1、1,R, R = alkyl groups with 4-15 carbon atoms,鄰苯二甲酸酯(phthalate ester),PAE,benzoic acid (苯甲酸),2,R, R = alkyl groups with 4-15 carbon atoms,鄰苯二甲酸酯(phthalate ester),Used as plasticiser Potential carcinogen New car smell,ortho-phthalic acid benzene-1,2-dicarboxylic acid (鄰苯二甲酸),3,鄰苯二甲酸酯(phthalate ester),
2、Used as plasticiser Potential carcinogen Endocrine disruption New car smell,4,dibutyl benzene-1,2-dicarboxylate,butyl pentyl benzene-1,2-dicarboxylate,5,isophthalic acid meta-phthalic acid 間苯二甲酸,terephthalic acid para-phthalic acid 對苯二甲酸,benzene-1,3-dicarboxylic acid,benzene-1,4-dicarboxylic acid,po
3、lyester,(terylene),Polyethylene terephthalate,PET or PETE,8,Isomerism,9,Isomerism,Compounds having the same molecular formula but different linkages or spatial arrangements of atoms,Occurs when certain compounds, having the same molecular formula, exist in different forms.,Isomers,10,Two main types
4、of isomerism: Structural isomerism different linkages of atoms. Stereoisomerism different spatial arrangements of atoms,Isomerism,11,Two main types of isomerism: Structural isomerism different linkages of atoms.,Isomerism,Same molecular formula Different structural formulae,12,Stereoisomerism differ
5、ent spatial arrangements of atoms,Isomerism,Same molecular formula & structural formulae,13,Categories of Isomerism,14,Categories of Isomerism,Optical isomerism,Diastereoisomerism,Stereoisomerism,Geometrical isomerism,Enantiomerism,Optical isomers that are NOT mirror images of each other,Optical iso
6、mers that are mirror images of each other,15,Structural Isomerism,16,1. Chain isomerism,due to the presence of different carbon skeletons.,17,1. Chain isomerism,C6H14,p.2, Q.2,18,1. Chain isomerism,Different physical propertiesb.p. : Straight-chain branched-chainReason : - larger surface area and th
7、us stronger v.d.w. forces,19,1. Chain isomerism,Different physical properties,m.p. : Symmetry of molecule Packing efficiency m.p. ,20,1. Chain isomerism,Different physical properties,Notes on Bonding and Structure p.81, Q.61,21,Chain isomers have different physical properties. What about their chemi
8、cal properties? Would they be different as well?,Chain isomers have similar chemical properties because they have the same functional groups.,22,2. Position isomerism,Same carbon skeleton Different positions of functional groups,23,2. Position isomerism,e.g. Butan-1-ol and butan-2-ol (molecular form
9、ula: C4H10O),24,Q.15,Are they position isomers ?,They are chain isomers,25,3. Functional Group Isomerism,Due to the presence of different functional groups,26,Functional Group Isomerism,C2H6O,27,Functional Group Isomerism,C3H6O,28,Functional Group Isomerism,C3H6O2,29,Chain isomers,C5H10,30,31,4. Met
10、amerism,Occurs when the functional group (-oxy or carbonyl) interrupts the main carbon skeleton at different positions,32,4. Metamerism,e.g. Methoxypropane and ethoxyethane (molecular formula: C4H10O),33,4. Metamerism,e.g. Pentan-2-one and pentan-3-one (molecular formula: C5H10O),can also be conside
11、red as position isomers,34,Position isomers,Position isomers,C4H10O,35,Position isomers,Metamers,C4H10O,36,5. Tautomerism,Occurs when functional group isomers are in dynamic equilibrium with each other.,37,5. Tautomerism,ethenol ethanal,enol keto tautomerism,38,5. Tautomerism,ethenol ethanal,Enol is
12、 a structure with OH attached directly to doubly-bonded C,39,5. Tautomerism,Not an enol,But-2-en-1-ol,Does not exhibit tautomerism,40,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 relea
13、sed as H+ more easily.,Q.16,41,More stable,Less stable,The equilibrium position lies to the right,stronger acid weaker acid,Q.16,42,Stereoisomerism,43,Stereoisomerism,occurs when compounds having the same structural formula show different spatial arrangements of atoms.,44,Stereoisomerism,Two categor
14、ies of stereoisomerism: Geometrical isomerism Optical isomerism,45,Geometrical Isomerism,arises from restricted rotation about a C=C double bond.,Stereoisomerism,46,cannot be inter-converted at lower temperatures,47,Rotation about the axis of a double bond through an angle of 90o results in the brea
