Week 2 L3 Video 2_default

Functional Groups Overview

  • Introduction to functional groups in organic chemistry, including alkanes, alkenes, alcohols, and amines.

Alkanes

  • Definition: Saturated hydrocarbons, typically represented in linear, ring (cycloalkane), or branched structures.

  • Arrangement: Can be open chain (aliphatic) or cyclic.

  • Naming Convention:

    • Ends in "-ane" (e.g., methane, ethane, propane, etc.) based on the number of carbon atoms.

    • Formulas: General formula CNH2n+2 for non-cyclic alkanes.

    • Cyclic alkanes have 2 fewer protons in their formula.

  • Structural Characteristics:

    • All alkanes exhibit tetrahedral geometry with sp3 hybridization and bond angles of approximately 109.5 degrees.

    • Main alkane names derived from Latin numerical roots:

      • 1 Carbon: Methane

      • 2 Carbons: Ethane

      • 3 Carbons: Propane

      • 4 Carbons: Butane

      • 5 Carbons: Pentane

      • 6 Carbons: Hexane

      • 7 Carbons: Heptane

      • 8 Carbons: Octane

      • 9 Carbons: Nonane

      • 10 Carbons: Decane

  • Line Drawings: Simplified representation omitting hydrogen atoms attached to carbon.

Alkenes

  • Definition: Unsaturated hydrocarbons with at least one double bond between carbon atoms.

  • Properties:

    • Bond angle: Approximately 120 degrees due to sp2 hybridization, results in trigonal planar geometry.

  • Naming Convention:

    • Ends in "-ene" to denote the presence of a double bond.

    • E.g., Ethene, Propene, Butene, etc.

  • Geometry Implications:

    • Presence of double bond prohibits free rotation, leading to locked planar structure, meaning it can not rotate - important. Happens for any double bond.

    • Example: Ethene described as entirely flat.

Alkynes

  • Definition: Hydrocarbons with at least one triple bond between carbon atoms.

  • Properties:

    • Geometry is linear with approximately 180-degree bond angles due to sp hybridization.

  • Naming Convention:

    • Ends in "-yne" (e.g., Ethyne, Propyne).

Nomenclature Principles

  • General Structure of Names:

    • Prefix indicates the number of carbon atoms.

    • Suffix indicates the functional group.

  • Examples of naming functional groups:

    • Alcohol: "-ol"

    • Aldehyde: "-al"

    • Amine: "-amine"

    • Ketone: "-one"

    • Carboxylic acid: "-oic acid"

Alcohols

  • Definition: Organic compounds with the hydroxyl (-OH) functional group.

  • Properties:

    • Alcohols introduce polarity; more interaction with water leads to higher boiling points than corresponding alkanes.

    • Examples: Ethanol (liquid) vs. Ethane (gas).

  • Naming Variants:

    • Primary (1°), Secondary (2°), Tertiary (3°) alcohols based on the position of the -OH group on the carbon chain.

    • Common names (e.g., butyl alcohol, isobutyl alcohol).

  • Dipole-dipole Interactions: tje attraction betweeen the positive end of one dipole and the negative end of another

  • Hydrogen bonding: when the +ve end of one dipole is a H bonded to F,O,N (atoms of high electronegativity)

Amines

  • Definition: Organic compounds containing nitrogen with at least one lone pair and bonds to hydrogen or hydrocarbon chains.

  • Properties:

    • Amines are somewhat weak bases, can form hydrogen bonds, and are generally polar compounds.

    • Classification:

      • Primary (1°) if nitrogen is bonded to one carbon, Secondary (2°) to two, Tertiary (3°) to three, and Quaternary (4°) if nitrogen is bonded to four groups.

    • Example names: Methylamine, Ethylamine, Dimethylamine.

Summary

  • The understanding of alkanes, alkenes, alkynes, alcohols, and amines forms the basis for organic chemistry.

  • Familiarity with nomenclature, structural formulas, and hybridization helps comprehend the properties and reactivities of various organic compounds.

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