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AS Chemistry

AS Chemistry. Introduction to organic chemistry. Candidates should be able: t o recall IGCSE work on crude oil and ‘cracking’. in a request for a structural formula, to give the minimal detail, using conventional groups, for an unambiguous structure.

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AS Chemistry

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  1. AS Chemistry Introduction to organic chemistry

  2. Candidates should be able: • to recall IGCSE work on crude oil and ‘cracking’. • in a request for a structural formula, to give the minimal detail, using conventional groups, for an unambiguous structure. • to draw and recognise displayed and skeletal formulae. • to recognise the shape of the benzene ring when it is present in organic compounds. • to interpret and use some of the terminology associated with organic chemistry. Learning Objectives

  3. Starter activity

  4. Why carbon? Carbon can form strong covalent bonds with itself to give chains and rings of its atoms joined by C-C covalent bonds. This property is called catenation and leads to the limitless variety of organic compounds possible.

  5. Straight or branched?

  6. Benzene – C6H6 Best representations – bonds are intermediate between single and double.

  7. UK oil and gas fields Norway Netherlands

  8. Fractionating columns

  9. Fractional distillation

  10. Uses of each fraction Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gas Fuel gas Petrol / gasoline Fuel for cars and motorcycles, also used to make chemicals. Naphtha Used to make chemicals. Paraffin / Kerosine Fuel for greenhouse heaters and jet engines, manufacture of chemicals. Diesel fuel Fuel for lorries, trains. Fuel and lubricating oil Fuel for the heating systems of large buildings, fuel for ships, lubricating oil. Bitumen Roofing, and road surfaces.

  11. Compounds in Crude Oil • Alkanes • Cycloalkanes • Arenes (A2)

  12. The names and molecular formulae of the first 10 alkanes

  13. Some more alkanes…….

  14. Key Terms • Homologous series: a series or family of organic compounds with the same functional group, whose members differ only in the addition of a CH2 group. • Functional group: the specific atom or group of atoms that confers a particular chemical property on a molecule, e.g. the –OH group in ethanol. • Saturated: the molecule contains the maximum amount of hydrogen atoms possible, with no double or triple bonds between atoms.

  15. Structural Isomerism butane methylpropane

  16. Cycloalkanes

  17. Naming the alkanes 2-methylpentane pent counts 5 carbons an tells you there aren't any double bonds 2-methyl tells you to add a methyl group on carbon 2 Finish by putting in the correct number of hydrogen atoms

  18. Naming the alkanes 2,2-dimethylbutane 2,3-dimethylbutane 3-ethyl-2-methylhexane

  19. Structural formulae Displayed formulae Skeletal formulae 3-dimensional structures

  20. “Stick” (skeletal) formulae Penguinone Penguin real name: 3,4,4,5-tetramethylcyclohexa-2,5-dienone

  21. windowpane “Stick” (skeletal) formulae butane cyclobutane brokenwindowpane

  22. benzene “Stick” (skeletal) formulae mercedes benzene

  23. AS Chemistry Structural isomerism

  24. Candidates should be able: • describe structural isomerism • deduce the possible isomers for an organic molecule of known molecular formula. Learning Objectives

  25. Chain isomerism

  26. Structural Isomerism What are isomers? Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. (That excludes any different arrangements which are simply due to the molecule rotating as a whole, or rotating about particular bonds.)

  27. TYPES OF ISOMERISM CHAIN ISOMERISM STRUCTURAL ISOMERISM POSITION ISOMERISM Same molecular formula but different structural formulae FUNCTIONAL GROUP ISOMERISM GEOMETRICAL ISOMERISM Occurs due to the restricted rotation of C=C double bonds... two forms… E and Z (CIS and TRANS) STEREOISOMERISM Same molecular formula but atoms occupy different positions in space. OPTICAL ISOMERISM Occurs when molecules have a chiral centre. Get two non-superimposable mirror images.

  28. What are Structural Isomers In structural isomerism, the atoms are arranged in a completely different order.

  29. STRUCTURAL ISOMERISM - INTRODUCTION COMPOUNDS HAVE THE SAME MOLECULAR FORMULA BUT DIFFERENT STRUCTURAL FORMULA Chain different arrangements of the carbon skeleton similar chemical properties slightly different physical properties more branching = lower boiling point

  30. STRUCTURAL ISOMERISM - INTRODUCTION COMPOUNDS HAVE THE SAME MOLECULAR FORMULA BUT DIFFERENT STRUCTURAL FORMULA Chain different arrangements of the carbon skeleton similar chemical properties slightly different physical properties more branching = lower boiling point Positional same carbon skeleton same functional group functional group is in a different position similar chemical properties - slightly different physical properties

  31. STRUCTURAL ISOMERISM - INTRODUCTION • COMPOUNDS HAVE THE SAME MOLECULAR FORMULA • BUT DIFFERENT STRUCTURAL FORMULA • Chain different arrangements of the carbon skeleton • similar chemical properties • slightly different physical properties • more branching = lower boiling point • Positional same carbon skeleton • same functional group • functional group is in a different position • similar chemical properties - slightly different physical properties • FunctionalGroup different functional group • different chemical properties • different physical properties • Sometimes more than one type of isomerism occurs in the same molecule. • The more carbon atoms there are, the greater the number of possible isomers

