3. haloalkanes

Question 1

why is the carbon-halogen bond polar

Answer 1

halogens more electronegative than C

Question 2

the positive dipole on the C means a haloalkane can be attacked by a

Answer 2

nucleophile

Question 3

what is a nucleophile

Answer 3

an electron pair donor (to somewhere without enough electrons)
negative ion / atom with lone pair

Question 4

nucleophiles which react with haloalkanes

Answer 4

OH- CN- and NH3

Question 5

haloalkanes

what kind of reactions

Answer 5

nucleophilic substitution (alcohol)

Question 6

hydrolysis of haloalkanes into alcohols

1. conditions/reagents for
2. general equation

Answer 6

1. aqueous alkali NaOH or KOH
   reflux
2. R-X + OH- -> R-OH + X-

Question 7

hydrolysis of haloalkanes into alcohols (using H2O as nucleophile)

1. water molecule is a
2. general equation

Answer 7

1. weak nucleophile= reaction slower

2. R-X + H2O -> R-OH + X- + H+

Question 8

how quickly different haloalkanes are hydrolysed depends on

Answer 8

bond enthalpy

weaker C-X bonds break more easily = react faster

Question 9

1. bond enthalpy of haloalkanes

2. which haloalkane hydrolyses fastest

Answer 9

1. decreases down group

2. iodoalkanes

Question 10

experiment to compare reactivity of haloalkanes

Answer 10

1. mix haloalkane with H2O -> alcohol
   R-X + H2O -> R-OH + H+ + X-
2. add silver nitrate solution -> silver ions react with halide ions as soon as they form (silver halide precipitate)
   Ag+(aq) + X-(aq) -> AgX(s)
3. compare reactivities 3 test tubes each containing different haloalkane, ethanol and silver nitrate solution
4. pale yellow precipitate forms quickest (iodoalkane)
   cream precipitate next quickest (Bromoalkane)
   white precipitate last (Chloroalkane)