IBDP Chemistry: Functional Groups Questions PDF

IB DP Chemistry 37 mins 37 questions Multiple Choice Questions Functional Groups: Classification of Organic Compounds Representing Formulas of Organic Compounds / Functional Groups / Homologous Series / IUPAC Nomenclature / Structural Isomers Easy (13 questions) /13 Scan here to return to the course or visit savemyexams.com Medium (14 questions) /14 Hard (10 questions) /10 Total Marks /37 © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 1 Easy Questions 1 Which of the following shows the correct order of boiling points for pentane, butane and propane? A. CH3CH2CH3 > CH3CH2CH2CH3 > CH3CH2CH2CH2CH3 B. CH3CH2CH2CH2CH3 > CH3CH2CH2CH3 > CH3CH2CH3 C. CH3CH2CH2CH3 > CH3CH2CH2CH2CH3 > CH3CH2CH3 D. CH3CH2CH3 > CH3CH2CH2CH2CH3 > CH3CH2CH2CH3 Answer The correct answer is B because: The strength of the intermolecular forces increases with the size of the molecule Therefore the molecule with the highest relative molecular mass will have the highest boiling point CH3CH2CH2CH2CH3 = 72 g mol-1 CH3CH2CH2CH3 = 58 g mol-1 CH3CH2CH3 = 44 g mol-1 Therefore pentane, CH3CH2CH2CH2CH3, will have the highest boiling point A, C & D are incorrect as these are not the correct order of increasing boiling points (1 mark) 2 Which pairs of homologous series do not have the same C:H ratio in their general formulae? A. aldehydes and ketones B. alkanes and alkenes C. carboxylic acids and esters D. alkenes and aldehydes © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 2 Answer The correct answer is B because: A homologous series is a group with the same functional group and similar chemical properties Alkanes and alkenes are different homologous series as they have a different functional group Alkanes have single carbon-carbon bonds and the general formula CnH2n+2 Alkenes have a double carbon-carbon bond and the general formula CnH2n A is incorrect as aldehydes and ketones both have the general formula of CnH2nO and so have the same C:H ratio C is incorrect as the general formula for carboxylic acids is CnH2n+1COOH. The general formula for an ester is R’COOR”. An ester is a carboxylic acid with the -OH of the carboxyl group replaced with a hydrocarbon chain. The C:H ratio is the same. D is incorrect as alkenes and aldehydes have the same carbon-hydrogen ratio in their general formula. Alkenes have the general formula CnH2n and aldehydes CnH2nO (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 3 3 Which of the following molecules are hydrocarbons? A. All B. 1 and 2 C. 1, 2 and 3 D. 2, 3 and 4 Answer The correct answer is B because: A hydrocarbon is a molecule with only carbon and hydrogen Molecule 1 shows a skeletal structure which only contains hydrogen and carbon; we know this as there are no other elements shown in the molecule Molecule 2 shows the displayed formula of a hydrocarbon A, C and D are incorrect as molecules 3 and 4 contain other elements (1 mark) 4 What is the correct formula for 1-fluoro-3-methylbut-2-ene? © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 4 A Molecular CH2FCH2C(CH3)CH3 B Empirical C5H9F C Displayed D Skeletal Answer The correct answer is B because: When naming a chemical using the IUPAC rules, the following steps are used: 1. Find the longest chain of carbons; this is the parent chain 2. Identify all the groups (substituents) coming off the parent chain 3. Number the carbons from the end that give the substituents the lowest numbers 4. If there are two or more substituents, they are listed in alphabetical order using the base name (ignore prefixes such a di or tri) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 5 The structures of 1-fluoro-3-methylbut-2-ene are: molecular skeletal displayed A is incorrect as this is not a correct formula as there are 10 H shown in the structure C is incorrect as the longest chain is 5 carbons so it is pentene not butene and the double bond is located in the wrong position D is incorrect as This skeletal formula is not showing the fluorine or the double bond, and the branch is from the wrong carbon (1 mark) 5 Considering only structural isomers, what is the number of alcohols of each type with the formula C5H12O? primary secondary tertiary A 3 3 2 B 4 2 2 C 4 3 1 D 5 2 1 Answer The correct answer is C because: © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 6 The structural isomers are primary, secondary and tertiary alcohols There are four primary alcohols There are three secondary alcohols There is one tertiary alcohol © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 7 (1 mark) 6 Which of the following is the displayed formula for ethylamine? Answer The correct answer is A because: ‘Ethyl’ means that the carbon chain consists of two carbon atoms ‘-amine’ means that the -NH2 group is located