Aldehydes and Ketones Flashcards
What are primary and secondary alcohols oxidised to
aldehydes and ketones
what are aldehydes and ketones reduced to with NaBH4
primary and secondary alcohols
what is the oxidising agent for primary and secondary alcohols to be oxidised into aldehydes and ketones
acidified potassium dichromate (VI)
what is the reducing agent for aldehydes and ketones to be reduced into primary and secondary alcohols
aqueous NaBH4
what happens in reduction of aldehydes and ketones with NaBH4
2 Hydrogen atoms are added to the carbon and to the oxygen
what are aldehydes reduced to
primary alcohols
what are ketones reduced to
secondary alcohols
what is a nucleophile
an electron pair donor
why can the C=O bond in aldehydes and ketones be attacked by nucleophiles
because it is a polar bond
what is a polar bond
a polar bond is the unequal distribution of electrons in a covalent bond because of a difference in electronegativity between atoms
what mechanism is used in the reduction of aldehydes and ketones to primary and secondary alcohols
nucleophillic addition
what is the reducing agent to form primary and secondary alcohol
what does the reducing agent for aldehydes and ketones provide in the nucleophillic addition mechanism
NaBH4
a hydride ion :H- (nucleophile) and it attacks the delta positive carbon
what mechanism is it when aldehydes and ketones react with potassium cyanide (KCN) and dilute HCl
what actually occurs in this mechanism
nucleophillic addition
reduction of aldehydes and ketones into hydroxynitriles
what has priority in the carbon chain - the hydroxy or nitrile
the nitrile
what is the nucleophile in nucleophillic addition mechanism to form hydroxynitriles
:CN-
from potassium cyanide
where does the proton H+ come from in the 2nd step for production of hydroxynitriles
the dilute acid (HCl)
what is the problem about KCN
what happens when KCN reacts with water
where should this experiment take place
it is an irritant and toxic when eaten
Hydrogen cyanide is produced which is a highly toxic gas
in a fume cupboard with glasses labcoat gloves
which group of isomers do optical isomers belong to
stereoisomers
what do all optical isomers contain
a chiral centre
what is a chiral centre
a single carbon atom bonded to 4 different atoms or groups
what is the word when optical isomers cannot be placed on top of its mirror image as they are different
non-superimposable
like a pair of hands
optical isomers have no:
no centre of symmetry
no plane of symmetry
no axis of symmetry
what is another word for optical isomers
enantiomers
what are the similarities of a pair of optical isomers
what are the differences
same physical and chemical properties
they rotate the plane of polarised light in opposite directions
how do light waves normally travel?
normally light waves vibrate in all directions perpendicular to the direction of travel
how do we make plane polarised light ?
when we pass the light through a polarising filter, only waves vibrating in one direction are allowed through
resulting in plane polarised light
what happens when this new plane of polarised light passes through a solution of an enantiomer
the plane gets rotated through a particular angle
essentially different enantiomers of the same sample rotate the plane differently
explain the differences on how enantiomers of the same sample rotate the plane
one enantiomers will rotate the plane polarised light in the left (anticlockwise) direction. it is also called laevorotary or (-) direction
the other enantiomer rotates the plane of light in the right (clockwise) direction. it is also called the dextrorotary direction or (+) direction
what happens to the rotation of light when there’s only one form of the optical isomer in the sample
and what is the sample called
when the sample only contains one form of the optical isomer then the plane of polarised light will be rotated in one direction
the sample is said to be optically active
what is a racemic mixture
when the sample contains both optical isomers in equal quantities so is optically inactive as 2 enantiomers rotate the plane of polarised light in opposite directions equally
what happens when both optical isomers in equal quantities are present in the sample
and what is the sample said to be
there will be no observation of the plane polarised light rotating
optically inactive
what is another word for clockwise
dextorotary direction
what’s another word for anticlockwise
laevatorotary direction
explain the formation of optical isomers from aldehydes and ketones
1) the carbonyl group is planar
2) this means the nucleophile has an equal chance of attacking from either side
3) a racemic mixture is formed
