Alcohols Flashcards
Alcohols general formula
CnH2n+1OH
What is the suffix nomenclature if there is two OH groups
Diol
Primary vs secondary vs tertiary
Dependant on the amount of alkyl groups that are bonded to the carbon which contains the OH
Eg. Ch3 ChOH CH3 would be secondary
Combustion of alcohols
Alcohol + oxygen —-> carbon dioxide + water
Occurs in air when ignited
What can alcohols be converted to by adding a halogen
Halogenoalkanes
How to do chlorination to an alcohol
Phosphorus chloride is added to the alcohol resulting in a vigorous reaction at room temperature
Results in the formation of phosphoryl chloride and hydrogen chloride and the halogenoalkane
CH3CH2CH2OH + PCl5 → CH3CH2CH2Cl + POCl3 + HCl
What type of alcohol does chlorination only occur in
Tertiary alcohols
Bromination process
Add warm potassium bromide and concentrated sulphuric acid
Sulphuric acid oxidises the bromine ions to bromine
2KBr + H2SO4 → K2SO4 +2HBr
The resulting bromide then reacts with the alcohol as HBr
CH3CH2CH2CH2OH + HBr → CH3CH2CH2CH2Br + H2O
Iodination process
Add red phosphorus and iodine with the alcohol and heat under reflux
Thus the PI3 is what reacts with the alcohol. Eg
3C2H5OH + PI3 → 3C2H5I + H3PO3
Dehydration of alcohols to alkenes process
Heat the alcohol with concentrated phosphoric acid
The OH group and hydrogen of adjacent carbons are remover to form a c=c bond
Hence the name H2O is also produced
CH3CH2OH → CH2=CH2 + H2O
The phosphoric acid doesn’t appear in eq because the water dilutes it
Oxidation of primary alcohols
Primary alcohols can be oxidised to ketones (aldehyde) then further oxidised to carboxylate acids
Oxidation of secondary alcohols
Can be oxidised to ketones only
Oxidation of tertiary alcohols
Can’t be
What is the oxidation agent for the alcohol oxidation
What colour does it go and why
Acidified (with sulfuric acid) potassium dichromate
It is reduced by hydrogen ions from the dulfuric acid
It turns green from orange
Process of forming a carboxylic acid from a primary alcohol
Add alcohol to oxidation agent
Heat
Distill off aldehyde
Reflux the aldehyde with excess oxidation agent then distill again to form a carboxylic acid
How can the presence of an unknown compound be determined
By the oxidising agents - feelings and trolleys reagents
What is feelings solution and what happens when added to an aldehyde to test for its presence
An alkaline solution containing copper ions which act as an oxidising agent
When warmed with an aldehyde , the aldehyde is oxidised to a carboxylic acid and the cu2+ ions are reduced to Cu +
The clear blue solution turns opaque due to the formation of a red precipitate - copper oxide
Ketones cannot be oxidised so give a negative test when warmed with feelings
Tollens reagent and what happens when added to aldehyde
An aqueous alkaline solution of silver nitrate in excess ammonia solution
When warmed with an aldehyde, the aldehyde is oxidised to a carboxylic acid and Ag + ions are reduced to Ag
The silver forms a mirror on the inside of the tube
How to heat under reflux and why to use the process
For when we need full oxidation
Means that any products of oxidation remain in mixture as the products that boil off are recondensed
Contains pear shaped flask
Antibumping granules
Condenser
Open top
How to distill and when
For when we do not want to complete oxidation and want to obtain an aldehyde rather than carboxylic acid
Only oxidation agent is heated while alcohol is slowly added
Aldehyde is formed and immediately distilled off
The aldehyde is the collected in the receiver
Contains the condenser at an angle to be collected in the recieving flask
When to use simple distillation
To separate a liquid and a soluble solid from a solution
Eg. Separating pure water from salt water
Process of simple distillation
Heat solution
Solution evaporates producing a vapour
Vapour passes through condenser into a liquid that can be collected
Once all the liquid has evaporated , only the products will be left
When to use fractional distillation
To separate 2 or more liquids that can mix with each other
Eg. Water and ethanol
Process of fractional distillation
Heat to the temperature of the substance with the lowest boiling point
Substance will rise and evaporate first and vapours will pass through the condenser
They are then cooled and collected as liquid
