Haloalkanes Flashcards
(18 cards)
What is nucleophilic substitution?
It is the replacement of a halogen in haloalkane compound with a nucleophile.
What is a nucleophile?
It is an atom or a group of atoms which is attracted to an electron deficient carbon atom. They donate their pair of electrons to the carbon to form a new covalent bond.
What is hydrolysis?
Hydrolysis is a chemical reaction involving water or an aqeous solution of a hydroxide that causes a break down of a bond in a compound. This results in two new products from the splitting of the compound.
Name the steps of nucleophilic substitution
- A nucleophile approaches a carbon attatched to a halogen.
- The direction of the nucleophile’s attack minimises the repulsion between the nucleophile and the delta negative halogen atom
- The lone pair from the nucleophile is attatched to the carbon atom and is donated to delta positive carbon atom
- A new bond is then made between the oxygen from the OH- and carbon atom
- The carbon-halogen bond is then broken down by heterolytic fission
- The organic compound, alcohol, is then formed along with a halide ion.
How is a haloalkane converted into an alcohol?
It is done by using aqueous sodium hydroxide. However, this reaction is very slow in room temperature. Thus, it is heated under reflux to obtain a good yield of the product
What does the rate of hydrolysis depend on?
The structure of the haloalkane and the halogen attatched in the haloalkane.
Is C-Cl a faster compound to break down compared to C-Br?
No, C-Cl is a slower haloalkane to break down as C-Cl is a stronger bond than C-Br. This is because Cl is more electronegative than Br. However, C-I is the fastest molecule to break down as it is the weakest bond of the halogens
What compound do you use to measure the rate of hydrolysis?
Aqueous silver nitrate
Why is ethanol solvent used in a hydrolysis reaction?
The ethanol solvent allows the haloalkane and water to mix together and produce a single solutions rather than two layers.
What is the compound if a white precipitate is formed slowly?
1-chlorobutane
What is the compound if a cream precipitate is formed faster than 1-chlorobutane but slower than 1-iodobutane?
1-bromobutane
What is the compound if a yellow precipitate is formed rapidly?
1-iodobutane
Do tertiary haloalkanes react faster or slower than primary haloalkanes?
Tertiary react faster as they have a two step process, whereas a primary only has one step process
What are the two steps to a tertiary haloalkane hydrolysis?
The carbon-halogen bond is broken down by heterolytic fission, forming a tertiary carbocation and halide ion. They hydroxide ion then attacks the carbocation to form an organic product.
What does the ozone molecule absorb?
UV-B radiation
What happens when CFCs get into the stratosphere?
They begin to break down into chlorine radicals, which then react with the ozone in the atmosphere. This then causes ClO radical to be formed along with O2. The ClO radical then reacts with O to form another Cl radical. This cycle then repeats itself. The overall reaction is O3 + 02–> 202
What is the estimated ozone molecules that one CFC can break down?
100,000
Are CFCs the sole reason in ozone depletion?
No, nitrogen oxide radicals also cause the depletion of ozone molecules in the stratosphere. These break down ozone molecules similarly to CFCs would. Nitrogen oxide radicals are formed naturally from lightning strikes and aircraft travel into the stratosphere
