Organic Chemistry CHEM 0901 Quiz
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Questions and Answers

What is the main focus of the CHEM 0901 course?

  • To provide an overview of historical chemistry discoveries
  • To teach only laboratory techniques in chemistry
  • To specialize in only inorganic chemistry concepts
  • To bridge the divide between CSEC and university-level chemistry (correct)

Which of the following branches of chemistry is NOT mentioned in the CHEM 0901 course content?

  • Analytical Chemistry (correct)
  • Organic Chemistry
  • Inorganic Chemistry
  • Physical Chemistry

What is the purpose of understanding reaction mechanisms in the context of organic chemistry?

  • To focus only on theoretical approaches without application
  • To eliminate the need for laboratory work
  • To analyze how reactions occur and predict outcomes (correct)
  • To memorize complex chemical formulas

What does the course propose as a potential outcome after successfully mastering its content?

<p>Access to higher levels of expertise within or beyond chemistry (D)</p> Signup and view all the answers

What type of reactions are specifically included in Season 3 of the course?

<p>Pericyclic reactions including the Diels-Alder reaction (B)</p> Signup and view all the answers

What reaction is favored at lower temperatures?

<p>Addition reactions (B)</p> Signup and view all the answers

Which halogens can be used effectively in halogenation to add across a C=C double bond?

<p>Cl2 and Br2 (A)</p> Signup and view all the answers

What is necessary for catalytic hydrogenation to occur efficiently?

<p>Metal catalyst (A)</p> Signup and view all the answers

What type of addition is observed during catalytic hydrogenation?

<p>Syn addition (A)</p> Signup and view all the answers

What type of addition is observed during halogenation?

<p>Anti addition (C)</p> Signup and view all the answers

What intermediate is formed during the halogenation process?

<p>Bromomium ion (D)</p> Signup and view all the answers

What is a potential health issue related to partially hydrogenated oils?

<p>Increased LDL cholesterol (A)</p> Signup and view all the answers

What happens to double bonds during the hydrogenation process that can lead to trans fats?

<p>They are isomerized by the catalyst (C)</p> Signup and view all the answers

Which statement is true regarding halogenation with Br2?

<p>The alkene acts as a nucleophile. (A)</p> Signup and view all the answers

Why is halogenation with I2 considered poor?

<p>I2 does not effectively induce a dipole. (B)</p> Signup and view all the answers

What is the result of the catalytic hydrogenation of an alkyne?

<p>It forms a cis alkene followed by an alkane. (B)</p> Signup and view all the answers

What type of catalyst is used to prevent the further reduction of a cis alkene during hydrogenation?

<p>Lindlar’s catalyst (C)</p> Signup and view all the answers

Which of the following correctly describes the outcome of dissolving metal reduction?

<p>It reduces an alkyne to a trans alkene. (A)</p> Signup and view all the answers

What does the $ ext{C=C}$ π bond get converted into during an addition reaction?

<p>Two new sigma bonds (A)</p> Signup and view all the answers

How does temperature affect the equilibrium between addition and elimination reactions?

<p>Higher temperatures make entropy more significant in determining the favored side. (B)</p> Signup and view all the answers

Which catalyst is known to be a poisoned catalyst for controlling alkyne reduction?

<p>Nickel Boride (B)</p> Signup and view all the answers

What is the mechanism by which the first addition of H2 occurs in the catalytic hydrogenation of alkynes?

<p>Syn addition (C)</p> Signup and view all the answers

What is the defining characteristic of the cis alkene produced in the first step of alkyne reduction?

<p>It has substituents on the same side. (D)</p> Signup and view all the answers

What is the primary regioselectivity observed during hydrohalogenation of alkenes?

<p>The halogen is generally installed at the more substituted carbon. (A)</p> Signup and view all the answers

What can influence the regioselectivity of HBr addition during hydrohalogenation?

<p>Presence of peroxides (D)</p> Signup and view all the answers

What observation did Markovnikov make regarding the addition of hydrogen atoms during hydrohalogenation?

<p>Hydrogen atoms add to the carbon already bearing more hydrogen atoms. (A)</p> Signup and view all the answers

In a reaction with an unsymmetrical alkene, what outcome can be expected from hydrohalogenation?

