Alkenes, Alkynes and Aromatic

Transcription

1 BIO-ORGANI EMISTRY (Organic hemistry for Biology Students) (SQBS 1603) Alkenes, Alkynes and Aromatic Dr Nik Ahmad Nizam Bin Nik Malek, BSc (Ind. hem.)(utm), MSc (hem)(utm), PhD (hem)(utm), A.M.I. Senior Lecturer, Department of Biotechnology and Medical Engineering Faculty of Biosciences and Medical Engineering

2 Functional groups What is functional group? Molecules possessing the same functional group belong to the same family of organic compounds. The chemical components that are added to the simple skeleton of an organic compound. To generate chemical diversity and functionality. ydrocarbon 2 Groups containing halogens Groups containing oxygen Groups containing nitrogen Groups containing phosphorus and sulfur

3 Functional groups hemical class Group Formula Structural Formula Prefix Suffix Alkane Alkyl R alkyl- -ane Alkene Alkenyl R 2 =R 2 alkenyl- -ene Alkyne Alkynyl R R' alkynyl- -yne Benzene derivative Phenyl R 6 5 RPh phenyl- -benzene Toluene derivative 3 Benzyl R RBn benzyl- 1- (substituent)tol uene

4 Alkenes Alkenes and alkynes Organic compounds that contain a carboncarbon double bond = ept-3-ene 4

5 Alkynes Alkenes and alkynes Organic compounds that contain a carboncarbon triple bond = ept-3-yne 5

6 Nomenclature (Alkenes) Find the base structure The longest chain that contains the largest possible number of double bonds. Naming suffix = ene (2 No. =:-diene, 3 No. =: -triene, 4 No. =: -tetraene and so on. 6 : 7 heptene

7 Nomenclature (Alkenes) Numbering start from the end closest to = heptene 7

8 Nomenclature (Alkenes) If there is substituent insert number before its name propyl Position propyl-1-heptene

9 Nomenclature (Alkenes) propyl ept-2,4-diene 2 1 Position 3 3-propyl-hept-2,4-diene

10 Nomenclature (Alkynes) IUPA or Systematic name Similar to the naming of alkenes But-2-yne 3-Methyl-hept-1-yne But-1-yne 5-Methyl-hept-3-yne 10 6-Methyl-octa-2,4-diyne 6-Methyl-oct-4-en-2-yne

11 ycloalkenes yclopropene yclobutene yclopentene yclopenta-1,3-diene yclohexene yclohexa-1,3-diene ycloheptene yclohepta-1,2,4- triene 11

12 Stereoisomers Stereoisomers posses the same atoms, which exhibits the same connectivity but the composite atoms are oriented differently in space. Different configuration. Differ only in the 3-dimensional arrangement of atoms. Two classes 1. Geometric (cis-trans) isomers. 2. Enantiomers But-2-ene But-2-ene But-2-ene 3 12

13 Geometric (cis-trans) isomers 3 3 But-2-ene But-2-ene 3 3 But-2-ene

14 Geometric (cis-trans) isomers A These two groups must be different from each other. B D And these two groups must also be different from each other. 14

15 Geometric (cis-trans) isomers 3 Methyl groups on the same side But-2-ene is-2-butene 3 is isomers 3 Methyl groups on the opposite side But-2-ene 3 Trans-2-butene Trans isomers 15

16 Reactions of Alkenes Addition reaction Reaction in which elements are added to a compound X Y X Y One bond is broken 2 single bonds are formed 16

17 Four addition reactions of alkenes Reactions of Alkenes 2 Metal catalyst ydrogenation X 2 X = l or Br X X alogenation X X ydrohalogenation 17 2 O 2 SO 4 O ydration

18 ydrogenation Addition of hydrogen catalyst by metal Alkene E.g. Pd Alkane 18

19 alogenation The addition of halogen (X 2 ) to an alkene X X X = l or Br X X Alkene Alkyl dihalide l 2 l l 19

20 ydrohalogenation The addition of X (X = l or Br) to an alkene -X Alkene X=l or Br X Alkyl halide l 20 l

21 ydrohalogenation Markovnikov s rule In the addition of X to an unsymmetrical alkene, the atom bonds to the less substituted carbon atom The carbon that has more s to begin with. 21

22 ydrohalogenation 3 l 3 or 3 Propene l 1-hloro-propane l 2-hloro-propane According to Markovnikov s rule 3 the atom bonds to the less substituted carbon atom (has more s ) Only product

23 ydration The addition of water ( 2 O) to an alkene -O 2 SO 4 O Alkene Alcohol -O 23 Ethene 2 SO 4 O Ethanol

24 ydration The hydration of unsymmetrical alkene follows markovnikov s rule 3 -O 3 or 3 Propene 2 SO 4 O Propan-1-ol O Propan-2-ol 24

25 Benzene and aromatic compounds Unsaturated hydrocarbons Benzene The simplest and widely known aromatic compound Six-membered ring and 3 double bonds. Molecular formula:

26 Resonance structures Benzene Lewis structure with the same arrangement of atoms but a different arrangement of electrons 26

27 Aromatic compounds and conjugated bonds ring structure of benzene created from the joint of atoms alternating - and = 27

28 Aromatic compounds and conjugated bonds Actually atoms are not joined by alternating - and =: But, by a network of bonds that fall halfway between single and double. So what is happening here? 28 ow can there be this special bond network?

