ORGANIC CHEMISTRY - haloalkanes Flashcards
Are halogenalkanes soluble in water?
No, they are insoluble in water because their dipole moment is too weak to form hydrogen bonds with water molecules.
Do halogenalkanes have a polar bond?
Yes they have a polar bond as halogen has a higher electronegativity than the carbon it is bonded to.
Which intermolecular forces do they have? ( C-X )
permanent dipole-dipole
van der waals forces of attraction
C-X bond polarity creates permanent dipoles
When would halogenalkanes have high boiling points?
When carbon chain increases and the halogen goes down group 7
How would the mass of a haloalkane differ from the mass of an alkane with the same chain length?
Haloalkanes mass will be greater
as the mass of a halogen is higher than the mass of Hydrogen
What is the most important factor in determining their reactivity?
Carbon-Halogen bond enthalpy
What is the order of reactivity of halogenalkanes?
Although C-F is the most polar bond, the bond enthalpy of C-X decreases as you go down the group therefore the reactivity increases down the group.
What is a nucleophile?
A negatively charged ion or atom which has lone pair of electrons which can be donated to an electron deficient atom.
Give 3 examples of nucleophiles?
:OH-
:NH3
:CN-
What is nucleophilic substitution?
A reaction where a nucleophile donates its lone pair of electron to an electron deficient C atom and the partially negative atom leaves the molecule and is replaced by the nucleophile.
Draw the mechanism for the reaction of bromoethane with NaOH?
draw partially positive charges on C and partially negative charge on Br
arrow of nucleophile attacking C
Br
Arrow from the bond to Br
what are the conditions/reactants needed for elimination reactions of haloalkanes?
NaOH and KOH dissolved in ethanol at high temperature.
What is formed in the elimination reaction of haloalkanes?
An alkene, water and halide
Describe the mechanism of elimination reaction?
The OH- ion acts as a base, removing an H+ from the halogenoalkane.
1- the OH- uses its lone pair to form a bond with one of the hydrogen atoms on the carbon on the C-X bond. These hydrogen atoms are slightly partially positive.
2- the electron pair form the C-X bond now becomes part of a carbon-carbon double bond.
3- the halogen takes the pair of the electrons in the C-X and leaves a halide ion, leaving the group.
what type of haloalkane tend to react by substitution?
primary halogenalkanes tend to react by substitution.
