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What is the trend in bond polarity of halogenoalkanes
Larger halogens causes a decrease in bond electronegativity
What IMF do halogenoalkanes have
Van Der Walls and dipole-dipole
Why don’t halogenoalkanes have no hydrogen bonds
No direct hydrogen and halogen bonds
What is the trend with boiling points in halogenoalkanes
Lower electronegativity increases boiling point
Why does boiling points increase despite decrease in polarity
Size of an atom has a greater effect on Van der walls
Define immiscible
Does not mix well with water
Why do halogenoalkanes not mix with water
They are generally non-polar
Why are halogenoalkanes reactive
Due to their polar C-halogen bond
What functional groups are halogenoalkanes
Alcohols, amines, nitriles and alkenes
How are alcohols, amines and nitriles reacted
via nucleophilic substitution
How are alkenes reacted
Via eliminations
Define nucleophilic
Positive-loving (attracted to positive) so most likely negative
Define a nucleophile
An electron pair donor
What does a curly arrow represent
Movement of an electron pair
What does the nucleophile do in nucleophilic substitution
Attacks the delta positive carbon
What does the electron pair from the nucleophile form
A new bond to C
What are the reagents for a alcohol nucleophilic substitution
KOH (aqueous)
What is a reagent
Added to react
What conditions are needed for nucleophilic substitution
Heat and reflux
What is a conditions
Helps a reaction
Where do the curly arrows go from
The bond
Where must the arrow go from on the nucleophile
The lone pairs
Define substitution reactions
Can involve nucleophile that are not charged but have a lone pair of electrons
Name 3 examples of nucleophiles for nucleophilic substitution
OH, C triple bond N, NH3,
why is excess NH3 used in nucleophilic substitution
To prevent secondary or tertiary amines
What mechanisms turns halogenoalkanes to alkenes
Elimination
How does eliminations of halogenoalkanes make alkenes
By losing the halogen atom and forming a C=C bond in the molecule without adding anything
What is used instead of a nucleophile in elimination
A base
Where does the first arrow go in elimination
From the base to the hydrogen of the H-C bond
What hydrogens can be used in elimination
Those bonded to carbons ADJACENT to the halogen
Why can the hydrogen in elimination not be connected to the halogen’s carbon
So the carbon doesn’t lose too many electrons when the halogen is displaced
Where does the second arrow in elimination go
From the carbon-halogen bond to the halogen
Why does the second arrow in elimination go from the C-halogen bond to the halogen
As carbon gives its electrons to the halogen so it can remove itself
Where does the third arrow go in elimination
From the hydrogen to the carbon connected to the halogen
Why does the third arrow go from the hydrogen to the carbon In elimination
Hydrogen gives its electrons to the C-C bond to make it C=C
What must the reagents be for elimination
Ethanoic KOH
What are the conditions for elimination
Warmth
what is the weakest carbon-halogen bond
C-I
what is the strongest carbon-halogen bond
C-F
What can halogenoalkanes react with to form a precipitate
aqueous silver nitrate solution
what will aqueous silver nitrate form with chlorides
white precipitate
what will aqueous silver nitrate form with bromides
cream precipitate
what will aqueous silver nitrate form with iodides
pale yellow precipitate
what are halogenoalkanes so reactive
due to the electronegative halogens
what two mechanisms can halogenoalkanes undergo
elimination, nucleophilic substitution
what is the issue with chlorofluorocarbons
their effect on the ozone layer
what happens to chlorofluorocarbons in the upper atmosphere
UV radiation is absorbed forming chlorine radicals which break down the ozone layer
what is used in replacement of chlorofluorocarbons
hydrofluorocarbons
why is the ozone layer important
it absorbs harmful UV which can cause skin cancer
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