AcaWiki - User contributions [en]

The electrodeless discharge lamp: a prospective tool for photochemistry

2013-05-02T12:13:19Z

Anoop:

{{Summary
|title=The electrodeless discharge lamp: a prospective tool for photochemistry
|authors=Petr Klan, Jaromir Literak, Milan Hajek
|summary=This paper describes a simple photochemical reactor developed and tested for photochemical reactions. It consists of electrode-less discharge lamp (MWL) in a commercial microwave (MW) oven. This technique can be helpful in studying simultaneous effects of both UV/VIS and MW irradiations on photochemical reactions.

Use of MWL has been studied by:

1)Operating MW power and temperature influence on the lamp – lamp produced enough heat to boil liquids, even transparent liquids in MW field.

2)Solvent polarity influence –
Polar solvents started to boil too quickly making application of MWL difficult.

3)MWL heating capabilities -
Initiation of polar liquids needed more energy whereas, MWL initiated in non-polar solvents at every power.

4)Dependence of the photoreaction efficiency on MW power output –
increase in efficiency of reaction was with increase in power output.
|journal=Journal of photochemistry and photobiology A: Chemistry 128
|pub_date=1991
|doi=10.1016/S1010-6030(99)00165-3
|subject=Chemistry
}}

Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer

2013-05-02T12:08:30Z

Anoop:

{{Summary
|title=Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer
|authors=Zhan Lu, Tehshik Yoon
|url=http://dx.doi.org/10.1002/anie.201204835
|doi=10.1002/anie.201204835
|tags=Photochemistry
|journal=Angewandte Chemie International Edition
|journal_volume=51
|pub_date=2012

|summary=The paper is about the prospects for the conduction of organic reactions that are useful for synthesis with visible light. The effort till now have been made in the direction of the study of photoredox properties of ruthenium and iridium polypyridyl complexes. The paper tend to discuss the numerous uses of carrying out organic reactions in visible light than in ultra-violet light like the lower cost, decreased energy requirements of visible light sources, no need of specialized photo reactors, etc. The paper discusses specially the visible light photocatalysis of cycloaddition reactions . In the paper, the photo-reduction and photo-oxidation reactions of Ru(bpy)3 2+ and the related ruthenium(II) chromophores to design [2+2], [3+2], and [4+2] cycloaddition reactions involving radical anion and radical cation intermediates are investigated. Although the diversity of products using this strategy is quite broad, the electron-transfer nature of these processes limit the scope of these reactions to either electron-rich and electron-deficient reactions that are agreeable to one-electron redox processes. Such electrochemical constraints will be important considerations in the design of any photoredox process, the paper explores the possibility of initiating similar transformations by energy transfer rather than by an electron- transfer mechanism. The results obtained are significant for numerous reasons. Firstly, the catalysis of reactions by energy transfer process upon irradiation with household visible light sources using the class of transition metal photocatalysts, that have recently come into limelight due to their ability to promote organic transformations by photoinduced electron transfer. Although the energy transfer cycloaddition is similar to the photoredox transformations, the scope of the reaction goes beyond the electrochemical properties of the substrates, and is instead governed by the relative excited state energies of the catalyst and styrenes. The findings suggest that the great number of organic reactions that were carried out in Ultra-violet light before can now be very well carried out in visible light.
}}

Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer

2013-05-02T12:06:16Z

Anoop:

{{Summary
|title=Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer
|authors=Zhan Lu, Tehshik Yoon
|url=http://dx.doi.org/10.1002/anie.201204835
|doi=10.1002/anie.201204835
|tags=Photochemistry
|journal=Angewandte Chemie International Edition
|journal_volume=51
|journal_issue=41
|page=10329–10332
|pub_date=2012

