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Chapter 24 and Beyond

Chapter 24 and Beyond. Organic Chemistry: Nomenclature and Reactions. Organic Chemistry. What does this branch of chemistry deal with?. Compounds that contain carbon (and hydrogen), called hydrocarbons Aliphatic – Chains Aromatic – Resonating rings of delocalized electrons

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Chapter 24 and Beyond

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  1. Chapter 24 and Beyond Organic Chemistry: Nomenclature and Reactions

  2. Organic Chemistry • What does this branch of chemistry deal with? • Compounds that contain carbon (and hydrogen), called hydrocarbons • Aliphatic – Chains • Aromatic – Resonating rings of delocalized electrons • Very specific hydrocarbon naming system - IUPAC • Different types are separated according to certain functional groups

  3. Aliphatic Hydrocarbons • What are the three main types of aliphatic hydrocarbons? • Based on the types of bonds: • Alkane – only single bonds • Saturated • i.e. hard to breakdown • Alkene – At least one double bond • Unsaturated • i.e. easy to breakdown • Alkyne – At least one triple bond • Unsaturated

  4. Notes About Drawing • What are the guidelines for drawing organic structures? • Structural Diagrams • Shows all atoms, bonds and structure • Structural Formulas • Shows all atoms and suggests structure CH3CH(OH)CH2CH3 • Skeletal Diagrams

  5. Structural Formula • How are structural formulas different from molecular and empirical? • Structural formulas show the basic structure and location of functional groups • CH3CH2CH2CH3 • Molecular formulas simply show the number of atoms • C4H10 • Empirical formulas are simplified molecular formulas • C2H5

  6. International Union of Pure and Applied Chemistry (IUPAC) • What is IUPAC? • IUPAC is an organization that has determined the internationally adopted way to name chemicals • Nomenclature – fancy word for naming • System is based on the longest hydrocarbon chain and the Greek prefixes

  7. IUPAC Nomenclature for Alkanes • What is the first rule? • Determine the parent chain and name • Find the longest hydrocarbon chain • May not be a straight line • Use the appropriate prefix • Meth – 1 • Eth – 2 • Prop – 3 • But – 4 • Pent – 5 • Hex – 6 • Hept – 7 • Oct – 8 • Non – 9 • Dec – 10

  8. IUPAC Nomenclature for Alkanes • If there are only single bonded carbons use the suffix – ane • Ex.

  9. IUPAC Nomenclature for Alkanes • What is the second rule? • If an alkane has a hydrocarbon (alkyl) group, determine its name and number • Use the suffix -yl • Make sure to assign it so that it has the lowest number possible • Ex.

  10. IUPAC Nomenclature for Alkanes • What is the third rule? • What is the fourth rule? • If more than one alkyl group exists then you must assign the lowest numbers possible • If there is more than one of the same group, use the prefixes di-, tri- and tetra- • Also in alphabetical order! • Ex.

  11. IUPAC Nomenclature for Alkanes

  12. IUPAC Nomenclature for Alkanes • Please name the following compounds.

  13. IUPAC Nomenclature for Alkanes • Please draw the following compounds. • 2-methyl heptane • 4-ethyl-3,4-dimethyl octane • 4-ethyl-2,2-dimethyl hexane • 2,4,4-trimethyl heptane • 3,3-diethyl-2,5-dimethyl nonane • 4-propyl-3-methyl heptane

  14. IUPAC Nomenclature for Alkanes • Please build the following compounds. • propane • 2-methyl butane • 2,2-dimethyl pentane

  15. Alkenes and Alkynes • How do we name hydrocarbons with a double or triple bond? • Double and triple bonds MUST have the lowest number possible • Determine the lowest number where the bond begins and place in or in front of the parent chain • Suffix added to the parent name • Alkenes use the suffix –ene • Alkynes with the suffix –yne • Ex.

  16. IUPAC Nomenclature for Alkanes • What is a functional group? • Functional group Anything that is not a C-C or H-C single bond OR not part of the main chain • Substituent Something that is substituted in for a H • Ex. -Br, -OH, -CH3,etc. • Alkyl Group  A hydrocarbon substituent • Ex. Methyl or ethyl group

  17. Functional Groups • How do we identify and name a(n)... • Alcohol • General Formula: R-OH • Naming: -e at the end of alkane replaced by –ol • Ex. Ethanol • Can also use hydroxy prefix • Halogenoalkane • General Formula: R-X • X=F, Cl, Br, I • Naming: fluoro-, chloro-, bromo-, iodo- place before parent chain • Ex. 2-chloro-propane

  18. Functional Groups • How do we identify and name a(n)... • Aldehyde • General Formula: R-CHO • Naming: -e at the end of alkane replaced by –al • Ex. Propanal • Keytone • General Formula: R-COR’ • Naming: -e at the end of alkane replaced by –one • Ex. 2-Butanone or Butan-2-one

  19. Functional Groups • How do we identify and name a(n)... • Carboxylic Acid • General Formula: R-COOH • Naming: -e at the end of alkane replaced by –oic acid • Ex. Propanoic Acid

  20. Functional Groups How do we identify an... • Amine • General Formula: R-NH2 • Ex. Propyl amine • Ester • General Formula: R-COOR’ • Ex. Ethyl ethanoate

  21. Reactivity of Alkanes • Why are alkanes very unreactive? • Strong C-C and C-H bonds • Very low polarity • Can only undergo combustion and halogen substitution reactions

  22. Combustion of Alkanes • What is required for combustion? • All hydrocarbons burn with large amounts of oxygen • When combusted they produce two products: • Carbon dioxide • Water

  23. Combustion of Alkanes • Why is this reaction exothermic? • C=O and O-H bonds are stronger than C-C and C-H, so energy is released • For this reason, alkanes (natural gases) make very good fuels

  24. Combustion of Alkanes • What happens when there is not enough oxygen? • Incomplete combustion • CO and other harmful chemicals are now made in addition to CO2 and water • Motor vehicles use catalytic converters to minimize this effect

  25. Alkane Substitution Reactions • What is a substitution reaction? • A functional group replaces a hydrogen • In this case, a halogen will replace a hydrogen • Typically Br2 or Cl2 • This cannot happen without a high energy catalyst, ultraviolet light

  26. Mechanism of Chlorination of Methane • What is a mechanism? • Breaks down the different parts of a reaction and shows the movement of electrons • Single electron movement • Electron pair movement

  27. Mechanism of Chlorination of Methane • What are the different types of chemical cleavage? • A bond can break: • Heterolytically • Both electrons go to one atom • Homolytically • One electron goes to each

  28. Mechanism of Chlorination of Methane • What is unique about homolytic cleavage? • It does NOT create ions, but something new called… FREE RADICALS! • Radicals are VERY reactive and are very complicated • NOTE: They play a large part in atmospheric chemistry, global warming and ozone depletion

  29. Mechanism of Chlorination of Methane • What is the mechanism for the chlorination of methane? • Three steps • Initiation • Cl2 homolytically cleaves • Propagation (chain reaction) • Radical Cl removes H from CH4 • Cl2 cleaves and a Cl radical attaches to the methane radical • Termination • Two Cl radicals combine with each other • One Cl radical attaches to the methane radical • Two methane radicals combine with each other

  30. Mechanism of Chlorination of Methane • What can be done with your chloromethane product? • It can continue to be substituted in the same manner to produce dichloromethane, trichloromethane and tetrachloromethane

  31. Mechanism of Chlorination of Ethane

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