29 Aromatic compounds and conjugated bonds 3 bonds containing 3 valence electrons from the central atom Each atom contributes 3 valence electrons to 3 single covalent 29 bonds The fourth valence electron occupies a p orbital

30 Aromatic compounds and conjugated bonds The p orbital on adjacent atoms overlap Two doughnut-shaped rings form a unique -bond above and below the benzene ring 30 The p orbitals of 6 atoms that form a benzene ring overlap to form an unusual pi ( ) orbital, which takes the form of two doughnut-shaped rings.

31 Aromatic compounds and conjugated bonds The valence electrons occupying the overlapping orbitals are not restricted to being associated with one or two specific atoms free to move anywhere within the doughnut-shaped bond 31

32 Aromatic compounds and conjugated bonds onjugated system Overlap of p-orbitals onjugation of bonds (to form a network of delocalized electrons) can occur wherever 2 double bonds are separated by one single bond. 32

33 Aromatic compounds and conjugated bonds 33

34 Aromatic compounds and conjugated bonds Resonance ybrid 34

35 Aromatic compounds and conjugated bonds Aromatic compounds in biological systems O O 2 N O 2 N O 2 2 Phenylalanine (amino acid) O tyrosine (amino acid) 35

36 Nomenclature Monosubstituted benzenes Name of substituents + benzene. l ethylbenzene butylbenzene chlorobenzene O 2 N 36 phenol IUPA name: hydroxybenzene aniline IUPA name: aminobenzene

37 Nomenclature Ortho Para Same disubstituted Benzene Meta 37

38 Nomenclature Disubstituted benzene X X X 1 Y ,2- or ortho- (o) 1,3- or meta- (m) Y Y 4 1,4- or para- (p)

39 Disubstituted benzene Example Nomenclature o-xylene 1,2-dimethylbenzene (IUPA) m-xylene 1,3-dimethylbenzene (IUPA) p-xylene 1,4-dimethylbenzene (IUPA) 39

40 Disubstituted benzene Example 2 3 Nomenclature ,2-Diethyl-benzene ortho-diethyl-benzene or o-diethyl-benzene 2 3 1,3-Diethyl-benzene meta-diethyl-benzene or m-diethyl-benzene 2 3 1,4-Diethyl-benzene para-diethyl-benzene or p-diethyl-benzene 40

41 Nomenclature Disubstituted benzene Different substituents alphabetize the name of the substituents. Br 3 l Bromo-2-chloro-benzene 1-Ethyl-3-methyl-benzene 41

42 Nomenclature Polysubstituted (Three or more substituents) benzenes 1. Assign the lowest set of number 2. Alphabetize the names of all the substituent 1 ethyl 1-ethyl-4-methyl-2-propylbenzene methyl 4 2 propyl 3 42

43 Nomenclature Polysubstituted (Three or more substituents) benzenes 1. The common root = aniline 2. Alphabetize the names of all the substituent 2,5-dichloroaniline l 2 3 N 2 1 l 4 aniline 5 43

44 Nomenclature Aromatic compounds with more than one ring Naphthalene 1,6-Dimethyl-naphthalene 1-Ethyl-2,6-dimethyl-naphthalene 44 Anthracene 3-Ethyl-1,10-dimethyl-anthracene

45 Reaction of aromatic compounds Aromatic compounds undergo substitution not addition Substitution A reaction in which an atom is replaced by another atom or a group of atoms. X X-Y -Y 45

46 Reaction of aromatic compounds No addition reaction for benzene = in Benzene = in alkene X X-Y Y 46

47 Reaction of aromatic compounds Three specific reactions hlorination -l Nitration -NO 2 Sulfonation -SO 3 47

48 Reaction of aromatic compounds l Benzene l l atalyze by Fel 3 Product: aryl halide l 48

49 Nitration NO 2 NO 3 atalyze by 2 SO 4 O Benzene Product: nitrobenzene 49

50 Sulfonation SO 3 SO 3 atalyze by 2 SO 4 Benzene Product: benzenesulfonic acid 50

51 REFERENES rowe, J., Bradshaw, T. and Monk, P. (2006), hemistry for the Biosciences: The Essential oncepts, Oxford University Press, Oxford. orton,.r., Moran, L.A., Scrimgeour, K.G., Perry, M.D. and Rawn J.D. (2006). Principles of Biochemistry, 4 th Edition. Pearson International Edition. Smith, J.G. (2010). General, Organic and Biological hemistry. McGraw-ill igher Education. Denniston, K.J., Toping, J.J. and aret, R.L. (2008). General, Organic and Biochemistry, 6 th edition. McGraw-ill igher Education.

52 MY PROFILE Dr Nik Ahmad Nizam Bin Nik Malek, BSc (Ind. hem.)(utm), MSc (hem)(utm), PhD (hem)(utm), A.M.I. Senior Lecturer, Department of Biotechnology and Medical Engineering, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia. Website: