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.
explain the facts and the properties of oils
they have unsaturated hydrocarbon chains. the double bonds means that the chains dont bend and do not pack well together. this decreases the effect of the van der waals forces meaning that they are easier to melt and are not solid at room temperature.
how do you hydrolyse fats and oils
you heat them up with sodium hydroxide
the OH- ions react with the fats and the oils forming carboxylate ion and a alcohol ( glycerol ) , then the carboxylate reacts with the Na+ to form a sodium salt ( which is a soap )
how do you reverse the hydroylsis of fatty acids
this is done by adding HCL. the H+ ion from the Hcl replaces the Na from the carboxylate ion.
how do you convert vegetable oils into biodiesel
This is done by reacting the vegetable oils with methanol under a strong alkali catalyst such as potassium hydroxide or sodium hydroxide. this forms a mixture of methyl esters of long chain fatty acids
is biodiesel 100% carbon neutral
the crops absorb the same amount of CO2 as they produce when they are burned. however energy is used to make the fertizers which if they are made using energy from fossils fuels then overall it is not carbon neutral
what is the functional group of acyl chloride
COCL
what generally happens when an acyl chloride group reacts with a molecule
the CL is substituted by an oxygen or nitrogen group and misty fumes of hydrogen chloride are given off.
explain the reaction of acyl chlorides and water
they react vigorously with cold water and producing a carboxylic acid.
explain the reaction of acyl chlorides and alcohols
they react vigorously with alcohols at room temperature producing an ester.
this is a faster method of producing an ester than esterification
explain the reaction of acyl chlorides and ammoina
they react vigorously with ammonia at room temperature to form amides
explain the reaction of acyl chlorides with primary amines
they react vigorously with primary amines at room temperature to produce N -substituted amides
what type of reaction occurs when you react acyl chloride and what are the steps
nucleophilic addition-elimination reaction
1- he nucleophile adds onto the acyl chloride, displacing a CL- ion
2-the hydrogen leaves to create an acyl chloride derivative
what is an acid anhydride made from
they are made from two identical carboxylic acids. they are joined by an oxygen between the two carboxylic acid molecules. the oxygen has come from one of the OH groups from the carboxylic acid molecule and from one hydrogen from the other molecule, it is released as water.
how do you names acid anhydrides
if you know the name of the carboxylic acid, you remove the acid from the name and replace it with anhydride
e.g butanioc acid - butanioc anhydride
what happens when you react an acid anhydride with water
you form a carboxylic acid
what happens when you react acid anhydrides with alcohols
you form an ester and carboxylic acid
what happens when you react an acid anhydride with ammonia
you form an amide and you also make a carboxylic acid
what happens when you react an acid anhydride with an amine
you produce an n-substituted amide and a carboxylic acid
how is aspirin manufactured
it is manufactured by by reacting salicylic acid ( has and alcohol group ) with either ethanoic anhydride or ethanoyl chloride
why is ethanoic anhydride used in industry rather than ethanoyl chloride in the production of aspirin
ehanoic anhydride is used because it is cheaper than ethanoyl chloride and it is also safer than ethanoyl as it is less corrosive, reacts slowly with water and doesn’t produce dangerous hydrogen chloride fumes.
why can aldehydes be easily oxidised to carboxylic acids
this is because there is a hydrogen attached to the carbonyl group
what tests can be used to distinguish between an aldehyde and a ketone and what are the positive results
tollens - aldehyde - silver mirror ( ketone no change )
felhings - aldehyde - blue solution to brick red precipitate ( ketone no change )
what type of reaction occurs when aldehydes and ketones are reduced back to alcohols
nueclophilic addition reactions
what is formed when you react a carboxylic acid with a carbonate compound ( e.g. NaCo3 sodium carbonate )
it forms a salt, carbon dioxide and water
how can you speed up the process of hydrolysising an ester
instead of just using water use a acid or alkali
what type of reactions occur with acyl chlorides
they are all nucleophillic addition-elimination reactions
