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SATURATED HIDROCARBONS ALKANE

SATURATED HIDROCARBONS ALKANE. Alkane = paraffin = saturated hidrocarbons = hydrocarbons with only single covalent bonds between the carbon atoms . Definition.

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SATURATED HIDROCARBONS ALKANE

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  1. SATURATED HIDROCARBONSALKANE

  2. Alkane = paraffin = saturated hidrocarbons = hydrocarbons with only single covalent bonds between the carbon atoms

  3. Definition Acyclic branched or unbranched hydrocarbons having the general formula CnH2n+2 , and therefore consisting entirely of hydrogen atoms and saturated carbon atoms. IUPAC Gold Book

  4. Sifat • Sukar bereaksi • C1 – C4 pada tekanan & suhu normal fase gas C5 – C17 pada tekanan & suhu normal fase cair PC18 pada tekanan & suhu normal fase padat • Mudah larut pada pelarut non polar • Berat jenis naik dengan penambahan atom C • Pada alkana rantai lurus  semakin panjang rantai maka titik didih & titik leleh semakin tinggi

  5. Carbon Bonding in Alkane Each carbon atom must have 4 bonds (either C–H or C–C bonds), and each hydrogen atom must be joined to a carbon atom (H–C bonds).

  6. Straight-chain alkanes are sometimes indicated by the prefix n- (for normal)

  7. Isomerism Alkanes with more than three carbon atoms can be arranged in a multiple number of ways, forming different structural isomers. Isomers are compounds that have the same molecular formula but different structural formulas. College Chemistry_ch.21.8_p.529

  8. Practice 1 : Write structural formulas and condensed structural formulas of : • Pentane C5H12 • Hexane C6H14

  9. Pentane

  10. Hexane

  11. Alkyl Number of carbons Molecule name 1 methyl 2 ethyl 3 propyl 4 butyl 5 pentyl/amyl 6 hexyl 7 heptyl 8 octyl 9 nonyl 10 decyl 11 undecyl 12 dodecyl

  12. sec-Butyl Isopropyl Isobutyl tert-Butyl

  13. IUPAC Nomenclature : Basic Principles (1) Select the longest continuous chain of carbon atoms as the parent compound, and consider all alkyl groups attached to it as side chains that have replaced hydrogen atoms of the parents hydrocarbon. The name of the alkane consists of the name of the parent compound prefixed by the names of the side-chain alkyl groups attached to it.

  14. IUPAC Nomenclature : Basic Principles (2) Number the carbon atoms in the parent carbon chain starting from the end closest to the first carbon atom that has an alkyl or other group substitued for a hydrogen atom.

  15. IUPAC Nomenclature : Basic Principles (3) Name each side-chain alkyl group and designate its position on the parent carbon chain by a number (for example, 2-methyl means a methyl group attached to carbon number 2).

  16. IUPAC Nomenclature : Basic Principles (4) When the same alkyl-group side chain occurs more than once, indicate this by a prefix (di-, tri-, tetra-, and si forth) written in front of the alkyl-group name (for example, dimethyl indicates two methyl groups). The numbers indicating the positions of these alkyl groups are separated by a comma and followed by a hypen and are placed in front of the name (for example, 2,3-dimethyl).

  17. IUPAC Nomenclature : Basic Principles (5) When several different alkyl groups are attached to the parent compound, list them in alphabetical order; for example, ethyl before methyl in 3-ethyl-4-methyloctane. College Chemistry_ch.21.9_p.533

  18. Practice 2 : The following names are incorrect. Tell why the name is wrong and gave the correct name. • 3-methylbutane • 2-ethylbutane • 2-dimethylpentane • 3-methyl-5-ethyloctane • 3,5,5-triethylhexane

  19. 3-methylbutane CH3 – CH2 – CH – CH3 CH3 2-methylbutane

  20. 2-ethylbutane CH3 – CH2 – CH – CH3 CH2 CH3 3-methylpentane

  21. 2-dimethylpentane CH3 CH3 – CH – CH – CH2 – CH3 CH3 2,2-dimethylpentane

  22. 3-methyl-5-ethyloctane CH3 – CH2 – CH – CH2 – CH – CH2 – CH2 – CH3 CH3 CH2 CH3 5-ethyl-3-methyloctane

