Alkane Slide


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Alkane Slide

  1. 1. Basic Organic Chemistry Nur Faralina Binti Asrab Ali D20101037415 Wan Norazwani Bt Mahusin D20101037533 Fatin Nasuha
  2. 2. HYDROCARBON ALPHATIC ALKANES (saturated) Contain only single bond CYCLOALKANES (saturated) Alkane which C atoms are join in rings ALKENES (unsaturated) Contain C=C CYCLOALKENES (unsaturated) ALKYNES (unsaturated) Contain C=C AROMATIC (contain one or more benzene ring)
  3. 3. ALKANES • Alkanes are known as saturated hydrocarbon which contain only single covalent bonds. • General formula for straight chain of alkanes is CnH2n+2 where n≥1 • Each carbon atom is alkanes is sp3 hybridised tetrahedral with four sigma bond (formed by the four sp3 hybrid orbitals) • Alkanes IUPAC names have the –ane suffix.
  4. 4. The First Ten Unbranched Alkanes Molecular formula Structural formula No. of C atoms Name CH4 CH4 1 Methane C2H6 CH3-CH3 2 Ethane C3H8 CH3-CH2-CH3 3 Propane C4H10 CH3-(CH2)2-CH3 4 Butane C5H12 CH3-(CH2)3-CH3 5 Pentane C6H14 CH3-(CH2)4-CH3 6 Hexane C7H16 CH3-(CH2)5-CH3 7 Heptane C8H18 CH3-(CH2)6-CH3 8 Octane C9H20 CH3-(CH2)7-CH3 9 Nonane C10H22 CH3-(CH2)8-CH3 10 Decane
  5. 5. • Starting from C4H10 onwards, the alkanes show the phenomenon of chain isomerism • They can exist as linear or branched alkanes.
  6. 6. Example C4H10 CH3CH2CH2CH3 CH3CHCH3 CH3
  7. 7. IUPAC NOMENCLATURE • IUPAC-International Union of Pure and Applied Chemistry • Branched-chain alkanes are named according to the following rules:
  8. 8. STEP 1 • Choose the longest continuous chain of carbon atoms; this chain determines the parent name for alkanes.
  9. 9. STEP 2 • Number the longest chain beginning with the end of the chain nearer the substituent.
  10. 10. STEP 3 • Use rule number 2 to locate the position of the substituent. • The position and the name of the substituent must be written in front of the parent chain.
  11. 11. STEP 4 –If two or more substituent are present, give each substituent a number corresponding to its location on the longest chain. The substituent should be listed alphabetically In alphabetizing, the prefixes di, tri, tetra, sec-, tert- are ignored except iso and neo
  12. 12. STEP 5 • If two substituent are present on the same carbon atom, use that number twice.
  13. 13. STEP 6 • If two or more identical substituent are present, use prefixes di-(two identical substituent), tri-(three identical substituent), tetra-(four identical substituent). • Commas are used to separate numbers from each other.
  14. 14. STEP 7 • If there are two chains of equal length as the parent chain, choose the chain with the greater number of substituent.
  15. 15. STEP 8 • If branching occurs at an equal distance from either end of the longest chain, choose the name that gives the lower number at the first point of difference.
  16. 16. Cycloalkanes ?
  17. 17. Introduction Called as naphthenes Types of alkanes that have one or more rings of carbon atoms Contain only carbon-carbon single bonds and are saturated hydrocarbons. General formula : CnH2n. Has less hydrogen atom than alkanes Drawn in simple polygons
  18. 18. Continue.. Each corner of polygon is a carbon atom attached to two hydrogen atoms. The single ring are named analogously to their normal alkanes counterpart of the same carbon count such as Cyclopropane, Cyclobutane, Cyclopentane,
  19. 19. Multiple rings Spiro cyclic compounds Fused rings compounds Bridged ring compounds
  20. 20. Continue.. One carbon atom shared between two rings known as spiro cyclic compounds. Fused ring compounds shared two common atoms and the bond between them. Bridged ring compound shared two nonadjacent carbon atoms.