at the end of the alkyl chain Therefore, compound A is the primary amine ethylamine B is incorrect as this compound is methylamine and consists of only one carbon atom instead of two © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 8 C is incorrect as this compound is a secondary amine dimethylamine (two methyl groups attached to an amine group), and although it has two carbons, they are not in a chain. This compound is an isomer of ethylamine D is incorrect as this compound is a tertiary amine trimethylamine consisting of three carbon atoms instead of two but not in a chain (1 mark) 7 Identify which of the hydrocarbons shown below does not belong in the same homologous series as the other compounds A. C5H12 B. C6H12 C. C7H16 D. C8H18 Answer The correct answer is B because: Compounds which belong to the same homologous series have the same general formula The general formulas of the three common families of hydrocarbons are Alkanes CnH2n+2 Alkenes CnH2n Alkynes CnH2n-2 In this case C6H12 fits the general formula for an alkene A, C and D are incorrect as they all fit the general formula for an alkane (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 9 8 Identify the functional group that is ringed in the molecule shown below: A. hydroxyl B. carboxyl C. ether D. carbonyl Answer The correct answer is D because: A C=O group is a carbonyl group, which can be a ketone or an aldehyde The generic formula is R-CO-R’, where R’ is an alkyl group (the molecule is a ketone) or R’ is a hydrogen (then the molecule is an aldehyde) A is incorrect as a hydroxyl group is -OH B is incorrect as a carboxyl group is -COOH C is incorrect as an ether is C-O-C, with only single bonds between the atoms (1 mark) 9 What is the IUPAC name of the following molecule? © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 10 A. 2-chloro-3-ethylbutane B. 3-methyl-4-chloropentane C. 2-ethyl-3-chlorobutane D. 2-chloro-3-methylpentane Answer The correct answer is D because: The naming rules begin with the longest carbon chain In this case, the longest chain is five, so the molecule root is pentane You then count the side groups and designate their position with the lowest number possible along the carbon chain The -CH3 group is a methyl group The -Cl is a chloro group 2-chloro and 3-methyl would give the smallest numbers possible in the name A is incorrect as the longest chain is 5 not 4, so it is not a butane © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 11 B is incorrect as the numbers do not give the lowest combinations of the positions of the side groups along the chain C is incorrect as the longest chain is 5 not 4, so it is not a butane (1 mark) 10 What is the IUPAC name of the following molecule? A. 3,3-dimethylpropanoic acid B. 1,1-dimethylpropanoic acid C. 3-methylbutanoic acid D. 2-methylbutanoic acid Answer The correct answer is C because: The naming rules begin with the longest carbon chain In this case the longest chain is four, so the molecule is a but- compound Identify any functional groups present and any side groups © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 12 In this case, the functional group is a carboxylic acid, so the molecule is derived from butanoic acid If there is a functional group like -COOH present, it takes priority in the numbering, so the carbon in -COOH is always the No.1 rather than No.4 carbon You then count the side groups and designate their position with the lowest number possible along the carbon chain, starting from -COOH The -CH3 group is a methyl group on the 3rd carbon (1 mark) 11 Which of the halogenoalkanes shown contains a secondary carbon atom? A. (CH3)2CHCH2Cl B. CH3(CH2)3CH2Cl C. (CH3)3CCl D. CH3CHClCH2CH3 Answer The correct answer is D because: The classification of the carbon atom depends on the number of carbons attached to the functional group carbon Primary have one carbon attached to the functional group carbon Secondary have two carbons attached to the functional group carbon Tertiary have three carbons attached to the functional group carbon © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 13 primary secondary tertiary A secondary carbon atom in a halogenoalkane has two more carbon atoms attached to the functional group carbon, along with the halogen atom This type of carbon is found in the middle of a chain A is incorrect as this molecule has a primary carbon atom B is incorrect as this also contains a primary carbon atom C is incorrect as this molecule contains a tertiary carbon atom (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 14 12 What is name of this compound applying IUPAC rules? A. Trans-pent-2-ene B. Trans-but-2-ene C. But-1-ene D. Cis-but-2-ene Answer The correct answer is D because: If the methyl groups in but-2-ene are on the same