O 鄰苯二甲酸酯(phthalate ester) OR OR' PAE O R, R’ = alkyl groups with 4-15 carbon atoms O OH 1 1 benzoic acid (苯甲酸) New Way Chemistry for Hong Kong A-Level Book 3A O OR OR' 鄰苯二甲酸酯(phthalate ester) Used as plasticiser Potential carcinogen O New car smell R, R’ = alkyl groups with 4-15 carbon atoms O OH OH 2 2 O ortho-phthalic acid benzene-1,2-dicarboxylic acid (鄰苯二甲酸) New Way Chemistry for Hong Kong A-Level Book 3A O OR OR' 鄰苯二甲酸酯(phthalate ester) Used as plasticiser Potential carcinogen O Endocrine disruption New car smell 3 3 New Way Chemistry for Hong Kong A-Level Book 3A O O CH3 O CH3 O dibutyl benzene-1,2-dicarboxylate space O O CH3 O CH3 O butyl pentyl benzene-1,2-dicarboxylate 4 4 space New Way Chemistry for Hong Kong A-Level Book 3A O OH O OH O OH OH O 5 5 isophthalic acid terephthalic acid meta-phthalic acid para-phthalic acid 間苯二甲酸 benzene-1,3dicarboxylic acid 對苯二甲酸 benzene-1,4dicarboxylic acid New Way Chemistry for Hong Kong A-Level Book 3A n HO O O C C OH n H + O H H C C H H O Ester linkage O O C C O H H C C H H O + n polyester (terylene) 6 New Way Chemistry for Hong Kong A-Level Book 3A (2n - 1)H 2O H CH2CH2 = ethene = ethylene O O C C O H H C C H H Polyethylene terephthalate PET or PETE 7 New Way Chemistry for Hong Kong A-Level Book 3A O n Isomerism 8 8 New Way Chemistry for Hong Kong A-Level Book 3A Isomerism Occurs when certain compounds, having the same molecular formula, exist in different forms. Isomers Compounds having the same molecular formula but different linkages or spatial arrangements of atoms 9 9 New Way Chemistry for Hong Kong A-Level Book 3A Isomerism Two main types of isomerism: 1. Structural isomerism – different linkages of atoms. 2. Stereoisomerism –different spatial arrangements of atoms 10 10 New Way Chemistry for Hong Kong A-Level Book 3A Isomerism Two main types of isomerism: 1. Structural isomerism – different linkages of atoms. Same molecular formula Different structural formulae 11 11 New Way Chemistry for Hong Kong A-Level Book 3A Isomerism 2. Stereoisomerism –different spatial arrangements of atoms Same molecular formula & structural formulae 12 12 New Way Chemistry for Hong Kong A-Level Book 3A Categories of Isomerism Optical isomerism p.24 13 13 New Way Chemistry for Hong Kong A-Level Book 3A Categories of Isomerism Stereoisomerism Geometrical isomerism Optical isomerism Diastereoisomerism Optical isomers that are NOT mirror images of each other 14 14 Enantiomerism Optical isomers that are mirror images of each other New Way Chemistry for Hong Kong A-Level Book 3A Structural Isomerism 15 15 New Way Chemistry for Hong Kong A-Level Book 3A 1. Chain isomerism due to the presence of different carbon skeletons. 16 16 New Way Chemistry for Hong Kong A-Level Book 3A 1. Chain isomerism 17 17 C6H14 p.2, Q.2 New Way Chemistry for Hong Kong A-Level Book 3A 1. Chain isomerism • Different physical properties b.p.: Straight-chain > branched-chain Reason : - larger surface area and thus stronger v.d.w. forces > 18 18 New Way Chemistry for Hong Kong A-Level Book 3A 1. Chain isomerism • Different physical properties m.p. : Symmetry of molecule Packing efficiency m.p. -20°C 19 19 > -136°C New Way Chemistry for Hong Kong A-Level Book 3A 1. Chain isomerism • Different physical properties Notes on ‘Bonding and Structure’ p.81, Q.61 -20°C 20 20 > -136°C New Way Chemistry for Hong Kong A-Level Book 3A Chain isomers have different physical properties. What about their chemical properties? Would they be different as well? Chain isomers have similar chemical properties because they have the same functional groups. 