Chemsheets often asks: "Why does iodoalkane react faster than chloroalkane in hydrolysis?"
Reactivity order in nucleophilic substitution:
RI > RBr > RCl >> RF
Common nucleophiles in Chemsheets exercises:
The Task: Converting the halogenoalkane into an alcohol. Reagent: NaOH (aq) Condition: Heat under reflux
Typical sections:
This report outlines the core concepts, answers, and reasoning typically found in the exclusive Chemsheets resource regarding the reactions of halogenoalkanes (AS Level). As direct reproduction of copyrighted material is restricted, this document provides a comprehensive educational breakdown of the tasks usually covered in this module, specifically focusing on nucleophilic substitution mechanisms (SN1 and SN2) and elimination reactions.
This is the advanced section on Chemsheets 1 that separates A/A* students from B/C students.
Both reactions start with the same halogenoalkane and a base/nucleophile (e.g., OH⁻). The outcome depends on:
| Factor | Favors Substitution (SN2 or SN1) | Favors Elimination (E2 or E1) | |---|---|---| | Temperature | Lower temp (25°C) | Higher temp (>60°C, reflux) | | Nucleophile/Base | Strong nucleophile, weak bulky base (e.g., OH⁻, CN⁻, NH₃) | Strong, bulky base (e.g., KOH in ethanol, not water; or tert-butoxide) | | Halogenoalkane structure | Primary (SN2 only); Tertiary (SN1) | Tertiary (E1 or E2); primary needs strong bulky base (E2) | | Solvent | Polar protic (water, alcohols) for SN1; Polar aprotic (DMSO, acetone) for SN2 | Polar protic also works; non-polar favors E2 | reactions of halogenoalkanes 1 chemsheets answers exclusive
Classic Chemsheets Question: “1-bromopropane is heated with NaOH(aq) and separately with NaOH in ethanol. State the major product in each case and explain.”
Your Exclusive Answer:
The Reagent: Water (often with silver nitrate – see Section 5). The Product: Alcohol + Hydrogen halide.
This is a slower, less vigorous reaction than with OH⁻. Chemsheets often asks: "Why does iodoalkane react faster
Example: 2-chlorobutane with water.
Exclusive Insight: This reaction is reversible. In the lab, we drive it forward by adding a base (like NaOH) to neutralize the HX produced.
Example question: Classify each as primary (1°), secondary (2°), or tertiary (3°) and name them.
Answers: | Structure | Name | Class | |-----------|------|-------| | CH₃CH₂CH₂CH₂Br | 1-bromobutane | Primary (1°) | | CH₃CHBrCH₂CH₃ | 2-bromobutane | Secondary (2°) | | (CH₃)₃CBr | 2-bromo-2-methylpropane | Tertiary (3°) | | CH₃CH₂I | iodoethane | Primary (1°) | Reactivity order in nucleophilic substitution: RI > RBr