|summary=The paper is about the prospects for the conduction of organic reactions that are useful for synthesis with visible light. The effort till now have been made in the direction of the study of photoredox properties of ruthenium and iridium polypyridyl complexes. The paper tend to discuss the numerous uses of carrying out organic reactions in visible light than in ultra-violet light like the lower cost, decreased energy requirements of visible light sources, no need of specialized photo reactors, etc. The paper discusses specially the visible light photocatalysis of cycloaddition reactions . In the paper, the photo-reduction and photo-oxidation reactions of Ru(bpy)3 2+ and the related ruthenium(II) chromophores to design [2+2], [3+2], and [4+2] cycloaddition reactions involving radical anion and radical cation intermediates are investigated. Although the diversity of products using this strategy is quite broad, the electron-transfer nature of these processes limit the scope of these reactions to either electron-rich and electron-deficient reactions that are agreeable to one-electron redox processes. Such electrochemical constraints will be important considerations in the design of any photoredox process, the paper explores the possibility of initiating similar transformations by energy transfer rather than by an electron- transfer mechanism. The results obtained are significant for numerous reasons. Firstly, the catalysis of reactions by energy transfer process upon irradiation with household visible light sources using the class of transition metal photocatalysts, that have recently come into limelight due to their ability to promote organic transformations by photoinduced electron transfer. Although the energy transfer cycloaddition is similar to the photoredox transformations, the scope of the reaction goes beyond the electrochemical properties of the substrates, and is instead governed by the relative excited state energies of the catalyst and styrenes. The findings suggest that the great number of organic reactions that were carried out in Ultra-violet light before can now be very well carried out in visible light.
}}

Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer

2013-05-02T11:59:17Z

Anoop:

{{Summary
|title=Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer
|authors=Zhan Lu, Tehshik Yoon
|url="http://onlinelibrary.wiley.com/doi/10.1002/anie.201204835/abstract"
|doi=10.1002/anie.201204835
|tags=Photochemistry
|journal=Angewandte Chemie International Edition
|Volume=51
|Issue=41
|pages=10329–10332
|pub_date=October 8, 2012

|summary=The paper is about the prospects for the conduction of organic reactions that are useful for synthesis with visible light. The effort till now have been made in the direction of the study of photoredox properties of ruthenium and iridium polypyridyl complexes. The paper tend to discuss the numerous uses of carrying out organic reactions in visible light than in ultra-violet light like the lower cost, decreased energy requirements of visible light sources, no need of specialized photo reactors, etc. The paper discusses specially the visible light photocatalysis of cycloaddition reactions . In the paper, the photo-reduction and photo-oxidation reactions of Ru(bpy)3 2+ and the related ruthenium(II) chromophores to design [2+2], [3+2], and [4+2] cycloaddition reactions involving radical anion and radical cation intermediates are investigated. Although the diversity of products using this strategy is quite broad, the electron-transfer nature of these processes limit the scope of these reactions to either electron-rich and electron-deficient reactions that are agreeable to one-electron redox processes. Such electrochemical constraints will be important considerations in the design of any photoredox process, the paper explores the possibility of initiating similar transformations by energy transfer rather than by an electron- transfer mechanism. The results obtained are significant for numerous reasons. Firstly, the catalysis of reactions by energy transfer process upon irradiation with household visible light sources using the class of transition metal photocatalysts, that have recently come into limelight due to their ability to promote organic transformations by photoinduced electron transfer. Although the energy transfer cycloaddition is similar to the photoredox transformations, the scope of the reaction goes beyond the electrochemical properties of the substrates, and is instead governed by the relative excited state energies of the catalyst and styrenes. The findings suggest that the great number of organic reactions that were carried out in Ultra-violet light before can now be very well carried out in visible light.
}}

Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer

2013-05-02T11:47:45Z

Anoop:

