Functional Groups Flashcards
What’s the general formula of alcohols?
hv the general formula of CnH2n+1OH or ROH
Describe the position of OH in primary, sec & tertiary alcohols
primary alcohol- the OH is attached the last carbon atoms in the structure
secondary alcohol- the OH is attached the middle carbon atom
tertiary alcohol- the OH is attached the the middle carbon not on the chain with the second carbon atom
Describe the oxidisation of alcohols
primary(to aldehydes to carboxylic acids)- oxidising agent is not in excess and the acid is fairly dilute & the aldehydes is distilled off immediately
oxidising agent is in excess and the acid is more concentrated & the reaction is carried out under reflux for 20 minutes
secondary- is oxidised into ketones, cannot be oxidised any further
tertiary- cannot be oxidised until the c-c bond is broken in alcohols
What is a dehydration compound?
is a reaction where water is eliminated from the compound
How can alcohols react with carboxylic acids to form esters?
catalysed by sulphuric acid, reversible, carried out under reflex
What is the general formula of halogenoalkanes?
has a general formula of CnH2n+1X
What is a nucleophile?
is a reagent that gives a pair of electrons to an electron deficient atom in a molecule
nucleophile is negatively charged ions or atoms or partially negatively charged
Describe the substitution of halogenalkanes
primary halogenalkanes react with OH- ions or water to form primary alcohols
tertiary halogenalkanes react with OH- ions or water to form tertiary alcohols
Describe aldehydes and ketones with carbonyl atoms
in aldehydes, the carbonyl carbon atom has at least 1 hydrogen atoms bonded to it eg methanal, ethanal
in ketones, the carbonyl atom has at least 2 carbon atoms bonded to it eg methadone, butane
Describe the test for a carbonyl group
add Brady’s reagent to a carbonyl compound, if the colour gives an orange red precipitates then a ketone/aldehyde is present, if we purify the precipitate by recrystillisation and determine its melting point we can identify the ketone/aldehyde present
Distinguish between aldehyde and ketones in tollens reagent
tollens reagent- is an aqueous solution of silver nitrate in excess ammonia
when its added to aldehydes its oxidised to carboxylic acids, the silver complex ions turns into silver, a silver mirror is seen on the side of the test tubes
ketones do not react with tollens reagent because it cannot be oxidised into carboxylic acids
Distinguish with fehlings solution
fehlings solution is mixed with 2 solutions(fehlings a and b) A beings Cu2+ ions and B a complexing reagent and an alkali
aldehydes is oxides into carboxylic acid, the blue colour in the Cu2+ ions changes to an orange red precipitate, the cu2+ ions oxidises into aldehydes and is reduced to a copper state
ketones do not react w fehlings solution because it cannot be oxidised into carboxylic acid
Distinguish with potassium manganate and dichromate
aldehyde- when reflux in excess potassium manganate the purple colour turns to brown because the manganate ions are reduced to Mn2+ to MnO2
when reflux in excess potassium dichromate, the colour changes from orange to green
ketones have no reaction bc it cannot react unless conditions are severe or the c-c bond is broken
What do carbonyl compound undergo addition reactions with?
undergo nucleophile addition reactions with cyanide ions
What are aldehydes and ketones reduced to?
aldehydes are reduced to primary alcohols by lithium aluminium hydride or hydrogen using a plantinum catalyst
ketones are reduced to secondary alcohols by lithium aluminium hydride or hydrogen using a platinum catalyst
What are carboxylic acids?
are weak acids, however there are strong enough to show their acid properties eg methanoic acid, ethanoic acid
What do carboxylic acids react with?
sodium hydroxide- react to form sodium salt and water
metals- react to form a metal salt and hydrogen
hydrogen carbonate & carbonate- react to form a salt, water, and carbon dioxide
alcohols- react to form ester
PCL5, PCL3 and SOCL2- react to form hydrogen chloride
What is general formula of esters?
have the general formula of COO eg methyl butanoate
What is hydrolysis?
is the breakdown on a compound with water, its sped up with either an acid or alkali
What does heating of an ester do?
by heating, the ester is under the reflux of an acid or base
heating is necessary because the reaction is slow, the acid or base acts as a catalyst, reflux is necessary to prevent the loss of volatile vapours of esters and alcohols
Describe the acid of hydrolysis and the base of hydrolysis
the ester is heated with dilute sulphuric acid, is not fully hydrolysed, its reversible, a carboxylic acid and alcohol are formed
the ester is heated with aqueous sodium hydroxide, is not reversible, is fully hydrolysed, an alcohol and a salt of a carboxylic acid is formed
Describe fats and oil
fats and oils are esters with long chain of carboxylic acid with glycerol
long chain of carboxylic acid are also fatty acids
the only difference between fats and oils is the fats is a solid and oil is a liquid
the chain in fatty acids are 12-18 carbon atoms
fatty acids can be the same or different
What is saponification?
is the making of soap from the hydrolysis of fats and oils
What are soaps made of?
are made from the hydrolysis of fats and oils with sodium hydroxide
