3.3- Halogenoalkanes Flashcards
What is the difference between primary secondary and tertiary halogenoalkanes
In a primary alkane 1 carbon is attached to the carbon bonded with the halogenoalkane, for secondary 2 carbons and for tertiary 3 carbons
What type of reactions do halogenoalkanes undergo
Substitution or elimination reactions
What does the rate of a substitution reaction depend on
The rate of the subsitution reaction depends on the strength of the C-Halogen bonds, the stronger the bond the slower the substitution
What is the definition of hydrolysis
This is defined the splitting of a molecule by a reaction with water
Why is aqueous silver nitrate added to halogenoalkane
The silver ions reacts to form a sliver halide precipitate, the colour of the precipitate depends on the halogenoalkane, the quicker the precipate is formed the faster the substiution reaction
What is the mechanism and the reagents/conditions for the reaction of halogenoalkane to alcohol
Reagents- Potassium/Sodium hydroxide
Conditions- In aqueous solution, heat under reflux
Mechanism- Nucleophillic substitution
Type of reagent- Nucleophile
The aqueous conditions are needed because then a elimination reaction occurs
For tertiary halogenoalkanes the substitution happens in 2 steps
What is the mechanism and the reagents/conditions for Halogenoalkane to Nitrile
Reagent-KCN dissolved in ethanol/water
Conditions- Heating under reflux
Mechanism - Nucleophillic substitution
This reaction increases the length of the carbon chain
How do you name nitriles
.Nitriles have to be at the end of the chain
.Add nitrile to the end of the name of the chain
What is the mechanism and the reagents/conditions for Halogenoalkane to Amine
Reagent- NH3 dissolved in ethanol
Conditions- Heating under pressure in a sealed tube
Mechanism- Nucleophillic substitution
What is the mechanism and the reagents/conditions for Halogenoalkane to Alkene
Reagents- Potassium/Sodium hydroxide
Conditions- In ethanol and heat
Mechanism- Elimination
Reagent- base, OH-
Elimination is the removal of a small molecule, often water from the organic molecule
What two different products can be made during a reaction via elimination or subsitution
With elimination, you can either form primary,secondary and tertiary alkenes, the product that has a tertiary and secondary carbocations in the reactions are more stable and hence they form the majority product
How does the structure of the halogenoalkane have an effect on whether substitution or elimination occurs
Primary tends towards substitution
Tertiary tends towards elimination
What are the different uses of halogenoalkanes
They can be used as solvents, refrigerants, pesticides and aerosol properties
Many of these uses have been stopped due to the toxicity of halogenoalkanes and also their detrimental effect on the atmosphere
How do chlorine free radicals from CFC cause harms to form in the Ozone layer
The chlorine free radical atoms catalyse the decompostition of ozone, they are regenerated and form holes in the ozone layer
What are now used rather than HFCs
Hydro flouro carbons are now being used for refrigerators and air conditioners, these are safer as they do not contain the C-Cl bond