15、king of the bond,maximum overlap of pz orbitals,minimum overlap of pz orbitals,48,Geometrical Isomerism - Criteria,where a b and c d,49,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 s
16、tereoisomers of a molecule. E : in opposition to trans Z : together cis,http:/en.wikipedia.org/wiki/Cahn-Ingold-Prelog_priority_rule,50,Q.17,Rotate the molecular plane w.r.t. the axis by 180,The same a = b,51,Q.17,The same a = b and c = d,52,Properties of Geometrical Isomers,They have significantly
17、different physical properties,53,Zero net dipole moment,van der Waals forces : cis trans b.p. depends on v.d.w. forces ONLY b.p. : cis trans,54,more symmetrical less symmetrical,Two planes of symmetry,Three planes of symmetry,55,more symmetrical less symmetrical,m.p. is more affected by symmetry of
18、molecules. m.p. : trans cis,higher packing efficiency,lower packing efficiency,56,2.,m.p. 130C 290C,57,58,weaker v.d.w. forces + lower packing efficiency much lower m.p.,59,Some geometrical isomers exhibit significantly different chemical properties,1.,K1 1.4102 mol dm3 9.3105 mol dm3,K2 8.0107 mol
19、dm3 3.6105 mol dm3,60,Formation of intra-molecular hydrogen bond helps to draw electrons from the OH,Weakening O H Ease of release of H+ , K1 : cis trans,61,In other words, the conjugate base is stabilized,Furthermore, the -ve charge produced is stabilized by forming intra-molecular hydrogen bond.,K
20、1 : cis trans,62,significant repulsion,repulsion is minimized,K2 : trans cis,63,Solubility in water (gram of solute per 100 g of water at 25C),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
21、 acid molecules of the cis-isomer more easily solubility of the cis-isomer in water is higher,Q.18,64,2.Thermal dehydration of butenedioic acid,150C,250C,-H2O,-H2O,250C,breaking and forming of bond by rotating by 180 about the axis of the C=C double bond,65,plane-polarized light,66,Optically active
22、substance can rotate the plane of polarization of plane-polarized light Measured by a polarimeter.,67,Dextrorotatory(+) : clockwise (to the right) Laevorotatory(-): anti-clockwise (to the left),Is the above sample dextrorotatory ? No. It is laevorotatory,68,Optical activity arises from lack of symme
23、try asymmetry (不對稱) chirality (手性),E.g. A molecule with an sp3 carbon atom bonded to FOUR different groups,69,The molecule has no plane or axis or center of symmetry. It is asymmetric,70,It is not superimposable with its mirror image It exhibits chirality,mirror,71,72,Enantiomers (對映異構體),Mirror imag
24、es of each other Non-superimposable with each other Rotate plane-polarized light to the same extent but in opposite directions,73,Enantiomers (對映異構體),The direction of optical rotation cannot be predicted from the structural formulae. It can only be determined experimentally.,74,Enantiomers (對映異構體),(
25、+) or (-)butan-2-ol,75,*C is known as the chiral center or asymmetric centre,Animation,76,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,77,sp2 hybrid
26、ized C atoms are NOT chiral centers,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,78,The molecule can be cut into two identical halves by the molecular plane It has a plane of symmetry It is NOT asymmetric,Q.19 Indicate the as
27、ymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,79,sp3 hybridized C atom bonded to three identical H atoms Not asymmetric,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,80,sp3
28、 hybridized C atom bonded to two identical Br atoms Not chiral,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,81,sp3 hybridized C atom bonded to two identical H atoms Not chiral,Q.19 Indicate the asymmetric carbon atom(s) in ea
29、ch of the following molecules. Which of them is/are optically active ?,82,sp3 hybridized C atom bonded to two identical H atoms Not chiral,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,83,sp3 hybridized C atoms bonded to three
30、 identical H atoms Not chiral,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,84,sp3 hybridized C atom bonded to two identical CH3 groups Not chiral,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules.
