unit 6 section 1 isomerism and carbonyl compounds Flashcards
what is a stereoisomer
they have the same structural formula, but their atoms are arranged differently in space.
what is a chiral carbon
a chiral carbon atom is a carbon atom that has four different groups/functional groups attached to it
what is an optical isomer
it is a type of stereoisomer that has a chiral carbon atom in it
what is it called when a chiral carbon atom functional group is arranged in a different way forming a different molecule ( kind of like a mirror image )
they are called enantiomers or optical isomers
what does superimposed mean
it means that no matter which way the molecule turned/arranged , it doesnt have and optical isomer
-enantiomers are not superimposed
how do you draw an optical isomer
-locate the chiral carbon atom
-draw the molecule in 3D
-then draw the isomer
are optical isomers optically active
yes- they rotate plane polarised light
what is a molecule that can be superimposed
achiral
what is plane polarised light
it is light that has passed through a polarising filter, this means that the light is vibrating in the same plane ( up or down, side to side)
- normal light vibrates in all directions.
how is plane polarised light rotated
when you pass plane polarised light through a optically active mixture, the molecule interacts with the light and rotates the plane of vibration of the light.
- the two enantiomers will rotate the plane polarised light in opposite directions ( clockwise and anticlockwise )
what is a racemate
it is a mixture that contains equal quantities of each enantiomer of a optically active compound
do racemates show any optical activity
no as the two enantiomers cancel out each others light rotating effect
what reagent is mainly used to reduce aldehydes and ketones
NaBH4 ( sodium borohydride ) , however in equations [H] is used to represent the hydrogen from it
what are hydroxynitriles
they are contain hydroxyl group (OH-) and nitrile groups (CN)
when naming them the nitrile group is more important, so you use nitrile at the end and hydroxy at the start for the alcohol
how to form a hydroxynitrile
they can be formed by reacting either a aldehyde or ketone with potassium cyanide(KCN) followed by a dilute acid.
you can also make it by reacting a ketone or aldehyde with hydrogen cyanide
explain why carboxylic acids dissociate
this is because carboxylic acids are weak acids, in water they partially dissociate in water to form a carboxylate ion and a H+ ion ( the H+ is removed from the OH of the carboxylic acid
how does an esterification reaction occur
this happens when you react a carboxylic acid with an alcohol in the presence of a strong catalyst, an ester is formed. this is called an esterification reaction
the catalyst could be sulfuric acid (H2SO4) or HCL or H3PO4
how do you name an ester
first you look at the part that came from the alcohol, the alkyl group and name that first and then name the carboxylic acid and replace the -oic acid with -oate
what are the useful properties of esters
- esters have a sweet smell, they can be used in perfumes.
- they are polar liquids, this means that they can dissolve polar compounds. they have low boiling points and evaporate easily from mixtures. they make good solvents in glues and printing inks
- they are used as plasticers, they are added to plastics during polymerisation to make them more flexible
what are the two types of hydrolysis of esters
acid hydrolysis and base hydrolysis
explain what happens in an acid hydrolysis reaction
the ester is split into an acid and alcohol.this happens when you react the ester with water and then reflux the ester with dilute acid, such as hydrochloric or sulfuric acid
explain what happens in a base hydrolysis reaction
the ester is split into carboxylate ion and alcohol. this happens when you react the ester with OH- ions from a dilute alkali under reflux
what are animal fats and vegetables oils
they are esters of glycerol and fatty acids
explain the facts and properties of fats
fats have mainly saturated hydrocarbon chains, and they fit neatly together which increases the van der waals forces between them. this means that they are solid at room temperature and require higher temperatures to melt them.
