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Chapter 2 carbon compound notes


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Chapter 2 carbon compound notes

  2. 2. A: CARBON COMPOUNDS -are compounds that contain Carbon as one of their constituent elements
  3. 3. Carbon Compound Organic Compound Inorganic Compound -Carbon containing compounds except oxides of carbon, carbonates, syanides and metallic carbides -non-carbon containing compounds Hydrocarbon Non-hydrocarbon -contain Carbon and Hydrogen only -contain C,H and O,N,P,S,F,Cl,Br,I Alkanes Alkenes (saturated hydrocarbons) (unsaturated hydrocarbons) -contain only single bond -contain at least one multiple bond Alcohols Esters Carboxylic acids
  4. 4. Inorganic Carbon compound Organic compound Similarity Both contain carbon atoms Diffenrences Protein, fats, cellulose, natural rubber, petroleum Examples Carbon dioxide, carbon monoxide Formed from living thing Origin Formed from minerals Effect of heat Have high boiling points and high melting point Have low boiling points and low melting point Dissolve in organic solvents such as ether, petrol, alcohol and chloroform Solubility Dissolve in inorganic solvents such as ether, water, acids and alkalis
  5. 5. Hydrocarbons Hydrocarbons are organic compound that contain only Carbon and Hydrogen Natural sources of hydrocarbons: • Petroleum • Coal • Natural gas • Rubber trees
  6. 6. B: ALKANES : CnH2n+2 , n=1,2,3… General Formula Naming alkanes: Number of Carbon atoms 1 2 3 4 5 6 7 8 9 10 Root name Meth- Eth- Prop- But- Pent- Hex- Hept- Oct- Non- Dec- Final name Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane
  7. 7. Structural Formula shows how the atoms in a molecule are bonded together and by what types of bonds Example : Ethane C2H6 molecular formula structural formula
  8. 8. Cannot conduct electricity Less dense than water dissolve in organic solvents Insoluble in water Physical properties of alkanes Low melting and boiling points- because the molecules are held together by weak intermolecular forces which can be overcome by small amount of energy
  9. 9. Chemical properties of alkanes a) Combustion 1. Complete combustion Alkanes burn in air to form carbon dioxide and water CH4 (g) + 2O2(g) CO2 (g) + 2H2O(l) More soot is given off when a higher alkane is burnt. For example, the burning of heptane produce more soot than the burning of ethane 2. Incomplete combustion If insufficient oxygen available, carbon monoxide or even carbon may be formed 2CH4 (g) + 3O2(g) 2CO (g) + 4H2O(l) CH4 (g) + O2(g) C (s) + 2H2O(l)
  10. 10. b) Halogenation -Reaction of alkanes with halogens. -readily takes place in sunlight (not occur in the dark) -carbon-hydrogen bonds are broken and new carbon-halogens bonds are formed -is a substitution reaction occurs when one atom or a group of atoms in a molecule is replaced by another atom or group of atoms
  11. 11. -Example: • when a mixture of CH4 and chlorine is exposed to ultraviolet light, 4 different products are formed CH4 (g) + Cl2(g) CH3Cl (g) + HCl(l) Chloromethane hydrogen chloride
  12. 12. C: ALKENES is a hydrocarbons containing at least one carbon-carbon double bond General Formula : CnH2n , n=2,3,4… Naming alkenes: Number 2 of Carbon atoms 3 4 5 6 7 8 9 10 Root name Eth- Prop- But- Pent- Hex- Hept- Oct- Non- Dec- Final name Ethene Propene But-1-ene Pent-1-ene Hex-1-ene Hept-1-ene Oct-1-ene Non-1-ene Dec-1-ene
  13. 13. Structural formula of alkenes Ethene: Propene : C2H4 C3H6
  14. 14. Low melting and boiling point Cannot conduct electricity at any state Less dense than water Physical properties of alkenes Soluble in organic solvents Insoluble in water
  15. 15. (a)Combustion reaction (c) Polymerization reaction Chemical properties of alkenes (b)Addition reaction (i)Addition of hydrogen (ii)Addition of halogens(halogenation) (iii) Addition of hydrogen halides (HCl, HBr, HI) (iv) Addition of water (hydration) (v) Addition of hydroxyl groups
  16. 16. Chemical properties of alkenes a) Combustion reaction Alkenes burn in excess oxygen to form carbon dioxide and water C2H4 (g) + 3O2(g) 2CO2 (g) + 2H2O(l) Alkenes burn with sootier flames as compared to alkanes because alkenes have a higher percentage of carbon in their molecules than alkanes
