28 Functional groups,nomenclature and drawing organic compounds Worked example The following questions relate to the synthesis of aspirin,which is shown below. OH CO2H CHgCO2COCH3 phenol Co. B aspirin then H A (a)Draw the skeletal structure of phenol. (b)Give the IUPAC name for compound A. (c)Draw the skeletal structure for compound B. (d)Given that the IUPAC name of aspirin is 2-ethanoyloxybenzoic acid,draw the skeletal structure of aspirin. (e)Draw the skeletal structure of p-ethanoyloxybenzoic acid. Answer ( OH Phenol is introduced in Section2.4 Naming substituted benzenes introduced in Section2.4 (b)2-Hydroxybenzoi cid (acid group has a higher prority than an OH group) (c) (d) nes is 2-ethanoyloxy skeletal structures in Section25 CO.H benzoic acid (e) CO2H para position
Worked example The following questions relate to the synthesis of aspirin, which is shown below. phenol then H OH CH3CO2COCH3 CO2H CO2 aspirin A B (a) Draw the skeletal structure of phenol. (b) Give the IUPAC name for compound A. (c) Draw the skeletal structure for compound B. (d) Given that the IUPAC name of aspirin is 2-ethanoyloxybenzoic acid, draw the skeletal structure of aspirin. (e) Draw the skeletal structure of p-ethanoyloxybenzoic acid. Answer (a) OH (b) 2-Hydroxybenzoic acid (the carboxylic acid group has a higher priority than an OH group) (c) O O O (d) CO2H O O 2-ethanoyloxy benzoic acid (e) CO2H O O 4 1 or the para position Hint: Compound A is a derivative of benzoic acid Hint: Compound B is an acid anhydride Phenol is introduced in Section 2.4 Naming substituted benzenes introduced in Section 2.4 Acid anhydrides are introduced in Section 2.1 and skeletal structures in Section 2.5 Naming substituted benzenes is introduced in Section 2.4 and skeletal structures in Section 2.5 28 Functional groups, nomenclature and drawing organic compounds
Problems 29 Problems 1.Draw skeletal structures for each of the following compounds. Sections2.4 and2.5 、苓 utyD)cyclohexanone ex-4-cn one 8aa xypropane ①2， -Dihydroxybutanedioic acid(tartaric acid) (j)5-Methylhex-4-enal 2.Name the following compounds. Sections 2.4and 25 OH O HO HN -CO.E (a) 6 CN HO d
Problems 1. Draw skeletal structures for each of the following compounds. (a) 1-Bromo-4-chloro-2-nitrobenzene (b) Methyl 3-bromobutanoate (c) N-Methylphenylethanamide (d) 2-(3-Oxobutyl)cyclohexanone (e) Hex-4-en-2-one (f) 2-Buten-1-ol (g) 6-Chloro-2,3-dimethylhex-2-ene (h) 1,2,3-Trimethoxypropane (i) 2,3-Dihydroxybutanedioic acid (tartaric acid) (j) 5-Methylhex-4-enal 2. Name the following compounds. O H OH (a) H CO2Et 2N (b) HO (c) HO O CN (d) Br (e) HO (f) O N H (g) Cl O (h) N (i) O (j) Sections 2.4 and 2.5 Sections 2.4 and 2.5 Problems 29
30 Functional groups,nomenclature and drawing organic compounds 3.The following questions are based on the synthesis of the medicine ibuprofen, which is shown below. CHaCOCI1-(4-isobutylphenyl)ethanone AlCh isobutylbenzene 1-(1-chloroethyl)-4-isobutylbenzene B COz NaCN 、t.He24-sobutyphenyipropanenine ibuprofen Section2.2 (a)Label each carbon atom in the isobutyl group as either a primary. Sections 2.4 and 2.5 4.Chlorphenamine G is an antihistamine used in the treatment of allergic conditions.It can be prepared using the 3-step approach shown below. 2-(4-chlorophenyl)ethanenitrile NaNH2 then N CN CI E N NaNH2 the chlorphenamine NC G (a)Draw a skeletal structure for compound D. Section2.4 (b)Give the IUPAC name of E. Sections2.5 and2.1 (c)Draw a skeletal structure for compound F.Is F a primary,secondary or tertiary amine? Section2.4 (d)Given that the IUPAC name of chlorphenamine(G)is N.N-dimethyl-3- phenyl-3-(pyridin-2-yl)propan-1-amine).draw a skeletal structure of G
3. The following questions are based on the synthesis of the medicine ibuprofen, which is shown below. isobutylbenzene 1-(4-isobutylphenyl)ethanone 1-(1-chloroethyl)-4-isobutylbenzene 2-(4-isobutylphenyl)propanenitrile CO2H A B C CH3COCl AlCl3 1. NaBH4 then H+ 2. HCl NaCN H+, H2O ibuprofen (a) Label each carbon atom in the isobutyl group as either a primary, secondary, tertiary or quaternary carbon atom. (b) Give the IUPAC name of CH3COCl. (c) Draw skeletal structures for compounds A, B and C. (d) Give the IUPAC name of ibuprofen. 4. Chlorphenamine G is an antihistamine used in the treatment of allergic conditions. It can be prepared using the 3-step approach shown below. Cl N E NaNH2 then Cl CN N NaNH2 then ClCH2CH2NMe2 NC N NMe2 F D 2-(4-chlorophenyl)ethanenitrile G H2SO4 chlorphenamine (a) Draw a skeletal structure for compound D. (b) Give the IUPAC name of E. (c) Draw a skeletal structure for compound F. Is F a primary, secondary or tertiary amine? (d) Given that the IUPAC name of chlorphenamine (G) is N,N-dimethyl-3- phenyl-3-(pyridin-2-yl)propan-1-amine), draw a skeletal structure of G. Sections 2.4 and 2.5 Section 2.2 Section 2.5 Section 2.4 Sections 2.5 and 2.1 Section 2.4 30 Functional groups, nomenclature and drawing organic compounds
