**3.3.3 Halogenoalkanes** Flashcards
1
Q
Are halogenoalkanes soluable in water?
A
- No.
- C-H bonds are non-polar, not compensated enough by C-X bond.
2
Q
Do halogenoalkanes have a polar bond?
A
- Yes, halogen higher electronegativity than C.
- Halogen δ-.
- Carbon δ+.
3
Q
What 2 factors affect their boiling points?
A
- Longer chain.
- Halogen further down grp 7.
4
Q
Which intermolecular forces do they have?
A
- Permanent dipole-dipole (due to C-X bond polarity).
- VdW forces of attraction.
5
Q
Mass of halogenoalkane compared to mass of alkane w/ same chain length?
A
- Greater, mass halogen > mass H.
6
Q
Most important factor in reactivity?
A
- C-X bond enthalpy.
7
Q
What is the order of reactivity in halogenoalkanes?
A
- C-X bond enthalpy decreases down group ∴ reactivity increases down the group.
8
Q
What is a nucleophile?
A
- Negatively charged ion w/ lone pair of e- which can be donated to an e- deficient atom.
9
Q
Give 3 examples of nucleophiles.
A
- :OH-
- :CN-
- :NH3
10
Q
What is nucleophilic substitution?
A
- Reaction where nucleophile donates lone pair e- to δ+ C atom.
- δ- atom leaves molecule.
11
Q
What does CFC stand for?
A
- Chlorine-fluoro-carbons.
12
Q
What are CFCs?
A
- Halogenoalkanes containing C,F + Cl only (no H).
13
Q
What is the problem w/ CFCs?
A
- Unreactive under normal conditions.
- Catalyse breakdown of ozone via free radical substitution.
14
Q
What are CFCs being replaced with?
A
- HCFCs (H,Cl,F,C).
- HFCs (H,F,C).
15
Q
What are conditions needed for elimination reaction of halogenoalkanes?
A
- NaOH or KOH dissolved in ethanol (no H2O present).
- Heated.
