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UNSATURATED HIDROCARBONS

UNSATURATED HIDROCARBONS. Unsaturated hidrocarbons contains carbon-carbon double bonds. Alkene = olefin Alkyne = acetylene Aromatic compound = benzene ring. ALKENE. Alkena disebut juga olefin Unsaturated hidrocarbon Double bond Pembentuk minyak Rumus: C n H 2n. Sifat.

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UNSATURATED HIDROCARBONS

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  1. UNSATURATED HIDROCARBONS

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

  3. ALKENE

  4. Alkena disebut juga olefin • Unsaturated hidrocarbon • Double bond • Pembentuk minyak • Rumus: CnH2n

  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) • Select the longest carbon-carbon chain that cantains the double bond. • Name the parent compound as you would an alkene but change the –ane ending to –ene; for example, propane is change to propene. CH3 CH2 CH3 CH3CH=CH2 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 : • 2-pentene • 7-methyl-2-octene • 3-hexene • 4-ethyl-2-heptene • 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, C5H10. 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 alkenehydrocarbon which contains a closed ring of carbonatoms, but has no aromatic character. 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: C16H34 C8H18 + C8H16 alkanealkanealkene

  16. Dehydration of Alcohols Alkohol dipanaskan pada asam sulfat terkonsentrasi Reaksi: Alkohol con.H2SO4 alkena + H2O 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 oC oC (g/ml) Ethylene C2H4 -170 -102 0.6128 Propene C3H6 -185 -47 0.6142 Butene C4H8 -130 -6.5 0.6356

  19. Chemical Properties of Alkenes(1) Combustion of Alkenes The alkenes are highly flammable and burn readily in air, forming carbon dioxide and water. C2H4 + 3 O2 2 CO2 + 2 H2O

  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=CH2 + 2 KMnO4 + 4 H2O  2MnO2 + 2KOH + CH2OHCH2OH 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. C2H4 + H2SO4 C2H5.HSO4 If this is treated with water and warmed, ethanol is formed. heat C2H5.HSO4 + H2O  C2H5OH + H2SO4

  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(C2H4)  (C2H4)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 : _________________________________________________ Molecular Structural Common IUPAC Formula formula name name _________________________________________________ C2H2 H-C≡C-H Acetylene Ethyne C3H4 CH3-C≡C-H Methylacetylene Propyne C4H6 CH3CH2-C≡C-H Ethylacetylene 1-Butyne C4H6 CH3-C≡C-CH3 Dimethylacetylene 2-Butyne

  28. Prepraration • From calcium carbide and water CaC2 + 2 H2O  HC≡CH + Ca(OH)2 • From cracking mathane 2 CH4 HC≡CH + 3 H2

  29. Chemical Properties • Hidrogenation • Halogenation • Hidrogen halida

  30. Aromatic Hydrocarbon

  31. Structure Aromatic compounds  benzene  C6H6

  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 Chlorobenzene Bromobenzene

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

  35. Toluene Phenol Styrene Benzoic acid Benzaldehyde Aniline

  36. C6H6– 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) (dari yang paling kuat)  NH2 NO2  OR  CN  OH  SO3H  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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