31、 Which of them is/are optically active ?,85,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,86,sp3 hybridized C atom bonded to four different groups,*,Asymmetric Optically active,(+) or (-),Q.19 Indicate the asymmetric carbon at
32、om(s) in each of the following molecules. Which of them is/are optically active ?,87,sp3 hybridized C atoms bonded to three identical H atoms Not chiral,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,88,sp3 hybridized C atoms b
33、onded to four different groups,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,89,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,90,Q.19 Indicate the asymm
34、etric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,91,Two chiral centers but optically inactive,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,92,The molecule has a plane of symmetr
35、y Not asymmetric,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,93,The optical rotation caused by the left chiral center is cancelled by the optical rotation caused by the right chiral center.,Q.19 Indicate the asymmetric carbo
36、n atom(s) in each of the following molecules. Which of them is/are optically active ?,Meso compound,internal cancellation,94,A meso compound is a compound whose molecules contain 2 or more asymmetric atoms but is optically inactive.,95,Two identical groups attached to the carbon Not asymmetric,The s
37、ame,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,96,The molecule has a plane of symmetry Not asymmetric,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,9
38、7,Four different groups attached to the carbon asymmetric,Not the same,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,98,*,*,Optically inactive A meso compound,Q.19 Indicate the asymmetric carbon atom(s) in each of the followin
39、g molecules. Which of them is/are optically active ?,99,Optically inactive A meso compound,*,*,Q.19 Indicate the asymmetric carbon atom(s) in each of the following molecules. Which of them is/are optically active ?,100,Properties of enantiomers,Identical physical properties except their optical acti
40、vities.,101,Properties of enantiomers,Identical chemical properties except their reactions with optically active substances.,102,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-clockwis
41、e rotation caused by the (-)isomer,external cancellation,103,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.,104,Identification of solid unknowns,By me
42、lting point determinationDetermine the m.p. of the unknown and compare the result with the m.p. of known compounds,105,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
43、compare the result with the m.p. of the known solid.,106,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.,107,Structure determination of organic compounds,from (i) mol
44、ecular formula (ii) reactions of functional groups (chemical properties) (iii) physical properties (iv) Infra-red / Mass spectra,108,CxHyOwNz X(halo) H,Index of unsaturation =,Acyclic with single bonds ONLYIOU = 0,CH4,109,CxHyOwNz,Index of unsaturated =,Acyclic with single bonds ONLYIOU = 0,C2H6O,11
45、0,CxHyOwNz,Index of unsaturated =,Acyclic with single bonds ONLYIOU = 0,+ three more,111,C2H6ClN,112,2. Acyclic with ONE double bondIOU = 1,C2H4,113,2. Acyclic with ONE double bondIOU = 1,C2H4O,114,2. Acyclic with ONE double bondIOU = 1,CH3O2N,115,*,CH3O2N,E/Z,(+)/(-),116,3. With ONE triple bondIOU
46、= 2,C2H2,117,4. One cyclicIOU = 1,C6H12,118,THREE C=C bonds + ONE ring IOU = 4,C6H6,119,Q.21,sp hybridized carbon atoms in triple bond should take a linear shape.,120,sp hybridized carbon atoms in triple bond should take a linear shape.,Q.21,121,The carbon atom at the 2nd position, C2, is sp hybridi
47、zed 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.,Q.21,122,Q.22(a) C3H6O,Index of unsaturation =, One C=O bond or one C=C bond,propanone,propanal,7 isomers !,123,(1E)-prop-1-en-1-ol(1Z)-prop-1-en-1-olProp-1-en-2-olprop-2-en-1-olmethoxyethene,C=C + OH,