side of the C=C, we can class this as cis-but-2-ene Trans isomers have two functional groups on opposite sides of the double bond / carbon ring, i.e. one above and one below the C=C bond as shown in the following molecule © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 15 Trans-but-2-ene A is incorrect as the molecule contains 4 carbons in the chain, not 5 so cannot have the prefix 'pent' B is incorrect as the isomer is not a trans isomer C is incorrect as the molecule is an isomer of but-2-ene (1 mark) 13 Which pair are cis and trans isomers? A. © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 16 B. C. D. Answer The correct answer is D because Cis-1,2-dibromoethene and trans-1,2-dibromoethene are cis and trans isomers: A, B and C are incorrect as these molecules are not cis and trans isomers of each other (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 17 Medium Questions 1 Xylitol is an artificial sweetener used in toothpastes and chewing gum to improve their taste without impairing dental hygiene. Which functional groups could be produced if Xylitol is oxidised under suitable conditions? 1 alkene 2 aldehyde 3 carboxylic acid 4 ketone A. 1 only B. 2 only © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 18 C. 2, 3 and 4 D. 2 and 4 Answer The correct answer is C because: A primary alcohol has a hydroxyl group (-OH) attached to a saturated carbon atom that has only 1 other carbon atom attached to it Secondary alcohol has a hydroxyl group (-OH) attached to a saturated carbon atom that has 2 other carbon atoms Xylitol has both primary and secondary hydroxyl groups Primary alcohols are oxidised to aldehydes and carboxylic acids Secondary alcohols are oxidised to ketones (1 mark) 2 How many structural isomers are there of tribromopropane, C3H5Br3? A. 4 B. 5 C. 6 D. 7 Answer The correct answer is B because: Structural isomers have the atoms arranged in a completely different order These can be chain isomers (branched chains), position isomers (groups moved on the carbon skeleton) and functional group isomerism (different functional groups and a member of a different homologous series) The five isomers of C3H5Br3 are shown below: © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 19 (1 mark) 3 How many isomeric esters have the molecular formula C5H10O2? A. 4 B. 5 C. 9 D. 7 Answer The correct answer is C because: Structural isomers have the atoms arranged in a completely different order Isometric esters are esters with a different location of the functional group The possible isomers of C5H10O2 are shown below: © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 20 (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 21 4 Which features about the members of a homologous series are correct? I. all members have the same general formul II. the members have similar chemical properties III. the members show a gradual change in physical properties A. I and II only B. I and III only C. II and III only D. I, II and III Answer The correct answer is D because: A homologous series is a family of carbon compounds that share few characteristics These characteristics are The same general formula Similar chemical properties - notice the word is similar, not the same As the chain length increases, it can affect the reactivity of any functional groups present so the reactions can change subtly Gradually changing physical properties such as density, melting point and boiling point These properties are influenced by chain length so they will change as the chain gets longer (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 22 5 Octane is a component of petrol or gasoline. Which of the following molecules could be an isomer of octane? A. CH3CH2CHCHCHCH2(CH3)2 B. (CH3)2CHCH(CH2)2(CH3)2 C. CH3(CH2)5CH3 D. CH3CHCHCH(CH2)2(CH3)2 Answer The correct answer is B because: Octane is an alkane with eight carbon atoms It fits the general formula CnH2n+2 It has the specific formula C8H18 (CH3)2CHCH(CH2)2(CH3)2 has the molecular formula C8H18 A is incorrect as it has the molecular formula C8H16 C is incorrect as it has the molecular formula C7H16 D is incorrect as it has the molecular formula C8H16 (1 mark) 6 Give the name of the following molecule © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 23 A. 2,4,4,4-trimethylethylbutane B. 3,3,5-trimethylhexane C. 2,4,4-trimethylhexane D. 1,1,3,3-tetramethylpentane Answer The correct answer is C because: The longest chain is 6 carbons, so the molecule is derived from hexane There are three -CH3 methyl side groups so the correct prefix is trimethyl The numbers indicating the location of the side groups should be the lowest combination possible In this case one -CH3 is located on the second carbon, the other two on the fourth carbon, so the name is 2,4,4-trimethylhexane (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 24 7 How many branched-chain isomers are there which have the molecular formula C5H12? A. 2 B. 3 C. 4 D. 5 Answer The correct answer is B because: To work out possible isomers you need to start by making the longest chain Then reduce the chain length by one carbon and place a methyl group along the chain in different positions Shorten the chain again and place a second methyl group along the chain Be careful not to create a new chain with a larger number of carbons, or you will be repeating an isomer you have already drawn Here are the three isomers: © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 25 (1 mark) 8 Study the diagram below and determine which of the three statements are correct I. A suitable name is hex-4-ene II. The empirical formula is CH2 III. It is an isomer of cyclohexane A. I and II only B. I and III only © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 26 C. II and III only D. I, II and III Answer The correct answer is C because: The longest chain is 6 carbons so it is a hex- compound There is a double bond present, so it is an isomer of hexene The lowest number for the double bond is 3, so the molecule is hex-3-ene Hex-4-ene does not exist- it would be the same as hex-2-ene The molecular formula is C6H12, so the empirical formula is CH2 Alkenes have the same molecular formula as cycloalkanes with the same number of carbons (1 mark) 9 Which of the molecules shown below contains an aldehyde functional group? A. CH3CH2CH2OOCH3 B. CH3CH2CH2COCH3 C. CH3CH2OCH2CH3 D. CH3CH2CH2CH2CHO Answer The correct answer is D because: The aldehyde group consists of a carbon double-bonded to oxygen and to one hydrogen atom The structure of the group is written like this -CHO and is shown below © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 27 It seems a bit strange to write the H before the O in the formula of an aldehyde, but it is done so you don’t confuse an aldehyde -CHO, with an alcohol (hydroxyl group) -OH Be careful not to lose marks in a written exam by drawing the O and H the wrong way round (1 mark) 10 Which of the halogenoalkanes shown below contains a tertiary carbon atom? A. CH3CH2CH2Cl B. CH3CH2CH(CH3)Br C. C(CH3)3Cl D. CH3CHBrCH2CH3 Answer The correct answer is C because: The classification depends on the number of carbons attached to the functional group carbon atom This is the same for halogenoalkanes, alcohols and amines Primary have one carbon attached to the functional group carbon © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 28 Secondary have two carbons attached to the functional group carbon Tertiary have three carbons attached to the functional group carbon primary secondary tertiary A tertiary carbon atom in a halogenoalkane has three more carbon atoms attached to the functional group carbon The molecule C(CH3)3Cl contains a tertiary carbon (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 29 11 What would be the name of the following compound using IUPAC rules? A. pentane B. ethylpropane C. 2-methylbutane D. 3-methylbutane Answer The correct answer is C because: The naming rules begin with the longest carbon chain In this case the longest chain is four, so the molecule is derived from butane Look for any side groups, in this case there is a methyl group -CH3 Choose the lowest number along the chain for the location of the methyl group, which in this case is the second carbon © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 30 (1 mark) 12 Which two molecules are cis-trans isomers of each other? A. X and Z B. X and Y C. W and Y D. W and Z © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 31 Answer The correct answer is A because: Cis and trans isomers differ by having two of the same groups on the same side or opposite side of the plane of double bond The identical groups are ethyl CH3CH2 which are the same side in X and on opposite sides in Z B and C are incorrect as Y is not an isomer of X or W (Y is short of an ethyl group) D is incorrect as W and Z are the same molecule. If you flip W by 180o you get Z (1 mark) 13 What is this molecule called? A. Z-2-bromo-1-chloro-2-fluoroethene B. E-2-bromo-1-chloro-2-fluoroethene C. Z-1-bromo-2-chloro-1-fluoroethene D. E-1-bromo-2-chloro-1-fluoroethene Answer The correct answer is C because: Following the naming rules: The carbon skeleton is a derivative of ethene The lowest number combination for substituents is 1,1, 2 The halogens are named in alphabetical order The CIP rule is that the two atoms with the highest atomic numbers on the same side of the double bond is the Z isomer, in this case Br and Cl © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 32 A & B are incorrect as this does not give the lowest numbering combination D is