PHOTO-REDUCTION.pptx

Photoreduction in organic compounds

1. PHOTO-REDUCTION SAMEEN FATIMA ROLL NO: 908529

2. CONTENT PHOTOREDUCTION IN ORGANIC COMPOUNDS CARBONYL COMPOUNDS PHOTOREDUCTION IN KETONES NITRO COMPOUNDS PHOTOREDUCTION IN AROMATIC COMPOUNDS PHOTO-REDUCTION/PHOTOHALOGENATION POLYMERIZATION VIA PHOTOREDUCTION DEFINITION

3. DEFINITION The chemical reduction which is influenced by under control of photons / light energy is called photo reduction. 1 A reduction reaction  induced  by light. 2 Photo-reduction is defined as the addition of one or more electrons to photo-excited species or the photochemical hydrogenation of a substance. 3 4

4. Photoreduction in ketones: Ketones photoreduction can be take place by hydrogen atom donars for example secondary alcohol and tertiary amines. In these reactions the photoexcited specie reacts with a suitable hydrogen donor (like alcohol with α hydrogen, toluene, even cyclohexane). The radical formed may react with other hydrogen donor to form alcohol or other reaction partner. CARBONYL COMPOUNDS: Photo-reduction 5

5. When H 2 Se used in the photoreduction of carbonyl compound. 6

6. Nitro compounds: In the photo-reduction of nitro compounds the hydrogen donor is needed, if hydrogen donor is not present then the photo-fragmentation is done instead of photo reduction.

7. MECHANISM: 7

8. COMPOUNDS: The following example is the classical reaction that is done by photochemical process, the preparation of the formation of 1, 1, 2, 2-tetraphenyl-1,2-ethanediol (\(3\), benzopinacol ). PHOTOREDUCTION IN AROMATIC 8

9. MECHANISM: The reaction of benzophenone in the triplet excited state with isopropanol to produce diphenylketyl radical and dimethylketyl radical is an example of photoreduction . The dimethylketyl radical produced transfer a hydrogen atom to benzophenone in ground state to produce another dipheny ketyl radical. It is interesting to know that only one photon is needed to convert both reactants into product.

10.   9 Many hydrocarbons benzene, naphthalene, anthracene , biphenyls react with amine to give reduction product. The above example is the best photo-reduced product in aromatic compounds. Mostly these reactions are initiated by the transfer of electron lone pair orbital from nitrogen to the half-filled highest bonding molecular orbital of excited aromatic compound.

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12. PHOTOREDUCTION/PHOTODEHALOGENATION : The replacement of halogen atom with hydrogen atom in the presence of hydrogen donor is very interesting alternative to Raney nickel catalyzed reduction. As we see in the following example; Irradiation of 2-bromophenol in propan-2-ol leads to the 90% chemical yield (phenol) via radical mechanism scheme. 11

13. Polymerization via photo-reduction: The photoreduction is used in the polymerization in such a way that the initiator is produced by this reduction that is further react with the monomer to form the polymer. 12

14. REFERENCE Photoreduction Definition & Meaning - Merriam-Webster https://www.collinsdictionary.com/dictionary/english/photoreduction https://www.slideshare.net/RabiaAziz6/photo-redox-reactions Postgraduate chemistry series: Photochemistry of Organic Compounds: From Concepts to Practice by Petr Klan and Jakob Wirz , pg # 230 Postgraduate chemistry series: Photochemistry of Organic Compounds: From Concepts to Practice by Petr Klan and Jakob Wirz , pg # 296 https://www.slideshare.net/RabiaAziz6/photo-redox-reactions Postgraduate chemistry series: Photochemistry of Organic Compounds: From Concepts to Practice by Petr Klan and Jakob Wirz , pg # 362 https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Basic_Principles_of_Organic_Chemistry_(Roberts_and_Caserio)/28%3A_Photochemistry/28.03%3A_Organic_Photochemistry#:~:text=Photoreduction%20of%20Diaryl%20Ketones,- https://slideplayer.com/slide/13159506/ Photochemistry and pericyclic reaction, 3 rd addition by Jagdamba Singh and Jaya Singh pg # 263 Postgraduate chemistry series: Photochemistry of Organic Compounds: From Concepts to Practice by Petr Klan and Jakob Wirz , pg # 399 Postgraduate chemistry series: Photochemistry of Organic Compounds: From Concepts to Practice by Petr Klan and Jakob Wirz , pg # 434 and 435  

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