Reactions: Of Halogenoalkanes 1 Chemsheets Answers Exclusive Work

It sounds like you’re looking for the answer sheet to a specific worksheet: Chemsheets A2 (or AS) 1190 or similar, often titled "Reactions of Halogenoalkanes 1" – likely covering nucleophilic substitution and elimination.

I can't distribute copyrighted teacher answer sheets (the "exclusive" version), but I can give you the fully worked answers and explanations for the typical questions on that sheet. This will help you check your work and understand the chemistry.

Based on standard Chemsheets content (e.g., Chemsheets A2 1190 or Chemsheets AS 1078), here are the core question types and their answers.

Typical Q2: Nucleophilic Substitution with NaOH(aq)

Reaction: Halogenoalkane + aqueous OH⁻ → alcohol + halide ion reactions of halogenoalkanes 1 chemsheets answers exclusive

Answers: | Halogenoalkane | Product alcohol | Rate (fastest → slowest) | |----------------|----------------|---------------------------| | CH₃CH₂CH₂Br | propan-1-ol | Medium (1°) | | (CH₃)₃CBr | 2-methylpropan-2-ol | Fastest (3°) | | CH₃CH₂CH₂I | propan-1-ol | Fastest overall (I best leaving group) |

Why?

Tertiary fastest (SN1 mechanism – stable carbocation).
Iodide best leaving group → fastest rate for same structure.

1. Main Reaction Types Covered in “Halogenoalkanes 1”

Chemsheets usually focuses on:

5. Testing for Halogenoalkanes (Chemsheets Practical Questions)

Add aqueous silver nitrate (in ethanol)
Warm gently
Rate of precipitate formation identifies halogen:

Chloroalkane – slow, white precipitate (AgCl)
Bromoalkane – faster, cream precipitate (AgBr)
Iodoalkane – fast, yellow precipitate (AgI)

But precipitate only appears after halogen leaves – so reaction must be nucleophilic substitution. Water is the nucleophile here.

Section 4: Reaction with Ammonia (Forming Primary Amines)

The Reagent: Excess concentrated ammonia in ethanol (under pressure in a sealed tube). The Product: Primary amine. The Mechanism: Nucleophilic substitution (SN2).

Example: 1-chloropropane with NH₃.

Equation: CH₃CH₂CH₂Cl + 2NH₃ → CH₃CH₂CH₂NH₂ + NH₄Cl
Product: Propylamine (1-aminopropane).

The Hidden Trap (Exclusive Insight): The reaction doesn’t stop at the primary amine. The product amine also has a lone pair and can act as a nucleophile, attacking another halogenoalkane molecule to form a secondary amine, then tertiary, then a quaternary ammonium salt.

Chemsheets expects you to know:

To get mostly primary amine, use excess ammonia (shifts equilibrium left).
Mechanism is SN2 – show curly arrow from lone pair on NH₃ to δ+ carbon, and loss of Cl⁻.

8. Common Mistakes (Chemsheets Mark Scheme Insights)

Forgetting that OH⁻ in ethanol (not water) mainly gives elimination
Drawing SN2 with inversion but omitting partial bonds or 3D dashes/wedges
Writing “HBr” as product in elimination – it’s KBr (ionic) in practice
Not distinguishing between hydrolysis (H₂O as nucleophile) and substitution (OH⁻ as nucleophile)

3. Nucleophilic Substitution Mechanisms

The Chemsheets resource typically requires students to draw mechanisms and explain the differences between primary and tertiary halogenoalkanes. It sounds like you’re looking for the answer

Q2: Reaction with NaOH(aq)

Write equation:
C₃H₇Br + NaOH → C₃H₇OH + NaBr
Mechanism: SN2 for primary, SN1 for tertiary

7. “Exclusive” Answers – Conceptual Key

Below are final answer patterns for a typical Reactions of Halogenoalkanes 1 Chemsheets sheet (assuming 15–20 questions). Check your work against these.

| Question type | Expected answer | |---------------|----------------| | Mechanism, 1° + NaOH(aq) | SN2, inversion, OH⁻ attacks C–Br | | Mechanism, 3° + H₂O | SN1, carbocation intermediate | | Elimination product from 2-bromopentane | Pent-2-ene (major – more substituted) + pent-1-ene (minor) | | Reagent for substitution to alcohol | Aqueous NaOH, warm | | Reagent for elimination | Ethanolic KOH, heat under reflux | | Why does iodoethane react faster than bromoethane in SN2? | C–I bond weaker, I⁻ better leaving group | | Test for chloroalkane vs iodoalkane | AgNO₃/ethanol – chloroalkane slow white ppt, iodoalkane fast yellow ppt |