incorrect as this is the right molecule, but the wrong E/Z isomer (1 mark) 14 What is the name of this molecule? A. cis-3-methyl-3-hexene B. trans-4-methyl-4-hexene C. cis-3-methyl-2-hexene D. trans-3-methyl-2-hexene Answer The correct answer is C because: Two methyl groups are on the same side of the double bond so this is a cis isomer The lowest number position for the double bond is 2, which makes the methyl group on the third carbon, so the molecule is cis-3-methyl-2-hexene It can also be named cis-3-methylhex-2-ene A is incorrect as this is not the lowest numbering combination © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 33 B is incorrect as this is not a trans isomer nor the lowest numbering combination D is incorrect as this is the right numbering but not the right isomer (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 34 Hard Questions 1 How many isomers, including structural and stereoisomers, with the formula C5H10 have structures that involve π bonding? A. 3 B. 4 C. 5 D. 6 Answer The correct answer is D because: There are 6 different isomers of C5H10 that involve π bonding (have a double bond). (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 35 2 Study the formulae shown below and determine which molecules are isomers of each other I. CH3(CH2)3CH2CH3 II. (CH3)2CHCH2CH3 III. CH3CH(CH3)CH2CH2CH3 A. I and II only B. I and III only C. II and III only D. I, II and III Answer The correct answer is B because: You need to count the atoms and find the molecular formula of each compound Molecules with the same molecular formula will be isomers of each other The molecular formulae are CH3(CH2)3CH2CH3 = C6H14 (CH3)2CHCH2CH3 = C5H12 CH3CH(CH3)CH2CH2CH3 = C6H14 The first and third molecules are isomers because they have the same molecular formula Be sure to count the atoms inside brackets very carefully as it is easy to forget multiples (1 mark) 3 What is the correct condensed structural formula for 2,2-dibromo-4-methylhexane? A. CH3CBr2CH(CH3)CH2CH2CH3 B. CH3CHBrCBr(CH3)CH2CH2CH3 © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 36 C. CH3CBr2CH2CH(CH3)CH2CH3 D. CH3CHBrCH(CH3)CHBrCH2CH3 Answer The correct answer is C because: For this type of question it's often easier to draw out the displayed structure of the molecule and then work out the correct structural formula Begin by drawing the carbon chain, hexane, in this case The side groups are two bromine atoms (from ‘dibromo’) which must be on the second carbon, and one methyl group (-CH3) on the fourth carbon CH3 CBr2 CH2 CH(CH3) CH2 CH3 Transpose the displayed formula into a condensed structural formula (1 mark) 4 What is the correct IUPAC name for the molecule shown? A. ethoxyethane © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 37 B. methoxyethane C. propanone D. propanal Answer The correct answer is B because: This molecule is an ether as it contains the C-O-C functional group Ethers are named according to the length of the two alkyl groups on either side of the oxygen The alkyl group joined to an oxygen is known as an group To the left of the oxygen is a methyl group and to the right is an ethyl group This molecule is named methoxyethane By convention the shorter chain comes first as the alkoxy group You need to learn all these functional groups: phenyl, hydroxyl, carbonyl, carboxyl, (carbox)amide, aldehyde, ester, ether, amine, nitrile, alkyl, alkenyl(alkene) and alkynyl(alkyne) and be able to recognise them from drawings or structural formulae (1 mark) 5 Which of the molecules shown below is not an isomer of pentan-2-ol? A. pentan-1-ol B. 2-methylbutan-2-ol C. 2-methylpentan-2-ol D. pentan-3-ol Answer The correct answer is C because: Pentan-2-ol will contain 5 carbon atoms, but 2-methylpentan-2-ol will contain 6 © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 38 carbon atoms, so it cannot be an isomer of pentan-2-ol A is incorrect as pentan-1-ol is a positional isomer of pentan-2-ol B is incorrect as 2-methylbutan-2-ol is a branch-chain isomer of pentan-2-ol D is incorrect as pentan-3-ol is a positional isomer of pentan-2-ol (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 39 6 Which of the following pairs are functional group isomers? I. CH3CH(OH)CH2CH2CH3 and CH3CH2CH(OH)CH2CH3 II. CH3CH2CH2COOH and HCOOCH2CH2CH3 III. CH3CH2CH2OH and CH3OCH2CH3 A. I and II only B. I and III only C. II and III only D. I, II and III Answer The correct answer is C because: The difference between CH3CH(OH)CH2CH2CH3 and CH3CH2CH(OH)CH2CH3 is that the hydroxyl group has been moved from the second to the third carbon atom, which is an example of positional isomerism CH3CH2CH2COOH and HCOOCH2CH2CH3 contain a carboxyl (-COOH) and ester (- COO-) group respectively. Carboxylic acids and esters with the same number of carbons oxygens