Organic Chemistry Season 1 Quiz

Chemistry Department

• The document introduces a Chemistry Department.

Organic Division

• The Organic Division is introduced.
• A list of faculty members is provided (Dr. Gallimore, Dr. Downer-Riley, Mr. Denny, Dr. Brown, Prof. Porter).

Organic Chemistry Course

• The course (CHEM 0901) bridges CSEC and university-level chemistry.
• The course will cover four areas of chemistry (Organic, General, Inorganic, and Physical).
• It will feature rules, jargon, and theory for these branches.
• Successful completion will prepare students for Level 1 expertise within the discipline, potentially expanding to others.

Season 1 of Organic Chemistry

• The course is presented in 10 episodes.
• The episodes cover:
  • Introduction to Organic Chemistry
  • Introduction to Reaction Mechanisms
  • Alkanes
  • Alkenes
  • Alkynes

Season 3 of Organic Chemistry

• The curriculum continues in season 3.
• Episodes detail:
  • Alkenes: Preparations and Reactions
  • Alkynes: Naming, Preparation, and Reactions

Reduction of Alkynes

• Catalytic hydrogenation converts alkynes to alkanes (100%) by adding two equivalents of H2.
• The first addition produces a cis alkene via syn addition.
• A deactivated or poisoned catalyst can halt the reaction at the cis alkene stage.
• Lindlar's catalyst and P-2 (Ni2B complex- Nickel Boride) are poisoned catalysts examples. The first addition is catalyzed, but the second isn't.
• Dissolving metal reduction (using sodium metal and ammonia) converts alkynes to trans alkenes (80%). This results in anti addition of H and H.
• A lithium atom donates an electron to the alkyne's carbon-carbon triple bond. An electron pair shifts. The alkene's hybridization changes from sp to sp2. A vinylic radical is formed, and then a trans-vinylic anion. A second lithium atom donates an electron to the radical. Finally, a proton from ethylamine is removed, resulting in a trans alkene.

Summary of Alkynes Reduction

• Know the reagents (H2, Lindlar’s catalyst, Na/NH3) used for reducing alkynes to alkanes.

Introduction to Addition Reactions

• Addition reactions are the opposite of elimination reactions.
• A π bond breaks, converting to two sigma bonds.
• Examples of addition reactions:
  • Hydrohalogenation
  • Hydrogenation
  • Halogenation
  • Dihydroxylation

Introduction to Addition Reactions (Additional details)

• The π bond acts as an electron-pair donor (as a base or a nucleophile).

Addition vs Elimination

• Addition and elimination reactions are equilibrating.
• The favored side depends on temperature.
• Higher temperatures favor entropy, and elimination.
• Lower temperatures favor enthalpy, and addition reactions.

Catalytic Hydrogenation

• Catalyzes the addition of hydrogen (H2) across a carbon-carbon double bond.
• Requires a metal catalyst (e.g., Pt).
• Conveys an alkene to the respective alkane.
• Stereo specific syn addition is observed with hydrogenation reactions.
• Without a metal catalyst, the addition of H2 is slow due to high activation energy.
• The metal surface binds H2 and the alkene, explaining a syn addition process.

Partially Hydrogenated Oils

• Catalysts during hydrogenation sometimes isomerize double bonds, creating trans double bonds.
• Trans fats are linked to increased LDL cholesterol and cardiovascular disease.
• Food companies are reducing trans fats.

Halogenation

• Halogenation adds two halogen atoms across a carbon-carbon double bond.
• A key step in PVC production.
• Practical for Cl2 and Br2 but not as ideal with I2 (poor addition) or F2 (too violent).
• Regioselectivity is observed with anti addition.

Halogenation - Mechanism

• Bromonium ion intermediate correlates with anti addition.
• This intermediate is likened to the mercurinium ion.
• The alkene acts as a nucleophile, attacking molecular bromine.

Hydrohalogenation

• Adds H-X to an alkene (using HCl, HBr, or HI).
• If the alkene isn't symmetrical, regioisomers are possible (depending on whether H or X is positioned).
• Markovnikov addition is the regioselective preference.

Hydrohalogenation - Regioselectivity

• Hydrohalogenation is regioselective for Markovnikov addition.
• Markovnikov observed H atoms preferentially attach to the more hydrogen-substituted carbon atom.
• The halogen generally attaches to the more substituted carbon.
• The alkene abstracts a proton to make the more stable carbocation. The bromide anion afterward attacks this carbocation to make the alkyl halide.

Hydrohalogenation - Regioselectivity (with peroxides)

• Peroxide use with HBr reverses regioselevicity, resulting in anti-Markovnikov addition.
• The reaction mechanism changes significantly when peroxides are present.

Hydrohalogenation - Regioselectivity Mechanism

• The process begins with chain initiation (using peroxide under heat).
• Heat causes homolytic cleavage of the oxygen-oxygen bond, producing alkoxyl radicals.
• Chain progression: bromine radicals add to the double bond. This creates a more stable alkyl radical.
• The process continues, abstracting a hydrogen from HBr to create a bromine radical and repeat the chain progression steps.

Hydrohalogenation - Regioselectivity (Controlled addition)

• Regioselectivity of HBr addition is controllable.
• Markovnikov addition occurs with regular HBr.
• Anti-Markovnikov addition occurs with HBr and peroxide.

Hydrohalogenation - Regioselectivity (Practice problems)

• Finding the major product from several hydrohalogenation reactions.

Acid-catalyzed Hydration

• Water (H and OH) joins across the π bond.
• Acid-catalyzed hydration follows Markovnikov regioselectivity.
• Sulfuric acid is often used as the acid catalyst.

Acid-catalyzed Hydration (Alkene hydration details)

• OH is attached to the more substituted carbon in the alkene.
• The relative speed of the reaction aligns with carbocation intermediates.

Hydration - Mechanism

• The process shows alkene, water, and a catalyst (H+) reactions in steps.
• The alkene's electron pairs bond with the hydrogen ion.
• The resulting carbocation reacts with a water molecule to form a protonated alcohol.
• The proton from the water molecule is transferred, resulting in the alcohol product.

Summary (Various reaction summaries)

• A range of reactions (Hydrogenation, Hydrohalogenation, Halogenation, Hydration) is summarized via visual diagrams. The reagents and the outcomes(products) of each are included.

Special Thanks

• A list of individuals contributing to the project.

Test your knowledge on key concepts from Season 1 of the Organic Chemistry course. This quiz covers elimination reactions, hydrogenation processes, and halogenation methods, along with the roles of catalysts. Challenge yourself to see how well you understand these fundamental topics.