page 31-35 Flashcards

1
Q

What type of anions are solvated more strongly in polar protic solvents?

A

A: Smaller, more electronegative anions.

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2
Q

How does strong solvation affect nucleophilicity?

A

A: It shields the anion, making it less reactive.

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3
Q

In polar protic solvents, how does nucleophilicity change down a column of the periodic table?

A

A: Nucleophilicity increases as the size of the anion increases.

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4
Q

What is the relationship between nucleophilicity and basicity in polar protic solvents?

A

A: They are opposite; smaller anions are better bases but poorer nucleophiles.

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5
Q

Which halide ion is the strongest nucleophile in polar protic solvents?

A

A: I⁻ (iodide ion).

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6
Q

Why is I⁻ a better nucleophile than F⁻ in polar protic solvents?

A

A: I⁻ is less strongly solvated due to its larger size, making it more reactive.

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7
Q

Which halide ion is the weakest nucleophile in polar protic solvents?

A

A: F⁻ (fluoride ion).

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8
Q

What is the primary role of polar protic solvents in substitution reactions?

A

A: To solvate and stabilize ions, influencing nucleophilicity.

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9
Q

How does the size of an anion affect its solvation?

A

A: Larger anions are less strongly solvated, making them better nucleophiles.

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10
Q

What is the trend in nucleophilicity for halides (F⁻, Cl⁻, Br⁻, I⁻) in polar protic solvents?

A

A: I⁻ > Br⁻ > Cl⁻ > F⁻.

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11
Q

What does strong solvation of F⁻ in water result in?

A

A: Reduced nucleophilicity due to shielding by water molecules.

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12
Q

In polar protic solvents, why does basicity not directly correlate with nucleophilicity?

A

A: Solvent interactions reduce the reactivity of smaller, stronger bases.

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13
Q

What effect does the electronegativity of an anion have in polar protic solvents?

A

A: Higher electronegativity leads to stronger solvation, reducing nucleophilicity.

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14
Q

Which property of solvents makes them “polar protic”?

A

A: The ability to form hydrogen bonds.

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15
Q

How does methanol (CH₃OH) compare to water (H₂O) in solvating anions?

A

A: Methanol solvates less strongly than water due to fewer hydrogen bonding interactions.

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16
Q

What are polar aprotic solvents incapable of?

A

A: Hydrogen bonding.

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17
Q

What type of interactions do polar aprotic solvents exhibit?

A

A: Dipole-dipole interactions.

18
Q

Name a common polar aprotic solvent with the formula CH₃COCH₃.

A

A: Acetone.

19
Q

What is the common abbreviation for tetrahydrofuran?

20
Q

Which polar aprotic solvent is represented by the structure HCON(CH₃)₂?

A

A: Dimethylformamide (DMF).

21
Q

Why are polar aprotic solvents commonly used in substitution reactions?

A

A: They do not solvate nucleophiles strongly, allowing them to remain reactive.

22
Q

What differentiates polar aprotic solvents from polar protic solvents?

A

A: Polar aprotic solvents lack O-H or N-H bonds and cannot form hydrogen bonds.

23
Q

Which solvent among the following is polar aprotic: water, acetone, ethanol?

A

A: Acetone.

24
Q

How do polar aprotic solvents interact with cations?

A

A: They stabilize cations through dipole-dipole interactions.

25
What is a key characteristic of all polar aprotic solvents?
A: They have a significant dipole moment but lack hydrogen bond donors.
26
26
Name two common applications of polar aprotic solvents.
A: Used in nucleophilic substitution reactions (e.g., SN2) and organometallic reactions.
27
What is a nucleophile?
A: A species that donates an electron pair to form a new covalent bond.
28
Give two examples of negatively charged oxygen nucleophiles.
A: −OH (hydroxide) and −OR (alkoxide).
29
Provide an example of a neutral oxygen nucleophile.
A: H2O (water) or ROH (alcohol).
30
What is a common nitrogen-based negatively charged nucleophile?
A: N3−(azide).
31
Name a neutral nitrogen nucleophile.
A: NH3 (ammonia) or RNH2(amine).
32
Identify two examples of carbon-based negatively charged nucleophiles.
A: −CN (cyanide) and −C≡CH (acetylide).
33
What halogens act as negatively charged nucleophiles?
A: C l − Cl − , B r − Br − , and I − I − .
34
Which sulfur species acts as a negatively charged nucleophile?
A: − H S −HS (hydrosulfide) and − R S −RS (thiolate).
35
Name a neutral sulfur nucleophile.
A: H 2 S H 2 ​ S (hydrogen sulfide) or R S H RSH (thiol).
36
What type of nucleophiles are C H 3 C O O − CH 3 ​ COO − (acetate)?
A: Negatively charged oxygen nucleophiles.
37
Which halide ion is the best nucleophile in polar protic solvents?
A: I − I − (iodide).
38
What distinguishes a neutral nucleophile from a negatively charged one?
A: Neutral nucleophiles do not carry a formal negative charge.
39
Why are sulfur-based nucleophiles often stronger than oxygen-based nucleophiles?
A: Sulfur is less electronegative and more polarizable than oxygen, making it more nucleophilic.
40
Which negatively charged nucleophile is commonly used in organic synthesis to introduce a carbon-nitrogen triple bond?
A: − C N −CN (cyanide).
41
How do halogen nucleophiles like C l − Cl − , B r − Br − , and I − I − behave in substitution reactions?
A: They act as good nucleophiles and displace leaving groups in nucleophilic substitution reactions.