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Nucleophilic Substitution (SN1 & SN2)

SN2 and SN1 mechanisms, substrate/nucleophile effects, solvent effects, and leaving groups

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🔀 Nucleophilic Substitution

Study SN2 (backside attack, inversion, bimolecular) and SN1 (carbocation intermediate, racemization, unimolecular) mechanisms. Understand how substrate, nucleophile, solvent, and leaving group determine the pathway.

📚 Practice Problems

1Problem 1medium

❓ Question:

Predict whether each substrate reacts predominantly by SN1 or SN2 with the indicated nucleophile, and predict the stereochemistry of the product. (a) (R)-2-bromobutane + NaI / acetone. (b) (R)-3-bromo-3-methylhexane + H₂O / acetone (heat). (c) Neopentyl bromide ((CH₃)₃CCH₂Br) + NaOMe / MeOH.

💡 Show Solution

(a) SN2 — Secondary substrate, strong nucleophile (I⁻ is excellent), polar aprotic solvent (acetone). Backside attack inverts the stereocenter → (S)-2-iodobutane.

(b) SN1 — Tertiary substrate (no SN2 possible), weak nucleophile (H₂O), polar protic solvent. The 3° carbocation is planar; water attacks both faces → racemic 3-methylhexan-3-ol (≈ 50:50 R:S).

(c) Neither — extreme steric inhibition. Neopentyl bromide is technically primary but has a quaternary β-carbon, which blocks SN2 backside attack catastrophically. SN1 is also disfavored because the resulting primary carbocation is very unstable (and rearrangement to a tertiary cation would change the carbon skeleton). The reaction is very slow; in practice only trace product forms.

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⚠️ Common Mistakes: Nucleophilic Substitution (SN1 & SN2)

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🌍 Real-World Applications: Nucleophilic Substitution (SN1 & SN2)

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📝 Worked Example: Stoichiometry — Limiting Reagent

Problem:

22 mol of H2H_2 reacts with 11 mol of O2O_2. How many grams of water are produced? Which is the limiting reagent? (2H2+O2→2H2O2H_2 + O_2 \to 2H_2O)

2Determine the limiting reagent
3Calculate moles of product
4Convert moles to grams
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Elimination Reactions (E1 & E2)
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Elimination Reactions (E1 & E2)

❓ Frequently Asked Questions

What is Nucleophilic Substitution (SN1 & SN2)?▾
SN2 and SN1 mechanisms, substrate/nucleophile effects, solvent effects, and leaving groups
How can I study Nucleophilic Substitution (SN1 & SN2) effectively?▾
Start by reading the study notes and working through the examples on this page. Then use the flashcards to test your recall. Practice with the 1 problems provided, checking solutions as you go. Regular review and active practice are key to retention.
Is this Nucleophilic Substitution (SN1 & SN2) study guide free?▾
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What course covers Nucleophilic Substitution (SN1 & SN2)?▾
Nucleophilic Substitution (SN1 & SN2) is part of the Organic Chemistry 1 course on Study Mondo, specifically in the Substitution & Elimination (Alkyl Halides) section. You can explore the full course for more related topics and practice resources.
Are there practice problems for Nucleophilic Substitution (SN1 & SN2)?▾
Yes, this page includes 1 practice problem with detailed solutions. Each problem includes a step-by-step explanation to help you understand the approach.