Isomerism and carobonyl compounds Flashcards
What is optical isomerism
type of stereoisomerism
- have chiral carbon atoms
Stereoisomerism
have same stu formula , but atoms arranged differently in space
Chiral
carbon atom that has 4 different groups attached to it
- possi to arrange group in 2 diff way around the chiral carbon atom ( 2 mole made )
- enantiomers
- optical isomers
what is enantiomers
mirror image
- can’t be superimposed ( can tell them apart )
if mole = superimposed
achiral and there is no optical isomer
drawing optical isomers
- find out the central chiral carbon
- draw one enantiomer in tetrahedral shape - just use stu f
- draw the mirror image of the enantiomer
Optical activity
rotate plane polarised light
plane polarised light
- normal light = vibrates in all direction
- if goes though polarised filter = the plane = polarised and light vibrates in same plane
Rotation of plane polarised light
polarised light - through optically active mixture - mole andlight react = polarisation of vibration of light
- 2 enantiomers - rotate in oppodireciton - cancel each other ( anti / clockwise
Carbonyl group
alde = end
ketone = middle
Aldehyde
easily oxidized to COOH
- att to hydrogen to carbonyl group
As aldehyde oxidised - another reduced
- reagent used that changes colour as get reduced
Ketone
can’t be easily oxidised
- for the hydrogen to attach - need to break C-C bond
Tollens reagent
- colourless solution of silver nitrate dissolved in aq ammonia
- heat in test tube
- alde = silver mirror
Fehlings solution
Blue solution of complexed copper (II) ions dissolved in NaOH
- heated
- brick red precipitate of copper oxide
Reducing aldehyde and ketone
- using NaBH4 ( sodium borohydride)
- [H] = used as reducing agent
Aldehydes = Produce primary alcohol
Ketone = secondary alcohol
- nucleophilic addition
H+ = from water or weak acid
Hydronitriles
Suffix = nitrile
Prefix = hydroxyl
Producing hydronitriles
Nucleophilic addition reaction
Need KCN, aldehyde/ketone and dilute acid
KCN = dissociates in water
CN = neg - attackers the carbon cation
Break the C=O bond
O forms bond with H from dilute acid
Racemic mixture of hydroxylnitrile
C=O & C=C bonds = planar
Nucleophile can attack either from the top / bottom of the plane = produces different enantiomers
Enantiomers = mirror image of each other , can’t be superimposed - can tell them apart ( most have chiral Center )
Equally likely to form any enantiomers
KCN
- toxic
Reaction need to be done in fume cupboard - risk of some HCN gas being released form solu
Dissociation of COOH
Carboxylate ion and H+
- reaction is reversible but equi lied to the left as much doesn’t dissociate
Carboxylic acid and carbonates/ hydrogen carbonates
Salt , CO2 and water
Carbonates ( CO3^ 2- )
Hydrogen carbonates ( HCO3^ - )
Esterfication
- heat COOH with alcohol in presence of strong acid
- get ester
Naming ester
- alkyl group form alcohol ( first )
- oic acid to oate
C=O : carboxylic acid (count the carbon with double bond O )
Useful properties of ester
- Ester have sweet smell = perfume / food flavouring
- ester = polar liquid so lots of polar mole dissolve
- plasticisers = make plastic more flexible
Hydrolysis of ester ( acid )
Hydrolysis = splitting of water
Acid = catalyst
Refluxwith dilute acid
Ester + water = COOH + OH
- reversible = put lot of water to push equi to right - get lot of product
Base hydrolysis of ester
- reflux ester with dilute alkali
- get carboxylate ion and alcohol
C=OOR + OH- = C=OO- + R-OH
Fats and oils
Satu - no double bond ( solid in room temp )
Unsatu - double bond
Satu = fit neatly- inc the van der walls force bet them - high temp
Unsatu - bent and form kinks
Hydrolysis of fat and oils
- hydrolyse by heating them in NaOH ( base hydrolysis)
- OH - react with fat / oil
Form carboxylate ion (sodium salt ) - soap and alcohol ( glycerol )
Soap to COOH
Sodium salt and HCL = COOH
Hydrogen subs out the Na+
Biodiesel
- oils be converted to biodiesel
- methanol + fat ( cata strong alkaline- KOH / NaOH)
- produce glycerol and methyl ester (biodisel )
Acyl chloride
General formula = CnH2n-1 OCL
Func group = COCl
-oyl chloride
Reaction of Acyl chloride and water
- Cl sub by O2
- react vigorously with cold water
- produce = COOH AND HCL
Reaction with Acyl chloride with alcohol
- react vigorously at room temp
- produce ester and HCL
- irreversible reaction = faster way to produce ester than esterfication
observation - smoky / misty / white fumes because HCL released
Reaction with Acyl chloride and ammonia
- react vigorously
- produce amine and HCL
Reaction with Acyl chloride and primary amines
- react vigorously
- produce N- substituted amide
And HCL
Acyl chloride and other reaction
-nucleophilic additions - elimination
Step 1 = nucleophile adds onto the acyl chloride, displacing the Cl
Step 2 = the hydrogen leaves to create an acyl chloride derivative
Step one
1. Break C=O, nucleophile attacks the carbon cation
2. Oxygen forms double bond with carbon, release Cl bond ( nucleophile = positive )
Step 2
1. Hydrogen donates it electron to positive nucleophile = release H + ION
The left nucleophile and other stuff = acyl chloride derivative
2. H+ ion and Cl- on join together = hydrochloric acid
Acid anhydride
- 2 identical COOH acid mole
- joined together via oxygen with carbonyl groups on either side
Produced water and anhydride
Reaction with acid anhydride and water
Produce COOH
2x ethanoic acid
Reaction with acid anhydride and alcohol
Ester
COOH - ethanoic acid
Reaction with acid anhydride and ammonia
- amide
- COOH = ehtanoic acid
Reaction with acid anhydride with amines
N substituted amide
COOH - ethanoic acid
Manufacturing of aspirin
- made by reacting salicylic acid with either ehtanoic anhydride or ethanol chloride
ethanoic anhydride more use - cheaper
- less corrosive
- react more slowly with water
- don’t predict dangerous hydrogen chloride fumes
racemates
- contains equal quantities of each enantiomers of optically active compound
- don’t show any optical activity - 2 enantiomers cancel each other light rotating effect
nucleophile can attack from above or below the place of the bond
