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UNSATURATED HIDROCARBONS. Unsaturated hidrocarbons contains carbon-carbon double bonds. Alkene = olefin Alkyne = acetylene Aromatic compound = benzene.

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Presentation on theme: "UNSATURATED HIDROCARBONS. Unsaturated hidrocarbons contains carbon-carbon double bonds. Alkene = olefin Alkyne = acetylene Aromatic compound = benzene."— Presentation transcript:


2 Unsaturated hidrocarbons contains carbon-carbon double bonds. Alkene = olefin Alkyne = acetylene Aromatic compound = benzene ring


4  Alkena disebut juga olefin  Unsaturated hidrocarbon  Double bond  Pembentuk minyak  Rumus: C n H 2n

5 Sifat  BM alkena < BM alkana  Titik didih alkena < alkana  Berat jenis alkena < air  Tidak larut dalam air & larut dalam pelarut organik  Alkena lebih reaktif daripada alkana  Produksi alkena menghasilkan alkana & alkohol

6 Nomenclature (1) 1. Select the longest carbon-carbon chain that cantains the double bond. 2. Name the parent compound as you would an alkene but change the –ane ending to –ene; for example, propane is change to propene. CH 3 CH 2 CH 3 CH 3 CH=CH 2 Propane Propene

7 Nomenclature (2) 3. Number the carbon chain of the parent compound starting with the end nearer to the double bond. Use the smaller of the two numbers on the double-bonded carbon atoms to indicate the position of the double bond. Place this number in front of the alkene name; for example, 2-butene means that the carbon-carbon double bond is between carbon numbers 2 and 3.

8 Nomenclature (3) 4. Side chains and other groups are treated as in naming alkanes, by numbering and assigning them to the carbon atom to which they are bonded. College Chemistry_ch.22.2_p.551

9 Practice 1 : Write structural formulas of : 1. 2-pentene 2. 7-methyl-2-octene 3. 3-hexene 4. 4-ethyl-2-heptene 5. 3,4-dimethyl-2-pentene

10 Geometric Isomerism in Alkenes (1) Geometric isomer = isomer that differ from each other only in the geometry of the molecules and not in the order of their atoms.

11 Geometric Isomerism in Alkenes (2) Geometric isomers are also called cis-trans isomers. If the two chlorine atoms are locked on opposite sides of the double bond, it is known as the trans isomer. (trans : from latin meaning "across" - as in transatlantic). If the two chlorine atoms are locked on the same side of the double bond, it is known as the cis isomer. (cis : from latin meaning "on this side")

12 Geometric Isomerism in Alkenes (3)

13 Practise 2 Draw structural formulas and names for all the isomers of pentene, C 5 H 10. Identify all geometric isomers. Identify which one that have cis-trans isomers, and draw the cis-trans isomers.

14 Cycloalkenes A cycloalkene or cycloolefin is a type of alkene hydrocarbon which contains a closed ring of carbon atoms, but has no aromatic character. alkenehydrocarboncarbonatoms aromatic cyclopropene cyclobutene cyclopentene cycloheptene

15 Preparation of Alkenes Cracking/Pyrolisis Adalah pemanasan hidrokarbon jenuh pada suhu yang sangat tinggi dan dengan bantuan katalis silika-alumina Contoh: C 16 H 34  C 8 H 18 + C 8 H 16 alkane alkane alkene

16 Dehydration of Alcohols Alkohol dipanaskan pada asam sulfat terkonsentrasi Reaksi: Alkohol con.H2SO4 alkena + H 2 O Contoh: 

17 C – C – C – C +H2SO4 OH  C – C = C – C +H2O  C – C – C = C +H2O

18 Alkenes Physical Properties The first three alkenes are gases, the intermediate alkenes are liquids and higher members of the olefin series are wax like solids at room temperature. The alkenes are insoluble in water, but are soluble in organic solvents. The liquids and solids have a density less than water. Compound Formula MP BP Density o C o C (g/ml) Ethylene C 2 H Propene C 3 H Butene C 4 H

19 Chemical Properties of Alkenes (1) Combustion of Alkenes The alkenes are highly flammable and burn readily in air, forming carbon dioxide and water. C 2 H O 2  2 CO H 2 O

20 Chemical Properties of Alkenes (2) Addition: Addition of Hydrogen (hidrogenation) Addition of Halogen (halogenation) Addition of Hydrogen Halide Addition of Water

21 Chemical Properties of Alkenes (3) Addition Reactions across the Double Bond (oxidation) 3 H2C=CH KMnO H 2 O  2MnO 2 + 2KOH + CH 2 OHCH 2 OH Ethylene Glycol During the oxidation of alkenes, the purple colour of the permanganate solution disappears and the reaction constitutes a test, known as Baeyer's Test, to detect unsaturation in any compound.