  17. 17. b) Addition reaction (i) Addition of hydrogen This process is called catalytic hydrogenation
  18. 18. (ii) Addition of halogens (halogenation) Observation: reddish-brown bomine is decolourised and colourless liquid is formed This reaction is used as a test for the presence of a carbon-carbon double bond in organic molecules
  19. 19. (iii) Addition of hydrogen halides(HCl, HBr, HI)
  20. 20. • (iv) Addition of water (hydration)
  21. 21. (v) Addition of hydroxyl groups Observation: purple solution of potassium manganate (VII) is decolourized
  22. 22. c) Poymerization reaction
  23. 23. Homologous Series A group or family of organic compounds that has the following characteristics: a) b) c) d) e) Members of the series can be represented by a general formula Successive members differ from each other by –CH2 Members can be prepared by similar methods Physical properties change regularly with increasing number of carbon atoms Members have similar chemical properties because they have the same functional group functional group : -a special group of atoms attached to an organic mlecule -determines the chemical properties of the molecule -chemical reactions occur at the functional group
  24. 24. 5 homologous series learnt in this chapter: Homologous series General formula Functional Group Alkane CnH2n+2 , n=1,2,3… Carbon-carbon single bond, C-C Alkene CnH2n , n=2,3,4… Carbon-carbon double bond, C=C Alcohol CnH2n+1OH ,n=1,2,3… Hydroxyl group, -OH Carboxylic Acid CnH2n+1 COOH ,n=0,1,2,… Carboxyl group, -COOH Ester CnH2n+1 COOCmH2m+1, n=0,1,2,… m=1,2,3… Carboxylate group, -COO-
  25. 25. Descending homologous series First member Second member Third member ….. ….. ….. As the number of carbon atoms per molecule increases: •Melting point increases •Boiling point increases •Volatility decreases •Density increases
  26. 26. D: ISOMERISM Isomerism is a phenomenon whereby 2 or more molecules are found to have same molecular formula but different structural formula Isomers: molecules with the same molecular formula but with different structural formula
  27. 27. • Example: C4H10
  28. 28. Steps to draw structural formula of isomers of alkanes Draw all the possible straight- chain and branched-chain carbon skeletons Place single bonds around every carbon atom. Ensure that each carbon atom has 4 bonds Place a hydrogen atom at each of the single bonds
  29. 29. Steps to draw structural formula of isomers of alkenes Draw all the possible carbon skeletons For each carbon skeleton, place a double bond at different locations Place single bonds around each carbon atom. Ensure that each carbon atom has 4 bonds Place a hydrogen atom at each of the single bonds
  30. 30. How to name isomers? Prefix Denotes the number and identity of attached branches Root Ending Denotes the longest carbon chain Denotes rhe family of the organic compound Steps to name an alkane: 1 : Find the longest continuous carbon chain in the molecule 2 : Give the name for this longest chain 3 : Number the carbon atoms in this longest chain beginning at the end nearest to the first branch (alkyl group) 4 : Locate and name the attached alkyl group 5 : Complete the name for the molecule by combining the three component parts together. Write the name as a single word. Use hyphens to separate numbers numbers and words, and commas to separate numbers
  31. 31. E: ALCOHOLS General Formula : CnH2n+1OH ,n=1,2,3… Functional Group : -OH (hydroxyl group)
  32. 32. Naming alcohols (a) straight-chain alcohol Step 1 Obtain the name of the alkane with the same number of carbon atoms as the alcohol Step 2 Replace the ending –e from the name of the alkane with -ol Step 3 A number is placed to in front of the –ol to indicate which carbon atom the hydroxyl group is attached to
  33. 33. (b) branched-chain alcohol Step 1 Find the longest continuous carbon chain containing the hydroxyl group Step 2 Name the longest chain by substituting the ending –ol for the –e of the corresponding alkane Step 3 Number of the carbon atoms in the longest chain beginning at the end nearer to the hydroxyl group Step 4 Step 5 Step 6 Identify the position of the hydroxul group by writing the number of the carbon atom to which it is attached in front of the ending -ol Locate and name all attached alkyl group Complete the name for the alcohol molecule by combining the 3 component parts together. Write the name as a single word
