(a) Describe the following:
(i) Acetylation (ii) Cannizzaro reaction
(iii) Cross aldol condensation (iv) Decarboxylation
(a) Describe the following:
(i) Acetylation (ii) Cannizzaro reaction
(iii) Cross aldol condensation (iv) Decarboxylation
(a) Acetylation:- Introducing an acyl group (R – C –) when alcohol reacts with carboxylic acid anhydride or acid chloride reacts forming ester is called acetylation.
(b) Cannizaro reaction: Aldehydes which do not have an -hydrogen atom, undergo self oxidation and reduction (disproportionation) on treatment with concentrated alkali.
HCHO+HCHO conc.NaOH−−−−−−−→ HCOOH+HCOONa
(c) Cross aldol condensation
CH3CHO+CH3CH2CHO 1 NaOH−−−−−→2Δ CH3−CH=CH−CHO+
CH3−CH2−CH=C−CHO
|
CH3
CH3−CH=C−CHO + CH3CH2−CH=CH−CHO
|
CH3
____________________________________________________
Cross aldol products
When 2 different aldehydes containing - hydrogen reacts with dilute NaOH 4 products are formed. 2 products are crossed and 2 are self products are formed.
(iv) De carboxylation
Carboxylic acids lose CO2 to form hydrocarbons when their sodium salts are heated with soda lime (NaoH + CaO)
RCOONa −→ΔNaOH+CaOR−H+Na2CO3
(a) Acetylation:- Introducing an acyl group (R – C –) when alcohol reacts with carboxylic acid anhydride or acid chloride reacts forming ester is called acetylation.
(b) Cannizaro reaction: Aldehydes which do not have an -hydrogen atom, undergo self oxidation and reduction (disproportionation) on treatment with concentrated alkali.
HCHO+HCHO conc.NaOH−−−−−−−→ HCOOH+HCOONa
(c) Cross aldol condensation
CH3CHO+CH3CH2CHO 1 NaOH−−−−−→2Δ CH3−CH=CH−CHO+
CH3−CH2−CH=C−CHO
|
CH3
CH3−CH=C−CHO + CH3CH2−CH=CH−CHO
|
CH3
____________________________________________________
Cross aldol products
When 2 different aldehydes containing - hydrogen reacts with dilute NaOH 4 products are formed. 2 products are crossed and 2 are self products are formed.
(iv) De carboxylation
Carboxylic acids lose CO2 to form hydrocarbons when their sodium salts are heated with soda lime (NaoH + CaO)
RCOONa −→ΔNaOH+CaOR−H+Na2CO3
