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Organic Chemistry

Organic Chemistry. Organic Chemistry: The chemistry of carbon and carbon-based compounds. Organic Chemistry in everyday life: Smells & tastes: fruits, chocolate, fish, mint Medications: Aspirin, Tylenol, Decongestants, Sedatives

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Organic Chemistry

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  1. Organic Chemistry Organic Chemistry: The chemistry of carbon and carbon-based compounds Organic Chemistry in everyday life: Smells & tastes: fruits, chocolate, fish, mint Medications:Aspirin, Tylenol, Decongestants, Sedatives Addictive substances: Caffeine, Nicotine, Alcohol, Narcotics Hormones/Neurotransmitters: Adrenaline, Epinephrine Food/Nutrients: Carbohydrates, Protein, Fat, Vitamins Genetics: DNA, RNA Consumer products: Plastics, Nylon, Rayon, Polyester

  2. Drawing Organic Structures Butane: C4H10 Shortcuts make structures easier & faster to draw Lewis Structure Carbon Atoms • Line Structure • Only shows bonds • C atoms assumed at each end and intersection of bonds • H atoms not shown • Assume 4 bonds to each C • Fulfill C’s 4 bonds by adding H’s Condensed Structures CH3CH2CH2CH3 CH3(CH2)2CH3

  3. Types of Organic Compounds Alkane Alcohol Carboxylic acid Alkene Ether Amine Alkyne Ketone Amide Haloalkane Aldehyde Amino acid Classified according to functional group

  4. Big Idea in Organic Chemistry Structure controls Function Each functional group has predictable reactivity

  5. Alkanes or Paraffins • All C atoms are tetrahedral and sp3 hybridized (only C-C single bonds) • General formula = CnH2n+2 (CH4, C2H6, C3H8, C4H10, etc.) • Can have linear or branched alkanes C5H12 1° 3° 2° • Same molecular formula, different structure: structural isomers • Branches are called substituents • Primary (1°) carbon atom:bound to one other C atom • Secondary (2°) C atom: bound to 2 other C atoms • Tertiary (3°) C atom: ” 3 ” • Quaternary (4°) C atom: ” 4 ”

  6. Names of Linear Alkanes and Alkyl Substituents # of C atoms Alkane Alkyl substituents CH4 CH3CH3 CH3CH2CH3 CH3CH2CH2CH3 Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane Methyl Ethyl Propyl etc. -CH3 -CH2CH3 -CH2CH2CH3 1 2 3 4 5 6 7 8 9 10 Root: number of C atoms Suffix: functional group (-ane for alkanes) (-yl for alkyl groups)

  7. H H C H H H H H H H ? R R C H ? C C C H C H H H H H H H H H H C C C H C H H H H Methane CH4 Butane C4H10 Methyl -CH3 Butyl -C4H9 Where R = any other C atom or arrangement of C atoms

  8. First Ten Hydrocarbons: Properties Number of Carbon Atoms Molecular Formula Melting Point, oC Boiling Point, oC # of Isomers Name • -182.5 • -183.2 • -187.7 • -138.3 • -129.7 • 95.3 • 90.6 • 56.8 • 53.6 • 29.7 • -161.5 • -88.6 • -42.1 • -0.5 • 36.1 • 68.7 • 98.4 • 125.7 • 150.8 • 174.0 • 1 • 1 • 1 • 2 • 3 • 5 • 9 • 18 • 35 • 75 Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane 1 2 3 4 5 6 7 8 9 10 CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18 C9H20 C10H22

  9. Properties of Alkanes Nonpolar → only London Dispersion Forces IMF Compound Methane Ethane Propane Butane Pentane Larger molecular weight → Stronger London dispersion forces Formula CH4 C2H6 C3H8 C4H10 C5H12 MW 16 30 44 58 72 Boiling point (°C) -164 -88.6 -42.1 -0.5 +36.0 Linear Alkanes: 1 - 4 C atoms: gas at room temp 5 - 15 C atoms: liquid at room temp >15 C atoms: solid at room temp

  10. Fractional Distillation of Crude Oil Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 429

  11. Naming Branched Alkanes (IUPAC) Octane 4-ethyl • Root name: name of longest continuous C chain (parent chain) • 2 equally long? Choose the one with more branches • Number C atoms in chain, starting at end with first branch • Identify substituents, give each a number (C it is connected to) • Two or more identical substituents: use prefixes (di-, tri-, tetra-, etc.) • List substituents alphabetically before root name • Do not alphabetize prefixes • Punctuation: commas separate numbers from each other hyphens separate numbers from names no space between last substituent & root name 2 6 4-ethyl-3,5-dimethyloctane 8 5 4 3 7 1 3-methyl and 5-methyl = 3,5-dimethyl

