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.