21 21 New Way Chemistry for Hong Kong A-Level Book 3A 2. Position isomerism Same carbon skeleton Different positions of functional groups 22 22 New Way Chemistry for Hong Kong A-Level Book 3A 2. Position isomerism e.g. Butan-1-ol and butan-2-ol (molecular formula: C4H10O) 23 23 New Way Chemistry for Hong Kong A-Level Book 3A Q.15 Are they position isomers ? Wrong ! They are chain isomers 24 24 New Way Chemistry for Hong Kong A-Level Book 3A 3. Functional Group Isomerism Due to the presence of different functional groups 25 25 New Way Chemistry for Hong Kong A-Level Book 3A Functional Group Isomerism H H H C C H H Alcohol H O H H C H O H Vs H Ether C2H6O 26 26 C New Way Chemistry for Hong Kong A-Level Book 3A H Functional Group Isomerism H H H C C H H O C Aldehyde H H H O H C C C H Vs H Ketone C3H6O 27 27 New Way Chemistry for Hong Kong A-Level Book 3A H Functional Group Isomerism H H H C C H H O C H OH Carboxylic acid H O C C O H Vs C H Ester C3H6O2 28 28 H New Way Chemistry for Hong Kong A-Level Book 3A H Position isomers Position isomers Chain isomers C5H10 29 29 New Way Chemistry for Hong Kong A-Level Book 3A Functional group isomers 30 30 New Way Chemistry for Hong Kong A-Level Book 3A 4. Metamerism Occurs when the functional group (-oxy or –carbonyl) interrupts the main carbon skeleton at different positions 31 31 New Way Chemistry for Hong Kong A-Level Book 3A 4. Metamerism e.g. Methoxypropane and ethoxyethane (molecular formula: C4H10O) 32 32 New Way Chemistry for Hong Kong A-Level Book 3A 4. Metamerism e.g. Pentan-2-one and pentan-3-one (molecular formula: C5H10O) can also be considered as position isomers 33 33 New Way Chemistry for Hong Kong A-Level Book 3A OH Position isomers C4H10O OH Chain isomers OH Position isomers 34 34 New Way Chemistry for Hong Kong A-Level Book 3A OH OH Position isomers C4H10O functional group isomers O O Metamers 35 35 New Way Chemistry for Hong Kong A-Level Book 3A OH 5. Tautomerism Occurs when functional group isomers are in dynamic equilibrium with each other. 36 36 New Way Chemistry for Hong Kong A-Level Book 3A 5. Tautomerism H OH C H C H H H C H ethenol C H ethanal enol – keto tautomerism 37 37 O New Way Chemistry for Hong Kong A-Level Book 3A 5. Tautomerism H OH C H C H H H ethenol O C H C H ethanal Enol is a structure with –OH attached directly to doubly-bonded C 38 38 New Way Chemistry for Hong Kong A-Level Book 3A 5. Tautomerism OH But-2-en-1-ol Not an enol Does not exhibit tautomerism 39 39 New Way Chemistry for Hong Kong A-Level Book 3A Q.16 H O H C H H H H O C H H Which one, the enol form or the keto form, is the stronger acid ? The enol form is the stronger acid because the H attached to the more electronegative O can be released as H+ more easily. 40 40 New Way Chemistry for Hong Kong A-Level Book 3A Q.16 H C C H O Less stable H H H C H H H More stable H O O H O C H H Less stable More stable stronger acid weaker acid The equilibrium position lies to the right 41 41 New Way Chemistry for Hong Kong A-Level Book 3A Stereoisomerism 42 42 New Way Chemistry for Hong Kong A-Level Book 3A Stereoisomerism occurs when compounds having the same structural formula show different spatial arrangements of atoms. 43 43 New Way Chemistry for Hong Kong A-Level Book 3A Stereoisomerism Two categories of stereoisomerism: 1. Geometrical isomerism 2. Optical isomerism 44 44 New Way Chemistry for Hong Kong A-Level Book 3A Stereoisomerism Geometrical Isomerism arises from restricted rotation about a C=C double bond. 45 45 New Way Chemistry for Hong Kong A-Level Book 3A cannot be inter-converted at lower temperatures 46 46 New Way Chemistry for Hong Kong A-Level Book 3A maximum overlap of pz orbitals minimum overlap of pz orbitals Rotation about the axis of a double bond through an angle of 90o results in the breaking of the π bond 47 47 New Way Chemistry for Hong Kong A-Level Book 3A Geometrical Isomerism - Criteria a c b d where a b and c d 48 48 New Way Chemistry for Hong Kong A-Level Book 3A E/Z notation If there are three or four different groups attached to the Cs of C=C double bond E/Z notation rather than the cis/trans notation is used to name the stereoisomers of a molecule. E : in opposition to trans Z : together cis http://en.wikipedia.org/wiki/Cahn-Ingold-Prelog_priority_rule 49 49 New Way Chemistry for Hong Kong A-Level Book 3A Q.17 H H H Cl 180 H Cl H H Rotate the molecular plane w.r.t. the axis by 180 The same a=b 50 50 New Way Chemistry for Hong Kong A-Level Book 3A Q.17 Cl H H Cl Cl H H Cl 180 The same a = b and c = d 51 51 New Way Chemistry for Hong Kong A-Level Book 3A Properties of Geometrical Isomers They have significantly different physical properties 1. 