Haloalkanes Flashcards
C-X bond polarity nature (5)
Polar
Halogens more electronegative than carbon
Down group, decrease polarity
Not polar enough to dissolve in water
Mix with HCs (remove oily stains)
Haloalkane IMFs
Permanent dipole
London forces
Boiling point haloalkanes (4)
Longer chain length, higher boiling point
Down group, increase boiling point
Higher bp than same carbon chain length alkanes
- More electrons
- More electron density
- Stronger London forces
More branching, decrease bp
Haloalkanes reactivity (6)
Down group, decrease polarity
Down group, decrease C-X bond enthalpy
Down group, increase reactivity
Bond enthalpy more important than polarity
Break C-X, hydrolyse
Increase halogen size, increase bond length, decrease bond enthalpy (easier to break)
C-F slowest
C-I fastest
Classification
No. Alkyl groups bonded to C-X carbon
Primary- 1
Secondary- 2
Tertiary- 3
Nucelophile
Electron pair donor
Negative ion/delta negative atom
Lone e pair (electronegative) - > cov bond
Donates es —> e deficient C atom
Name 3 nucleophiles
:OH-
:NH3
:CN-
Replace halogen in haloalkane
Heterolytic fission
Splitting of a covalent bond to give 1 atom both electron previously in a shared pair
Alcohol nucleophilic substitution
Nucleophile
Reagant
Conditions
:OH-
KOH/NaOH
Warm, aqueous, reflux
Alcohol primary/tertiary nucleophilic substitution difference
Primary, 1 step
Tertiary, 2 step, electron to X, then nucleophile bonds
Nitrile nucleophilic substitution
Nucleophile
Reagant
Conditions
:CN-
KCN(aq), water/ethanol
Heat under reflux
Makes a alkanenitrile
Amine nucleophilic substitution
Nucleophile
Reagant
Conditions
:NH3
Warm, excess ethanolic ammonia
Pressure
Makes a alkylamine
2 step, forms a NH3+, then a NH2 and NH4Br
Elimination
Removal of small compounds (H2O/HCl)
Form a double bond
Hydrogen halide —> alkene
Elimination using OH- ion conditions
Ethanolic solution (KOH/NaOH)
Reflux high temp
Elimination using OH- ion procedure
OH- is a base
Accepts H+ from haloalkane adjacent to halogen
Halogen gains electrons from haloalkane
Forms water, hydrogen and an alkene
Substitution vs elimination
Solvent, temp, product, OH- action
S - water, warm, alcohol, nucelophile
E - ethanol, hot, alkene, base
Classifications, sub vs elim
Prim, sub
Sec, both
Tert, elim
Hydrolysis procedure
Molecule broken down using water
Water is nucleophile, breaks C-X bond
Slower than KOH/NaOH
Hydrolysis testing results
Add AgNO3
X- reacts AgNO3 —> ppte
Compare reactivity/rate of formation
Ammonia test
Fastest, lowest enthalpy, longest bond length, easiest to break, increase hydrolysis rate
Hydrolysis conditions
Warm 50*C
Water bath
Ethanol, dissolve haloalkane and AgNO3
