aldehydes and ketones Flashcards
can ketones be oxidised
no but aldehydes can
what are aldehydes oxidised to
COOH
what can aldehydes be reduced to
primary alcohols
what can ketones be reduced to
ketones
other definition of oxidised
molecule is oxidised when a carbon atom forms a bond with a more electronegative element
reduction in organic chem
when a carbon atom forms a bond with a less electronegative element
reducing agent
sodium borohydride
how to reduce aldehyde or ketone
add solution to test tube and add excess reducing agent AQ
-reaction takes place to reduce to alcohol
how is reducing agent made
take solid sodium borohydride and add to water
-salt dissacociates which leave Na+ and BH4- ions
what happens when BH4- ions react
one B-H bonds breaks
both electrons in bond go to hydrogen
-giving it negative charge
role of negatively charged hydrogen in reduction
reacts with aldehyde or ketone as nucleophile
-BH4- source of hydride ions
first step of reduction of aldehydes mechanism steps
lone pair of hydride ions to carbon atom and carbon to oxygen
-lone pair from hydride ion goes to oxygen
second step of reduction of aldehydes
lone pair of oxygen to hydrogen plus ion
-alcohol formed OH group
first step of reduction of ketones
hydride ions to carbon bond and carbon bond breaks C-0 bond
-O gets lone pair
second step of ketone reduction
OH group forms
feature of Cdouble O bond in carbonyls
bond is polar so greater electronegativity
oxygen partially negative and carbon positive
-hydride ion will bond with positive carbon
-
reduction equations
reactant plus 2 Hydride ions with product and OH on end if aldehyde
cyanide composition
carbon triple bonded to nitrogen
is cyanide organic or inorganic
inorganic
how to name nitriles
-have cyanide in them
-longest chain with nitrile on end
bond angle for CN
180
HCN
-hydrocyanic acid
-weak acid forms H+ and CN-
-HCN covalently bonded gas not solid ionic salt
product when aldehydes and ketones react with cyanide
form hydroxynitriles
-OH and nitrile group
2 substances that are sources of cyanide ions
KCN
NaCN
other reactants when hydroxynitriles
aqueous potassium cyanide
-aqueous sodium cyanide
dilute sulfuric acid
first step of nucleophilic addition
CN lone pairs to carbon in aldehyde
-carbon double to oxygen bond breaks
second step of nucleophillic addition hydroxynitriles
intermediate of negative oxygen with CN
-lone pairs from oxygen to positive hydrogen
formation of OH
naming hydroxynitriles
count carbon in nitrile group as position number on in carbon chain and find longest chain
-eg 2-ethyl-2-hydroxupentanenitrile
full equation for production of 2-hydroxypropannitrile
CH3CHO+ H2SO4 + KCN = CH3CH(OH)CN + KHSO4
do hydroxynitriles have optical isomerism
yaaarrr