  34. 34. Industrial production of ethanol a) Making ethanol by fermentation C6H12O6 (aq) 2CH3CH2OH (aq) + 2CO2 (g) Glucose Temperature Catalyst Other condition Ethanol : 18-20 °C : zymase from yeast : absence of oxygen
  35. 35. b) Making ethanol by hydration CH2=CH2 (g) + H2O (g) Ethene Steam CH3CH2OH (g) Ethanol (From the cracking of petroleum fractions) Temperature Pressure Catalyst : 300 °C : 60 atm : phosphoric acid
  36. 36. Sharp smell Completely miscible with water Liquid at room conditions Physical properties of ethanol colourless Highly volatile (easily change into a gas) Low boiling point
  37. 37. Oxidation Chemical properties of ethanol Combustion Dehydration
  38. 38. Chemical properties of ethanol a) Combustion Ethanol burns with a non-smoky blue flame C2H5OH (l) + 3O2 (g) 2CO2 (g) + 3H2O (l) Combustion of ethanol releases large amount Of heat. Ethanol suitable as a fuel
  39. 39. b) Oxidation CH3CH2OH (l) + 2[O] CH3COOH (l) + H2O (l) ethanoic acid oxidising agent: acidified potassium dichromate (VI) solution ( colour change from orange to green) acidified potassium manganate (VII) solution ( colour change from purple to colourless)
  40. 40. c) Dehydration txt bk pg 64 module pg 72
  41. 41. 2 methods to carry out a dehydration of ethanol (a) Ethanol vapour is passed over a heated catalyst such as unglazed porcelain chips, porous pot, pumice stone or aluminium oxide (a) Ethanol is heated under reflux at 170 °C with excess concentrated sulphuric acid
  42. 42. Uses of alcohols (a) As a solvent (a) as a fuel -perfumes, cosmetics -thinners for lacquers, varnishers - a mixture of petrolwith 10-20 % ethanol (gasohol) - methanol (as a fuel for racing cars) (a) As a source of chemicals - as a raw material in the manufacture of polymers, fibres, explosives and plastics - ethanol ethanoic acid (vinegar) (a) As a source of medicinal products - ethanol- as a solvent in the preparation of cough syrups - propan-2-ol –as a rubbing alcohol (bring down high fever)
  43. 43. E: CARBOXYLIC ACIDS General Formula Functional Group : CnH2n+1COOH ,n=0,1,2… : -COOH (carboxyl group)
  44. 44. Naming carboxylic acids Find the longest continuous carbon chain containing the carboxyl group Name this longest chain by replacing the ending –e of the corresponding alkane with –oic acid Number the carbon atoms in this longest chain beginning at the carboxyl group Locate and name the attached alkyl group Complete the name for the carboxylic acid molecule by combining the 2 component parts together
  45. 45. Making ethanoic acid - oxidation of ethanol by refluxing ethanol with an oxidising agent such as acidified potassiun dichromate (VI) solution or acidified potassium manganate (VII) solution
  46. 46. Refluxing : prevent the loss of a volatile liquid by vaporisation Ethanoic acid formed is removed by fractional distillation
  47. 47. Very soluble in water Physical properties of ethanoic acid Sour smell like vinegar Colourless liquid at room conditions
  48. 48. Chemical properties of ethanoic acid (a) Acid properties- ethanoic acid is a weak monoprotic acid CH3COOH (aq) ↔ CH3COO⁻ (aq) + H⁺ (aq) Ethanoic acid Ethanoate ion (b) Reactions with metals 2CH3COOH (aq) + Zn(s) ↔ Zn(CH3COO)2 (aq) + H2 (g) (c) Reactions with base 2CH3COOH (aq) + CuO(s) ↔ Cu(CH3COO)2 (aq) + H2O (l)
  49. 49. (d) Reactions with carbonate 2CH3COOH (aq) + CaCO3(s) ↔ Ca(CH3COO)2 (aq) + CO2(g)+ H2O (l) (e) Reactions with alcohols (esterification)
  50. 50. Chemical reactions of other carboxylic acid • • • • Carboxylic acid + reactive metal carboxylate salt + hydrogen Carboxylic acid + base carboxylate salt + water Carboxylic acid + metal carbonate carboxylate salt + CO2 + H2O Carboxylic acid +alcohol ester + water
  51. 51. Uses of carboxylic acids Ethanoic acid (acetic acid) Methanoic acid (formic acid) Benzoic acid • As food flavouring • As preservative • Coagulate latex • As preservative in foods
  52. 52. G: ESTERS General Formula : CnH2n+1COOCmH2m+1 ,n=0,1,2… m=1,2,3… Functional Group : -COO (carboxylate group)
