15. Haloalkanes Flashcards
Define a nucleophile.
an electron pair donor
What do all nucleophiles possess?
at least one lone pair
What are the 4 common nucleophiles?
OH- , CN- , NH3, H2O
Define hydrolysis.
the breaking of a chemical compound into 2 products, using H2O or OH-
What governs the rate of hydrolysis? Therefore do weaker or stronger bonds hydrolyse faster?
bond strength
weaker bonds: e.g. C-I
Why is C-I the weakest C-halogen bond?
I = larger atom = more shielding = less nuclear attraction to bonding pair = weaker bond
Does the rate of hydrolysis increase or decrease from C-I to C-F ?
decreases up the group
C-I hydrolyses faster than C-F
Which is the most polar C-halogen? What does this mean for it?
C-F
greatest difference in electronegativity
it attracts nucleophiles better an has the highest bond enthalpy
Describe an experiment to measure RoH.
- add equal vol. 1-iodopropane, 1-bromopropane and 1-chloropropane to equal vol. of ethanol in separate test tubes
- warm mixture to 50 degrees in a water bath and add equal vol. of AgNO3
- record time taken for precipitate to form
- -white (Cl) appears last, yellow (I) appears first
Why do you add ethanol to the haloalkane when measuring RoH?
ethanol = v good solvent
has H bonding so dissolves aqueous/ionic and LDFs so dissolves organic
What does ozone do for us?
prevents genetic damage and cancer by absorbing UVB rays from the sun
What is the steady state of ozone? (reversible reaction)
O2 + O. <> O3
What happens to CFCs when they reach the ozone layer?
UV rays break C-Cl bond, as it has the lowest enthalpy, into Cl. radicals.
Write out the set of equations for ozone depletion by chlorine radicals.
go find it somewhere in ur little book
What is the overall equation for ozone depletion?
O3 + O => 2O2
