Alcohols Unit 4 Flashcards
Define an alcohol
Compounds in which one or more hydrogen atoms in an alkene have been replaced by a hydroxyl Group
Why does the boiling point of alcohols increase with increasing chain length
The attractions get stronger as the molecules get longer and have more electrons- increase size of temporary dipoles
What is complete oxidation called
Combustion
C2H5OH + O2 –> CO2 + H2O
How to oxidise alcohols
Add acidified potassium dichromate
What colour changes happens when you oxidise Butan-1-ol
Orange to green
Balanced equation for the oxidation of Butan-1-ol to a carboxylic acid
C4H9OH + 2[O] —> C3H7COOH + H2O
What conditions are need for the dehydration of an alcohol?
An acid catalyst phosphoric or sulphuric acid
And heat
What does the dehydration of an alcohol form
An alkene and a molecule of water
Which alcohol reacts the fastest with concentrated hcl
Tertiary
What are primary alcohols oxidised to and what does it require?
Aldehydes
Distillation
What happens to an aldehyde if heated further with excess acidified potassium dichromate and under reflux?
Carboxylic acid
What are secondary alcohols oxidised to and what does it require?
Ketones
Reflux
Colour changed of the three types of alcohols
Primary- green
Secondary- green
Tertiary- orange (no change)
Why can’t tertiary alcohols be oxidised
They don’t have a hydrogen atom attached to that carbon
Physical properties of haloalkanes
Immiscible with water
Boiling point depends on size and number of halogens
Define a nucleophile
An electron pair donor
What is nucleophillic substitution and what does it require
Hydrolysis reaction that requires aqueous NaOH
Must be under reflux
How does the nucleophillic substitution bond break
Heterolytic fission
How is heterolytic fission facilitated
By a negatively charged substance reacting with the positively charged carbon atom in a haloalkane
Why is dilute nitric acid added to haloalkane with ethanol
Prevents unreacted hydroxide ions reacting with the silver ions
Colour of Cl- precipitate
White precipitate
Colour of Br- precipitate
Very pale cream precipitate
Colour of I- precipitate
Very pale yellow precipitate
What happens to the precipitate when ammonia solution is added to AgCl
Precipitate dissolves to give a colourless solution
What happens to the precipitate when ammonia solution is added to AgBr
Precipitate is almost unchanged using dilute ammonia solution, but dissolves in concentrated ammonia solution to give a colourless solution
What happens to the precipitate when ammonia solution is added to AgI
Precipitate is insoluble in ammonia solution of any concentration
Hydrolysis rates of primary, secondary and tertiary alcohols
Tertiary halide produces a precipitate almost instantly
The secondary halide gives a slight precipitate after a few seconds. The precipitate thickens up with time
The primary halide May take considerably longer to produce a precipitate
Reagents and conditions needed to mix 2 alcohols
Acid catalyst
Steam
High temp
Why are some solutions more soluble than others
Weak intermolecular forces
OH- Group is polar as is water
OH- group can hydrogen bond with water
Who concluded that CFCs remain stable until they reach the stratosphere
Rowland and Molina
How do CFCs deplete the ozone layer
UV radiation breaks C-Cl bonds by homolytic fission
What is it called when radiation initiates the breakdown
Photodissociation
What was the global agreement called to protect the ozone layer
Montreal protocol
Alternatives to CFCs
Coolants- hydrocarbons, ammonia, CO2
HCFCs and HFCs
in carboxylic acids, how do you count the chain
count from the carbon atom in the -COOH group as being number 1
symbol equation for the oxidation of ethanol to ethanoic acid under reflux
CH3CH2OH + [O]–> CH3CHO + H2O
CH3CHO + [O] –> CH3COOH
CH3CH2OH + 2[O] –> CH3COOH + H2O
why is ethanol added to a haloalkane to determine it
it dissolves the haloalkane
general equation for radicals affecting the ozone
R. + O3 –> RO. + O2
RO. + O –> R + O2
O3 + O –> 2O2
what is ozonolysis
breaks open a C=C bond
what is the purpose of adding sodium carbonate solution to the round bottomed flask
neutralises excess acid
what is the purpose of adding anhydrous magnesium sulfate
acts as a drying agent