22 Chemical Properties of Alkenes (4) Reaction with Sulphuric Acid Similarly, fuming sulphuric acid absorbs ethylene at room temperature to form ethyl hydrogen sulphate, with much evolution of heat. C 2 H 4 + H 2 SO 4  C 2 H 5.HSO 4 If this is treated with water and warmed, ethanol is formed. heat C 2 H 5.HSO 4 + H 2 O  C 2 H 5 OH + H 2 SO 4

23 Chemical Properties of Alkenes (5) Polymerisation Reactions due to the Double Bond When ethylene is heated under great pressure in the presence of a catalyst a large number of the molecules combine to form polythene, (C2H4)n, (i.e. Polyethylene). This particular kind of reaction is called an addition polymerisation and the mechanism by which it takes place is a reaction is a free radical chain reaction. The overall reaction is n(C 2 H 4 )  (C 2 H 4 )n Ethene Polythene

24 Alkynes/Acetylene

25 Sifat:  Sifat hampir sama dengan alkena  Berupa gas tidak berwarna  Tidak larut dalam air & gas pada tekanan & suhu normal  Sangat mudah terdekomposisi  Sebagai asetilen cair, bersifat sangat sensitif dan dapat meledak.

26 Nomenclature The procedure for naming alkynes is the same as that for alkenes, but the ending used is –yne to indicate the presence of a triple bond.

27 The name of some common alkynes : _________________________________________________ MolecularStructuralCommon IUPAC Formulaformulaname name _________________________________________________ C 2 H 2 H-C≡C-HAcetylene Ethyne C 3 H 4 CH 3 -C≡C-HMethylacetylene Propyne C 4 H 6 CH 3 CH 2 -C≡C-HEthylacetylene 1-Butyne C 4 H 6 CH 3 -C≡C-CH 3 Dimethylacetylene2-Butyne

28 Prepraration  From calcium carbide and water CaC H 2 O  HC ≡ CH + Ca(OH) 2  From cracking mathane 2 CH 4  HC ≡ CH + 3 H 2

29 Chemical Properties  Hidrogenation  Halogenation  Hidrogen halida

30 Aromatic Hydrocarbon

31 Structure Aromatic compounds  benzene  C 6 H 6

32 Naming : Monosubstitued Benzenes Monosubstitued benzenes are named by adding the name of the substituent group as a prefix to the word benzene. Examples :

33 Nitrobenzene Ethylbenzene ChlorobenzeneBromobenzene

34 Certain monosubstitued benzenes have special names. Methylbenzene = Toluene Hydroxybenzene = Phenol Vinylbenzene =Styrene Benzene carboxylic acid = Benzenic acid Benzene carboxaldehyd = Benzaldehyde Aminobenzene =Aniline

35 ToluenePhenolStyrene Benzoic acidBenzaldehydeAniline

36 C 6 H 6 – group is known as phenyl/venil The name phenyl is used to name compounds that cannot easily be named as benzene derivatives. Example :

37 Naming : Disubstitued Benzenes Names  monosubstitued benzene Except dimethylbenzene have special name xylene.

38 Ortho, meta, and para substitution

39 Ketentuan Ortho / para :Meta :(dari yang paling kuat)  NH 2  NO 2  OR  CN  OH  SO 3 H  OCOR  CHO  R  COR  X  COOH  COOR

40 Naming : Polysubstitued Benzenes  When there are more than two substituents on a benzene ring, the carbon atoms in the ring are numbered starting at one of the substituted groups.

41 Polycyclic Aromatic Compounds

42 Chemical Properties  Halogenation (chlorination/bromination)  Nitration  Alkylation (Friedel-Crafts reaction)  Oxidation of side chain

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