heptane, 2,2,3-dimethylbutane D Heptane, 2-methylhexane, 2,2,3- dimethylbutane, 2,2-dimethylpentane 12. Which of the following reaction involves free radical substitution? A Halogenation of alkanes. B Dehydration of alcohols. C Hydration of alkenes. D Combustion of alkanes. 13. Alkanes undergo halogenation. It is an example of A substitution reaction. B addition reaction. C rearrangement. D elimination reaction. 14. Which of the following is the general formula of alkanes? A CnH2n+2 B CnHn+1 C CnH2n−1 D CnH2n+1 15. An alkane with 7 carbon atoms contains _______ hydrogen atoms. A 16 B 14 C 20 D 18 16. What is the type of reaction between propane and bromine? A Halogenation B Addition C Elimination D Substitution 17. What is the name of the following compound? A Cyclohexane B Hexane C Heptane D Hexene 18. Which of the following is not an alkane isomer with 6 carbon atoms? A Hexane B 2,3-dimethylbutane C 2,2-dimethylbutane D Neopentane 19. Cyclohexane, a hydrocarbon floats on water because A It is immiscible in water. B Its density is low as compared to water. C It is non-polar substance. D It is immiscible and lighter than water. 20. Which of the following has maximum boiling point? A 2,2,4-trimethylpentane B Octane. C 2,2,3,3-tetramethylbutane. D Butane
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 65 CHAPTER 6 ALKENES
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 66 SUBJECTIVE PRACTICES 1. Draw the structural formula for each of the following alkenes: a) 2,3-dimethyl-2-butene b) 4,5-dibromo-1-pentene c) trans-2-hexene d) cis-4-octene e) 1,2-dichlorocyclobutene f) trans-1-chloro-2-butene g) 3-methyl-2-pentene ANSWER a) b) c) d) e) f) g)
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 67 2. Give the IUPAC names for the following alkenes: a) CH3CH2CH=CH2 b) c) d) e) f) g) h) ANSWER a) 1-butene b) 2-methylpropene c) 2-methyl-2-hexene d) cis-3-heptene e) trans-3-heptene f) 3,5-dimethylcyclohexene g) 4-ethyl-2-nonene h) 1-ethyl-2-isopropylcyclopentena 3. The following names are incorrect. Suggest the correct names and give your reason(s). a) trans-3-pentene b) 2-methylcyclohexene ANSWER a) Start numbering the carbon from the end that gives lower number to the carbon-carbon double bond.
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 68 b) For cyclic structure, start numbering the carbon in the ring that gives lower number to the substituent. 4. Write the equation for the preparation of propene from a) 2-chloropropane b) Propanol ANSWER a) b) 5. Draw the structural formulae and name the major and minor products for the following reaction: ANSWER Structure A: Structure B: 6. a) Define Markovnikov's rule. b) Write an equation of the reaction between 2-methylpropene and hydrogen bromide to form the product. c) State the type of reaction involved. d) Write the mechanism that accounts for the formation of the product. ANSWER a) In the addition of hydrogen halides, HX to asymmetrical alkenes, the hydrogen atom attaches itself to the carbon atom (of the double bond) with the LARGER number of H atoms.
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 69 b) c) Electrophilic addition reaction. d) 7. Draw the structural formulae of the products formed when 1-butene reacts with each of the following reagents: a) HI b) H2, Pt c) HBr in the presence of H2O2 d) Br2 in CH2Cl2 e) Cl2 (aq) f) acidified water ANSWER a) b) c) d) e) f)
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 70 8. Draw the structural formulae of compounds A to O in the following reactions: a) b) c) d) e) f) g) h) i) j)
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 71 ANSWER a) Structure A: Structure B: b) Structure C: c) Structure D: d) Structure E: e) Structure F: f) Structure G: Structure H: g) Structure I: h) Structure J:
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 72 i) Structure M: Structure N: MnO2 (s) j) Structure O: 9. Propose a chemical test to differentiate between butane and butene. State the observation and write the reaction equation involved. ANSWER Test: Bromine test Observation: reddish-brown solution remains. Observation: reddish-brown solution decolourised. OR Test: Baeyer’s test Observation: purple solution remains. Observation: purple solution decolourised.
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 73 10. Compound A, C3H7OH is treated with concentrated sulphuric acid to give the only product B, C3H6. Compound B decolourises potassium permanganate solution and brown precipitate is formed. Bromination of B in different solvents give C, C3H6Br2 and D, C3H7OBr. a) Suggest the structural formulae of A, B, C and D. b) Write the chemical equations for all the reactions involved. c) Name the rule used in determining the structure of D. ANSWER a) A: CH3CH(OH)CH3 OR CH3CH2CH2(OH) B: CH3CH=CH2 C: CH3CHBrCH2Br D: CH3CH(OH)CH2Br b) c) Markovnikov’s rule.
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 74 11. By referring to the reaction scheme below e) Give the IUPAC name of compound X. f) Draw the structural formulae of compounds A to G. g) Suggest a test distinguish compound X from compound E. Write down the chemical equations and state the observations. ANSWER a) 1,3-dimethylcyclopentene b) A: B: C: D: E: F: G: X A B C D E F G
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 75 c) Test: Bromine test Observation: reddish-brown colour of bromine decolourised. Observation: reddish-brown colour of bromine remains unchanged. OR Test: Baeyer’s test Observation: purple colour of KMnO4 decolourised. Brown precipitate of MnO2 formed. Observation: purple colour of KMnO4 remains unchanged.
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 76 12. Outline the synthetic pathway for the formation of: a) 1,2-dibromocyclopentane from bromocyclopentane b) chlorocyclohexane from cyclohexanol ANSWER a) b)
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 77 MCQ PRACTICES 1. The IUPAC name for the following compound is … A. cis-3,4,6-trimethylhept-3-ene B. trans-3,4,6-trimethylhept-3-ene C. cis-2-ethyl-3,5-dimethylhex-2-ene D. trans-2-ethyl-3,5-dimethylhex-2-ene 2. By using Saytzeff’s rule, the most stable alkene is … A. (C2H5)2C=CH2 B. CH2=CHC4H9 C. (CH3)2C=C(CH3)2 D. C2H5CH=CHC2H5 3. Dehydration of an alcohol is shown below: The major product formed is … A B C D 4. When propene is oxidised by cold, dilute KMnO4 in NaOH solution, the product formed is … A. CH3CH(OH)CH3 B. CH3COCH3 C. CH3CH2CH2OH D. CH3CH(OH)CH2OH
CHAPTER 6 ALKENES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 78 To answer question 5 – 10, consider the following options: A B C D I only I and II II and III I, II and III 5. Cyclohexane and cyclohexene can be differentiated by using the following reagents except … I. NaOH (aq) II. Br2, CH2Cl2 III. cold KMnO4, OH6. Propene reacts with hydrogen halide, HX, according with the equation: Which of the following statement is/are correct? I. The intermediate is carbocation. II. The product forms follow Markovnikov’s rule. III. The rate of reaction increases in order: HCl < HBr < HI. 7. Choose the CORRECT statement(s) about anti-Markovnikov addition of propene. I. Platinum can be used to replace peroxides. II. The reaction does NOT occur with HCl in the presence of peroxide. III. The product is 2-bromopropane when it reacts with HBr in presence of peroxide. 8. Which compound(s) show(s) cis-trans isomerism? I. ClCH2CH=CHCH2Cl II. CH3CH2CH=CH2 III. (CH3)2C=C(CH3)2 9. 2-Methylbuta-1,3-diene can be polymerised to make synthetic rubber. The structure of the compound is … Which of the following statement(s) about 2-methylbuta-1,3-diene is/are CORRECT? I. It decolorizes bromine water. II. It undergoes electrophilic addition. III. It can be oxidized by cold alkaline potassium permanganate solution. 10. Which of the following reaction(s) is/are suitable in the preparation of but-2-ene? I. Dehydration of butan-2-ol. II. Dehydrohalogenation of 2-chlorobutane. III. Reaction of but-1-ene with acidified water.
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 79 CHAPTER 7 BENZENE & ITS DERIVATIVES
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 80 SUBJECTIVE PRACTICES 1. Describe the aromaticity of benzene. ANSWER It possesses a cyclic, planar and conjugated pi system. It contains (4n + 2) π electrons that obey Huckel’s rule. The π electrons are delocalised in the unhybridized p orbitals of the benzene ring. It has Kekule structure of benzene. 2. Classify the following molecules as aromatic or not aromatic. a) b) c) d) ANSWER a) Not aromatic b) Aromatic c) Aromatic d) Aromatic
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 81 3. Draw the structural formula for each of the following compounds. a) m-bromophenol b) p-methylbenzaldehyde c) o-nitrotoluene d) isopropylbenzene e) benzoic acid f) benzaldehyde ANSWER a) b) c) d) e) f) 4. Write the IUPAC name for the following compounds. a) b) c) d) ANSWER a) Benzyl chloride b) p-bromoiodobenzene @ 1-bromo-4-iodobenzene c) o-chlorobenzoic acid @ 2-chlorobenzoic acid d) 2-phenylbutanoic acid
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 82 5. Draw the structural formulae of compounds A to C in the following reactions. a) b) c) ANSWER a) b) c) 6. a) Give a complete equation for the chlorination reaction of benzene and cyclopentene. b) Both benzene and cyclopentene undergo different types of reaction. Explain. ANSWER a) b) Cyclopentene undergoes electrophilic addition, but benzene undergoes electrophilic substitution reaction. The delocalised pi electrons give special stability to benzene. In order to maintain its special stability (aromaticity), benzene undergoes electrophilic aromatic substitution reaction.
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 83 7. a) Give the IUPAC name for the following hydrocarbons: b) State the observation(s) and write the appropriate equation for the following experiments: A mixture of benzene, concentrated nitric acid and sulfuric acid was heated to 50-55oC and the reaction products were then poured into water. ANSWER a) 1,4-dimethylbenzene b) Equation: Observation: Formation of yellow oil.
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 84 MCQ PRACTICES 1. Organic compounds that contain benzene ring structure are known as A Covalent compounds. B Aromatic compounds. C Saturated compounds. D Aliphatic compounds. 2. Which of the following is not Huckel’s number? A 2 B 6 C 14 D 16 3. All of the following statements indicate aromaticity EXCEPT: A Completely conjugated π system. B Acyclic. C Planar geometry. D Obey Huckel’s rule. 4. Choose the correct statement. A Carbon to carbon bonds in benzene have the same bond length. B Cyclobutene has delocalized electrons. C C=C bond in cyclobutene is longer than C-C bond in butane. D All atoms in cyclobutene, pentane and benzene are planar. 5. Choose the correct statement for the reaction below. A It is an addition reaction. B The electrophile is H2SO4. C It is an electrophilic aromatic substitution. D HNO3 gains a pair of electrons. 6. What is the function of Lewis acid in halogenation of benzene? A It produces a nucleophile. B It produces an electrophile. C It initiates the formation of halogen radical. D It decreases the polarity of halogen molecule. 7. Toluene is prepared from benzene and bromomethane in the presence of iron (III) bromide. Which of the following is involved in this reaction? A Br+ B Br− C CH3 + D CH3 − 8. Name the mechanism involved in the above equation and write the formula of the attacking species. A Electrophilic addition, Br− B Electrophilic aromatic substitution, Br+ C Free radical substitution, Br • D Nucleophilic substitution, Br− 9. Which of the following compounds can undergo a substitution reaction with bromine under suitable condition? I. Hexane II. Benzene III. Toluene A All of the above. B I and II only. C I and III only. D I only.
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 85 10. Which reagent give isopropylbenzene as a product upon reaction with benzene? A (CH3)3CCl, AlCl3 B CH3CH2CH2Cl, AlCl3 C CH3CH2CH3(Cl)CH3, AlCl3 D (CH3)2CHCl, AlCl3 11. What is the compound formed when benzene undergoes Friedel-Crafts alkylation with methyl chloride and aluminium chloride? A Benzoic acid B Aniline C Methylbenzene D Phenol 12. Which of the following acids is NOT used in any benzene reactions? A AlCl3 B H2SO4 C FeBr3 D H3PO4 13. The correct IUPAC name for the structure in diagram below is A benzyl ethanol B benzyl propan-2-ol C 1-phenylpropan-2-ol D 2-phenylpropan-1-ol 14. The correct IUPAC name for the structure in diagram below is A o-dibromobenzene B m-dibromobenzene C p-dibromobenzene D o-ethylbenzoic acid 15. How would you synthesize the following reaction? A Conc. HNO3, conc. H2SO4, 50-55℃. B Conc. HNO3, conc. AlCl3, 50-55℃. C Conc. HNO3, conc. FeCl3. D Conc. HNO3, conc. CH2Cl2. 16. Which of the following statements represents the reaction? A The reaction is an electrophilic substitution reaction. B X and Y are uv light and Cl2 respectively. C X and Y are acidified potassium permanganate and heat. D The electrophile for this reaction is NO2 + . 17. The reaction below is known as A Friedel-Crafts acylation B Friedel-Crafts alkenylation C Friedel-Crafts nitration D Friedel-Crafts alkylation
CHAPTER 7 BENZENE & ITS DERIVATIVES Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 86 18. Which of the following compounds would react with hot acidified potassium permanganate to give benzoic acid? I. II. III. A All of the above. B I and II only. C I and III only. D I only. 19. The correct structural formula for 2- isopropylbenzaldehyde is A B C D 20. Which compound below is aromatic? A B C D
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 87 CHAPTER 8 ALCOHOLS