  21. 21. Naming Cycloalkanes  Cycloalkanes are named according to the IUPAC system by using the prefix cyclo-.  There are only two steps: 1) Find the parent. 2)Number of substituent and write the name.
  22. 22. Step 1: Find the parent Count the number of carbon atoms in the ring and the number in the largest substituent If the number of carbon atoms in the ring greater or equal to substituent, it is called alkyl-substituent If the number of carbon atom in the largest substituent is greater than the number in the ring, it named as a cycloalkyl-substituted alkane.
  23. 23. Step 2: Number of Substituent and Write The Name For alkyl or halo-substituent(i) • If two or more substituents, choose a point of attachment as carbon 1 such that the second substituent has a low number as possible For different alkyl(ii) • Number them by alphabetical priority, ignoring numerical prefixes such as di- and tri-. For halogen(iii) • Treat them just like alkyl groups.
  24. 24. PHYSICAL PROPERTIES OF ALKANES • Different physical properties of alkanes is resulting from different range of molecular weight( different of c ) • On this subtopic we will cover about  boiling point Melting point solubilty
  25. 25. Boiling Point 1) Increase smoothly with increasing number of c atoms(molecular weight/molar mass) •Greater number of C atom •Large molecule •Greater surface area •Stronger Van Der Waals attraction •Higher boiling point
  26. 26. Example CH3CH2 CH2 CH3 CH3 CH2 CH2 CH2 CH3 CH3 CH2 CH2 CH2 CH2 CH3 Butane Pentane Hexane Bp=0° C Bp=36° C Bp=79° C Increasing surface area Increasing boiling point
  27. 27. Effect of Chain Branching 2) Branching of alkane chain lowers boiling point  More branches Molecular shapebecomes more compact Surface area reduced Weaker Van Der Waals attraction Lower boiling point
  28. 28. Example
  29. 29. Straight with Cycloalkane • When compairing at the same number of C, cycloalkanes has slightly higher boiling point than alkanes. Compairing Boiling Points to More Polar Compounds •Alkanes have low boiling points compared to more polar compounds of comparable size
  30. 30. Example CH3CH2 CH3 CH3CHO CH3CH2OH Propane Acetaldehyde Ethanol VDW VDW, DD VDW,DD,HB MW=44 MW=44 MW=46 Bp= -42° C Bp=21° C Bp=79° C Increasing surface area Increasing boiling point
  31. 31. Melting Point • Alkanes have low melting point compared to more polar compounds CH3CH2 CH3 CH3CHO Propane Acetaldehyde VDW VDW, DD MW=44 MW=44 Mp= -190° C Mp=-121° CZ Increasing strength of intermolecular forces Increasing melting point
  32. 32. • Melting point increase as the number of carbons increase because of increase of surface area CH3CH2 CH2 CH3 CH3 CH2 CH2 CH2 CH2 CH3 Butane Hexane Mp=-138° C Mp=-95° C Increasing surface area Increasing boiling point
  33. 33. • Melting point increases with increased symmetry CH3CH2CH(CH3)2 (CH3)4C Mp=-160° C Mp=-17° C Increasing symmetry Increasing melting point
  34. 34. Solubility in Water • Alkanes are almost totally insoluble in water • They have low polarity and unable to form hydrogen bonds Solubility in Solvents •Normally dissolve in solvent of low polarity such as benzene. Chloroform, CCl4 and other hydrocarbons.
  35. 35.
  36. 36.
  37. 37. 1.The root name is based on the longest chain containing the halogen. 2.This root give the alkane part of the name. 3.The type of halogen defines the halo prefix, e.g. chloro- 4.The chain is numbered so as to give the halogen the lowest possible number
  38. 38. 1.Functional group is an alkane, therefore suffix = -ane 2.The longest continuous chain is C3 therefore root = prop 3.The substituent is a chlorine, therefore prefix = chloro 4.The first point of difference rule requires numbering from the right as drawn, the substituent locant is 1- 1-chloropropane CH3CH2CH2Cl 1-chloropropane