H H | | HO:¯ H—C—C—Br ---> H2O + CH2=CH2 + :Br¯ | | H H OH−OH raised to the negative power ion removes a proton ( H+H raised to the positive power -carbon atom. The electron pair from the broken C–HC–H bond collapses inward to form a carbon-carbon double bond (
of CFCs and ozone depletion Let me know what you'd like to dive into next! Chemsheets As 1140 (Reactions of Halogenoalkanes) - Scribd
When a halogenoalkane reacts with a hydroxide ion under different conditions, a competing reaction takes place: . Instead of acting as a nucleophile, the hydroxide ion acts as a base (a proton acceptor), removing a hydrogen atom to form an alkene. Reagent: Potassium Hydroxide ( ) or Sodium Hydroxide (
Mastering the Reactions of Halogenoalkanes: A Deep Dive into Chemsheets AS 1030
When halogenoalkanes react with hydroxide ions under different conditions, they can produce alkenes instead of alcohols. This is known as elimination. Sodium or potassium hydroxide ( Conditions: Ethanolic solution (not aqueous), hot/reflux. Product: Alkene, water, and salt. Mechanism: The OH−OH raised to the negative power reactions of halogenoalkanes 1 chemsheets answers exclusive
) shift roles. Instead of acting as a nucleophile, they can act as a (a proton acceptor), causing an elimination reaction that yields an alkene . Reagents: Potassium hydroxide ( ) or Sodium hydroxide (
If the halogenoalkane is unsymmetrical (e.g., 2-bromobutane), elimination can yield a mixture of structural isomers (e.g., but-1-ene and but-2-ene).
: Favored by hot, ethanolic conditions (e.g., KOH in ethanol). Common Worksheet Reactions Reagent Conditions Type of Reaction Organic Product Warm, aqueous Nucleophilic Substitution Alcohol (e.g., Ethanol) Hot, ethanolic Nucleophilic Substitution Nitrile (e.g., Propanenitrile) NH₃ (excess) Hot, concentrated Nucleophilic Substitution Amine (e.g., Ethylamine) Hot, ethanolic Elimination Alkene (e.g., Ethene) Mechanism Tips
This reaction produces a primary amine, but it requires careful control to prevent further substitution. Excess ethanolic ammonia. H H | | HO:¯ H—C—C—Br ---> H2O
Some common reactions of halogenoalkanes include:
Halogenoalkanes undergo nucleophilic substitution to form alcohols, nitriles, or amines, and elimination reactions to produce alkenes, depending on the reagent and conditions. Key reactions include the use of hydroxide, cyanide, and ammonia, with reactivity influenced by the C-X bond strength. For the full study guide and answer keys, visit scisheets.co.uk . REACTIONS OF HALOGENOALKANES 1 | Chemsheets
. The nucleophile concentration has no effect on the initial rate. Why do Secondary ( 2∘2 raised to the composed with power ) Halogenoalkanes Do Both?
Nucleophilic substitution is the primary reaction type for halogenoalkanes. A nucleophile (a species with a lone pair that attacks the carbon) replaces the halogen atom. A. Reaction with Aqueous Sodium Hydroxide ( NaOH(aq)NaOH sub open paren a q close paren end-sub Instead of acting as a nucleophile, the hydroxide
Heated in a sealed copper tube (under pressure). Nucleophile: Ammonia ( :NH3:NH sub 3 Mechanism Breakdown (Two Stages): Stage 1 (Attack): The lone pair on :NH3:NH sub 3 attacks the carbon. The bond breaks. This creates an intermediate: R-NH3+R-NH sub 3 raised to the positive power alongside an X−X raised to the negative power
Converting the halogenoalkane into an alcohol. Reagent: NaOH (aq) Condition: Heat under reflux
Secondary halogenoalkanes possess moderate steric hindrance and moderate carbocation stability, allowing them to react via a mixture of both SN1cap S sub cap N 1 SN2cap S sub cap N 2