52 52 Cl Cl Cl H H H H Cl m.p. 80C 50C b.p. 60C 48C New Way Chemistry for Hong Kong A-Level Book 3A Zero net dipole moment Cl H Cl Cl H Cl H H van der Waals’ forces : cis > trans b.p. depends on v.d.w. forces ONLY b.p. : cis > trans 53 53 New Way Chemistry for Hong Kong A-Level Book 3A 54 54 Cl H Cl Cl H Cl H H more symmetrical less symmetrical Three planes of symmetry Two planes of symmetry New Way Chemistry for Hong Kong A-Level Book 3A Cl H Cl Cl H Cl H H more symmetrical higher packing efficiency less symmetrical lower packing efficiency m.p. is more affected by symmetry of molecules. m.p. : trans > cis 55 55 New Way Chemistry for Hong Kong A-Level Book 3A 2. m.p. 56 56 H COOH H H COOH HOOC 130C << New Way Chemistry for Hong Kong A-Level Book 3A COOH H 290C less extensive intermolecular hydrogen bond O OH O OH 57 57 intra-molecular hydrogen bond less extensive intermolecular hydrogen bond New Way Chemistry for Hong Kong A-Level Book 3A less extensive intermolecular hydrogen bond O OH weaker v.d.w. forces + lower packing efficiency O OH 58 58 much lower m.p. less extensive intermolecular hydrogen bond New Way Chemistry for Hong Kong A-Level Book 3A Some geometrical isomers exhibit significantly different chemical properties 1. 59 59 H COOH H H COOH HOOC K1 1.4102 mol dm3 K2 8.0107 mol dm3 COOH H >> 9.3105 mol dm3 < 3.6105 mol dm3 New Way Chemistry for Hong Kong A-Level Book 3A H+ H Formation of intra-molecular hydrogen bond helps to draw electrons from the –OH O Weakening O – H OH Ease of release of H+ O O 60 60 K1 : cis > trans New Way Chemistry for Hong Kong A-Level Book 3A O O K1 : cis >> trans OH O Furthermore, the -ve charge produced is stabilized by forming intra-molecular hydrogen bond. In other words, the conjugate base is stabilized 61 61 New Way Chemistry for Hong Kong A-Level Book 3A O O H O O O O H O O significant repulsion K2 : 62 62 repulsion is minimized trans >> cis New Way Chemistry for Hong Kong A-Level Book 3A Q.18 H COOH H H COOH HOOC COOH H Solubility in water (gram of solute per 100 g of water at 25°C) 78.8 0.7 Intra-molecular hydrogen bonds in cis-isomer reduce the extent of formation of intermolecular hydrogen bonds. Thus, water molecules can separate the acid molecules of the cis-isomer more easily solubility of the cis-isomer in water is higher 63 63 New Way Chemistry for Hong Kong A-Level Book 3A 2.Thermal dehydration of butenedioic acid O O O C HO H C HO C C O H 150°C -H2O H C O C C H H 250°C -H2O HO C C C C O O 250°C breaking and forming of bond by rotating by 180° about the axis of the C=C double bond 64 64 New Way Chemistry for Hong Kong A-Level Book 3A OH H plane-polarized light Light vibrating in ALL possible planes 65 65 Light vibrating in only ONE plane New Way Chemistry for Hong Kong A-Level Book 3A Optically active Optically active substance can rotate the plane of polarization of plane-polarized light Measured by a polarimeter. 66 66 New Way Chemistry for Hong Kong A-Level Book 3A Optically active Dextrorotatory(+) : clockwise (to the right) Laevorotatory(-): anti-clockwise (to the left) Is the above sample dextrorotatory ? 