2971-22-4Relevant academic research and scientific papers
The laser-drop method: A new approach to induce multiple photon chemistry with pulsed lasers. Examples involving reactions of diphenylmethyl and cumyloxyl radicals
Banks,Scaiano
, p. 6409 - 6413 (1993)
A new method, described as the laser-drop technique, is presented which allows preparative experiments in laser-induced multiphoton chemistry. The technique shares most of the advantages of the successful laser-jet technique but allows the use of pulsed lasers that are readily available in many laboratories. The laser-drop method has been tested with two photochemical systems. The well-studied diphenylmethyl radical system allows a direct comparison of results from laser-drop, laser-jet, lamp, and two-color two-laser studies. The laser-jet and laser-drop techniques show comparable performance for two-photon processes, but the latter has advantages in reactions of higher order in light intensity. The photolysis of dicumyl peroxide has been used to demonstrate for the first time laser-induced β-cleavage of alkoxyl radicals. Photolysis of dicumyl peroxide in methanol leads to dramatically different product distributions under conditions of lamp and laser-drop photolysis.
Two-photon chemistry in the laser jet: Photoionization of the diphenylmethyl radical generated by norrish type I photocleavage of benzhydryl phenyl ketone
Adam, Waldemar,Oestrich, Rolf Schulte
, p. 6031 - 6034 (2007/10/02)
It is shown that in the laser jet (LJ) mode (argon ion laser) the benzhydryl phenyl ketone (1) undergoes a two-photon reaction in CC14 to yield benzhydryl chloride. The one-photon products are 1,1,2,2-tetraphenylethane (3), benzophenone, and 1,1,1-trichloro-2,2-diphenylethane (4). In methanol, on the other hand, our results suggest even a three-photon reaction in which benzhydryl methyl ether (5) is produced besides the one-photon products 3 and benzophenone. The ratios of the three-photon to one-photon products, i.e. 5 to 3, depended on the wavelength (333 or 351 nm). The three-photon mechanism was established by a competition experiment, in which ketone 1 was irradiated in mixtures of CCI4 and methanol. The ratio of the two high-intensity products ether 5 and benzhydryl chloride showed a strong intensity dependence. We propose that the electronically excited diphenylmethyl radical 2*is photochemically ionized to the diphenylmethyl cation 2+ under the high-intensity LJ photolysis conditions and the latter trapped with methanol and deuteriomethanol to give the identical benzhydryl methyl ether (5). The fact that no deuterium-incorporated ether 5 was observed eliminates the carbene mechanism proposed in the literature, at least under our LJ photolysis conditions.
Studies on the rearrangement of (trichloromethyl)carbinols to α-chloroacetic acids
Reeve, Wilkins,McKee, James R.,Brown, Robert,Lakshmanan, Sitarama,McKee, Gertrude A.
, p. 485 - 493 (2007/10/02)
Phenyl(trichloromethyl)carbinol undergoes an unimolecular, predominantly intramolecular conversion into potassium α-chlorophenylacetate on stirring with 10percent aqueous potassium hydroxide at 0 deg C for several days.Besides providing an interesting example of a 1-2 chlorine shift, the reaction is of potential importance for the synthesis of α-chloro acids.The study of a variety of (trichloromethyl)carbinols shows the reaction is general for secondary (trichloromethyl)carbinols as well as trichloroethanol.The mechanism of the reaction involves the preliminary formation of an epoxide.Several mechanisms are considered for the conversion of the epoxide to the α-chloroacetate anion, but none accounts for all of the experimental facts.Tertiary carbinols break down at the epoxide stage into a ketone and carbon monoxide.