<p>Two different regioisomers can be formed. (B)</p> Signup and view all the answers

What characterizes the bromomium ion intermediate in hydrohalogenation?

<p>It involves electrophilic attack on the pi bond. (B)</p> Signup and view all the answers

Which alkyl group is favored in carbocation stabilization during hydrohalogenation?

<p>Tertiary carbocations are the most stable. (C)</p> Signup and view all the answers

What type of addition does the bromomium ion intermediate facilitate during hydrohalogenation?

<p>Anti addition. (C)</p> Signup and view all the answers

How does the addition of H-X to an alkene change when peroxides are included?

<p>The regioselectivity switches from Markovnikov to anti-Markovnikov. (A)</p> Signup and view all the answers

Flashcards

Organic Chemistry

A branch of chemistry focusing on the structure, properties, composition, reactions, and preparation of carbon-containing compounds.

Reaction Mechanism

A step-by-step description of how a chemical reaction occurs, showing the movement of electrons and formation of intermediates.

Alkanes

Hydrocarbons (compounds containing only carbon and hydrogen) with single bonds between carbon atoms.

Alkenes

Hydrocarbons with at least one double bond between carbon atoms.

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Alkynes

Hydrocarbons with at least one triple bond between carbon atoms.

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Alkyne Reduction

The process of converting an alkyne into a simpler hydrocarbon, usually an alkene or alkane, by adding hydrogen atoms (H2).

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Catalytic Hydrogenation

A chemical reaction where hydrogen gas (H2) is added to an alkyne in the presence of a metal catalyst, like platinum or palladium, to form an alkane.

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Syn Addition

A type of addition reaction where two atoms or groups add to the same side of a double bond, creating a cis alkene.

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Poisoned Catalyst

A catalyst modified to slow down or stop a specific reaction, often used to control the reduction of alkynes, producing only the cis alkene.

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Lindlar's Catalyst

A poisoned catalyst (Pd metal with lead and quinoline) used in the reduction of alkynes to cis alkenes.

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Dissolving Metal Reduction

A reaction using sodium metal and ammonia to reduce an alkyne to a trans alkene. It involves the addition of hydrogen atoms to opposite sides of the double bond.

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Anti Addition

A type of addition reaction where two atoms or groups add to opposite sides of a double bond, forming a trans alkene.

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Addition vs. Elimination

Addition reactions involve the addition of atoms or groups to a molecule, while elimination reactions involve the removal of atoms or groups.

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Stereospecificity in Hydrogenation

Catalytic hydrogenation is stereospecific, meaning it always results in a syn addition of hydrogen atoms. This means the hydrogen atoms are added to the same side of the double bond.

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Why Catalyst for Hydrogenation?

A metal catalyst is crucial for hydrogenation because it lowers the activation energy, making the reaction happen at a reasonable rate. Without the catalyst, the reaction would be very slow due to the high activation energy.

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Trans Fats and Hydrogenation

During hydrogenation, the catalyst can sometimes isomerize double bonds, forming trans fats. These trans fats can raise LDL (bad) cholesterol levels and increase the risk of cardiovascular disease.

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Halogenation

The addition of two halogen atoms across a carbon-carbon double bond. This reaction is crucial for producing PVC.

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Regioselectivity in Halogenation

In halogenation, the addition of halogens occurs with anti addition, meaning the halogens attach to opposite sides of the double bond.

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Bromine as a Nucleophile

Bromine (Br2) acts as a nucleophile in halogenation. It can induce a dipole, making it react with the alkene (acting as an electrophile).

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Bromonium Ion Intermediate

A bromonium ion intermediate is formed during halogenation. It is a three-membered ring containing bromine and is similar to a mercurinium ion.

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Anti Addition in Halogenation Mechanism

The formation of a bromonium ion intermediate explains why only anti addition is observed in halogenation. Syn addition is not possible due to the cyclic intermediate.

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Hydrohalogenation

The addition of a hydrogen halide (HCl, HBr, or HI) to an alkene.

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Markovnikov's Rule

In hydrohalogenation, the hydrogen atom of the hydrogen halide preferentially adds to the carbon atom of the alkene that already has more hydrogen atoms.

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Regioselectivity

A reaction where one product is formed preferentially over other possible products.

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Carbocation Stability

Tertiary carbocations are more stable than secondary carbocations because they have more alkyl groups donating electron density, stabilizing the positive charge.