67 67 No. It is laevorotatory New Way Chemistry for Hong Kong A-Level Book 3A Optical activity arises from lack of symmetry asymmetry (不對稱) chirality (手性) E.g. A molecule with an sp3 carbon atom bonded to FOUR different groups 68 68 New Way Chemistry for Hong Kong A-Level Book 3A The molecule has no plane or axis or center of symmetry. It is asymmetric 69 69 New Way Chemistry for Hong Kong A-Level Book 3A mirror It is not superimposable with its mirror image It exhibits chirality 70 70 New Way Chemistry for Hong Kong A-Level Book 3A 71 71 New Way Chemistry for Hong Kong A-Level Book 3A OH OH C H C2H5 CH3 C2H5 H3C C H Enantiomers (對映異構體) Mirror images of each other Non-superimposable with each other Rotate plane-polarized light to the same extent but in opposite directions 72 72 New Way Chemistry for Hong Kong A-Level Book 3A OH OH C H C2H5 CH3 C2H5 H3C C H Enantiomers (對映異構體) The direction of optical rotation cannot be predicted from the structural formulae. It can only be determined experimentally. 73 73 New Way Chemistry for Hong Kong A-Level Book 3A OH OH C H C2H5 CH3 C2H5 H3C C Enantiomers (對映異構體) (+) or (-)butan-2-ol 74 74 New Way Chemistry for Hong Kong A-Level Book 3A H OH OH *C H C2H5 CH3 C2H5 H3C * C H *C is known as the chiral center or asymmetric centre Animation 75 75 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? sp3 hybridized C atoms each bonded to THREE identical H atoms Not asymmetric 76 76 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? sp2 hybridized C atoms are NOT chiral centers 77 77 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? The molecule can be cut into two identical halves by the molecular plane It has a plane of symmetry It is NOT asymmetric 78 78 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Br OH Br sp3 hybridized C atom bonded to three identical H atoms Not asymmetric 79 79 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Br OH Br sp3 hybridized C atom bonded to two identical Br atoms Not chiral 80 80 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Br OH Br sp3 hybridized C atom bonded to two identical H atoms Not chiral 81 81 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Br OH Br sp3 hybridized C atom bonded to two identical H atoms Not chiral 82 82 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Br Br sp3 hybridized C atoms bonded to three identical H atoms Not chiral 83 83 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Br Br sp3 hybridized C atom bonded to two identical CH3 groups Not chiral 84 84 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? H Br bromo ethyl Br 85 85 (1-bromoisopropyl) New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Br * Asymmetric Optically active (+) or (-) Br sp3 hybridized C atom bonded to four different groups 86 86 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? OH OH sp3 hybridized C atoms bonded to three identical H atoms Not chiral 87 87 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? OH OH sp3 hybridized C atoms bonded to four different groups 88 88 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? OH methyl hydroxy OH (1-hydroxyethyl) H 89 89 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? H OH methyl hydroxy OH 90 90 (1-hydroxyethyl) New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? OH * Two chiral centers but * optically inactive OH 91 91 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? HO HO OH OH free rotation about the axis of bond The molecule has a plane of symmetry Not asymmetric 92 92 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? HO OH Meso compound The optical rotation caused by the left chiral center is cancelled by the optical rotation caused by the right chiral center. 93 93 internal cancellation New Way Chemistry for Hong Kong A-Level Book 3A A meso compound is a compound whose molecules contain 2 or more asymmetric atoms but is optically inactive. 