halogenoalkanes Flashcards
how to form a chloroalkane from an alcohol
dry PCl5 (or conc HCl)
room temperature
nucleophilic substitution
how to form a bromoalkane from an alcohol
KBr + conc H2SO4
heat under reflux
nucleophillic substitution (HBr attacks)
how to form a iodoalkane from an alcohol
damp red phosphorus + I2
warm
nucleophilic substitution
how to form an alkene from a halogenoalkane
conc KOH or conc NaOH
in ethanol
heat under reflux
elimination reaction
how to form an amine from a halegenoalkane
NH3 (ammonia)
heat in a sealed tube in ethanol
nucleophilic substitution
how to form an alcohol from halogenoalkane with water
add H2O
warm
ethanol co solvent
nucleophilic substitution
how to form a nitrile from a halogenoalkane
KCN
in ethanol
heat under reflux
nucleophilic substitution
what is a nucleophile
chemical species with a lone pair of electrons (can donate electrons)
define substitution reaction
where one atom or group of atoms is replaced by another atom or group of atoms
why are the C-halogen bonds easier to break going down the group
bond length increases
weaker bond
broken faster
how to form an alcohol with halogenoalkane and aqueous alkali
dilute NaOH or KOH (aqueous)
heat (60°)
which mechanism do tertiary halogenoalkanes react by
SN1
which mechanism do primary halogenoalkanes react by
SN2
which mechanism has the transition state
SN2 (primary halogenoalkanes)
what colour ppt Cl
white
what colour ppt Br
cream
what colour ppt I
yellow
order in which halogenoalkane ppt appears
1 Iodo
2 Bromo
3 Chloro
order ppt appears (1° 2° or 3°)
1 3°
2 2°
3 1°
why does the 3° react faster than 1° with water
weak nucleophile
mechanism is SN1
devise an experiment to compare rates of hydrolysis of halogenoalkanes
- 3 test tubes with each halogenoalkane in equal volume
- warm water bath, reach same temperature
- ethanol as co solvent
- add silver nitrate
- time how long each takes to produce ppt
state trends in rate of reaction and justify answer (hydrolysis of halogenoalkanes)
iodo>bromo>chloro
bond enthalpy decreases from C-Cl to C-I
bonds become easier to break down the group
define elimination reaction
reaction where an atom or group of atoms is removed from a molecule
leaves an unsaturated product
when forming an alkene from a halogenoalkane, which carbon is the hydrogen removed from
the C adjacent to the C the halogen is bonded to
not the same C the halogen is bonded to
