Module 3 Flashcards
Chirality
A compound that forms non superimopsable mirror images
Anticlockwise rotation
R or D enantiomer
Clockwise rotation
S or L enantiomer
Priority order
Higher priority given to electrons with larger atomic number
Z enantiomer
‘Zee-same’
On the same side (cis)
E antiomer
On opposite site (trans)
Nucleophilic Substitution SN1
1 step reaction
Nu- attaches opposite as leaving group departs
Slow step is removal of leaving group
Fast step is nucleophilic addition
Secondary and tertiary reactions are normally SN1
Needs good leaving group
Polar protic solvent
Nucleophilic Substitution SN2
2 step reaction
X leaves in slow step followed by fast attachment of Nu:-
Methyl, primary and secondary are SN2 reactions
If more steric hinderance than Nu- harder to attack C
Strong Nu can make up for poor leaving group
Polar aprotic solvent
Bond lengths
Longer the bond elongates the more the electronegative X atom becomes - shorter bond = better electrophile
E1 reaction
Weak base
1st step is rate determining
2nd step = base removes H+ to form C=C
strong base not required
common when leaving group on tertiary carbon
E2 reaction
Must have strong base/nucleophile
Possible for primary, secondary and tertiary
Requires backside attack
Difficult if reaction centre crowded
Solvents in Nu:- substitution
The rate of nucleophilic substitution reactions is influenced by the solvent
Enantiomer properties
Same melting point, boiling point and chemical reactivity
Do not have same specific rotation
Cellulose properties
Cellulose is a polymer of glucose with B-1,4-glycosidic linkages
Cotton contains close to 100% cellulose
The geometry of linkages within cellulose leads to straight molecular rods stabilised by hydrogen bonds
Humans cannot digest cellulose