Stereochemistry Key point.The spatial arrangement of atoms determines the stereochemistry.and hence the shape,of organic molecules.When different shapes of the same molecule are interconvertable on rotating a bond,they are called conformational isomers.In contrast,configurational isomers cannot be interconverted without breaking a bond and examples include alkenes and isomers with chiral centres. which rotate plane-polarised light. HH OH The R-isomer of 2-hv cid ethane (CH3-CHa) (D(actic acid) 3.1 Isomerism Iso nbers and kinds of atoms.but they Isomers may have different carbon y that the omegd.The presenceof skeletons,different functional merism (constitutional)isomers are compounds which have the sam ular toms joined together in a different way. They have different physical and chemical properties
3 Stereochemistry Key point. The spatial arrangement of atoms determines the stereochemistry, and hence the shape, of organic molecules. When different shapes of the same molecule are interconvertable on rotating a bond, they are called conformational isomers. In contrast, configurational isomers cannot be interconverted without breaking a bond and examples include alkenes and isomers with chiral centres, which rotate plane-polarised light. H H H H H H Newman projection of the staggered conformation of ethane (CH3–CH3) CO2H The E–isomer of but-2-enoic acid OH CO2H H The R–isomer of 2-hydroxypropanoic acid (D–(–)-lactic acid) 3.1 Isomerism Isomers are compounds that have the same numbers and kinds of atoms, but they differ in the way that the atoms are arranged. The presence of different isomers is called isomerism. Structural (constitutional) isomers are compounds which have the same molecular formula, but have the atoms joined together in a different way. They have different physical and chemical properties. Isomers may have different carbon skeletons, different functional groups, or the same functional groups at different positions Keynotes in Organic Chemistry, Second Edition. Andrew F. Parsons. 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd
32 Stereochemistry Examples:chain isomers.position isomers and functional group isomers CH3 HaC-C-CH3 and HjC-CH2-CH2-CH3 Both CaHao 日 tranche na chain isomers OH -CH3 and HaC-CHz-CH2-OH OH Diethyl ether is a common Both HaC-C-CH3 and HaC-CH2-O-CHz-CHa CHa functional groups 2e83 Conformational isomers (conformers)are different shapes of the same mole- cule resulting from rotation around a single bond,such as C-C.They are not different c unds (i.e.they have the sa physical and chemical properties) and are readily interconvertable(Section 3.2). rs have the same molecular formula and,although the (withresp are not readily inter 3.2 Conformational isomers The different ar ments of atoms used by rotation about a single bond are called conformations.A confo mati al iso conform s or Newman projection 3.2.1 Conformations of ethane(CH3CH3) Rotation about the C-C bond produces two distinctive conformations. Eclipsed conformation-C-H bonds on each carbon atom are as close as possible
Examples: chain isomers, position isomers and functional group isomers C CH3 H3C CH3 H H3C CH2 CH2 CH3 2-methylpropane (branched chain) butane (straight chain) and C OH H3C CH3 CH3 H3C CH2 O CH2 2-methylpropan-2-ol (tertiary alcohol) diethyl ether (ether) and Both C4H10 but different carbon skeleton: chain isomers C OH H3C CH3 H H3C CH2 CH2 OH propan-2-ol (secondary alcohol) propan-1-ol (primary alcohol) and Both C3H8O but different position of the functional group: position isomers CH3 Both C4H10O but different functional groups: functional group isomers Conformational isomers (conformers) are different shapes of the same molecule resulting from rotation around a single bond, such as CC. They are not different compounds (i.e. they have the same physical and chemical properties) and are readily interconvertable (Section 3.2). Configurational isomers have the same molecular formula and, although the atoms are joined together in the same way, they are arranged differently in space (with respect to each other). They are not readily interconvertable (Section 3.3). 3.2 Conformational isomers The different arrangements of atoms caused by rotation about a single bond are called conformations. A conformational isomer, or conformer, is a compound with a particular conformation. Conformational isomers can be represented by Sawhorse projections or Newman projections. 3.2.1 Conformations of ethane (CH3CH3) Rotation about the CC bond produces two distinctive conformations. Eclipsed conformation–CH bonds on each carbon atom are as close as possible. Naming organic compounds is introduced in Section 2.4 Functional groups are discussed in Section 2.1 Position isomers are often called regioisomers (Section 4.8) Diethyl ether is a common solvent in organic synthesis (Section 8.3.4.2) Conformational isomers are sometimes called rotamers 32 Stereochemistry