Halogenoalkanes and aromatics Flashcards
Nomenclature of halogen alkanes
- The halogen and o e.g. floro, bromo
- Location and number must be specified e.g. di, tri, tetra
What intermolecular forces do halogenalkanes have
- Due to the high electronegativity of the halogen atom it will attract electrons making it slightly negative and the carbon will be slightly positive.
- They have a permanent dipole so have permanent dipole-permanent dipole interactions
What is a chloroflourocarbon
- Halogenalkene with all the hydrogens relaced by flourene or chlorine
- CFC’s are damaging to the ozone layer
Whats homolytic fission
The breaking of a covalent bond such that both atoms have an unpaired electron
Initiation of chlorine
Uv light breaks the bond between a Cl2 molecule to produce 2 chlorine free radicals
Propogation of Cl
The reaction of any particals that produces a free radical so the reactions can keep occuring
Termination of Cl
Any reaction that doesnt form a free radical such as 2 free radicals coming together or 2 carbons bonding
Whats a nucleophile
A chemical species that donates an electron pair to an electron deficient centre
Nucleophilic substitution (SN2)
- The nucleophile attacks the electron deficient carbon atom
- An intermediate with both atoms bonded is formed
- The bond between the carbon and halogen breaks giving the halogen the electrons
Nucleophilic substitution (SN1)
- The bond to the halogen breaks
- A carbonium ion intermediate is formed
- The nucleophile attacks the carbon
How to test for halide ions
- The halogenalkane must be hydrolysed by boiling it in sodium hydroxide
- It is acified with dilute nitric acid
- Aqueous silver nitrate is added
- A precipitate is formed
- If chloride is its white, bromide is cream and iodide is yellow
Elimination of halogenalkanes
- High temp without air
- In the presence of a strong base
- The halogen accepts the electrons breaking the bond between it and the carbon
- The electrons between carbon and hydrogen then form a C=C and the base accepts the proton given off
- Whats produced is an alkene, Base-H and lone halogen atom
Whats a leaving group
- An atom that can accept electrons and leave a molecule
- Often a halogen
- A good leaving group has a high electronegativity
What is an aromatic compound
Any compound that contains atleast one benzene ring
Describe the bonding in a benzene ring
- Sigma bonds between carbons
- Pi bonds above and below due to P-orbitals
- Rings of 6 delocalised electrons above and below the ring