ORGANIC - HALOGENOALKANES Flashcards
What are halogenoalkanes
functional group which is a halogen atom. much more reactive than alkanes as the C in C-X bonds is e- deficient and the C-X bonds are weak
Halogenoalkanes boiling point trend
Increase with
- Chain length = longer chain greater the bp
- Down the group bp increase
Halogenoalkanes key points
Polar - due to permanent dipole-dipole forces
Larger molecule, more e- so stronger VdW forces
Nucleophilic substitution - nucleophile key points
- A nucleophile is an electron-rich species that can donate a pair of electrons to form a covalent bond
- it will attack a positively charged carbon atom
- either negatively charged ion or contains a partially negative atom
- contains a lone pair of electrons on the electronegative atom
Nucleophilic substitution - conditions
aqeous sodium or potassium hydroxide mixed with ethanol and the halogenoalkane
water is present
warm conditions
product is an alcohol
cyanide mechanism
reagent = potassium cyanide
product - nitrile
= look at notes for diagram
hydroxide mechanism
reagent = sodium hydroxide
product = alcohol
= notes for diagram
ammonia mechanism
reagent = ammonia
product = amine
second NH3 acts as a base and removes a proton. The pair of e- in the N-H bond are transferred to the N atom (bond breaks heterolytically) leaving the final product as an amine
what is nucleophilic elimination
the removal of a small molecule from organic molecule
nucleophilic elimination key points
- hot, ethanoic KOH
- loses X and H from adjacent C
- forms alkene
- OH- acts as a base not a nucleophile
nucleophilic elimination mechanism
notes
uses of halogenoalkanes
pvc
teflon
solvents
anaesthetics
what does ozone act as (importance)
Ozone in the upper atmosphere acts as chemical sunscreen absorbing a lot of UV radiation from sun - cause skin cancer and sunburj
ozone natural reactions
- O2 —> 2O(.)
- O2 + O(.) —> O3
What are chlorofluorocarbons
CFCs are:
- all H atoms replaced by either F or Cl
- used to be widely used as refrigerants (coolants)
- also in aerosols as the propellant gas
- CFCs can be very damaging to the ozone layer