WM Flashcards
Why are alcohols polar?
Because of the polarised O-H bond
Which bond type is stronger; Covalent or Hydrogen?
Covalent
Describe the trend in solubility as you increase the length of the carbon chain on an alcohol.
Solubility decreases due to the polarity of the O-H bond becoming less important to the molecule compared to the carbon chain.
Give the definition for a primary alcohol
-OH bonded to a carbon bonded to one other carbon atom
Give the definition for a secondary alcohol
-OH bonded to a carbon bonded to two other carbon atoms
Give the definition for a tertiary alcohol
-OH bonded to a carbon bonded to three other carbon atoms
What colour change would we see when an acidified dichromate ion is used to oxidise an alcohol group
orange to green
Give the conditions required to go from ethanol to ethanal
Oxidation with potassium dichromate with the alcohol in excess (no reflux)
Give the conditions required to go from ethanol to ethanoic acid
Oxidation with potassium dichromate with the Oxidising agent in excess under reflux
When under reflux, what is the maximum height the vapour should condense at in the condenser?
halfway up
What colour would potassium dichromate be when added in excess to 2-methylpropan-2-ol and refluxed
Remains orange because 2-methylpropan-2-ol will only oxidise once to form the ketone.
What conditions are required for the dehydration for alcohol to the alkene
aluminium oxide catalyst at 300 degrees
or
refluxed with conc. sulfuric acid
What conditions are required for the esterification of an alcohol with a carboxylic acid
HCl catalyst heated under reflux
Give the three compounds we find an OH group in organic chemistry
Phenol
Carboxylic Acid
Alcohol
What ion is formed that makes -OH groups acidic
Hydronium ion (H3O)+
Put the following in order of increasing acidity
(low to high):
Phenol, Water, Ethanol, Carboxylic acid
- ethanol
- water
- phenol
- carboxylic acid
How could you determine the identities of 3 unknown samples of ethanol, phenol and ethanoic acid?
ethanoic acid will fizz when it reacts with Sodium carbonate and release carbon dioxide gas
phenol will turn purple with Iron(III) Chloride
ethanol could be identified by discolouration of acidified potassium dichromate
Describe the changing effect of the -OH group on a HC chain
Alcohol molecules are polar. As a hydrocarbon chain gets longer, the -OH group has less effect.
What is produced when an alcohol is dehydrated?
An alkene and water.
Describe 3 ways how esters are produced
Alcohol + carboxylic acid, strong acid catalyst, under reflux.
Acid anhydride + alcohol.
Phenol + acid anhydride
Describe trends in carboxylic acids, phenols and alcohols.
Strength of acids: ethanol, water, phenol, carboxylic acid.
Carboxylic acids make carbonates fizz, phenols and alcohols do not.
Describe the iron (III) chloride test.
The enol group of a phenol forms a purple complez with Fe3+.
What is the process of mass spectrometry?
Ionisation, acceleration, deflection, detection.
What are the principles of green chemistry? (12)
Safer chemical products Use safer solvents Prevention of waste products Energy usage Reduce reagents Catalysts Atom economy Real time process monitoring Safer chemical processes
Less hazardous chemical synthesis
Design for degradation
Renewable feedstocks.
What is the functional group of a carboxylic acid?
COOH
double bond to a oxygen and hydroxyl group
What is the functional group of a phenol?
A benzene ring with a hydroxide group
What is the functional group of an acid anhydride?
R-c-o-c-R
|| ||
O O
What is the functional group of an Ester?
O
||
R-C-O-R
What is the functional group of an aldehyde?
O
||
R-C-H
What is the functional group of a ketone?
O
||
R-C-R
What is the functional group of an ether?
R-O-R
What two substances react with alkalis?
Phenols and carboxylic acid
What do carboxylic acids react with that phenols don’t?
Carbonates
Not strong enough to remove hydrogen from phenol
What is the test for phenols?
Adding iron (iii) chloride
Turns purple
What can phenols react with that carboxylic acids can’t and what does it form?
Phenols react with acid anhydrides to form esters
What forms what you oxidise a primary alcohol under distillation and what is the catalyst?
Aldehyde is formed
Catalyst is acidified potassium dichromate
orange –> green
What forms what you oxidise a primary alcohol under reflux and what is the catalyst?
Carboxylic acid is made
Acidified potassium dichromate is used as a catalyst
orange –> green
What forms when you oxidise a secondary alcohol under reflux?
A ketone is formed
orange –> green
What happens when you oxidise a tertiary alcohol?
Nothing - remains orange
Why do you need to use distillation to make an aldehyde?
You need to get it out of the oxidising solution as soon as it’s formed before it is further oxidised
What can you also react with alcohol to produce an Ester?
Acid anhydride
More reactive and reacts completely on warming to give a much higher yield
Or carboxylic acid with concentrated HCl catalyst
How can you form haloalkanes from alcohol?
Substitution reaction with halide ions
Strong acid
What does vacuum filtration do?
Removes insoluble part of a mixture
What do you use recrystilation to do?
Separate soluble parts of a mixture
How do you choose the solvent used in recrystallisation?
Choose a solvent which the desired product is really soluble in when hot but in soluble when cool
What is the M+peak?
The molecule in a sample is bombarded with electrons, this removes an electron from the molecule to form a molecular ion M+
The molecular job peak shows the molecular mass of the compound
What is theM+1 peak caused by?
The presence of 13C isotope
What are peaks on a mass spectrometry?
Due to positive ions and other fragments
What happens when specific frequencies of infrared radiation act on a bond?
The bond in the organic molecule vibrates
What are the steps of recrystallisation?
Dissolve the substance in hot solvent
Use the minimum amount of solvent
Filter hot solution to remove minimum amount of insoluble impurities
Allow to cool/ crystallise
Filter and wash with cold ethanol and dry in oven
Give 4 reasons why recrystallisation can have a low percentage yield?
Loss of product when transferring between beakers
Reaction doesn’t go to completion
Some solid remains in solution after
Loss of solid when washing the final product
how do you remove traces of water to purify?
add ahydrous sodium sulphate
how do you remove acid traces?
add sodium carbonate and shake in a spearating funnel