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Peroxide Effect

When peroxides are present during the hydrohalogenation of alkenes using HBr, the reaction proceeds via a free radical mechanism, leading to the anti-Markovnikov product.

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Anti-Markovnikov Addition

The hydrogen halide adds to the alkene in a way that the hydrogen atom goes to the carbon with fewer hydrogen atoms, opposite to Markovnikov's rule.

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Free Radical Mechanism

A reaction mechanism that involves species with unpaired electrons, called free radicals.

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Controlling Regioselectivity

The regioselectivity of hydrohalogenation can be controlled by the reaction conditions. For example, using peroxides with HBr can give the anti-Markovnikov product.

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Study Notes

Chemistry Department

  • This is a chemistry department

Organic Division

  • Individuals listed include Dr. Gallimore, Dr. Downer-Riley, Mr. Denny, Dr. Brown, and Prof. Porter

Course Information

  • The course, CHEM 0901, aims to bridge CSEC and university-level chemistry
  • The course covers four types of chemistry: organic, general, inorganic, and physical
  • Successful completion of the course could lead to further expertise within the discipline or other disciplines

Season 1 of Organic Chemistry

  • The first season includes 10 episodes
  • Topics covered in Season 1 include introduction to organic chemistry, reaction mechanisms, alkanes, alkenes, and alkynes

Season 3 of Organic Chemistry

  • Topics in Season 3 include:
    • Alkenes: Preparation and Reactions
    • Alkynes: Naming, Preparation & Reactions

Reduction of Alkynes

  • Catalytic hydrogenation converts alkynes to alkanes via syn addition of two Hâ‚‚ equivalents
  • A poisoned catalyst (e.g., Lindlar's catalyst) stops the reaction at the cis alkene, preventing further reduction
  • Dissolving metal reduction (using sodium metal and ammonia) produces a trans alkene via anti addition

Introduction to Addition Reactions

  • Addition is the reverse of elimination reactions
  • A C=C bond is converted to two new sigma bonds
  • The addition reactions listed include hydrohalogenation, hydrogenation, halogenation, dihydroxylation

Introduction to Addition Reactions - π bond

  • The Ï€ bond is an electron-pair donor
  • It can act as a base or nucleophile

Addition vs. Elimination

  • Addition and elimination reactions are equilibrating
  • The favored reaction is determined by temperature
  • Higher temperature favors elimination, while lower temperature favors addition

Catalytic Hydrogenation

  • The addition of Hâ‚‚ across a C=C double bond, using a metal catalyst, converts an alkene into an alkane
  • The addition occurs via syn addition
  • The metal catalyst lowers the activation energy needed for the addition to occur

Catalytic Hydrogenation Selectivity

  • Catalytic hydrogenation is stereospecific (only syn addition)

Partially Hydrogenated Oils

  • Catalysts during hydrogenation can isomerize some double bonds, producing trans double bonds
  • Trans fats are believed to increase LDL cholesterol and contribute to cardiovascular disease
  • Food industries often boast '0 grams of trans fats' on labels to minimize the trans fats in products

Halogenation

  • Halogenation adds two halogen atoms across a C=C double bond
  • Halogenation is a key step in PVC production and is primarily conducted using Cl2 and Br2
  • Halogenation is regioselective and occurs through anti addition
  • A key intermediate in the mechanism may be a bromonium ion

Hydrohalogenation

  • Hydrohalogenation adds an H-X molecule across a C=C double bond
  • This reaction, involving HCl, HBr, or HI, is regioselective and typically follows Markovnikov addition (more substituted carbon)
  • When peroxides are present, anti-Markovnikov addition occurs

Acid-catalyzed Hydration

  • Hydration adds water across a C=C double bond, with sulfuric acid typically as a catalyst
  • This reaction follows Markovnikov regioselectivity (OH goes to the more substituted carbon)
  • The addition occurs through a carbocation intermediate, with a higher rate for a more substituted carbon

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CHEM 0901 Episode 6: Alkenes PDF

Description

Test your knowledge on the key concepts of the CHEM 0901 Organic Chemistry course. This quiz covers reaction mechanisms, types of reactions, and health implications related to process outcomes. Assess your understanding of halogenation and catalytic hydrogenation as vital components of organic chemistry.

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