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11 Cards in this Set
- Front
- Back
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What are primary, secondary and tertiary halogenoalkane schools |
Primary halogenoalkane: a halogen is attached to a carbon that itself is attached to one other alkyl group Secondary = a halogen is attached to a carbon that itself is attached to two other alkyl groups Tertiary = a halogen is attached to a carbon that itself is attached to 3 other alkayl groups |
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What is a nucleophile |
An electron rich species that can donate a pair of electons. They are attracted to postively charged species. Refers to positive charge loving |
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Explain the formation of alcohols |
The nucleophile in the reaction would be a hydroxide. An aqueous solution of NAOH or potassium hydroxide with ethanol is used. This is hydrolysis and the rate depends on the strongest carbon halogen bond. Water could be used as a nucleophile but it would be slow so OH Ion is better cuz it carries full negative charge. The halogen is replaced by the nucleophile C-F>C-Cl>C-Br>C-I |
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explain the reaction of nucleophiles with water |
The water molecule is a weak nucleophile but it will substitute for the halogen. An alcohol is produced: RX + H2O -> ROH+ H+ + X- CH3CH2BR + H20 -> CH3CH2OH + H+ + Br- If silver nitrate solution in ethanol is added to the solution, the silver ions will react with the halide ions as soon as they form giving a silver halide precipitate Ag (aq)+ + X- (aq) -> AgX (s) |
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Explain the formation of nitriles |
The nucleophile here is the cynaide ion, CN- An ethanolic solution of potassium cyanide is heated under reflux with the halogenoalkane. The product is a nitrile. The nucleophilic substitution of halogenoalkanes with KCN adds an extends the carbon chain by adding an extra carbon atom. |
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Explain the formation of primary amines by reaction with ammonia |
the nucleophile in this reaction is the ammonia molecule, NH3 an ethanolic solution of excess ammonia is heated under pressure with a primary halogenoalkane. An excess of ammonia is used because the product is more reactive than ammonia so further substitution reactions could occur. This product is a primary amine. |
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How is ethylamine formed by this |
Bromoethane reacts with excess ethanolic ammonia when heated under pressure to form ethylamine CH3CH2BR+ NH3 -> CH3CH2NH2 + HBR Halogen was replaced by amine group |
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Explain the formation of alkenes |
Halogenoalkanes are heated with ethanolic sodium hydroxide causing the C-X bond to break heterolytically, forming an X- ion and leaving an alkene as an organic product |
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What causes polar bonds |
Large differences in electronegativity between the carbon and halogen the C-X is polar. In nucleophilic subs |
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Explain the mechanism with aqueous potassium hydroxide |
A halogenoalkane reacts with aqueous alkali to form an alcohol. The halogen is replaced by a nucleophile (OH-). |
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Explain Mechanism with ammonia |
When ammonia reacts with a haloalkane a nucleophilic substitution reaction takes place formung a primary amine. Excess ammonia is used to prevent further substitution and favour the formation of a primary amine CH3CL + NH3 -> (CH3NH3)+ Cl- (CH3NH3)+Cl- + NH3 -> CH3NH2 + NH4 + Cl- |
