C14 Alcohols Flashcards
Functional group of alcohol
-OH (hydroxyl group)
Physical properties of alcohols compared to alkanes
Less volatile
Higher MPs
Greater H2O solubility
Reason for physical properties of alkanes
Non-polar bonds as EN of C + H very similar
IMFs between non-polar molecules are very weak LFs
Reason for physical properties of alcohols
Polar O-H bonds (diff in EN of O and H atoms)
IMFs are very weak LFs but theres also strong HBs between polar O-H
Why do alcohols have higher BPs and lower volatility than alkanes
HBs require more energy to break than weaker LFs in alkanes
Solubility of alkanes in water
Non-polar
Cannot form HBs with H2O
Solubility of alcohols in water
Completely soluble in water
HBs form between polar -OH groups of alcohol + H2O
What happens to solubility as chain length increases
C chain length increases
Influence of -OH becomes smaller
Solubility decreases
What’s a primary alcohol
-OH attached to C that’s attached to 2 H atoms + 1 alkyl group
What’s a secondary alcohol
-OH attached to C that’s attached to 1 H + 2 alkyl groups
What’s a tertiary alcohol
-OH attached to C that’s attached to no H + 3 alkyl groups
What is the colour change when alcohols are oxidised
Orange to green
Dichromate (VI) ions reduced to chromium (III) ions
What do primary alcohols oxidise to
Aldehyde or carboxylic acid
Oxidation of primary alcohol to form aldehyde
Gentle heating
K2Cr2O7/H2SO4
Aldehyde distilled out as it forms
Colour change : orange to green
Oxidation of primary alcohol to form carboxylic acid
Reflux
Excess K2Cr2O7/H2SO4
Orange to green
Form carboxylic acid + water
What does oxidising secondary alcohols produce
Ketones
Oxidising tertiary alcohols
Don’t undergo oxidation reactions
Oxidation mixture remains orange
Oxidising secondary alcohol to produce ketone
Reflux
K2Cr2O7/H2SO4
Orange to green
Produce ketone + water
Word equation of complete combustion of alcohol
Alcohol + O2 —> CO2 + H2O
what is the oxidising agent that oxidises primary and secondary alcohols?
primary/secondary alcohol
heat under reflux
acid catalyst (conc H2SO4 or conc H3PO4)
form alkene and water
what type of reaction is combustion?
exothermic reaction as it releases a large amount of energy in the form of heat.
what conditions are needed for an alcohol to undergo a substitution reaction with a hydrogen halide?
hydrogen halide
reflux
sulfuric acid
sodium halide
forms haloalkane
what is a dehydration reaction?
any reaction in which a water molecule is removed from the starting material
What’s the general formula of an alcohol
CnH2n+1 OH
How do you name alcohols (one prefix, one suffix)?
Hydroxyl- or -ol
What kind of IMFs do alcohols have and why
Hydrogen bonding
Due to electronegativity difference in OH bond
Hoe do alcohols MP and BP compare to other hydrocarbons’ of similar C chain lengths? Why?
Higher, because they have HB (strongest type of IMF) —> stronger than LFs
Are alcohols soluble in water? Why does solubility depend on chain length?
Soluble when short chain - OH HBs to HB in water
Insoluble when long chain - non-polarity of C-H bond takes precedence
What makes an alcohol primary
C bonded to OH is only bonded to 1 other C atom
What makes an alcohol secondary
C bonded to OH is bonded to 2 other C atoms
What makes an alcohol tertiary
C bonded to OH is bonded to 3 other C atoms
What forms if you partially oxidise a primary alcohol
An aldehyde
What conditions are needed to partially oxidise a primary alcohol
Dilute H2SO4, potassium dichromate (VI), distill product as its produced, gentle heating
What forms if you fully oxidise a primary alcohol
A carboxylic acid
What conditions are needed to fully oxidise a primary alcohol
Conc H2SO4, potassium dichromate (VI), reflux, strong heating
What forms if you oxidise a secondary alcohol
A ketone
What conditions are needed for the oxidation of a secondary alcohol
Conc H2SO4, potassium dichromate (VI), strong heating
Is it possible to oxidise a tertiary alcohol
No
What’s a dehydration reaction
A reaction where water is lost to form an organic compound
What are the products of dehydration reaction of alcohol
Alkene and water
What are the conditions required for dehydration of alcohol
Conc H2SO4 or conc H3PO4 and 170*C
What are the products of the halide substitution reaction with alcohol
Haloalkane and water
In what form is the halide used in halide substitution reaction
In the form of hydrogen halide, e.g. HBr
How is hydrogen halide made in situ? Give examples
A salt is reacted with acid to form the hydrogen halide
E.g. sodium bromide reacts with sulfuric acid to form HBr
When iodine is reacted phosphoric acid is used as sulfuric acid oxidises iodide ions into iodide