{{Summary
|title=Visible Light Photocatalysis of 2+2 Styrene Cycloadditions by Energy Transfer
|authors=Zhan Lu, Tehshik Yoon
|url=http://onlinelibrary.wiley.com/doi/10.1002/anie.201204835/abstract
|tags=Photochemistry
|summary=The paper is about the prospects for the conduction of organic reactions that are useful for synthesis with visible light. The effort till now have been made in the direction of the study of photoredox properties of ruthenium and iridium polypyridyl complexes. The paper tend to discuss the numerous uses of carrying out organic reactions in visible light than in ultra-violet light like the lower cost, decreased energy requirements of visible light sources, no need of specialized photo reactors, etc. The paper discusses specially the visible light photocatalysis of cycloaddition reactions . In the paper, the photo-reduction and photo-oxidation reactions of Ru(bpy)3 2+ and the related ruthenium(II) chromophores to design [2+2], [3+2], and [4+2] cycloaddition reactions involving radical anion and radical cation intermediates are investigated. Although the diversity of products using this strategy is quite broad, the electron-transfer nature of these processes limit the scope of these reactions to either electron-rich and electron-deficient reactions that are agreeable to one-electron redox processes. Such electrochemical constraints will be important considerations in the design of any photoredox process, the paper explores the possibility of initiating similar transformations by energy transfer rather than by an electron- transfer mechanism. The results obtained are significant for numerous reasons. Firstly, the catalysis of reactions by energy transfer process upon irradiation with household visible light sources using the class of transition metal photocatalysts, that have recently come into limelight due to their ability to promote organic transformations by photoinduced electron transfer. Although the energy transfer cycloaddition is similar to the photoredox transformations, the scope of the reaction goes beyond the electrochemical properties of the substrates, and is instead governed by the relative excited state energies of the catalyst and styrenes. The findings suggest that the great number of organic reactions that were carried out in Ultra-violet light before can now be very well carried out in visible light.

|journal=Angewandte Chemie International Edition
|pub_date=2012
|doi=Volume 51, Issue 41, Pg 10329
|subject=Chemistry
}}

PHOTOCHEMISTRY OF ISOPIPERITENONE AND 4-ACETOXYISOPIPERITENONE : An unprecedented photochemical reaction of an α &β unsaturated ketone*

2013-04-22T12:50:59Z

Anoop:

{{Summary
|title=PHOTOCHEMISTRY OF ISOPIPERITENONE AND 4-ACETOXYISOPIPERITENONE : An unprecedented photochemical reaction of an α &β unsaturated ketone*
|authors=Willum F. Erman and Thomas W. Gibson
|url=http://ac.els-cdn.com/S0040402001827964/1-s2.0-S0040402001827964-main.pdf?_tid=b628e114-a2bd-11e2-ac97-00000aab0f01&acdnat=1365694826_1ad1525dfa0d5f73295d551b59cadbbf
|summary=Objective: Photochemical analysis of isopiperitenone and 4-acetoxyisopiperitenone

When (+)-isopiperitenone and 4-acetoxyisopiperitenone are exposed to ultravoilet radiation using a Pyrex filter give (+)-1,2-dimethyltricyclo[3.3.0.0]octan-6-one in 35-42% yield and 5-acetoxy-1,2-dimethyltricyclo[3.3.0.0]octan-6-one in 42% yield. Mechanism involved in above two reaction is a noval cleavage of α,β unsaturated ketone.

Tricycloketone is produced by photochemical transformation of (+)-isopiperitenone. Intermediate involved in this reaction is a biradical species generated by the cleavage of α,β unsaturated ketone. The intermediate undergoes cyclization with alkene group present in above isopoperitenone . The asymmetric center is not affected in the above photochemical reaction and therefore final product will be optically active.
In photocycloaddition reaction, stereochemistry and thermodynamic factors are important parameters. Orbital orientation of (+)-isopoperitenone facilitate a particular stereo product.

On exposing 4-acetoxyisopiperitenone in ultraviolet radiation form a 5-acetoxy-1,2-dimethyltricyclo[3.3.0.0]octan-6-one and yield of this reaction is slightly higher than other one (isopiperitenone). That is because in this reaction biradical is stabilized by acetoxy group. Intermediate involve in this reaction is similar to the isopiperitenone photocyclization reaction.

The formation of product by cleavage of bond between α,β and β,ϒ unsaturated ketone is novel and this type of reaction (photocycloaddition) is very rare in case of β,ϒ unsaturated allylic ketones.

|journal=Tetrahedron,vol.25, page 2493 to 2515
|pub_date=1969/01/20
|subject=Chemistry
}}