Alcohols Flashcards
What are alcohols?
homologous series of organic compounds that have the functional group -OH
How do you name alcohols?
using the iupac based on the number of carbon atoms and end the phrase with ‘anol’
What is the general formula of alcohols?
CnH2n+1-OH
How do the properties of alcohols differ as they increase in size?
change as the molecules get bigger, first 4 alcohols have similar properties
How do the properties of alcohols differ as the molecules increase in size?
boiling point increases as chains get longer, as there are more bonds to break
solubility in water decreases as chains get longer, as longer chains are more hydrophobic
flammability decreases as chains get longer, as smaller molecules vapourise more easily
viscosity increases as chains get longer
What are the properties of alcohols?
flammable: can undergo complete combustion in air
soluble: can dissolve in water to form a solution with a neutral pH
oxidised: if oxygen is added to an alcohol it will be oxidised and become a carboxylic acid, since it gains an oxygen and has the functional group -COOH
What are the uses of alcohols?
can use alcohols as fuels as they are flammable and releases lots of energy
can be uses as solvents in the industry, as can dissolve many things that water can’t (lipids and hydrocarbons)
How is ethanoic acid produced?
oxidation of ethanol by complete combustion with excess oxygen in air, with presence of a microorganism.
Describe the complete combustion of ethanol
ethanol burns in oxygen/air requiring heat/flame and produces carbon dioxide and water
What is the equation for the complete combustion of ethanol?
C2H5OH + 3O2 -> 2CO2 + 3H2O
Describe the microbial oxidation of ethanol
ethanol is exposed to air, and acetobacer bacteria (naturally present in air) works to convert ethanol to ethanoic acid (producing vinegar). no conditions needed, but slower process than other methods
Describe the chemical oxidation of ethanol
uses potassium dichromate (VI) and dilute sulfuric acid (catalyst) to produce ethanoic acid
orange dichromate solution turns green
much faster reaction than microbial oxidation, common lab method
How can ethanol be produced?
industrial hydration: reacting ethene with steam in the presence of a phosphoric acid catalyst at a temperature of about 300 degrees celsius and 60-70 atmosphere
or
fermentation:
fermentation of glucose in absence of air (anaerobic), at optimum temperature 30 degrees celsius and normal atmospheric pressure as well as using the enzymes in yeast. used in brewing.
What is the chemical equation of producing ethanol from the fermentation of glucose?
C6H12O6 -> 2C2H5OH + 2CO2
What happens when fermentation is conducted in presence of air?
in aerobic conditions enzymes in yeast product carbon dioxide and water instead of ethanol
Why is the optimum temperature for fermentation 30 degrees celsius?
below 30 degrees the reaction is too slow
above 40 degrees the enzyme denatures
