Organic Chemistry Exam 2 Flashcards
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Questions and Answers

Identify the relationship between these two structures.

  • Diastereomers (correct)
  • Enantiomers
  • The same compound
  • Unrelated compounds

What is the relationship of the following two structures?

  • Constitutional isomers
  • Identical (correct)
  • Enantiomers
  • Diastereomers

Which of the following is the correct IUPAC name of the following structure?

  • (S)-3-ethyl-2-methylpentane
  • (R)-3-ethyl-2-methylpentane
  • (R)-3-ethyl-2-methylhexane (correct)
  • (S)-3-ethyl-2-methylhexane

Identify the relationship between these two structures.

<p>The same compounds (B)</p> Signup and view all the answers

What is the relationship between the following two molecules?

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

Identify the relationship between the following two structures.

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

Identify the relationship between the following two structures.

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

What is the relationship between the following two compounds?

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

What is the specific rotation of pure (S)-carvone if a sample of (R)-carvone of 85% ee has a specific rotation of −54?

<p>64 (D)</p> Signup and view all the answers

If the specific rotation for Crestor (rosuvastatin) is +100, what would be the specific rotation for the stereoisomer shown at the right?

<p>Impossible to predict (B)</p> Signup and view all the answers

Identify the relationship between the following two structures.

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

What is the relationship between the two structures shown?

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

What is the specific rotation of a sample of carvone that is an equal mixture of the R and S enantiomers?

<p>0 (D)</p> Signup and view all the answers

Identify the relationship between these two structures.

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

What is the relationship of the following two structures?

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

Which of the following is the correct IUPAC name of the following structure?

<p>(R)-3-ethyl-2-methylhexane (D)</p> Signup and view all the answers

Identify the relationship between these two structures.

<p>The same compounds (A)</p> Signup and view all the answers

What is the relationship between the following two molecules?

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

Identify the relationship between the following two structures.

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

Identify the relationship between the following two structures.

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

What is the relationship of the following two structures?

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

What is the relationship between the following two compounds?

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

What is the specific rotation of pure (S)-carvone if a sample of (R)-carvone of 85% ee has a specific rotation of −54?

<p>64 (B)</p> Signup and view all the answers

If the specific rotation for Crestor (rosuvastatin) is known to be +100, what would be the specific rotation for the stereoisomer shown at the right?

<p>Impossible to predict (B)</p> Signup and view all the answers

Identify the relationship between the following two structures.

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

How many distinct signals would appear in the (proton-decoupled) 13C NMR spectrum for the following compound?

<p>5 (D)</p> Signup and view all the answers

What is the relationship between the two structures shown?

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

What is the percentage of the R enantiomer in a sample of carvone that has a specific rotation of 30, given that the specific rotation of (R)-carvone is −61?

<p>51% (A)</p> Signup and view all the answers

What is the specific rotation of a sample of carvone that is an equal mixture of the R and S enantiomers? (R)- carvone has a specific rotation of −61.

<p>0 (A)</p> Signup and view all the answers

What is the relationship between the following two molecules?

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

Identify the relationship between the following two structures.

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

What is the relationship between the following two compounds?

<p>Constitutional Isomers (A)</p> Signup and view all the answers

How many distinct resonances would appear in the (proton-decoupled) 13C NMR spectrum for the following compound?

<p>4 (C)</p> Signup and view all the answers

Which of the following is the correct IUPAC name of the following structure?

<p>(2S,4S)-2-Bromo-4,5-diethylheptane (B)</p> Signup and view all the answers

What is the percentage of the R enantiomer in a sample of carvone that has a specific rotation of −20, given that the specific rotation of (R)-carvone is −61?

<p>66.5% (A)</p> Signup and view all the answers

How many possible stereoisomers are there for Crestor (rosuvastatin), a medication used to reduce cholesterol?

<p>8 (B)</p> Signup and view all the answers

Which of the following describes the effect of a catalyst on a reaction?

<p>It lowers the energy of activation. (C)</p> Signup and view all the answers

What is wrong with the following mechanism?

<p>An arrow is also needed to indicate the loss of the leaving group. (D)</p> Signup and view all the answers

What pattern of curved arrow pushing represents the second step of this reaction?

<p>Nucleophilic attack (A)</p> Signup and view all the answers

Identify the electrophilic site in the following molecule.

<p>C of carbonyl (B)</p> Signup and view all the answers

What type of bond cleavage does the following reaction involve?

<p>homolytic</p> Signup and view all the answers

Flashcards

Diastereomers

Stereoisomers that are not mirror images.

Enantiomers

Stereoisomers that are mirror images.

