F322 - Alcohols, Halogenoalkanes and Analysis Flashcards
Why do alcohols have a low volatility?
Hydrogen bonds are formed between the alcohol molecules which are a stronger force of attraction.
Why are alcohols water soluble?
Form hydrogen bonds with the water molecules which allow the alcohol molecules to be pulled apart and mix with the water molecules.
What is fermentation?
The process of glucose being converted to ethanol and carbon dioxide using yeast as a catalyst.
What are the advantages of using fermentation as a method of ethanol production?
Can be done at a lower temperature (yeast is killed off above 47 degrees), and glucose is a renewable resource (can be grown).
How is ethanol produced using addition reactions?
Reaction of ethene with steam in the presence of an acid catalyst (usually phosphoric acid).
What are the advantages of using addition reactions to make ethanol?
Can be done at high temperature so reaction rate can be quicker, 100% atom economy.
What is the most common use of ethanol?
Alcoholic drinks or in methylated spirits/solvent (this cannot be drunk!)
What is the most common use of methanol?
Petrol additive to improve combustion or as a feedstock in the production of organic chemicals.
What is a primary alcohol?
Where the carbon that the OH group is attached to is attached to one other C.
What is a secondary alcohol?
Where the C that the OH group is attached to is attached to two other C’s.
What is a tertiary alcohol?
Where the C that the OH group is attached to is attached to 3 other C’s.
When primary alcohols are oxidised using acidified potassium dichromate under reflux what type of product is formed? What colour change would be seen?
Carboxylic acid and orange to green
When primary alcohols are oxidised using acidified potassium dichromate under distillation what type of product is formed? What colour change would be seen?
Aldehydes and orange to green
When secondary alcohols are oxidised using acidified potassium dichromate under reflux what type of product is formed? What colour change would be seen?
Ketones and orange to green
When tertiary alcohols are oxidised using acidified potassium dichromate under reflux what type of product is formed? What colour change would be seen?
No reaction, would remain orange
What are the reagents required for esterification?
Alcohol, carboxylic acid and an acid catalyst (sulphuric acid usually)
What are the reagents needed for the dehydration of an alcohol?
Alcohol and hot pumice/aluminium oxide or concentrated sulphuric acid
What type of reaction takes place for the hydrolysis of a halogenoalkane?
(Nucleophilic) substitution
What is a nucleophile?
An electron pair donor
What is PTFE used for and why?
Non-stick saucepans and waterproof clothing. It is chemically inert, has a high melting point and is smooth and slippery.
What are CFC’s used for and why?
Propellants, refrigerants, blowing agents or cleaning solvents because they are inert, non-toxic, and non-flammable.
What problems have the use of CFC’s contributed to?
Thinning the ozone layer in the stratosphere.
What breaks down CFC’s in the atmosphere?
Ultraviolet radiation
What happens when covalent bonds absorb energy?
The bonds vibrate/bend/stretch
How do IR spectrometers work?
Analyse the radiation absorbed by different covalent bonds.
How do breathalysers work?
IR spectroscopy is used to measure the ethanol content of a driver’s breath.
What are the reagents for the hydrolysis of a halogenoalkane?
Halogenoalkane and hot aqueous alkali
How do the rates of hydrolysis vary for primary halogenoalkanes down group 7?
Rate of hydrolysis increases down group 7. (Due to weaker C-halide bonds)
Which functional group absorption indicates an alcohol?
O-H bond
Which functional group absorption indicates a ketone or aldehyde?
C=O bond
Which functional group absorption indicates a carboxylic acid?
C=O bond and O-H bond
How does a mass spectrometer find the relative atomic mass of an element?
It measures the mass of each different isotope and measures the relative abundance of each isotope. A vaporised sample of the element is injected and the atoms are turned into positive ions by electron bombardment.
How is a mass spectrometer used to identify unknown compounds?
Inject a vapourised sample and turn them into slightly charged positive ions with the same molecular mass as the molecules. This gives the molecular ion peak. Electron bombardment can also be used to break apart the molecules to make fragments.
