CHAPTER 11 MODIFIED

Chapter 11: Unsaturated Hydrocarbons

Alkenes and Alkynes

• General formulas:

  • Alkane: CnH2n+2

  • Alkene: CnH2n

  • Alkyne: CnH2n-2

  • Example: CH3CH3

• Physical properties:

  • Intermolecular forces: London-dispersion forces

  • Higher mass leads to higher boiling and melting points

  • Density: less dense than water

  • Polarity: Non-polar, insoluble in water

Nomenclature

• Rules for Parent Compound:

  • Identify the longest continuous chain containing alkene or alkyne groups.

  • Number the parent chain to minimize the number of the double or triple bond.

  • Examples to illustrate the rules.

Multiple Double Bonds in Alkenes and Alkynes

• Alkenes with more than one double bond:

  • 2 double bonds: alkadiene

  • 3 double bonds: alkatriene

• Follow the same numbering rules for alkynes as alkenes.

• Numbering starts from the end closest to the double or triple bond.

Cycloalkene Nomenclature

• Parent compound contains prefix "cyclo" and ends with "ene".

• Numbering begins at one end of the double bond and passes through it.

• Substituents receive the lowest possible numbers.

• Example: 6-bromo-1-ethyl-1,4-cycloheptadiene.

Geometric Isomers

• Definition: Restricted rotation around double bonds leads to geometric isomers.

• Form when there are two different groups or atoms on each carbon of the double bond.

  • Types: cis and trans isomers.

Identifying Geometric Isomers

• Practice distinguishing between cis, trans, or neither for given compounds.

Reactions of Alkenes and Alkynes

• Key reactions include addition reactions:

  • Hydrogenation (H-H)

  • Halogenation (Br-Br, Cl-Cl)

  • Hydration (H-O-H)

  • Hydrohalogenation (H-Cl, H-Br)

• Double bond is replaced by two single bonds to new atoms/groups in these reactions.

Hydrogenation Reaction

• Description: Also called a reduction reaction.

• Example of an alkene and the balanced equation resulting in an alkane.

  • Alkene → Corresponding alkane

• Example with 2-Butyne reacting to form butane.

Halogenation Reaction

• Addition of Cl2 or Br2:

  • Resulting in an haloalkane.

• Example with alkenes converting to 3,4-dimethyl-2-pentene and 2,3-dichloro-3,4-dimethylpentane.

Practice for Hydrogenation and Halogenation

• Predict products from given reagents.

Hydration Reaction

• Addition of Water (Markovnikov's Rule):

  • The carbon with more hydrogens gets the new hydrogen bond, forming an alcohol.

  • Provide examples of predicting products with major emphasis.

Hydration in Alkynes

• Reaction results in a carbonyl group from an alkyne:

  • Example of product formation resulting in ketones or aldehydes.

Hydrohalogenation Reaction

• Addition of HCl or HBr:

  • Major product determined by Markovnikov's rule.

  • Illustrated with structures showing reaction processes.

Hydrohalogenation with Alkynes

• Similar reactions to alkenes with HCl or HBr.

Practice for Hydration and Hydrohalogenation

• Predict products and identify which compounds cannot be formed from a specified hydration.

Aromatic Carbons

• Properties differ from alkanes, alkenes, and alkynes.

  • Example: Benzene structure.

  • Illustrate common drugs like Ibuprofen and Acetaminophen.

IUPAC Naming of Benzene Derivatives

• Familiarize with common structures and substitutions (Cl, NO2, CH2-CH3).

  • The structure of Toluene, Phenol, Aniline.

Positions on Benzene

• Understand ortho, meta, para positions using dichlorobenzene examples.

• Different positions: 1,2-dichlorobenzene (ortho), 1,3-dichlorobenzene (meta), 1,4-dichlorobenzene (para).

Reactions Involving Benzene

• Typical benzene reactions include:

  • Substitution with Cl2 or Br2.

  • Substitution with sulfur trioxide.

Nitration Reaction of Benzene

• Process that leads to nitrobenzene:

  • Requires HNO3 and H2SO4.

  • Key process temperature: 50-55°C.

Final Problems for Chapter 11

• Complete exercises identifying products from hydration of alkynes and reduction of alkenes.

Polymers

• Definition: Macromolecules made of repeating monomer units.

• Examples include:

  • Polyethylene

  • Polyvinyl chloride (PVC)

  • Polytetrafluoroethylene (Teflon).

• Common uses: Milk containers, PVC pipes.