94 94 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? The same Two identical groups attached to the carbon Not asymmetric 95 95 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? The molecule has a plane of symmetry Not asymmetric 96 96 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? Not the same Br Br Four different groups attached to the carbon asymmetric 97 97 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? * * Optically inactive A meso compound 98 98 New Way Chemistry for Hong Kong A-Level Book 3A Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ? * * Optically inactive A meso compound 99 99 New Way Chemistry for Hong Kong A-Level Book 3A Properties of enantiomers Identical physical properties except their optical activities. m.p. 100 100 (+)butan-2-ol (-)butan-2-ol 99.5C 99.5C New Way Chemistry for Hong Kong A-Level Book 3A Properties of enantiomers Identical chemical properties except their reactions with optically active substances. 101 101 New Way Chemistry for Hong Kong A-Level Book 3A Racemic mixture (racemate) An equimolar mixture of a pair of enantiomers Opically inactive The clockwise rotation caused by the (+)isomer is cancelled by the anti-clockwise rotation caused by the (-)isomer external cancellation 102 102 New Way Chemistry for Hong Kong A-Level Book 3A Racemic mixture (racemate) The (+)isomer and (-)isomer are different structures One serves as the impurity of the other in a racemic mixture. A racemic mixture has a lower m.p. than its components. (+)butan-2-ol (-)butan-2-ol ()butan-2-ol m.p. 103 103 99.5C 99.5C New Way Chemistry for Hong Kong A-Level Book 3A <99.5C Identification of solid unknowns 1. By melting point determination Determine the m.p. of the unknown and compare the result with the m.p. of known compounds 104 104 New Way Chemistry for Hong Kong A-Level Book 3A Identification of solid unknowns 2. By mixed melting point determination (more reliable) Mix the unknown solid with a pure solid with known m.p. Determine the m.p. of the mixture and compare the result with the m.p. of the known solid. 105 105 New Way Chemistry for Hong Kong A-Level Book 3A Q.20 Different structures may have the same melting point. In mixed melting point determination, different structures with the same melting point behave as impurities to each other. 106 106 New Way Chemistry for Hong Kong A-Level Book 3A Structure determination of organic compounds from (i) molecular formula (ii) reactions of functional groups (chemical properties) (iii) physical properties (iv) Infra-red / Mass spectra 107 107 New Way Chemistry for Hong Kong A-Level Book 3A CxHyOwNz X(halo) H y z Index of unsaturation = x 1 2 2 1. Acyclic with single bonds ONLY IOU = 0 CH4 4 11 0 2 H H C H 108 108 New Way Chemistry for Hong Kong A-Level Book 3A H CxHyOwNz y z Index of unsaturated = x 1 2 2 1. Acyclic with single bonds ONLY IOU = 0 C2H6O 6 2 1 0 2 O OH 109 109 New Way Chemistry for Hong Kong A-Level Book 3A CxHyOwNz y z Index of unsaturated = x 1 2 2 1. Acyclic with single bonds ONLY IOU = 0 C2H6ClN 7 1 2 1 0 2 2 Cl H Cl + three more Cl NH2 110 110 NH2 New Way Chemistry for Hong Kong A-Level Book 3A C2H6ClN Cl H N N Cl N H 111 111 New Way Chemistry for Hong Kong A-Level Book 3A Cl 2. Acyclic with ONE double bond IOU = 1 C2H4 H 4 2 1 1 2 H C H 112 112 New Way Chemistry for Hong Kong A-Level Book 3A C H 2. Acyclic with ONE double bond IOU = 1 C2H4O 4 2 1 1 2 O H3C C OH C H 113 113 H H New Way Chemistry for Hong Kong A-Level Book 3A C H 2. Acyclic with ONE double bond IOU = 1 3 1 11 1 2 2 CH3O2N O H3C N HO O 114 114 O C NH2 New Way Chemistry for Hong Kong A-Level Book 3A OH NH HO N C H E/Z C OH H H 115 115 C H C OH O NH2 (+)/(-) O HO H2C H O O C * N N OH O H OH N O H3C O N New Way Chemistry for Hong Kong A-Level Book 3A CH3O2N 3. With ONE triple bond IOU = 2 C2H2 H 116 116 2 2 1 2 2 C C H New Way Chemistry for Hong Kong A-Level Book 3A 4. One cyclic IOU = 1 C6H12 117 117 12 6 1 1 2 New Way Chemistry for Hong Kong A-Level Book 3A THREE C=C bonds + ONE ring IOU = 4 C6H6 118 118 6 6 1 4 2 New Way Chemistry for Hong Kong A-Level Book 3A Q.21 o 180 o 180 H H sp hybridized carbon atoms in triple bond should take a linear shape. 