BARTON REACTION.pptx
- 1. BARTON REACTION BY SAMDANIEL S IV M.Sc (int) CHEMISTRY
- 2. What is Barton reaction ? The Barton reaction, also known as the Barton nitrite ester reaction, is a photochemical reaction that involves the photolysis of an alkyl nitrite to form a δ-nitroso alcohol which can dimerises (or) form an oxime . Alkyl nitrites having minimum two hydrogens at δ-position are involved in this reaction.
- 3. • Nobel laureate Sir Derek Barton discovered this reaction in 1960. • In 1969, Barton was awarded Nobel prize in chemistry for his work on understanding conformations of organic molecules, work which was key to realizing the utility of the Barton Reaction
- 4. Mechanism of Barton reaction The reaction involves a homolytic RO–NO cleavage, followed by δ-hydrogen abstraction, free radical recombination, and tautomerization to form an oxime. The reaction involving migration of the nitric oxide is known as Barton reaction
- 5. Barton reaction of Butyl nitrite Butyl nitrite is prepared from n-Butanol on reaction with nitrosyl chloride in presence of pyridine at 25° C
- 6. 1. The reaction starts from singlet state S1 (n-л* transition) with the homolytic cleavage of R-O—NO bond to produce nitric oxide radical and an activated butoxy radical.
- 7. 2. Butoxy radical abstracts a hydrogen from δ-carbon via six membered cyclic transition state and a hydroxy butyl radical is newly formed
- 8. 3. Hydroxy butyl radical combines with nitric oxide radical to give δ-Nitroso butyl alcohol.
- 9. 4. The nitoso alcohol can be tautomerised into its oxime in presence of a protic solvent (or) dimerized
- 10. Applications of Barton reaction Barton reaction is potentially useful in the synthesis of natural products such as hormones and alkaloids. synthesis of aldosterone acetate corticosterone acetate on reaction with nitrosyl chloride in dry pyridine yields its nitrite and desired oxime is obtained . The oxime is then acetylated and hydrolyzed to yield the natural product hemiacetal( aldosterone acetate)
- 12. REFERENCE https://en.wikipedia.org/wiki/Barton_reaction Photochemistry and pericyclic reactions by Jagdamba Singh and Jaya Singh,New Age International Publishers
- 13. Thank you