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 88 SUBJECTIVE PRACTICES 1. Classify the following compounds as primary, secondary, or tertiary alcohol and give their IUPAC names. (a) (d) (b) (e) (c) ANSWER a) 1° alcohol 2-ethyl-2-methyl-1-pentanol b) 3° alcohol 1-methylcyclopentanol c) 3° alcohol 2-methyl-2-butanol d) 1° alcohol 2,2-dimethyl-1-propanol e) 2° alcohol 4-methylcyclohexanol 2. Write the structural formulae of these compounds and classify them as primary, secondary or tertiary alcohols. a) Isopropyl alcohol b) Neopentyl alcohol ANSWER a) 2° alcohol b) 1° alcohol
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 89 3. The following names are incorrect. Draw the structural formulae and give the correct IUPAC names. a) 2-cyclobutanol b) 6-methyl-3-ethylcyclohexanol ANSWER a) Cyclobutanol b) 5-ethyl-2-methylcyclohexanol 4. Which of the following compound has a lower boiling point? Explain your answer. a) Ethanol and 1-pentanol b) Hexane and 1-hexanol c) Butane and 2-propanol ANSWER a) Intermolecular forces exist in both ethanol and 1-pentanol is hydrogen bonding. Ethanol has 3 carbon atoms but 1-pentanol has 5 carbon atoms. Ethanol has smaller size compared to 1-pentanol (stronger van der Waals forces). Boiling point of ethanol is lower. b) Intermolecular forces exist in 1-hexanol is hydrogen bonding. Intermolecular forces exist in hexane is van der Waals forces. Hydrogen bonding is stronger than van der Waals forces. Thus, hexane has a lower boiling point. c) Intermolecular forces exist in 2-propanol is hydrogen bonding. Intermolecular forces exist in butane is van der Waals forces. Hydrogen bonding is stronger than van der Waals forces. Thus, butane has a lower boiling point.
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 90 5. Which of the following compound is more soluble in water? Explain your answer. a) Ethanol and 1-pentanol b) 2-methyl-1-propanol and 1-hexanol c) 3-heptanol and 2-methyl-2-propanol ANSWER a) Ethanol has 2 carbon atoms and 1-pentanol has 5 carbon atoms. 1-pentanol is larger than ethanol. Thus, the alkyl group is larger too. The hydrophobic area in 1-pentanol molecules is larger than ethanol. Therefore, ethanol is more soluble in water. b) 1-hexanol has 6 carbon atoms and 2-methyl-1-propanol has 4 carbon atoms. 1-hexanol is larger, thus the alkyl group is larger too compared to 2-methyl-1-propanol. The hydrophobic area in 1-hexanol is larger than 2-methyl-1propanol. Therefore, 2-methyl-1-propanol is more soluble in water. c) 3-heptanol contains more carbon atom, thus the size is larger than 2-methyl-2-propanol. The alkyl group of 3-heptanol is larger causing the hydrophobic area is bigger compared to 2- methyl-2-propanol. Therefore, 2-methyl-2-propanol is more soluble in water. 6. Outline the following synthesis. Give reagents and reaction conditions. a) b) Cyclohexanol to 1,2-dichlorocyclohexane c) 1-butanol to 2-butanol d) Cyclobutanol to 1,2-cyclobutanediol ANSWER a) b)
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 91 c) d) 7. Write the complete equation for each of the following reactions: a) 2-butanol heated with acidified KMnO4 solution. b) 2-propanol heated with concentrated H2SO4. c) 2-methyl-1-propanol heated with acidified K2Cr2O7 solution. d) Ethanol with potassium. e) 1-hexanol reacts with PCC in CH2Cl2. f) Butene reacts with acidic water. ANSWER a) b) c) d) 3 2 3 2 2 1 2 CH CH OH K CH CH O K H − + + → + e) f)
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 92 8. Write a balanced chemical equation for the reactions between the following substances: a) Cyclohexanol and sodium b) Methanol and methanoic acid c) 2-propanol and ethanoic acid ANSWER a) b) c) 9. Write the equations to show the reaction (if any) of each of the following alcohols with hot acidified potassium dichromate (VI), KMnO4. a) 2-methyl-1-propanol b) 2-methyl-2-propanol c) 2-butanol ANSWER a) b) c)
