2. Different Types of Addition
Addition of HCN
Addition of RNH2
Addition of H2O
Addition of ROH
Addition of RMgX
Addition of ylide: Wittig reaction
4. Addition of HCN
cyanohydrin
Reagent: (i) KCN, (ii) HCl or (i) NaCN, (ii) HCl
O
H
HCN
H
HO CN
1. LiAlH4, THF
2. H2O
CH2NH2
OH
CO2H
OH
H3O+
Heat
Importance of cyanohydrin
5. Addition of Ammonia derivatives
Mechanism
Z = OH, NH2, PhNH2, NHCONH2 and more
9. Wittig Reaction
O
H
Ph3P
H
H
+
H
H
H
Aldehydes and ketones react with phosphorous ylide to form alkenes.
Ylide: Compounds wherein two adjacent atoms contain complete octet
electronic configuration and hold opposite charges are called Ylides
12. Aldol Condensation
In aldol condensation, an enolate ion reacts with a carbonyl compound in presence
of base or acid catalyst to form a β–hydroxy aldehyde or β–hydroxy ketone
followed by dehydration to give a conjugated enone.
14. For crossed aldol reaction one carbonyl compound does not contain any
α-hydrogen. Enolate is formed from the other carbonyl compound.
Aldehyde containing α-hydrogen is added slowly to a mixture of aldehyde without
α-hydrogen and alkali.
16. Cannizzaro reaction
Aldehydes which do not have any α-hydrogen atom, undergo self
oxidation and reduction (disproportionation) reaction on treatment with
concentrated alkali. In this reaction, one molecule of the aldehyde is
reduced to alcohol while another is oxidized to carboxylic acid salt. This is
called as Cannizzaro Reaction.
17. Dieckmann Condensation: Cyclisation 2
Intramolecular Claisen Condensation is termed as Dieckmann Condensation
Reaction.
1,6-Diester forms 5 membered ring and 1,7-Diester forms 6 membered ring
18. Robinson annulation: Cyclisation 3
The Robinson Annulation is a useful reaction for the formation of six-
membered rings in polycyclic compounds, such as steroids. The method uses
a ketone and a methyl vinyl ketone to form an α,β-unsaturated ketone in a
cyclohexane ring by a Michael addition followed by an aldol condensation.
Example:
19. Diels Alder Reaction: Cyclisation 4
Diels-Alder reaction is very useful in forming six membered ring. The
reaction takes place between a conjugated diene and a double bond or
triple bond co-reactant called dienophile. This reaction forms two carbon-
carbon bonds simultaneously and the arrangement of electron takes place
very quickly in a single step.
20. Acyloin Condensation: Cyclisation 5
When CARBOXYLIC ACID ESTERS are refluxed with metallic
Sodium in aprotic solvents such as Ether, Benzene, Tolune or Xylene,
free from Oxygen then α-hydroxy ketones also known as ACYLOINS
are formed. Long chain dicarboxylic esters have been converted to
large ring compounds without the use of dilution technique. It is used
best for closing rings of ten members or more.
