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