and hydrogens are functional group isomers CH3CH2CH2OH and CH3OCH2CH3 contain a hydroxyl (-OH) and ether (-COC-) group respectively. Alcohols and ethers with the same number of carbons, oxygens and hydrogens are functional group isomers Functional group isomers have the same atoms present but a different arrangement of the atoms. They have different chemical and physical properties although they may be closely related, for example, many of the reactions of ketones and aldehydes are similar There are four pairs of functional group isomers that you should know and be able to recognise from drawings or structural formulae: alcohols and ethers; aldehydes and ketones; carboxylic acids and esters; and alkenes and cycloalkanes. (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 40 7 What is the correct name of the following molecule using IUPAC rules? A. propyl methanoate B. methyl propanoate C. methoxypropane D. butoxymethanal Answer The correct answer is A because: The molecule contains an ester group R-COO-R Esters are named according to the carbon chains on either side of the ester group They follow the nomenclature alkyl alkoxide R-COO-R’ R-COO = alkoxide R’ = alkyl In this case the alkyl group contains 3 carbons so it is a propyl group, CH3CH2CH2- The alkoxide group contains one carbon so it is a methanoate group, HCOO- This makes the molecule propyl methanoate © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 41 Careful: make sure you count the carbon in the alkoxide group as part of the carbon chain. It is a common mistake to forget this and name the ester incorrectly. For example, naming an ester incorrectly as methanoate instead of as ethanoate CH3-COO- H-COO- ethanoate methanoate (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 42 8 What types of isomerism can the following molecule show? I. Branch-chain II. Positional III. Functional group A. I and II only B. I and III only C. II and III only D. I, II and III Answer The correct answer is B because: This molecule contains a ketone group, R-CO-R so it will have an aldehyde R-CHO as a functional group isomer since aldehydes and ketones show functional group isomerism Moving the oxygen along the chain will only result in the same molecule, butan-2- one, as there are only four carbons so positional isomerism is not possible Branch-chain isomerism is possible, since when you create an aldehyde group, R- CHO, there are two possible ways to rearrange the carbon chain, one branched and one chain version Here are the two aldehydes © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 43 The test to see if you have truly drawn a new isomer is to try and name your new molecule. If you follow the correct naming rules you should not come up with the same name if it is an isomer (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 44 9 How many five ringed membered isomers are there of dimethyl cyclopentane? A. 3 B. 4 C. 5 D. 6 Answer The correct answer is C because: Stereoisomers are possible with dimethylcyclopentane with cis / trans or E / Z isomers being shown This is due to the fact in a cyclic compound, the bonds are not able to fully rotate The isomers are as follows 1,1-dimethylcyclopentane cis 1,2-dimethylcyclopentane trans 1,2-dimethylcyclopentane cis 1,3-dimethylcyclopentane trans 1,3-dimethylcyclopentane The distractor in this question is option A with 3 isomers as students can assume that stereoisomerism does not count with cyclic compounds A, B and D are incorrect as these are not the correct number of five-membered ring isomers of dimethylcyclopentane (1 mark) 10 Which structure is the correct cis trans isomer of trans-1,2-dibromocyclobutane? © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 45 A. B. © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 46 C. D. © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 47 Answer The correct answer is B because; The question asks for the cis isomer, not the trans isomer This is a classic example of why reading the question is so important Many students would opt for option C The cis isomer is option B as the bromine atoms are on the same sides of the bonds to one another The trans isomer is option C as the bromine atoms are on the opposite sides of the bonds to one another trans-1,2-dibromocyclobutane cis-1,2-ibromocyclobutane A is incorrect as the bromine atoms are on the same carbon so this would be 1,1- dibromocyclobutane C is incorrect as this is trans-1,2-dibromocyclobutane D is incorrect as the bromine atoms are on carbons 1 and 3 and on opposite sides of the ring so this would be trans-1,3-dibromocyclobutane (1 mark) © 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 48

IBDP Chemistry: Functional Groups Questions PDF

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