1 / 61

Topic 10 Organic chemistry

Topic 10 Organic chemistry. Inorganic chemistry? Chemistry of life (now biochemistry)  Carbon chemistry Introduction Alkanes Alkenes Alkohols Halogenalkanes Reaction pathways. 10.1 Carbon molecules. Carbon has 4 valence electron’s (1s 2 2s 2 2p 2 )

traci
Download Presentation

Topic 10 Organic chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Topic 10Organic chemistry • Inorganic chemistry? Chemistry of life (now biochemistry)  Carbon chemistry • Introduction • Alkanes • Alkenes • Alkohols • Halogenalkanes • Reactionpathways

  2. 10.1 Carbon molecules • Carbon has 4 valence electron’s (1s22s22p2) • Tetrahedral structures if single bonds • Planar triangular if double bond • Linear if triple bonded

  3. Organic substances • Carbon is often (almost always) covalently bonded • Other common atoms is hydrogen, oxygen, nitrogen ….. • Molecules can be long chains or ring form • Hydrocarbons: Compounds only containing carbon and hydrogen

  4. HYDROCARBONS • Molecules containing only C and H • Alkanes, alkenes, alkynes, arenes, cycloalkanes

  5. Homologous series • Same general formula • Neighbouringmembersdiffer by –CH2- • Similarchemicalproperties • Gradation in physicalproperties, such as boilingpoint

  6. The first straight-chain alkanes, general formula CnH2n+2 Explain the trend! Predict the boilingpointofheptane!

  7. Different ways of representing structural formulas Skeletal formula Empiricalformula?

  8. IsomersSame molecular formula but different structural formulas Butane have 2 isomers: • CH3-CH2-CH2-CH3 Butane • CH3-CH-(CH3)-CH3 Methyl-propane

  9. Methyl-group 1 2 3 4 5 6 7 Find the longestcarbonchain and youhave the ”last name” of the compound: 7→ heptane Find and namesubstituents: 1 metyl-group Number the carbons in the chain so thatsubstituents gets as low no. as possible: the methyl-group is attached at carbon no. 2 Put it together: 2-methyl-heptane

  10. Ethyl-group Methyl-group 1 2 3 4 5 Find the longestcarbonchain and youhave the ”last name” of the compound: 5→ pentane Find and namesubstituents: 1 metyl-group and 1 ethyl-group Number the carbons in the chain so thatsubstituents gets as low no. as possible: the methyl-group is attached at C no. 3, and the ethyl-group at C no. 2 Put it together: 3-etyl-2-methyl-pentane

  11. Whichnames?

  12. The names 2-methyl-propane 2-methyl-butane 2,2-dimethyl-propane 2, 3-dimethyl-butane 2,2-dimethyl-butane 2-methyl-pentane

  13. 10.2 Alkanes • Homologous series of a saturated hydrocarbon with only single bonds between carbon atoms • General formula CnH2n+2 • Low m.p. and b.p. due to only van der Waal´s forces • Often gases and liquids at room temperature • Low reactivity

  14. Alkaneshavehighbondentalpiesand lowreactivity

  15. Alkaneshavelowbondpolarityand lowreactivity The higher the difference in electronegativity, the higher the reactivity in reactionswithe.g. nucleophiles (as weshallsee later…)

  16. Abouthydrocarbons • Alkanes and other hydrocarbons are good fuels • Complete combustion: Hydrocarbons + oxygen Carbon dioxide + water +heat • If oxygen is limited then incomplete combustion: carbon monoxide, CO and elementary carbon, C, may be formed

  17. Combustionofoctane • Complete (withplentyof O2): C8H18 + 25 O216 CO2 + 18 H2O • Incomplete (not enough O2): C8H18 + 9 O2 C + CO +2 CO2 + 9 H2O

  18. Reactivity • Alkanes can react with radicals- eg. chlorine in UV-light Cl-Cl2 Cl• unpaired electron • Compounds with unpaired electrons are called free radicals and are very reactive • Cl-Cl 2 Cl• homolytic fission • A-B A+ + B-heterolytic fission UV UV

  19. The reaction of methane and chlorine by radical reactions • 2 Cl• + CH4 CH3Cl + HCl • 2 Cl• + CH3Cl  CH2Cl2 +HCl • 2 Cl• + CH2Cl2  CHCl3+ HCl • 2 Cl• + CHCl3  CCl4 + HCl • Amixture of chlorinated methanes is achieved • Radical reactions involve an initiation step, one or more propagation steps, and a termination step

  20. Radicalreactions

  21. 10.3 Alkenes • Homologous series of unsaturated hydrocarbons with one or more double bonds between carbon atoms • General formula CnH2n • Low m.p. and b.p. due to only van der Waal´s forces • Often gases and liquids at room temperature

  22. Ethene CH2=CH2 Propene CH3-CH=CH2 ButeneCH3-CH2-CH=CH2 1-Butene or But-1-ene CH3-CH2=CH-CH3 2-Butene or But-2-ene Pentene CH3-CH2-CH2-CH=CH2 1-Pentene or Pent-1-ene CH3-CH2-CH2=CH-CH3 2-Pentene or Pent-2-ene

  23. Reactions of alkenes • Reactivedouble bonds • Lowactivationenergy • Addition and polymerizationreactions

  24. Addition reactions with bromine and hydrogen chloride • H2C=CH2 + Br2 H2BrC-CH2Br Spontaneous at NTP colourless red/brown colourless Used as proof of C-C-double bonds • H2C=CH2 + HCl  H3C-CH2ClSpontaneous at NTP

