Chapter 7 OCHEM

Overview of Organic Chemistry I Topics

  • Structure and Bonding

  • Polar Covalent Bonds; Acids and Bases

  • Alkanes & Their Stereochemistry

  • Cycloalkanes & Their Stereochemistry

  • Stereochemistry at Tetrahedral Centers

  • Overview of Organic Reactions

  • Organohalides

  • Nucleophilic Substitutions and Eliminations

  • Alkenes: Structure and Reactivity

Degrees of Unsaturation

  • Formula for saturated hydrocarbons: CnH2n+2C_nH_{2n+2}

  • Degrees of unsaturation:
      - CnH2nC_nH_{2n} : 1 double bond or ring
      - CnH2n−2C_nH_{2n-2} : 2 double bonds, 1 double bond & 1 ring, or 1 triple bond

  • Halogens (F, Cl, Br, I) behave like H; O has no effect; N adds an extra H.

Nomenclature of Alkenes

  • Infixes indicate CC double/triple bonds:
      - -an- (single), -en- (double), -yn- (triple)

  • Alkene priority in numbering > halides and alkyl groups.

  • Cycloalkenes assume starting at carbon 1.

Isomers and Stability

  • E/Z nomenclature for stereoisomers in alkenes:
      - Assign priorities; higher = E (entgegen), lower = Z (zusammen).

  • Stability of alkenes = More substituted alkenes are more stable.
      - Heat of hydrogenation indicates stability: more heat released from less substituted alkenes.

Electrophilic Addition Mechanisms

  • Alkenes act as Lewis bases and nucleophiles.

  • Addition of HX (HBr, HCl) involves a proton transfer mechanism leading to carbocation formation.

  • Markovnikov's Rule: H adds to the carbon with the most Hs attached.

Carbocation Rearrangements

  • 1,2-Hydride shifts and 1,2-alkyl shifts lead to more stable cations.

  • The preference is to shift that increases stability the most.