  23. 3,5,5-triethylhexane CH2 CH3 CH3 – CH2 – CH – CH2 – C – CH3 CH2 CH2 CH3 CH3 3,5-diethyl-3-methylheptane

  24. Reaction of Alkane : Halogenation Halogenation means substitution of halogens for hydrogen. RH + X2 RX + HX X = F, Cl, Br, I Example : CH3CH3 + Cl2  CH3CH2Cl + HCl chloroethane

  25. Reaction of Alkane : Dehydrogenation Dehydrogenation means removal of hydrogen. CnH2n+2 700 – 900 oCCnH2n + H2 Example : CH3CH2CH3 CH3CH=CH2 + H2 propene

  26. Reaction of Alkane : Cracking Cracking means breaking up large molecules to form smaller ones. Example : C16H34 C8H18 + C8H16 alkanealkanealkene

  27. Reaction of Alkane : Isomerization Isomerization means rearrangement of molecular structures. Example :

  28. Chlorination Products of Methane(1) CH4 + Cl2 CH3Cl CH3Cl + Cl2 CH2Cl2 CH2Cl2 + Cl2 CHCl3 CHCl3 + Cl2 CCl4 + HCl

  29. Chlorination Products of Methane(2) Formula IUPAC name Common name CH3Cl Chloromethane Methyl chloryde CH2Cl2 Dichloromethane Methylene chloryde CHCl3 Trichloromethane Chloroform CCl4 Tetrachloromethane Carbon tetrachloride

  30. Cycloalkane/cycloparaffin/naphtane • Cycloalkanes are types of alkanes which have one or more rings of carbon atoms in the chemical structure of their molecules  struktur alisiklik. • Rumus: CnH2n • Contoh:

  31. Cyclopropane Cyclobutane Cyclopentane Cyclohexane C3H6 C4H8 C5H10 C6H12

  32. Sources of Alkanes

  33. The two main sources of alkanes are natural gas and petroleum / crude oil. Natural gas consists of : • Methane • Other hydrocarbons • Hydrogen • Nitrogen • Carbon monoxide • Carbon dioxide • Hydrogen sulfide (just in some location)

  34. Petroleum is formed by the decomposition of plants and animals over million of years. Composition: • Carbon • Hydrogen • Nitrogen • Oxygen • Sulfur • Metals Four different types of hydrocarbon molecules appear in crude oil : • Paraffins • Naphthenes • Aromatics • Asphaltics

  35. Fractional Distillation of Crude Oil

  36. Crude oil is separated into fractions by fractional distillation. The fractions at the top of the fractional column have lower boiling points than the fractions at the bottom. The heavy bottom fractions are often cracked into lighter, more useful products. All of the fractions are processed further in other refining units.

  37. Octane Rating

  38. Octane CH3(CH2)6CH3 Octane has 18 structural isomers : • Octane (n-octane) 0 • 2-Methylheptane • 3-Methylheptane • 4-Methylheptane • 3-Ethylhexane • 2,2-Dimethylhexane • 2,3-Dimethylhexane • 2,4-Dimethylhexane • 2,5-Dimethylhexane • 3,3-Dimethylhexane • 3,4-Dimethylhexane • 2-Methyl-3-ethylpentane • 3-Methyl-3-ethylpentane • 2,2,3-Trimethylpentane • 2,2,4-Trimethylpentane (isooctane) 100 • 2,3,3-Trimethylpentane • 2,3,4-Trimethylpentane • 2,2,3,3-Tetramethylbutane

  39. The octane rating was developed by chemist Russel Marker at the Ethyl Corporation at 1926. The selection of n-heptane as the zero point of the scale was due to the availability of very high purity n-heptane, not mixed with other isomers of heptane or octane, distilled from the resin of the Jeffrey Pine. Other sources of heptane produced from crude oil contain a mixture of different isomers with greatly differing ratings, which would not give a precise zero point. Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause detonation.

  40. The alternative method to boost octane rating and minimize engine knocking is too add small amounts of an additive to the fuel. One such additive commonly used in gasoline was tetraethyllead, (C2H5)4Pb. The function of tetraethyllead is to prevent the premature explosions that constitute knocking. Use of tetraetthyllead additives poses a serious enviromental hazard. Lead becomes pollutant in air, water, and sovent. Current additives in anleaded gasoline : • Toluene • Xylene • Methyl tert-butyl ether (MTBE)

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