Chirality And Carbonyls Flashcards
Optical isomers
4 different groups on a C
Mirror image but not super imposable
Chiral
Atom in molecule that exists as non-superimposable
Asymmetric
C joined to 4 different groups
Enantiomers
Pair of molecules that exist as optical isomers
Polarised vs unpolarised light
Oscillations on one plane
Oscillations on any plane
Polarimetry
Some fibres absorb all light expect one plane
Monochromatic light —> polariser
Polarised light —> sample tube
Plane rotates if optically active
2nd polarised rotated to max light intensity
Angle recorded
Unpolarised —> polarised
Optical activity
Different directions of polarisation planes
CW +
ACW -
Enantiomer physical properties
Identical
Expect PoP rotation
Enantiomer chemical properties
Identical
Except reaction with other enantiomers
Racemic mixture
Race mate
50:50 mix of enantiomers
Drug industry and enantiomers
Optically active
Often 1 Enantiomer works
In/on cell receptor
Only 1 Enantiomer fits
Other could be dangerous
Separate, difficult, expensive
Sell, dangerous, wasteful
Alternative synthesis
Aldehyde FG
RCHO
End of chain
Aldehyde suffix
Al
When are aldehydes formed
Oxidation of P alcohols
Properties of aldehydes
Short chain - unpleasant smell, soluble (HB with water not each other)
Long chain - perfume
Alkanes < bp < ketones, acid, alcohol
Properties of ketones
Short chain - solvents, soluble (HB with water not each other)
Alkanes, aldehydes < bp < acid, alcohol
Carbonyls
C=O
Aldehydes/ketones
Nucleophilic addition
Electronegative
Nucleophile attacks C*+
Bonding and properties of carbonyls
Polar/permanent dipole
Very strong
Sigma and pi bonding
High electron density around O
Oxidation test A VS K
Acidified potassium dichromate, water bath,
Aldehyde: O (6+)—> G (3+), A —> CA
Ketone: no change
Fehling’s/Benedict’s solution A VS K
Water bath
Aldehyde: deep blue solution (11+) —> brick red ptte (1+), A —> CA
Ketone: no change
Tollen’s solution A VS K
V hot water bath
Aldehyde: colourless (red 1+) —> silver mirror (solid Ag)
Ketone: no change
Reduction A VS K
H- nucelophile
LiAlH4
Lithium aluminium hydride
Dry + acid, no water, powerful, reacts with water, flames
A VS K iodine reactions
Yellow insoluble solid, CHI3
Alkaline solution, warmed, pooled
Ethanol, Propan2ol, butan2ol give positive results and carbonyls
3 H in CH3 substituted with I using OH-
Carbonyl + I2 + OH- —> CHI3 + RCOO- + I- + H2O
CI3 bond broken triiodomethane and acid salt
Brady’s reagant A VS K
Most carbonyl compounds
Brightly coloured orange solid
Derivatives have different melting points
Makes a hydrazone
Purified, filtered, dried
