4.2.2 Haloalkane hydrolysis

Question 1

what is a primary, secondary and tertiary haloalkane

Answer 1

primary -> halogen + 1 C
secondary -> halogen + 2C
tertiary -> halogen + 3C

Question 2

why are c-halogen polar

Answer 2

this is due to the difference in electronegativity

halogen more electronegative so its partially negative and carbon is partially positive

Question 3

how do haloalkanes attract nucleophiles

Answer 3

the C in the haloaklane is partially + so it can attract a negative pair of e-

Question 4

give 3 examples of nucleophiles

Answer 4

:OH-
H2O:
:NH3

Question 5

what is the products of hydrolysis of haloalkane

Answer 5

haloalkane -> alcohol + halogen atom

Question 6

how does hydrolysis happen for a haloalkane

Answer 6

1. -OH comes in from water and attaches to partially + C (comes in from the opp. side than halogen to reduce repulsion)
2. the halogen which is partially - breaks off as it takes both e- from C
3. alcohol formed and halide ion comes off

Question 7

2 conditions needed

Answer 7

sodium hydroxide in aq form as a catalyst

and under reflux as it is very slow at room temp

Question 8

what happens to the bond enthalpy as you go from F-> Cl -> Br -> I

Answer 8

the bond enthalpy decreases as the bonds strength decreases so less energy is required

Question 9

what 2 things can u predict

Answer 9

1. that the lower the bond enthalpy so it reacts faster

2. F is unreactive as the bond enthalpy is so hugh

Question 10

how can you test the speed of Cl/Br/I alkane

Answer 10

1. add 1cm^3 of ethanol and 2 drops of each into seperate test tubes
2. heat until 60 degrees in a water bath
3. put 0.1dm^3 of silvernitrate and heat into water bath
4. pour silvernitrate into each test tube
5. time and see percipitate change

cl should be slowest while I is the fastest
cl-> white ppt
br-> cream ppt
i-> yellow ppt