119 119 New Way Chemistry for Hong Kong A-Level Book 3A Q.21 o 180 H sp hybridized carbon atoms in triple bond should take a linear shape. 120 120 New Way Chemistry for Hong Kong A-Level Book 3A o 180 Q.21 3 C 2 1 The carbon atom at the 2nd position, C2, is sp hybridized it takes a linear shape. Side-way overlap between py orbitals of C1 and C2 gives a bond between C1 and C2. Side-way overlap between pz orbitals of C2 and C3 gives another bond between C2 and C3. Systems with adjacent C=C bonds are less stable than conjugated systems due to a lack of delocalization of electrons. 121 121 New Way Chemistry for Hong Kong A-Level Book 3A Q.22(a) C3H6O 7 isomers ! 6 Index of unsaturation = 3 1 1 2 One C=O bond or one C=C bond O O 122 122 propanone 1 enol propanal 2 enols H New Way Chemistry for Hong Kong A-Level Book 3A Q.22(a) C=C + OH (1E)-prop-1-en-1-ol HO (1Z)-prop-1-en-1-ol OH OH Prop-1-en-2-ol OH prop-2-en-1-ol C=C + -O123 123 O methoxyethene New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) C3H6O2 24 isomers ! 6 Index of unsaturation = 3 1 1 2 One C=O bond or one C=C bond 124 124 New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) Carboxylic acid or ester O propanoic acid OH O O O 125 125 H methylethanoate ethylmethanoate O New Way Chemistry for Hong Kong A-Level Book 3A C=C + two -OH HO Should have ‘e’ for diol H Prop-1-ene-1,1-diol 1 HO H H 1 H OH Prop-2-ene-1,1-diol HO 126 126 Q.22(b) New Way Chemistry for Hong Kong A-Level Book 3A C=C + two -OH HO OH (1Z)-prop-1-ene-1,2-diol H HO H HO OH H OH (1E)-prop-1-ene-1,2-diol 127 127 Q.22(b) New Way Chemistry for Hong Kong A-Level Book 3A H H 128 128 Q.22(b) OH 1 Prop-2-ene-1,2-diol OH New Way Chemistry for Hong Kong A-Level Book 3A HO 3 Q.22(b) OH 1 H H HO H (1E)-prop-1-ene-1,3-diol 1 H 129 129 3 (1Z)-prop-1-ene-1,3-diol OH New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) C=C + OH + -O- HO H 1 O H HO O 1 H H HO H 1 130 130 H O 1-methoxyethenol (Z)-2-methoxyethenol (E)-2-methoxyethenol New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) C=C + oxy + -OH ethenyl oxy O OH (ethenyloxy)methanol 131 131 New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) C=O + OH O 1 OH 1-hydroxypropanone Ketone + alcohol ketol 132 132 New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) Aldehyde + alcohol aldol 1 HO O 3-hydroxypropanal H H 1 * H3C 133 133 O OH H O HO H 1 H * CH 3 (+) or (-)2-hydroxypropanal New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) Aldehyde + oxy 2 H O O 2-methoxyethanal 134 134 New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) ene + peroxy O OH prop-2-en-1-yl hydroperoxide peroxy O O 135 135 methyl (methylperoxy) (methylperoxy)ethene Ethenyl methyl peroxide New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) H ene + peroxy O OH H (1E)-prop-1-en-1-yl hydroperoxide H H O OH (1Z)-prop-1-en-1-yl hydroperoxide 136 136 New Way Chemistry for Hong Kong A-Level Book 3A Q.22(b) HO O H H prop-1-en-2-yl hydroperoxide 137 137 New Way Chemistry for Hong Kong A-Level Book 3A Q.22(c) C5H8 Alkyne : 3 Diene : 8 138 138 New Way Chemistry for Hong Kong A-Level Book 3A HC CH3 CH3 H3C H3C CH H3C 139 New Way Chemistry for Hong Kong A-Level Book 3A pentadienes H2C CH3 CH3 H2C H2C CH3 H2C CH2 H3C CH3 H3C C 140 New Way Chemistry for Hong Kong A-Level Book 3A C CH3 CH2 CH2 H3C 2-methylbuta-1,3-diene H3C C H3C 141 CH2 3-methylbuta-1,2-diene New Way Chemistry for Hong Kong A-Level Book 3A C5H8 Cycloalkene : 10 Bicyclic : 2 Spiro : 1 142 New Way Chemistry for Hong Kong A-Level Book 3A CH3 * 143 CH3 H3C * New Way Chemistry for Hong Kong A-Level Book 3A H3C H3C H3C CH3 CH3 H3C CH3 H3C * 144 CH3 H3C * New Way Chemistry for Hong Kong A-Level Book 3A bicyclo[2.1.0]pentane bicyclo[1.1.1]pentane spiro[2.2]pentane 145 New Way Chemistry for Hong Kong A-Level Book 3A