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 93 10. Write the structural formulae of the organic compounds (if any) for the following reactions. a) 2 2 butanol NaOH − + ⎯⎯⎯→ I b) 2 2 1 propanol CH Cl − + ⎯⎯⎯→ PCC c) 2 2 7 2 methyl 2 butanol H K Cr O + − − − + ⎯⎯→ ANSWER a) b) c) No reaction (tertiary alcohol does not undergoes oxidation) 11. Describe how you would distinguish between 1-propanol and 2-propanol using Lucas test. ANSWER Add Lucas reagent to 1-propanol and 2-propanol. Then, shake the reaction mixture. 1-propanol is primary alcohol, and the solution does not turn cloudy after 10 minutes. 2-propanol is secondary alcohol. Cloudy solution formed within 5 to 10 minutes. Lucas test
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 94 12. Give a chemical test to distinguish between: a) 2-methyl-1-propanol and 2-methyl-2-propanol b) 3-pentanol and 2-butanol c) Methylcyclohexanol and 2-methylcyclohexanol ANSWER a) Lucas test b) Iodoform test c) Lucas test 13. Suggest chemical test(s) to distinguish the following pairs of compounds. Include the reagents, reaction conditions and observations. Write the equations involved. a) Cyclopentanol and 1-methylcyclopentanol b) 1-propanol and 2-methyl-2-propanol c) 2-butanol and 3-buten-2-ol d) Methanol and 2-propanol ANSWER a)
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 95 b) c)
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 96 d) 14. Consider the following reaction scheme. a) Draw the structures of compounds A, B, C, D, F, and G. b) State the rule used to determine the major products B. c) Give reagent E. ANSWER a) b) Saytzeff’s rule c) I2 , OH-
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 97 15. Based on the reaction below: a) Draw the structure of H. b) Name the test used in the above reaction. c) State your observation. ANSWER a) b) Lucas test. c) Cloudy solution is formed within 5 to 10 minutes. 16. When 2-butanol, J, is heated with concentrated sulphuric acid, a mixture of compounds K and L is formed while oxidation of J yields M. a) Give the structures of K, L and M. b) Suggest the oxidising agent to form M and give the IUPAC name of M. c) Name the reaction to convert J to mixture of compounds K and L. d) Suggest one-step reaction for the preparation of J from an alkene. e) Give the products formed when J reacts with i. Sodium ii. CH3CH2COOH , H+ , reflux ANSWER a) b) Oxidizing agent: KMnO4,H +, ∆ @ K2Cr2O7,H +, ∆ IUPAC name of M: butanone @ 2-butanone c) Dehydration of alcohols d)
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 98 e) i) ii) 17. A secondary alcohol P with molecular formula C6H12O undergoes oxidation to form ketone Q. Dehydration of alcohol P produces compound S and T. The structure of T is shown below. a) Draw the structures of P, Q, and S. b) Give the major product for dehydration of P. Name the rule used and explain how to determine the major product. c) Draw the structure of product when P is treated with ethanoic acid in the presence of H2SO4. d) State a test used to differentiate P from 1-methylcyclopentanol and give the reagent used in the test. ANSWER a) b) Saytzeff’s rule. In elimination reaction, the major product is the most stable alkene that gas greater number of alkyl group attached to the carbon-carbon double bond. c) d) Lucas test. Reagent: Concentrated hydrochloric acid in zinc chloride
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 99 18. a) Give a two-step preparation of 2-butanol from 1-butanol. b) Dehydration of 2-methyl-2-butanol gives a mixture of alkenes. i. Draw all the possible products form and write the chemical equation involved. ii. State the observation when 2-methyl-2-butanol is treated with hot acidified potassium dichromate. ANSWER a) b) i) b) ii) Orange colour of potassium dichromate remains unchanged (tertiary alcohol). 19. a) Give the products formed when 2-methyl-1-butanol reacts with the following reagents: i. PCC in CH2Cl2 ii. HCOOH, H2SO4, reflux iii. Na iv. conc HCl, ZnCl2 b) Suggest a reagent in a chemical test that can be used to differentiate between 1-propanol and 2-propanol. Give the observations and write the chemical equations involved. ANSWER a) i) a) ii)
CHAPTER 8 ALCOHOLS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 100 a) iii) a) iv) b) Lucas test. OR Iodoform test