Identical Compounds

Structurally the same with same physical properties.

(R)-3-ethyl-2-methylhexane

An example of IUPAC naming based on stereochemistry.

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Stereochemistry

The study of the spatial arrangement of atoms in molecules.

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Specific Rotation

Used to determine chirality and optical purity.

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Enantiomeric Excess (ee)

The purity of one enantiomer compared to another.

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Pure (S)-carvone

Specific rotation can be calculated from (R)-carvone's specific rotation.

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Equal Mixture

A mix of (R) and (S) carvone giving zero specific rotation.

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13C NMR Signals

Indicate unique carbon environments in a compound.

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Constitutional Isomers

Same molecular formula, different connectivity.

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Catalysts

Substances that lower activation energy without changing equilibrium.

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Transition States

High-energy states that are not isolable intermediates.

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Entropy Changes

Can be positive or negative, indicating disorder in a reaction.

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Proton Transfer

The process of a proton moving from one molecule to another.

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Nucleophilic Attacks

When nucleophiles approach and bond to electrophilic sites.

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SN1 vs. SN2

SN1 is unimolecular, SN2 is bimolecular in substitution reactions.

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Strong Nucleophiles

Favored in SN2 reactions, especially in aprotic solvents.

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Protic Solvents

Stabilize carbocations in SN1 mechanisms.

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Aprotic Solvents

Enhance SN2 reactivity by not stabilizing protons.

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Reactants and Functional Groups

Essential for understanding reactivity in organic chemistry.

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Rearrangement in Solvolysis

Stable carbocations can form during solvolysis reactions.

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Structure-Rate Relationship

How molecular structure influences reaction rate and mechanism.

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Electrophilic Sites

The regions in a molecule that attract nucleophiles.

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Mechanisms of Reaction

Step-by-step pathways outlining how reactions occur.

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Study Notes

Diastereomers and Enantiomers

  • Diastereomers are stereoisomers that are not mirror images of each other.
  • Enantiomers are stereoisomers that are mirror images.
  • Identical compounds are structurally the same and have the same physical properties.

IUPAC Nomenclature

  • (R)-3-ethyl-2-methylhexane is the correct IUPAC name based on stereochemistry.
  • Identify stereochemistry and carbon chain length for accurate naming.

Specific Rotations

  • Specific rotation can help determine chirality and optical purity.
  • If (R)-carvone has a specific rotation of -54 and is 85% ee (enantiomeric excess), the specific rotation of pure (S)-carvone is calculated to be 64.
  • The specific rotation for an equal mixture of (R) and (S) carvone is 0.

NMR Spectroscopy

  • Distinct signals in 13C NMR spectrums indicate unique carbon environments; for certain compounds, the expected signals can vary significantly.

Isomer Relationships

  • Constitutional isomers are compounds with the same molecular formula but different connectivity.
  • Understanding the relationships between structures, such as diastereomers, enantiomers, and identical compounds, is crucial for stereochemistry.

Catalysis and Reaction Kinetics

  • Catalysts lower the energy of activation, thus increasing reaction rates without altering the equilibrium constant.
  • Transition states represent high-energy points that are not isolable intermediates.

Entropy and Gibbs Free Energy

  • Entropy changes can be positive or negative depending on the reaction conditions, such as ring closures which typically have a negative ΔS due to restrictions on rotation.

Mechanisms of Reaction

  • Proton transfer, nucleophilic attacks, and loss of leaving groups are key steps in organic reaction mechanisms.
  • Identifying the electrophilic and nucleophilic sites in molecules helps predict reaction pathways.

Substitution and Elimination Reactions

  • SN1 and SN2 mechanisms differ in their pathways; SN1 is unimolecular while SN2 is bimolecular.
  • Strong nucleophiles in aprotic solvents favor SN2 reactions over SN1, which can be influenced by the degree of substitution of the alkyl halide.

Reaction Conditions

  • Specific solvents can facilitate reaction mechanisms; protic solvents can stabilize carbocations in SN1 processes, whereas aprotic solvents enhance SN2 reactivity.
  • Identifying the functional groups and the structure of the molecules involved is important for understanding reactivity in organic chemistry.

Additional Concepts

  • Rearrangement during solvolysis can occur when more stable carbocations are formed.
  • It is crucial to understand the influence of structure on the rate and mechanism of reactions in organic chemistry.

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Test your knowledge of organic chemistry concepts with these flashcards focusing on structural relationships like diastereomers and enantiomers. This quiz is designed to help you understand complex relationships between compounds and IUPAC nomenclature. Perfect for students preparing for their second exam in organic chemistry.

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