  12. Common Names of other Alkyl Substituents 3 carbons R R Tertiary carbon Secondary carbon 4 carbons R R Remember that R =any carbon chain R isopropyl alphabetized as “i” “iso” indicates symmetry R isobutyl alphabetized as “i” 2o R 2o sec-butyl alphabetized as “b” 3o 3o tert-butyl alphabetized as “b” R

  13. Naming Practice H H H H C C H C H C H H H C H H H Line Structure Expanded Structure butane 2 - methylbutane

  14. Naming Practice CH3 CH3 1 2 3 6 5 4 3 4 5 2 6 1 Lowest sum of numbers is correct H H H C C C Line Structure H H H C C H H H C H H 4,4-dimethyl hexane 3,3-dimethyl hexane

  15. Isomers The fat dog shook himself, and then rolled over on the wet rug. OR The dog shook the fat rug, then rolled over and wet on himself. These two statements use the same words... but have very different meanings! Likewise, isomers may have the same formula, but have very different structures…

  16. Structural Isomers of C4H10 2-methylpropane or

  17. Structural Isomer Practice • On piece of your own paper, draw AND name ALL of the isomers for the following alkanes: # isomers Formulas C5H12 C6H14 C7H16 • Pentane • Hexane • Heptane 3 5 9 Some of your drawings may look different, but they are only different structures (isomers) if they also have different names If you complete that, try to draw and name all of the isomers for octane (C8H18). There are 18 of them!

  18. Structural Isomers: Pentane (C5H12) pentane 2-methylbutane 2,2-dimethylpropane

  19. Structural Isomers: Hexane (C6H14) hexane 2,3-dimethylbutane 2-methylpentane 2,2-dimethylbutane 3-methylpentane

  20. Structural Isomers: Heptane (C7H16) heptane 2,2-dimethylpentane 2-methylhexane 2,3-dimethylpentane 3-methylhexane

  21. Structural Isomers: Heptane (C7H16) 2,4-dimethylpentane 3-ethylpentane 3,3-dimethylpentane 2,2,3-trimethylbutane

  22. Comparing Structural Isomers (Same formula, different structure) C5H12 Structure Name Boiling point (°C) pentane 36.0 2-methylbutane 27.9 2,2-dimethylpropane 9.5 More branching → weaker London dispersion forces BP/MP of Linear alkanes > BP/MP of branched alkanes

  23. Chemical Bingo: Naming Review • There are 27 structures or names drawn on the next slide. Select 24 of them to be placed on your bingo card. • Because of space issues, I would number each bingo square and then list the names or structures on a separate sheet of paper • If I give you a name, you must match it to a structure. If I give you a structure, you must match it to a name • Any bingo winner will be awarded 1 bonus point on the quiz (5% pts)

  24. Chemical Bingo: Alkanes isopropyl sec-butyl tert-butyl isobutyl decane nonane 2,3,4,5-tetramethylhexane 3,4-diethylhexane 3,5-diethyl-4-isopropylheptane 4-tert-butyl-3,5-dimethylheptane 4-ethyl-2,2,3,5,6,6-hexamethylheptane Any isomer of C5H12 Any isomer of C6H14 Any isomer of C7H16

  25. Reactions of Alkanes Combustion • exothermic reaction • alkanes used as fuel source 13/2 4 5 C4H10 + ___ O2 ___ CO2 + ___ H2O • Incomplete Combustion with insufficient O2 produces CO • Poor ventilation, cigarettes 9/2 4 5 C4H10 + ___ O2 ___ CO + ___ H2O CO is poisonous because it binds to the hemoglobin in the blood, preventing the absorption of O2

  26. Radical Halogenation Terms • Mechanism • How the reaction occurs through multiple steps (most reactions actually occur in many steps) • Chain Reaction • Reactions that occur on their own after some initiating event • Free Radicals • Atoms that have one free electron—highly reactive

  27. Radical Halogenation Terms • Initiation Step • Step where a bond is split by heat/light, producing free radicals • Propagation Step • Step where free radicals react with non-radicals, producing more free radicals and continuing the “chain reaction” • Termination Step • Step where free radicals react with each other, producing non-radicals and terminating the “chain reaction”

