Photodecarbonylation of Dibenzyl Ketones and Trapping of Radical Intermediates by Copper(II) Chloride in Frozen Aqueous Solutions

RŮŽIČKA, Radovan, Lenka BARÁKOVÁ and Petr KLÁN. Photodecarbonylation of Dibenzyl Ketones and Trapping of Radical Intermediates by Copper(II) Chloride in Frozen Aqueous Solutions. Journal of Physical Chemistry B. USA: The American Chemical Society, 2005, vol. 109, No 19, p. 9346-9353. ISSN 1089-5639.

Basic information

• Original name: Photodecarbonylation of Dibenzyl Ketones and Trapping of Radical Intermediates by Copper(II) Chloride in Frozen Aqueous Solutions
• Name in Czech: Photodecarbonylation of Dibenzyl Ketones and Trapping of Radical Intermediates by Copper(II) Chloride in Frozen Aqueous Solutions
• Authors: RŮŽIČKA, Radovan (203 Czech Republic), Lenka BARÁKOVÁ (203 Czech Republic) and Petr KLÁN (203 Czech Republic, guarantor).
• Edition: Journal of Physical Chemistry B, USA, The American Chemical Society, 2005, 1089-5639.

Other information

• Original language: English
• Type of outcome: Article in a journal
• Field of Study: 10403 Physical chemistry
• Country of publisher: United States of America
• Confidentiality degree: is not subject to a state or trade secret
• Impact factor: Impact factor: 2.898
• RIV identification code: RIV/00216224:14310/05:00012596
• Organization unit: Faculty of Science
• UT WoS: 000229134000024
• Keywords in English: photochemistry; ice; debenzyl ketone
• Tags: debenzyl ketone, ice, Photochemistry
• Tags: International impact

Abstract

This paper presents a quantitative and qualitative study of the Norrish type I reaction of dibenzyl ketone(DBK) and 4-methyldibenzyl ketone (MeDBK), producing the benzyl radicals and consequently recombination products, in frozen aqueous solutions over a broad temperature range (-80 to 20 oC). This work extends previous research on the cage effects in various constrained media to provide information about the dynamics and reactivity of the photochemically generated intermediates at the grain boundaries of ice matrix. As the temperature of aqueous solutions decreases, the solute concentrations become high at layers covering ice crystals, causing efficient molecular segregation. The cage effect experiments have shown that diffusion of the benzyl radicals within such reaction aggregates is still remarkably efficient at temperatures below -50 oC, independently of the initial ketone concentration in the range of 10(-6)to -10(-4) mol L(-1). In addition, the study of trapping the benzyl radicals formed in situ by CuCl2 was used as a qualitative probe of heterogeneous bimolecular reactions in the frozen aqueous matrix and on its surface. Molecules of both solutes were found to be segregated from the ice phase to the same location and underwent chemical reactions within diffusion and intermediates lifetimes limits. Understanding the fundamental physicochemical processes in ice is unquestionably important in related environmental or cosmochemical investigations.

Abstract (in Czech)

This paper presents a quantitative and qualitative study of the Norrish type I reaction of dibenzyl ketone(DBK) and 4-methyldibenzyl ketone (MeDBK), producing the benzyl radicals and consequently recombination products, in frozen aqueous solutions over a broad temperature range (-80 to 20 oC). This work extends previous research on the cage effects in various constrained media to provide information about the dynamics and reactivity of the photochemically generated intermediates at the grain boundaries of ice matrix. As the temperature of aqueous solutions decreases, the solute concentrations become high at layers covering ice crystals, causing efficient molecular segregation. The cage effect experiments have shown that diffusion of the benzyl radicals within such reaction aggregates is still remarkably efficient at temperatures below -50 oC, independently of the initial ketone concentration in the range of 10(-6)to -10(-4) mol L(-1). In addition, the study of trapping the benzyl radicals formed in situ by CuCl2 was used as a qualitative probe of heterogeneous bimolecular reactions in the frozen aqueous matrix and on its surface. Molecules of both solutes were found to be segregated from the ice phase to the same location and underwent chemical reactions within diffusion and intermediates lifetimes limits. Understanding the fundamental physicochemical processes in ice is unquestionably important in related environmental or cosmochemical investigations.

Links

• GA205/05/0819, research and development project: Name: Environmentální důsledky fotochemických transformací v ledu a sněhu

Investor: Czech Science Foundation, Enviromental consequences of photochemical processes in ice and snow

• MSM0021622412, plan (intention): Name: Interakce mezi chemickými látkami, prostředím a biologickými systémy a jejich důsledky na globální, regionální a lokální úrovni (INCHEMBIOL) (Acronym: INCHEMBIOL)

Investor: Ministry of Education, Youth and Sports of the CR, Interactions among the chemicals, environment and biological systems and their consequences on the global, regional and local scales (INCHEMBIOL)

• SB/660/01/03, research and development project: Name: Geologický výzkum Antarktidy

Investor: Ministry of the Environment of the CR, Geological Research of Antarctica