  32. STRUCTURAL ISOMERISM - CHAIN caused by different arrangements of the carbon skeleton similar chemical properties slightly different physical properties more branching = lower boiling point There are two structural isomers of C4H10. One is a straight chain molecule where all the carbon atoms are in a single row. The other is a branched molecule where three carbon atoms are in a row and one carbon atom sticks out of the main chain. BUTANE straight chain 2-METHYLPROPANE branched C4H10

  33. STRUCTURAL ISOMERISM - CHAIN DIFFERENCES BETWEEN CHAIN ISOMERS ChemicalIsomers show similar chemical properties because the same functional group is present. Physical Properties such as density and boiling point show trends according to the of the degree of branching Boiling Point“straight” chain isomers have higher values than branched ones the greater the degree of branching the lower the boiling point branching decreases the effectiveness of intermolecular forces less energy has to be put in to separate the molecules - 0.5°C straight chain - 11.7°C branched greater branching = lower boiling point

  34. STRUCTURAL ISOMERISM - POSITIONAL molecule has the same carbon skeleton molecule has the same same functional group... BUT the functional group is in a different position have similar chemical properties / different physical properties Example 1 POSITION OF A DOUBLE BOND IN ALKENES 1 2 2 3 PENT-1-ENE double bond between carbons 1 and 2 PENT-2-ENE double bond between carbons 2 and 3 There are no other isomers with five C’s in the longest chain but there are three other structural isomers with a chain of four carbons plus one in a branch.

  35. Complete task 1 and task 2 in your hand out…..

  36. Chain isomerism – isomers of pentane

  37. STRUCTURAL ISOMERISM - POSITIONAL molecule has the same carbon skeleton molecule has the same same functional group... BUT the functional group is in a different position have similar chemical properties / different physical properties Example 2 POSITION OF A HALOGEN IN A HALOALKANE BUT 1 2 2 1-CHLOROBUTANE halogen on carbon 1 2-CHLOROBUTANE halogen on carbon 2 is NOT 3-CHLOROBUTANE Moving the chlorine along the chain makes new isomers; the position is measured from the end nearest the functional group... the third example is 2- NOT 3-chlorobutane. There are 2 more structural isomers of C4H9Cl but they have a longest chain of 3

  38. STRUCTURAL ISOMERISM - POSITIONAL molecule has the same carbon skeleton molecule has the same same functional group... BUT the functional group is in a different position have similar chemical properties / different physical properties RELATIVE POSITIONS ON A BENZENE RING Example 3 1,2-DICHLOROBENZENE ortho dichlorobenzene 1,3-DICHLOROBENZENE meta dichlorobenzene 1,4-DICHLOROBENZENE para dichlorobenzene

  39. Complete task 3 ,4 and 5 in your hand out..

  40. Chain and position isomers of C4H9OH butan-1-ol 2-methylpropan-1-ol butan-2-ol 2-methylpropan-1-ol

  41. Chain isomerism – isomers of hexane

  42. Position isomerism

  43. STRUCTURAL ISOMERISM – FUNCTIONAL GROUP molecules have same molecular formula molecules have different functional groups molecules have different chemical properties molecules have different physical properties ALCOHOLS and ETHERS ALDEHYDES and KETONES ACIDS and ESTERS MORE DETAILS FOLLOW

  44. STRUCTURAL ISOMERISM – FUNCTIONAL GROUP ALCOHOLS and ETHERS NameETHANOL METHOXYMETHANE ClassificationALCOHOLETHER Functional GroupR-OHR-O-R Physical propertiespolar O-H bond gives rise No hydrogen bonding to hydrogen bonding. low boiling point get higher boiling point insoluble in water and solubility in water Chemical properties Lewis base Inert Wide range of reactions

  45. STRUCTURAL ISOMERISM – FUNCTIONAL GROUP ALDEHYDES and KETONES Name PROPANAL PROPANONE ClassificationALDEHYDEKETONE FunctionalGroupR-CHOR-CO-R Physicalpropertiespolar C=O bond gives polar C=O bond gives dipole-dipole interaction dipole-dipole interaction Chemical properties easily oxidised to acids of undergo oxidation under same number of carbons extreme conditions only reduced to 1° alcohols reduced to 2° alcohols

  46. STRUCTURAL ISOMERISM – FUNCTIONAL GROUP CARBOXYLIC ACIDS and ESTERS NamePROPANOIC ACID METHYL ETHANOATE ClassificationCARBOXYLIC ACIDESTER Functional GroupR-COOHR-COOR Physical propertiesO-H bond gives rise No hydrogen bonding to hydrogen bonding. insoluble in water get higher boiling point and solubility in water Chemical properties acidic fairly unreactive react with alcohols hydrolysed to acids

  47. What about benzene rings?

  48. Functional group isomerism A molecular formula C3H6O could be either propanal (an aldehyde) or propanone (a ketone).

  49. All three compounds are aromatic. Aspirin is also a carboxylic acid ( CO2H) and an ester ( CO2CH3). Tylenol is also an alcohol ( OH) and an amide ( CONH ). Ibuprofen contains alkanesubstituents and a carboxylic acid functional group

  50. AS Chemistry Combustion

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