CHAPTER 14 - ALCOHOLS Flashcards
What do alcohols contain?
-OH functional group - Hydroxyl group
What is the formula for methanol
CH3OH
What is methanol used for
High performance fuel (efficient combustion)
Chemical feedstock
Converted into polymers, paints, solvents, insulation, adhesives etc…
What is Ethanol used for
Alcoholic drinks
Solvent
Fuel
Feedstock
What is the suffix used for an alcohol
-ol (diol, triol etc..)
What are the physical properties of alcohols compared to the Alkanes with the same amount of carbons (eg methane and methanol)
Alcohols are:
Less volatile
Higher MP/BP (pg 223 for diagram)
Greater water solubility
(Differences become smaller as chain length increases)
Why do alcohols act differently to alkanes?
The alkane have non-polar bonds
Very Weak London Forces (LDF)
Alcohols are polar
Strong H bonds, Very weak LDF
Why are Alcohols soluble in water
Form Hydrogen bonds in water
Polar groups -OH
(Increase in carbon chain, decrease in solubility)
What does Ethylene Glycol (ethane 1,2 diol) do and how does it work?
De-Icer
Water freezes at 0 and ethane diol at -13, but when combined, freezing point can be as low as -40, which means that the frozen waster changes state
How can alcohols be classified?
Primary, Secondary, Tertiary
What is a primary alcohol?
When the carbon which the -OH group is attached to is attached to 2/3 other Hydrogens (no or one alkyl group) (eg. Ethanol, Methanol)
What is a secondary alcohol?
When the carbon which the -OH Group is attached to is only attached to 1 Hydrogen or 2 carbon (or 2 alkyl groups) (eg Pentan-3-ol)
What is a tertiary alcohol?
When the carbon which the -OH Group is attached to no Hydrogens or 3 carbons (or 3 alkyl groups) (eg 2-methylpropan-2-ol)
What is the word equation for the combustion of alcohols
Alcohol + Oxygen = Carbon dioxide and water
Eg. C2H5OH + 3 O2 = 2 CO2 + 3 H2O
What type of reaction is the combustion of alcohols
Exothermic, releases large quantity of energy from heat
Increase in carbon chain increase in heat released per mole
What colour change does the oxidation of alcohols undergo?
Orange - Green
Dichromate (VI) ions - Chromium (III) ions
What is added to the alcohols for them to be oxidised?
acidified K2Cr2O7 and dilute H2SO4
What do Primary alcohols oxidise to?
Aldehydes, then further to Carboxylic acid
How is an Aldehyde prepared?
Heating of a primary alcohol with acidified potassium dichromate and dilute sulfuric acid
Distilled off - to prevent further oxidation
How is a carboxylic acid prepared
Heating of a primary alcohol with acidified potassium dichromate and dilute sulfuric acid under reflux conditions
What is produced in the oxidation of a secondary alcohol?
Ketone
How is a Ketone prepared
Heating of a secondary alcohol with acidified potassium dichromate and dilute sulfuric acid
Under reflux conditions
Change from orange to green
What happens when a tertiary alcohol is oxidised?
Nothing - they do not oxidise
Solution remains orange
What is formed when an alcohol is dehydrated?
Alkene and water
What is needed as reagents for the dehydration of alcohol?
Acid catalyst eg. conc Phosphoric acid or conc sulfuric acid
Reflux conditions
What type of reaction is Dehydration?
Elimination reaction
What is formed when alcohols react with hydrogen halides
Haloalkanes and water
How is a Haloalkane prepared?
Alcohol in reflux conditions with added sulfuric acid and a sodium halide (eg HBr)
(page 228 for diagram)