  53. 53. Naming esters • pg 77 • The name of an ester consists of 2 separate words. The alcohol part is named fist followed by the acid part Identify and name the alcohol part of the ester (alkyl group) Identify and name the acid part of the ester (change –oic acid to –oate) Combine the both parts to obtain the name of the ester
  54. 54. Formation of esters Esters are produced by an esterification reaction (carboxylic acid reacts with alcohol in the presence of concentrated sulphuric acid as a catalyst) Example : HCOOH + CH3OH methanoic acid H2SO4 HCOOCH3 + H2O methyl methanoate
  55. 55. Low density, less dense than water Colourless liquid at room temperature Sweet smell Very volatile Physical properties of esters Insoluble in water
  56. 56. Use of esters Used in the preparation of cosmetics and perfumes As artificial flavour in processed food and drinks Used in the production of polyester (synthetic fibers for makng textiles) Most are found naturally in fruits and flowers(Their fragrance are due to the presence of esters)
  57. 57. H: FATS • Fats found in animals are solids at room temperature. Eg: butter • Fats from plants are liquids. oils • Fats and oils are esters (fatty acids + glycerol) • Fatty acids containing 12-18 Carbon atoms per molecule
  58. 58. Source of energy Thermal insulation The importance of oils and fats protection Source of nutrients
  59. 59. Saturated and unsaturated fats Saturated fats • Fats which contain esters of glycerols and saturated fatty acids • saturated fatty acids : has all carbon atoms joined together by carbon-carbon single bond
  60. 60. Unsaturated fats • Fats which contain esters of glycerols and unsaturated fatty acids • Unsaturated fatty acids: carbon chain has one or more carboncarbon double bond
  61. 61. Converting unsaturated fats into saturated fats • By a process called catalytic hydrogenation ( by bubbling hydrogen gas through hot liquid oil) catalyst temperature pressure Module 88 : nickel : 200oC : 4atm
  62. 62. Effects of fats on health obesity Plant or vegetable oil do not contain cholesterol: not cause cardiovascular problems Saturated fats raise the level of cholesterol: the flow of the blood in the arteries might be blocked and lead to heart attack and stroke
  63. 63. Extraction process of palm oil
  64. 64. Rich in Vitamin E(powerful antioxidant) Advantages of palm oil Cholesterol free Rich in betacarotene which contains Vitamin E
  65. 65. I : NATURAL RUBBER • Natural polymers are polymers that exist in nature and not man-made Natural polymer Monomer Protein Amino acid Carbohydrate Glucose Natural rubber Isoprene
  66. 66. Natural rubber • Monomer: isoprene (2-methylbut-1,3-diene) • Nota pg 38
  67. 67. Coagulation process of latex Each rubber particle is made up of rubber polymers covered by a layer of protein membrane Negative charges are found on the surface of the membrane, making each rubber particle negatively charged. The negatively charged rubber particles repel each other, preventing themselves from combining and coagulating
  68. 68. When acid is added to latex: Hydrogen ion from the acid nautralise the negative charges on the surface of the membrane. A neutral rubber particle is formed. When these neutral particles collide with each other, their outer membrane layers break up. The rubber polymers are set free. The rubber polymers start to coagulate by combining together
  69. 69. •Bacteria from the air attack the protein on the membrane to produce lactic acid •Alkalis such as ammonia solution are added to latex to prevent coagulation •The hydroxide ions from alkali neutralise hydrogen ions produced by lactic acid as aresult of bacterial attack on protein •Bcause there are no hydrogen ions to neutralise the negative charges on the rubber particles, they remain negatively charged and hence cannot combine and coagulate
  70. 70. Insoluble in water Unstable to oxidation Properties of natural rubber elastic Unstable to heat
  71. 71. Vulcanization • Is a process whereby rubber is reacted wth sulphur to improved the properties of natural rubber  Sulphur is heated together with natural rubber  Rubber stripe is soaked in sulphur monochloride solution in methylbenzene for a few hours, then dried Txt bk 95