Functional groups

• Functional groups

  • groups of atoms with characteristic properties
  • unreactive FGs: C-C and C-H bonds
  • reactive FGs: contain heteroatoms (non C,H), pi bonds, usually double and triple bonds
• heteroatoms confer reactivity to a molecule

  • they usually form polarized bonds to C
  • have non-bonded electron pairs that can behave as B-L or lewis bases
  • they can have X-H bonds (X = heteroatoms), which can be acidic
• pi bonds confer reactivity

  • they are relatively weak
  • the electron pair that makes up the bond can be nucleophile (Lewis or B-L base)
• R notation: an carbon skeleton attached to an FG
• Hydrocarbons: consists of C + H only, but contain multiple bonds (pi bonds)

  • aliphatic hydrocarbons
  • aromatic hydrocarbons
• aliphatic hydrocarbons

  • alkanes: only C-C sigma bonds, no FGs
  • alkenes: have C=C, with FG
  • alkynes: have C triple bond C, with FG
• aromatic hydrocarbons

  • C-H sigma bonds
  • ring-like structure
  • delocalized pi bonds
• bonds

  • one bond: 1 sigma bond
  • two bonds: 1 sigma + pi bonds
  • three bonds: 1 sigma + 2 pi bonds
• FGs with C=O groups are called carboxylic acids

  • polarized toward oxygen
  • CR2O
  • O has two lone pairs
  • double bond (pi) can be broken easily
• C=O FGs

  • aldehyde, RCH=O
  • ketone, RCR=O
  • carboxylic acid, RC(OH)=O
  • ester (carboxylic ester), RC(OR)=O
  • anide, RC(NR2)=O
  • acid chloride (very reactive), RC(Cl)=O