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
What conditions are needed for the oxidation of an alcohol to form a Carboxylic acid
Heat a primary alcohol to reflux with excess K2CR2O7/ H2SO4.
What conditions are needed for the oxidation of an alcohol to form a Ketone
Heat a secondary alcohol to reflux with Acidified K2CR2O7
What symbol do you use to represent the oxidising agent
[ O ]
When it is in excess 2[O]
Show reaction of propan-1-ol heated to reflux with excess acidified Potassium dichromate
CH3CH2CH2OH + 2[O] → CH3CH2COOH + H2O
Propanoic acid
Show reaction for gentle oxidation methylpropan-1-ol
CH3CH(CH3)CH2OH + [O] →CH3CH(CH3)CHO + H2O
methylpropanal
Show reaction of propan-2-ol when heated under reflux with acidified potassium dichromate
CH3CH(OH)CH3 + [O] →CH3COCH3 + H2O
propanone is formed
Describe how to create a haloalkane form an alcohol
Alcohols react with hydrogen halides to produce a haloalkane
- The alcohol is heated under reflux with sulfuric acid and a sodium halide (Bromide)- Hydrogen Bromide is formed in situ
- The HBr formed reacts with the alcohol to produce the haloalkane
Write an equation to show the production of HBr form sodium bromide and sulfuric acid
NaBr + H2SO4 → NaHSO4 + HBr
Write an equation to show the substitution reaction of propan-2-ol with hydrogen bromide
CH3CHOHCH3 +HBr → CH3CHBrCH3 + H2O
Write the overall equation for the reaction of propan-2-ol with H2SO4 and NaBr
CH3CHOHCH3 +NaBr + H2SO4 → CH3CHBrCH3 + NaHSO4 + H2O
What type of reaction is the reaction of alcohols and hydrogen halides
Substitution
Write general equation for formation of an ester from an alcohol and state the conditions
Carboxylic acid + Alcohol ↔ Ester + Water
Conc sulfuric acid catalyst
Heat under reflux
How do you name an ester
- The first part comes from he alcohol and ends in -yl e.g If the alcohol was methanol it would begin with methyl
- The second part comes form the Carboxylic acid and ends in -oate. e.g If the carboxylic acid was ethanoic acid it would end with ethanoate
- So if it was the reaction of methanol and ethanoic acid the ester formed would be methyl ethanoate
Name and draw the ester formed from the reaction of ethanoic acid and propan-1-ol
Propyl ethanoate
CH3COOCH2CH2CH3
Drawing p26 of study pack
