Halogenoalkanes Flashcards
Give another word halogenoalkanes
Haloalkanes
What are halogenoalkanes
Alkanes with Halogen atoms
What type of bond is the Carbon-halogen in halogenoalkanes
Polar
How are the bonds between carbon and halogens polar?
Halogens are more electronegative than carbon
What is a nucleophile
An electron pair donor
Give me examples of nucleophiles
OH-, CN- and NH3
What charge is found on carbon
Delta +
How is the movement of electron pairs shown?
Using curly arrows
What type of reactions do halogenoalkanes undergo?
Nucleophilic substitution reactions
How do nucelophilic substitution reactions work?
• The lone pair of electrons in the nucleophile attacks the delta + carbon
• C-X bond breaks
• The halogen leaves taking both electrons with it
• A new bond forms between the carbon and the nucleophile
What do halogenoalkanes form when they react with hydroxides?
Alcohols
What conditions are required to form alcohols
Warm, aqueous hydroxides and reflux
What is formed when halogenoalkanes react with Cyanide
Nitriles
How many bonds are found in cyanide
3 bonds
What conditions are required to form nitriles
Warm, ethanolic potassium cyanide, reflux, ethanol
What is formed when halogenoalkanes react with ammonia
Amines
What conditions are required to form amines
• Warm halogenoalkanes, excess ethanolic ammonia
The amine group formed can still act as what and why?
• A nucleophile
• Because it still has a lone pair of electrons
Which will react the fastest, iodoalkanes or fluoroalkanes?
Iodoalkanes because bond enthalpy esp decrease down the group so they are easier to break and are substituted quickly
What other type of reactions do halogenoalkanes undergo?
Elimination reactions
What is formed in an elimination reaction?
Alkene
What conditions are required for elimination reactions
• Warm halogenoalkanes
• Hydroxides dissolved in ethanol
• Heat the moisture under reflux
• Anhydrous (dry) conditions
Which molecule acts as a base in elimination reactions?
OH-, it takes away a proton e.g hydrogen
Why does ammonia act as a nucleophile despite not having a negative charge?
It has a lone pair of electrons
Where are nucleophiles attracted to?
Electron deficient areas
Which will react faster 1-chloropropane or 1-bromopropane and why?
• 1-bromopropane
• C-Br bond is weaker than C-Cl bond
Identify the characteristic of a haloalkane that enables it to undergo a Nucleophilic substitution reaction
A polar C-Br bond
Explain why the halogenoalkane is attacked by the nucleophile in this reaction
- Bromine is more electronegative than carbon
- C is partially positive / electron deficient
- Lone/electron pair (on the nucleophile) donated to the partially
positive carbon
