4) Alcohols and Haloalkanes Flashcards
What is the functional group of alcohols?
-OH.
Why are alcohol molecules polar?
Alcohols have a polar O-H bond because of the difference in electronegativity of the oxygen and hydrogen atoms.
If the carbon that the -OH group is attached to is attached to 1 other carbon itself, what is the classification of that alcohol?
Primary.
If the carbon that the -OH group is attached to is attached to 2 other carbons itself, what is the classification of that alcohol?
Secondary.
If the carbon that the -OH group is attached to is attached to 3 other carbons itself, what is the classification of that alcohol?
Tertiary.
What do alcohols produce when they burn completely in a plentiful supply of oxygen?
Carbon dioxide and water.
What is used to represent an oxidising agent?
[O].
Primary and secondary alcohols can be oxidised using an oxidising agent. What is the usual mixture used?
- Potassium dichromate (VI) acidified with dilute sulfuric acid.
- K2Cr2O7/H2SO4.
On oxidation, what does a primary alcohol form?
- Aldehyde.
- Carboxylic acid.
How can you ensure an aldehyde is made when oxidising a primary alcohol?
Distil.
How can you ensure a carboxylic acid is made when oxidising a primary alcohol?
Heat strongly under reflux.
On oxidation, what does a secondary alcohol form?
Ketone.
On oxidation, what does a tertiary alcohol form?
No reaction.
How is an alkene made from an alcohol?
- An acid is heated under reflux in the presence of an acid catalyst, H2SO4 or H3PO4 to produce an alkene.
- Plus water as a by-product.
What do alcohols form when they react with hydrogen halides?
Haloalkanes.
How are haloalkanes formed from alcohols?
Substitution with halide ions in the presence of an acid (NaBr/H2SO4) to form haloalkanes.
Explain why ethane-1,2-diol is very soluble in water.
- Has O–H bonds.
- Which forms hydrogen bonds with water.
Butan-1-ol can be oxidised to form butanal. State a suitable oxidising mixture for this reaction.
- H+.
- Cr2O7^2-.
State the colour change you would see during the oxidation of butan-1-ol to form butanal.
Orange to green.
Explain what is meant by low volatility.
High boiling point/difficult to vapourise.
Define intermolecular forces.
Bonds between molecules.
What happens in the hydrolysis of a haloalkane?
The halogen atom is replaced by an -OH group. This is an example of nucleophilic substitution.
Define what is meant by a nucleophile.
An electron pair donor.
Use this card to test knowledge of the nucleophilic substitution mechanism.
Rate knowledge 1-5.
Which haloalkanes react the quickest and slowest?
- 1-chlorobutane reacts the slowest and the C-Cl bond is the strongest.
- 1-iodobutane reacts the fastest and the C-Cl bond is the weakest.
What is the trend in the rate of hydrolysis in terms of the carbon-halogen bond?
The rate of hydrolysis increases as the strength of the carbon-halogen bond decreases.
Suggest three reasons why there is still concern about ozone depletion.
- CFCs take many years to reach the ozone layer.
- CFCs are still being used.
- There are other ozone depleting substances.
State a suitable reagent for dehydrating an alcohol.
H2SO4 (heat).
Suggest a property that made CF3Cl suitable as a propellant in an aerosol.
Volatile.
Suggest which bond is most likely to be broken when CF3Cl is exposed to ultraviolet radiation. Explain your answer.
C-Cl because it is the weaker bond.
The rates of hydrolysis of chloroethane, bromoethane and iodoethane are different. Explain why.
- I>Br>Cl.
- C-I bond weakest and C-Cl bond strongest.
