Journal of Photochemistry and Photobiology A: Chemistry 172 (2005) 146–150 The electrodeless discharge lamp: a prospective tool for photochemistry Part 6. Photochemistry of valerophenone and 4-nitroanisole in high-temperature water Pavel M¨ uller a , Andr´ e Loupy b , Petr Kl´ an a,∗ a Department of Organic Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic b Laboratoire des R´ eactions S´ electives sur Supports, ICMMO, Universit´ e Paris-Sud, CNRS, UMR 8615, Bˆ atiment 410, 91405 Orsay Cedex, France Received 21 October 2004; received in revised form 3 December 2004; accepted 7 December 2004 Available online 12 January 2005 Abstract Two temperature-sensitive model photochemical reactions, the Norrish Type II reaction and photochemical nucleophilic aromatic substi- tution on 4-nitroanisole by the hydroxide ion, carried out in high-temperature water (100–200 ◦ C) in a pressurized vessel under microwave heating, are reported. The observed chemoselectivity and the ability to increase the solubility of hydrophobic organic compounds in this environmentally friendly solvent are promising results for prospective green (photo)chemical applications. © 2004 Elsevier B.V. All rights reserved. Keywords: Photochemistry; Microwave; Electrodeless discharge lamp; High-temperature water; Valerophenone 1. Introduction Recent experiments have shown that supercritical (above its critical point) but also high-temperature water (HTW) (over 100 ◦ C) has the ability to accelerate organic reactions and enhance their reaction selectivities [1–3]. Such a research is motivated by a great variety of applications: from geo- chemical production of petroleum to destruction of hazardous waste [4,5] or even environmentally benign organic synthe- sis [6,7]. The synthetic chemists have been striving to limit the use of dangerous organic solvents and to look for alterna- tives. The “solvent-free” experiments rarely evade the use of organic solvents at least during the subsequent isolation pro- cedures. The attempts to use water as a solvent for organic reactions did not appear to be predetermined to a success be- cause of the low water-solubility of most organic compounds. Nevertheless, a decrease in relative permittivity in line with increasing temperature enhances solubility even of relatively non-polar organic compounds. ∗ Corresponding author. Tel.: +420 549494856; fax: +420 549492688. E-mail addresses: aloupy@icmo.u-psud.fr (A. Loupy), klan@sci.muni.cz (P. Kl´ an). The application of microwave (MW) heating in chem- istry often means a significant reduction of reaction times, cleaner reactions, and higher chemical yields [8–10]. Re- cently, we have successfully utilized electrodeless discharge lamps (EDLs), which are able to generate ultraviolet UV radiation when placed into the microwave field, in the microwave-assisted photochemistry studies [11]. In the field of analytical chemistry, an efficient microwave-assisted pho- tolytical reactor for high-temperature water digestion proce- dures has been developed by Florian and Knapp [12]. This work is a part of our program, in which simultaneous effects of both UV and MW irradiation on chemical reactions, and new MW/UV techniques are investigated [13–17]. We wish to report on the study of two models photochemical transfor- mations carried out in high-temperature water using EDLs. 2. Experimental 2.1. Chemicals and solvents Valerophenone (VP) (>99%) and hexadecane (99%) were obtained from Aldrich Chemicals Co. and were used as 1010-6030/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jphotochem.2004.12.003