  25. Addition reactions with hydrogen and water • H2C=CH2+ H2H3C-CH3 E.g. Ni-catalyst. Industrially important when transformation of vegetable oil to margarine • H2C=CH2 + H2O H3C-CH2OH Catalyst: H2SO4, H3PO4or Al2O3 ~300oC, 7 MPa. At 1 atm the reversed reaction is favoured. Synthesis of alcohols

  26. Polymerisation reactions • Alkenes forming plastics, making plastics • Radical reactions involving Cl2 and UV-light • Initiation: Cl-Cl2 Cl• • Propagation; adding monomers to a long chain, e.g. H2C=CH2+ Cl• •H2C-CH2Cl monomer •H2C-CH2Cl + H2C=CH2•H2C-CH2-H2C-CH2Cl •H2C-CH2-H2C-CH2Cl + H2C=CH2•H2C-CH2-H2C-CH2-H2C-CH2Cl UV

  27. Termination Two radicals meet and a bond is formed. R-CH2•+ R’-CH2•  R-CH2-CH2-R’ • The polymer is ready!

  28. Addition polymerisation reactions (I)

  29. Addition polymerisation reactions (II) Teflon

  30. Benzene ring • Identify when present in structural formula, phenyl ring

  31. Functional groups • C-C double and triple bonds, phenyl ring • Other elements bonded in different ways with the carbon chain; alcohol, aldehyde, keton, carboxylic acid, amine, ester, halide • Give the molecule other chemical and physical properties

  32. 10.4 Alcohols • The functional group –OH • Name: stem + the suffix –anol(or as prefix: hydroxy) • H-bonds => higher b.p., smaller ones (C1-C3) are water-soluble

  33. Methanol CH3OH Wood spirit, formed by pyrolysis of wood. Highly toxic! Ethanol CH3-CH2-OH Alcohol, formed during fermentation of sugar. Technically very important; In drinks, as a solvent, desinfectant and fuel

  34. Propanol CH3-CH2-CH2-OH 1-propanol or propan-1-ol a primary alcohol CH3-CHOH-CH3 2-propanol or propan-2-ol a secondary alcohol Isopropanol, used as windscreen de-icer

  35. Butanol CH3-CH2-CH2-CH2-OH 1-butanol or butan-1-ol Non-water soluble CH3-CCH3OH-CH3 2-metyl-2-propanol or 2-metylpropan-2-ol,a tertiary alcohol Water soluble

  36. Combustion Alcohol + Oxygen  Carbon dioxide + water CH3-CH2-OH + 3 O2 2 CO2 + 3 H2O

  37. Redox reactions in organic chemistry • The carbon with a functional group (eg. –OH) will be oxidised first • Oxidation: Add oxygen and/or remove hydrogen from the carbon • Reduction: Add hydrogen and/or remove oxygen from the carbon

  38. The morebondsto oxygen, the higher oxidation stateof a carbon • oxidation  reduction  Alcohol Aldehyde Carboxylic acid CH4CH3OH HCHO H-COOH CO2 Methane Methanol MethanalMethanoic Carbon acid dioxide

  39. Oxidation of alcohols • Primary alcohol  Aldehyde Carboxylic acid • Secondary alcohol Ketone • Tertiary alcohol  no oxidation (unless C-C-bonds are broken)

  40. K2Cr2O7, Potassiumdichromate, a common oxidizing agent CH3CH2OH + Cr2O72- + H+ CH3CHO  CH3COOH + Cr3+ + H2O Reactive. Stable. Distill of Reflux when formed Otheroxidizing agents KMnO4, CuO, CuSO4

  41. Aldehyde • The functional group –CHO or • Name: stem + suffix: -anal • Dipoles => slightly higher bp’s, smaller ones are water-soluble etc. • Quite reactive compounds • Methanal H-CHO • EthanalCH3-CHO • Formed by light oxidation of primary alcohols

  42. Ketone • The functional group –CO- or • Name: stem + suffix: -anone • Dipoles => slightly higher bp’s, smaller ones are water-soluble etc. • Propanone (acetone) CH3-CO-CH3 • Pentane-2-one CH3-CO-CH2-CH2-CH3 • Formed by oxidation of secondary alcohols

  43. Carboxylic acids • The functional group –COOH or • Name: stem + suffix: -anoic acid • H-bonds => higher bp’s, smaller ones are water-soluble etc. • Acidic reactions • Methanoic acid H-COOH • Ethanoic acid CH3-COOH • Formed by strong oxidation of primary alcohols

  44. Salt of Carboxylic acids • Salt form: -COO-or • Name: stem + suffix: -oate ion • Methanoate H-COO- • Ethanoate CH3-COO- • Formed by reactionofcarboxylicacid and base: NaOH + CH3COOH Na+ + CH3COO-

  45. Halogenoalkane • Functional group: -X (-F, -Cl, -Br, -I) • Name: e.g. prefix: Chloro- + alkane • Chloromethane CH3-Cl • Bromoethane CH3-CH2-Br

  46. Ester • Identify when present in structural formula • Functional group: -COOC- • Alcohol + carboxylic acid  ester + water • Condensation reaction or esterification

  47. Amines • Identify when present in structural formula • Relatives to ammonia; weak base • Functional group –NH2 • H-bonds => higher bp’s, smaller ones are water-soluble etc. • Name: stem + suffix: -ylamine(or prefix amino-) • Ethylamine CH3-CH2-NH2

  48. 10.5 HalogenoalkanesReactions C—X d+ d- => Iodine compounds most reactive

  49. Nucleophiles and electrophiles- oftenneeded in organicreactions • Nucleophile- nucleuslover • Has freeelectronpair and whole or part negative charge • The larger the negative charge - the better the nucleophile • Eg: C=C, H2O, -OH, -CN, NH3 • Electrophile-electronlover • Has wholeor part positive charge • The larger the positive charge - the better the Electrophile • Eg: C=O, H+, C-Cl,

More Related