Notes on Organic Chemistry: Hydrocarbon Structure
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Introduction to Organic Chemistry: Hydrocarbon Structure
- The study of organic compounds and their reactions.
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Contents
- 10.1 Introduction to Organic Chemistry and Hydrocarbons
- 10.2 Alkanes and Cycloalkanes
- 10.3 Writing Condensed and Skeletal Line Structures of Alkanes and Cycloalkanes
- 10.4 Alkenes and Alkynes
- 10.5 Aromatic Hydrocarbons
- 10.6 Naming Substituted Hydrocarbons
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10.1 Introduction to Organic Chemistry and Hydrocarbons
- Organic compounds contain one or more carbon (C) and hydrogen (H) atoms.
- 95% of all compounds are organic; most biological compounds are organic.
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Common Organic Compounds
- Biological Compounds:
- Carbohydrates, proteins, lipids, DNA, RNA, hormones.
- Fuels:
- Natural gas, propane, gasoline, etc.
- Consumer Products:
- Styrofoam, plastics, Teflon, Kevlar, polyester, neoprene.
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Introduction to Hydrocarbons
- Hydrocarbons contain only carbon and hydrogen.
- Carbon has four valence electrons which allows for four covalent bonds.
- Bonds can be with other carbon atoms, hydrogen atoms, or other nonmetals (N, O, S, P, F, Cl, Br, I).
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Different Ways Carbon Can Bond
- Alkanes/Cycloalkanes: Four single bonds
- Alkenes/Aromatic Hydrocarbons: One double bond and two single bonds
- Alkynes: One triple bond and one single bond
- Bond geometries: Tetrahedral, trigonal planar, linear.
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Bonding Arrangement of Carbon in Hydrocarbons
- Hydrocarbons are nonpolar and interact through dispersion forces, the weakest intermolecular force of attraction.
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Organic or Inorganic?
- Identify hydrocarbons among:
- a. C₆H₁₂O₆
- b. NaCl
- c. HCl
- d. C₃H₈
- e. C₃H₇NO
- f. Water
- g. Fats
- h. CO₂
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The Simplest Alkanes
- Methane, CH₄
- Ethane, C₂H₆
- Propane, C₃H₈
- H H H
| | |
H-C-C-C-H
| | |
H H H
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- Molecules exhibit constant motion; alkanes can freely rotate around single bonds, creating various conformations.
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Identifying Equivalent Lewis Structures
- Analyze structures to find equivalent forms.
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Structural Isomers
- For larger alkanes (> 3 carbon atoms), multiple bonding arrangements exist.
- Structural isomers: Different compounds with the same molecular formula but different atom connectivity; they exhibit different physical and chemical properties.
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Identifying Structural Isomers
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Explanation of Structural Isomers
- Not conformations.
- The number of possible structural isomers increases with the number of carbon atoms in the formula (C₁₀H₂₂ has 75 structural isomers).
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Determining Structural Isomers
- Identify pairs of isomers.
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Physical Properties of Structural Isomers
- Variations in dispersion forces.
- Greater surface area = stronger dispersion forces.
- More branching = less surface area = weaker dispersion forces.
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Writing and Naming Straight-Chain Alkanes
- Straight-chain alkanes have no branching.
- Follow IUPAC system for naming based on the number of carbon atoms in the chain; “-ane” indicates an alkane.
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Alkane Base Names
- Structure and base names for various alkanes.
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Writing and Naming Cycloalkanes
- Follow similar naming conventions as alkanes.
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Cycloalkane Structures
- Examples of molecular formulas and Lewis structures for cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane.
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Writing Condensed Structures
- Representing each C and attached H atoms as groups CHn: C, CH, CH₂, CH₃ without showing bonds.
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Writing Condensed Structures for Branched-Chain Alkanes
- Sequence of carbon groups shows main chain; branches are shown appropriately.
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Example: 2-methylbutane
- Condensed structures and Lewis structure representation shown.
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Example: Name It
- Determining the name from structures.
