2.6 Halogenoalkanes Flashcards
What is a halogenoalkane
Homologous series which a H atom in an alkane is replaced by a halogen
Why are halogenoalkanes polar
Give the charges
And effect of this
Halogens are more electronegative than carbon
Halogen is delta -
Carbon is delta +
The carbon is electron deficient and susceptible to attack by a nucleophile
What is a substitution reaction and give an example
Reaction in which one atom/group is replaced by another
Aqueous sodium hydroxide attacking 1-chlorobutane to produce butan-1-ol
Why can a nucleophilic substitution be classified as hydrolysis when water is used to source the OH-
As it is a reaction with water to produce a new product
Why is using water during nucleophilic substitution a slow reaction
low concentration of OH-
How to achieve hydrolysis of a halogenoalkane
Heated under reflux with water or aqueous sodium hydroxide
What are 2 things to consider when changing the halogen to change the rate of the hydrolysis reaction
Electronegativity and bond strength
Which halogen makes the hydrolysis fastest and why
An iodocompound
Although it has the smallest electronegativity value as it has the weakest bond to break during hydrolysis
The bond strength factor outweighs the effect of the charge on the carbon
Why can the hydrolysis of a halogenoalkane be used to show tye functional group
As it produced a halide ion
Steps for test for the presence of a halogen in an organic compound
1 heat organic compound with aqueous sodium hydroxide
2 add HNO3 to remove any remaining NaOH
3 add AgNO3 to produce a precipitate
4 further addition of NH3 to the precipitate
What is an elimination reaction
one that involves the loss of
a small molecule to produce
a double bond.
What does the elimination reaction for a halogenoalkane involve
Loss of hydrogen halide
Formation of a double bond
Why can the hydrogen halide after an elimination reaction be removed using an alkali
It is acidic
What is done during an elimination reaction to avoid hydrolysis
The alkali must be in solution in ethanol
Why is refluxing useful
Allows prolonged heating of volatile chemicals without loss
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