Alcohols Flashcards
Name CH3CH(OH)CH(CH3)CH3
3-methylbutan-2-ol
Name CH3CH(OH)CH(OH)CH3
Butane-2,3-diol
How do you say if an alcohol is primary or seondary
If the OH group is attached to a Carbon which is only attached to 1 other carbon - Primary
If the OH group is attached to a Carbon which is attached to 2 other carbons -Secondary
etc
What is the trend in boiling points as you go down the alcohol homologous series
- The boiling points increase.
- This is because they have more electrons so the strength of their London Forces increase- fluctuations in their electron cloud is more likely
- So more energy is needed to overcome the force and separate the molecules
Explain in terms of intermolecular bonding why methanol has a significantly higher boiling point than ethane
- Methanol has an OH alcohol group
- This means it will form hydrogen bonds with other methanol molecules.
- Ethane only experiences London forces.
- H bonds are stronger than London forces so require more energy to overcome
Explain why the water solubility of the alcohols decreases as the chain length increases
- The –OH group is the only part that interacts with (or dissolves in) water. (It is polar)
- As the chain length increases, the effect of the –OH decreases and that of the non-polar (water insoluble) carbon chain becomes more important.
Suggest a solvent large alcohols will dissolve in
Hexane
Write down the general equation for the Combustion reaction of alcohols
Alcohol + Oxygen → Carbon dioxide + Water
List the reactions with alcohols you need to know
- Combustion
- Elimination
- Oxidation
- Esterification
- Substitution
Write equation to show the combustion of cyclohexanol and methylpropan-1-ol
- CH3CH(CH3)CH2OH + 6O2 → 4CO2 + 5H2O
2. (structural drawing of CHOHCH2CH2CH2CH2CH2+ 8½O2 → 6CO2 + 6H2O
Write down displayed formula to show elimination of water (dehydration) from propan-1-ol.
CH3CH2CH2OH → CH3CH=CH2 + H2O
State conditions necessary for dehydration of alcohols
- Heat under reflux
2. Catalyst- Concentrated sulfuric acid/ Phosphoric acid
Explain the meaning of elimination
The opposite of addition- removal of a small molecule from a larger one
Describe what happens in an elimination reaction of a alcohol
- The alcohol is heated with an acid catalyst
- It loses it’s OH group and a hydrogen atom form the next carbon
- There could be several neighbouring carbons, so you get a mixture of products- including E/Z isomers
Write equations to show the elimination reaction of methylpropan-1-ol
CH3CH(CH3)CH2OH → CH3C(CH3)=CH2 + H2O
Write down two chemicals required to make oxidising agent for alcohols
K2Cr2O7 (Potassium dichromate solution)
Dilute H2SO4
What is the observation for a successful oxidation
Colour change form orange to green
Define reflux
Continuous boiling and condensing of a reaction mixture to prevent the loss of volatile components
Show the Aldehyde functional group and name when formed from ethanol
- A primary C with a double bond to an O and a single bond to H
- It is called Ethanal
- Written as CH3CHO
Show the Ketone functional group and name when formed from Propan-2-ol
- A secondary carbon with a double bond to an O and to single bonds to C
- It is called Propanone
- Written as CH3COCH3
Show the Carboxylic acid functional group and name when formed from butan-1-ol
- A primary C with double bond to O and single bond to OH group
- It is called Butanoic acid
- Written as CH3CH2CH2COOH
What type of alcohol can’t undergo oxidation
Tertiary alcohols
What are the two products formed from a primary alcohol
Aldehyde or Carboxylic acid
What conditions are needed for the oxidation of an alcohol to form an aldehyde
Gentle heating of primary alcohols with acidified Potassium dichromate.
The aldehyde is distilled out of the reaction mixture as it forms to prevent further reaction