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Write a condensed structure for the Lewis structure
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Writing Skeletal Line Structures (Part 1)
- Based on zigzag conformation; each C corresponds to a point.
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Writing Skeletal Line Structures (Part 2)
- Omitting C atom labels; representing structure efficiently without showing all H bonds.
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Writing Skeletal Line Structures (Part 3)
- Predict C–H bonds by visible bonds structure.
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Write the Skeletal Line Structure
- Task to create a skeletal structure.
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Cycloalkane Structure
- Typically represented as skeletal line structures.
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Write Skeletal Line Structures for Butane and Cyclobutane
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Writing Skeletal Line Structures of Branched-Chain Alkanes (Part 1)
- Arrange longest chain correctly when representing branches.
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Writing Skeletal Line Structures of Branched-Chain Alkanes (Part 2)
- Task: Naming branched structures.
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Writing Skeletal Line Structures of Branched-Chain Alkanes (Part 3)
- Dealing with rotations about branches.
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Skeletal Line Structures: Two Branches on a Single Branch Point
- Naming example with ethyl group.
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Naming Substituted Hydrocarbons
- Identifying parent chain and substituents in IUPAC naming system.
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Naming Substituted Alkanes (Continued)
- Select parent chain from longest branches and with most substituents.
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Proper IUPAC Naming
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Write a Lewis Structure and a Condensed Structure
- Task related to skeletal line structure.
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Alkenes
- Contain at least one C=C; trigonal planar geometry.
- Simplest alkene: Ethene (ethylene).
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Drawing Alkene Structures
- Skeletal line structures and condensed structures representation.
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Naming Straight-Chain Alkenes
- Use IUPAC rules; number chain toward the double bond for locator number.
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Alkene Examples
- Different lengths and structures labeled (e.g., 1-Octene, Cyclooctene).
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Name These Alkenes
- Task: Identify given alkenes.
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Dienes and Polyenes
- Diene: Alkene with two C=C bonds.
- Polyene: Alkene with several C=C bonds; example includes β-carotene.
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Label the Compounds as Alkenes, Dienes, or Polyenes
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Geometric Isomers
- Alkenes can display geometric isomerism due to restricted rotation around C=C bond.
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Geometric Isomers: Cis and Trans
- Distinction based on placement of groups around double bonds.
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Saturated and Unsaturated Fats
- Unsaturated fats contain cis double bonds causing bends, affecting packing and dispersion forces compared to saturated fats.
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How Do Unsaturated and Saturated Fats Differ?
- Discussion of structural implications on melting points and physical states.
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Label These Pairs of Compounds
- Task to classify isomers.
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Alkynes
- Hydrocarbons characterized by C≡C bonds, exhibiting linear geometry with 180° bond angles.
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Drawing Alkyne Structures
- Structures shown with appropriate representations for triple bonds.
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Alkynes Are Not Common in Nature
- Discussion point on occurrence frequency.
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Naming Alkynes
- Follow the same naming principles of alkenes, using the –yne suffix.
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Provide the IUPAC Name for Alkynes
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Aromatic Hydrocarbons
- Aromatic compounds discovered for strong aromatic characteristics; classified by common structure known as the aromatic ring.
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Benzene
- Simplest aromatic compound with characteristics including alternating bond types and delocalized electrons contributing to stability and reactivity.
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Depicting the Delocalized Electrons
- Trigonal planar arrangement with flat ring structure.
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Benzene and Cyclohexane
- Comparison highlighting structural differences and chemical properties.
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Aromatic Rings in Analgesics
- Contextual information on medicinal properties.
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End of Chapter & More
- Introduction to the Chemistry of Vision; highlight on age-related macular degeneration.
Page 64
The Chemistry of Vision (Part 1)
- Description of photoreceptors and their role in vision.
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The Chemistry of Vision (Part 2)
- Mechanism of light absorption and its impact on retinal structure.
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The Chemistry of Vision (Part 3)
- Discuss age-related degeneration impacts and chemical connections to dietary factors.