15.0 Alcohols Flashcards
(17 cards)
What is the functional group in an alcohol?
-OH
Why do alcohols have higher melting and boiling
points than the equivalent alkanes?
Hydrogen bond is a stronger intermolecular force than van der Waals.
Write a balanced equation for fermentation.
C6H12O6 → 2CH3CH2OH + 2CO2
What are the conditions needed for fermentation?
Warm temperature (25-40oC)
Yeast
Anaerobic/no oxygen
Write an equation and describe the conditions for
hydration of ethene to form ethanol.
CH2=CH2 + H2O → CH3CH2OH
Phosphoric acid catalyst (sulfuric)
High temperature and pressure
Give one advantage and one disadvantage for both
methods of ethanol production.
Fermentation:
ADV Low energy use, raw material can be re grown DIS
batch/slow process, land needed for crops
Hydration:
ADV high atom economy/single product, fast reaction
rate DIS high energy use, finite crude oil for ethene.
Write equations to support the idea that ethanol from fermentation is a carbon-neutral fuel.
6CO2 + 6H2O → C6H12O6 + 6H2O (photosynthesis uses 6CO2)
C6H12O6 → 2CH3CH2OH + 2CO2
(fermentation produces 2CO2)
2CH3CH2OH + 6O2 → 4CO2 + 6H2O
(combustion produces 4CO2)
Give reasons why the statement ‘ethanol from
fermentation is a carbon-neutral fuel’ is not valid.
Additional fossil fuels are usually burned in tractors
during harvesting/planting of crops, transport of the
products. This produces additional CO2.
Describe the structure of a primary, secondary, and
tertiary alcohol.
Primary the C atom bonded to OH is bonded to one other carbon, secondary bonded to two other carbon, tertiary
to three other carbon atoms.
Primary alcohols can be oxidised to which two types
of compounds? Give the reagents and conditions for
both.
Aldehydes. Distillation, acidified potassium dichromate.
Carboxylic acids. Reflux, acidified potassium dichromate
Secondary alcohols can be oxidised to form which new type of compound? Give the reagents and conditions.
Ketones. Reflux, acidified potassium dichromate.
What colour change takes place in the potassium
dichromate during the oxidation of alcohols?
Orange to green
Why are aldehydes more volatile than alcohols or
carboxylic acids?
They only exert dipole-dipole forces between molecules, which are weaker than hydrogen bonds.
Why do tertiary alcohols not oxidise easily?
A C-C bond would need to be broken. Not able to break C-C bond with acidified potassium dichromate.
Write an equation to show the full oxidation under
reflux of propan-1-ol.
CH3CH2CH2OH + 2[O] → CH3CH2COOH + H2O
Write an equation to show the oxidation of ethanol by distillation.
CH3CH2OH + [O] → CH3CHO + H2O
Describe a method and expected observation for
distinguishing ethanol from ethanal.
Tollen’s reagent: ethanal gives a silver mirror, ethanol no change.
Fehling’s solution: ethanal gives a brick red precipitate,
ethanol no change.
