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Heating in a sealed copper tube or under pressure (to prevent volatile ammonia gas from escaping). Nucleophile: Ammonia molecule ( :NH3:NH sub 3 Why Excess Ammonia? The primary amine product ( R-NH2R-NH sub 2
A classic exam question asks you to predict and explain the trend in reactivity as you go down Group 7 from fluoroalkanes to iodoalkanes. Two competing factors dictate this behavior: Factor 1: Bond Polarity Fluorine is the most electronegative halogen. The bond is the most polar ( ), giving the carbon the highest partial positive charge.
R-NH3+X−R-NH sub 3 raised to the positive power X raised to the negative power ). Then, a second ammonia molecule removes a proton ( H+H raised to the positive power ) to yield the final neutral primary amine ( R-NH2R-NH sub 2
| Halogenoalkane | Precipitate Color | Rate of Precipitation | Bond Enthalpy (C-X) | |---|---|---|---| | Fluoroalkane | No precipitate (AgF soluble) | Very slow (usually not seen) | Very high (484 kJ/mol) | | Chloroalkane | White (AgCl) | Slow (minutes, needs warming) | 338 kJ/mol | | Bromoalkane | Cream (AgBr) | Faster (seconds to minutes) | 276 kJ/mol | | Iodoalkane | Yellow (AgI) | Instant (room temperature) | 238 kJ/mol |
Radical nucleophilic substitution (SRN1) and other radical transformations can affect haloalkanes under specific conditions.
The carbon atom gains a partial positive charge ( ), while the halogen atom gains a partial negative charge (
Halogenoalkanes (or haloalkanes) are organic compounds where one or more hydrogen atoms in an alkane chain have been replaced by halogen atoms (F, Cl, Br, I). Why are Halogenoalkanes Reactive? The carbon-halogen bond (
Hot, ethaanolic KOH (not warm, aq NaOH) Lose X and H from adjacent C. (if there is one) Forms alkene(s) Can get different alkenes. Scribd REACTIONS OF HALOGENOALKANES 1 | Chemsheets
C–F is the strongest bond (highest bond enthalpy); C–I is the weakest bond (lowest bond enthalpy).
carbon of the alkyl group. For example, bromoethane turns into propanenitrile.
Excess concentrated ammonia in ethanol (under pressure in a sealed tube). The Product: Primary amine. The Mechanism: Nucleophilic substitution (SN2).
Understanding the reactions of halogenoalkanes is crucial for building a foundation in organic chemistry. The key is to move beyond memorization and focus on the why — why the C–X bond is polar, why one halogen reacts faster than another, why reaction conditions favor substitution over elimination, and why primary and tertiary halogenoalkanes react via different mechanisms. Mastering these core principles is the most effective way to answer any question on the topic, from simple naming to complex mechanism drawing. Use the detailed information in this guide to check your Chemsheets answers and solidify your understanding.
Dissolved in pure ethanol (ethanolic), heated intensely under reflux. Role of OH−OH raised to the negative power : Base. The Elimination Mechanism: The lone pair on :OH−:OH raised to the negative power
The nucleophile attacks the planar carbocation. Because the carbocation is flat, the nucleophile has an equal (50/50) probability of attacking from either the front or the back. If the starting material was optically active, this results in a racemic mixture (optically inactive). Rate Law:
Chemsheets worksheet assignments frequently test your ability to predict whether substitution or elimination will dominate. Use this structural summary matrix to verify your answers: Favors Substitution ( Favors Elimination ( 1∘1 raised to the composed with power Tertiary ( 3∘3 raised to the composed with power Reagent / Ion Role acting as a Nucleophile acting as a Base Solvent Condition or aqueous ethanol) Alcoholic (Pure Ethanol) Temperature Warm / Moderate heat Hot / High temperature reflux
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Heating in a sealed copper tube or under pressure (to prevent volatile ammonia gas from escaping). Nucleophile: Ammonia molecule ( :NH3:NH sub 3 Why Excess Ammonia? The primary amine product ( R-NH2R-NH sub 2
A classic exam question asks you to predict and explain the trend in reactivity as you go down Group 7 from fluoroalkanes to iodoalkanes. Two competing factors dictate this behavior: Factor 1: Bond Polarity Fluorine is the most electronegative halogen. The bond is the most polar ( ), giving the carbon the highest partial positive charge.
R-NH3+X−R-NH sub 3 raised to the positive power X raised to the negative power ). Then, a second ammonia molecule removes a proton ( H+H raised to the positive power ) to yield the final neutral primary amine ( R-NH2R-NH sub 2
| Halogenoalkane | Precipitate Color | Rate of Precipitation | Bond Enthalpy (C-X) | |---|---|---|---| | Fluoroalkane | No precipitate (AgF soluble) | Very slow (usually not seen) | Very high (484 kJ/mol) | | Chloroalkane | White (AgCl) | Slow (minutes, needs warming) | 338 kJ/mol | | Bromoalkane | Cream (AgBr) | Faster (seconds to minutes) | 276 kJ/mol | | Iodoalkane | Yellow (AgI) | Instant (room temperature) | 238 kJ/mol |
Radical nucleophilic substitution (SRN1) and other radical transformations can affect haloalkanes under specific conditions.
The carbon atom gains a partial positive charge ( ), while the halogen atom gains a partial negative charge (
Halogenoalkanes (or haloalkanes) are organic compounds where one or more hydrogen atoms in an alkane chain have been replaced by halogen atoms (F, Cl, Br, I). Why are Halogenoalkanes Reactive? The carbon-halogen bond (
Hot, ethaanolic KOH (not warm, aq NaOH) Lose X and H from adjacent C. (if there is one) Forms alkene(s) Can get different alkenes. Scribd REACTIONS OF HALOGENOALKANES 1 | Chemsheets
C–F is the strongest bond (highest bond enthalpy); C–I is the weakest bond (lowest bond enthalpy).
carbon of the alkyl group. For example, bromoethane turns into propanenitrile.
Excess concentrated ammonia in ethanol (under pressure in a sealed tube). The Product: Primary amine. The Mechanism: Nucleophilic substitution (SN2).
Understanding the reactions of halogenoalkanes is crucial for building a foundation in organic chemistry. The key is to move beyond memorization and focus on the why — why the C–X bond is polar, why one halogen reacts faster than another, why reaction conditions favor substitution over elimination, and why primary and tertiary halogenoalkanes react via different mechanisms. Mastering these core principles is the most effective way to answer any question on the topic, from simple naming to complex mechanism drawing. Use the detailed information in this guide to check your Chemsheets answers and solidify your understanding.
Dissolved in pure ethanol (ethanolic), heated intensely under reflux. Role of OH−OH raised to the negative power : Base. The Elimination Mechanism: The lone pair on :OH−:OH raised to the negative power
The nucleophile attacks the planar carbocation. Because the carbocation is flat, the nucleophile has an equal (50/50) probability of attacking from either the front or the back. If the starting material was optically active, this results in a racemic mixture (optically inactive). Rate Law:
Chemsheets worksheet assignments frequently test your ability to predict whether substitution or elimination will dominate. Use this structural summary matrix to verify your answers: Favors Substitution ( Favors Elimination ( 1∘1 raised to the composed with power Tertiary ( 3∘3 raised to the composed with power Reagent / Ion Role acting as a Nucleophile acting as a Base Solvent Condition or aqueous ethanol) Alcoholic (Pure Ethanol) Temperature Warm / Moderate heat Hot / High temperature reflux