  28. Reactions of Alkanes Radical Halogenation of Alkanes CH4 + Cl2 CH3Cl + HCl Mechanism (chain reaction): Step 1 Cl2⇌ Cl· + Cl · Step 2 Cl· + CH4  CH3· + HCl Step 3 CH3· + Cl2  CH3Cl + Cl· Step 4 Cl· + Cl·  Cl2 Type of Step Initiation Propagation Propagation Termination h (Free Radicals) Overall reaction: CH4 + Cl2 CH3Cl + HCl  chloromethane Why not 1-chloromethane? Halogenated product is a haloalkane Naming: halogen atom is a substituent, replace –ine ending with –o -F fluoro -Cl chloro -Br bromo -I iodo

  29. Radical Halogenation of Alkanes Halogen substitutes for hydrogen in alkane →multiple results Cl2  Cl2  Cl2  Cl2  CH4 CH3Cl CH2Cl2 CHCl3 CCl4 Compound CH3Cl CH2Cl2 CHCl3 CCl4 IUPAC Name Chloromethane Dichloromethane Trichloromethane Tetrachloromethane Common Name Methyl chloride Methylene chloride Chloroform Carbon tetrachloride • All are liquids at room temperature • Heavy Cl atoms increase LDF • Polar C-Cl bonds – can have polar molecules

  30. Textbook Resource Chemistry: An Intro to General, Organic and Biological Chemistry by Timberlake (Green/Tan Book) Sections 10.1-10.6 already covered Currently Section 11.2 (Haloalkanes) Can be used as an outside reference

  31. Naming Practice: Haloalkanes 3 6 2 2 4 1 1 4 5 5 6 3 Two equal numbering options? Number based on alpha order 5-chloro-2-fluorohexane 2-chloro-4-fluoro-2,3-dimethylpentane 2-chloro-5-fluorohexane 2-bromo-3-ethyl-4-iodopentane 2-bromo-4-chloro-3-isopropylpentane

  32. Radical Halogenation: Predict the Product ? + Cl2 → + HCl OR ? ? 1-chloropropane 2-chloropropane OR 3-chloropropane? Remember that any H on the alkane can be replaced by a halogen + Br2 → OR 2-bromo-2-methylbutane 1-bromo-2-methylbutane

  33. Radical Halogenation: Predict the Product + Br2 → OR 2-bromo-2-methylbutane 1-bromo-2-methylbutane OR OR 1-bromo-2-methylbutane 2-bromo-3-methylbutane 1-bromo-3-methylbutane

  34. Structural Isomers What are the possible structural isomers of C3H7Br? 1-bromopropane 2-bromopropane What are the possible structural isomers of C4H9Cl? 1-chlorobutane 2-chloro-2-methylpropane 1-chloro-2-methylpropane 2-chlorobutane

  35. Structural Isomer Practice On piece of your own paper, draw AND name ALL of the isomers with the following formulas: # isomers Formulas C4H9I C3H6Cl2 C5H11Br C4H8Cl2 4 4 8 9 To be honest, there may be more…this is what I found, so try and prove me wrong! Extra Credit to anyone who can find more structures… Some of your drawings may look different, but they are only different structures (isomers) if they also have different names

  36. Structural Isomers: C4H9I I I 2-iodobutane 1-iodobutane I I 1-iodo-2-methylbutane 2-iodo-2-methylbutane

  37. Structural Isomers: C3H6Cl2 1,1-dichloropropane 1,2-dichloropropane 1,3-dichloropropane 2,2-dichloropropane

  38. Structural Isomers: C5H11Br 2-bromopentane 1-bromopentane 3-bromopentane 1-bromo-3-methylpentane

  39. Structural Isomers: C5H11Br 2-bromo-3-methylbutane 1-bromo-2-methylbutane 2-bromo-2-methylbutane 1-bromo-2,2-dimethylbutane

  40. Structural Isomers: C4H8Cl2 1,2-dichlorobutane 1,1-dichlorobutane 1,4-dichlorobutane 1,3-dichlorobutane

  41. Structural Isomers: C4H8Cl2 1,1-dichlorobutane 1,2-dichloro-2-methylpropane 2,2-dichlorobutane 1,3-dichloro-2-methylpropane 2,3-dichlorobutane

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