Nucleophilic Substitution Quiz

What does a nucleophile do?

Donates a lone pair to an electrophilic carbon.

What does a leaving group do?

Departs with its bonding electrons.

At what type of carbon does nucleophilic substitution occur?

At an sp³‑hybridized carbon.

What is nucleophilic aliphatic substitution?

Substitution of one group for another at a saturated sp³ carbon.

Which mechanism involves simultaneous attack and leaving?

SN2.

Which mechanism forms a carbocation intermediate?

SN1.

Which mechanism prefers primary > secondary > tertiary carbons?

SN2.

Which mechanism prefers tertiary > secondary > primary carbons?

SN1.

Why can’t SN2 occur on a tertiary carbon?

Steric hindrance blocks backside attack.

What is the rate‑determining step in SN1?

Loss of the leaving group to form the carbocation.

What solvent type favors SN1?

Polar protic solvents (like HCl/water).

Why is HCl required in this reaction?

OH is a poor leaving group; HCl protonates it to form water, a better leaving group.

What is the leaving group after protonation?

Water.

What mechanism does this reaction follow?

SN1.

Why does SN1 occur here?

The starting alcohol is tertiary and forms a stable carbocation.

What percent yield is expected for this reaction?

Around 65% (typical range 30–50%).

Why might yield be lower than expected?

Product volatility, E1 side reactions, washing losses, incomplete drying, or incomplete reaction.

Why is the product easy to lose?

2‑chloro‑2‑methylbutane is very volatile.

What result do you expect for a tertiary chloride in the NaI test?

No precipitate.

What does no precipitate indicate?

The compound does NOT undergo SN2 → confirms tertiary halide.

Why does SN2 not occur?

Backside attack is impossible on a tertiary carbon.

What problems can interfere with this test?

Wet acetone, cloudiness mistaken for precipitate, contamination with alcohol.

What result do you expect for a tertiary chloride in the AgNO₃ test?

Fast formation of a precipitate (AgCl).

What does fast precipitate formation indicate?

The compound undergoes SN1 readily.

Why does AgNO₃ cause precipitation?

Ag⁺ removes Cl⁻ to form solid AgCl.

What issues can slow the test?

Wet sample, too little sample, alcohol contamination.

What is the functional group region?

4000–1250 cm⁻¹.

What peak MUST be absent in the product?

O–H stretch at 3200–3600 cm⁻¹.

What does an O–H peak indicate?

Water contamination or unreacted alcohol.

What peak should be present in the product?

Strong alkane C–H stretches at 2800–3000 cm⁻¹.

Should there be a C–O stretch (1050–1250 cm⁻¹)?

No — its presence means unreacted alcohol.

Should there be a carbonyl peak (1650–1750 cm⁻¹)?

No — carbonyl indicates contamination.

What is the fingerprint region?

1250–400 cm⁻¹.

What is the purpose of the fingerprint region?

To compare experimental vs known spectra for structural confirmation.

What stretch corresponds to C–Cl?

Around ~700 cm⁻¹ (often weak or outside resolution).

What indicates a correct product in the fingerprint region?

Pattern matches known 2‑chloro‑2‑methylbutane and no unexpected peaks.

What does an O–H peak mean?

Water or unreacted alcohol.

What does a C–O peak mean?

Unreacted alcohol or oxygen‑containing impurity.

What does a carbonyl peak mean?

Contamination.

What do broad unexpected peaks mean?

Impurities.

What are the IR rules?

Clean area, clean instrument, follow instructions.

Why must HCl be handled in the hood?

It fumes and can irritate the respiratory system.

What is the functional group region?

4000–1250 cm⁻¹.

What peak MUST be absent in the product?

O–H stretch (3200–3600 cm⁻¹).

What does an O–H peak indicate?

Water contamination or unreacted alcohol.

What peak SHOULD be present in the product?

Strong alkane C–H stretches (2800–3000 cm⁻¹).

Should a C–O stretch (1050–1250 cm⁻¹) be present?

No — its presence means unreacted alcohol.

Should a carbonyl peak (1650–1750 cm⁻¹) be present?

No — carbonyl indicates contamination.

What is the fingerprint region?

1250–400 cm⁻¹.

What is the purpose of the fingerprint region?

Compare experimental vs known spectra for structural confirmation.

Where is the C–Cl stretch?

Around ~700 cm⁻¹ (often weak or outside resolution).

What indicates a correct product in the fingerprint region?

Pattern matches known 2‑chloro‑2‑methylbutane with no unexpect