Michael E. Sigman

Photochemistry of anthracene in water

Abstract Photolysis of anthracene (350 nm) in aerated water yields endoperoxide and 9,10-anthraquinone as the major primary photoproducts. Photolysis of anthracene in oxygen-deficient aqueous solutions yields the three isomers of 10,10′-dihydroxy-9,9′,10,10′-tetrahydro-9,9′-bianthryl as the primary photoproduct. Involvement of a cation radical mechanism is suggested.

PHOTOLYSIS OF SUBSTITUTED NAPHTHALENES ON SiO2 AND Al2O3

Abstract— Photolysis of naphthalene on the surface of SiO2 under an atmosphere of air produces phthalic acid as the only major photoproduct, accounting for 49%o of the consumed naphthalene. Photolysis on Al2O3 also produces phthalic acid, in 31% yield. Photolysis of 1 ‐methylnaphthalene on SiO2 proceeds under similar conditions to produce 2‐acetylbenzoic acid (35%) as the major photoproduct with the production of a small amount of I‐naphthaldchyde (6%). 1‐Cyanonaphthalene does not photooxidize under similar conditions. The presence of oxygen is necessary for the photodecomposition of naphthalene and 1‐methylnaphthalene to proceed. Superoxide formed from the photolysis of naphthalene at the SiO2/air interface is readily observed by electron paramagnetic resonance spectroscopy. In the absence of naphthalene no superoxide is observed. A mechanism involving electron transfer from the S1 state of the naphthalene to O2 is proposed on the basis of these observations and related literature precedent.

Simultaneous measurement of photosynthetic oxygen evolution and carbon dioxide assimilation under anaerobiosis

Instrumentation has been developed for measuring absolute simultaneous assimilation of carbon dioxide and evolution of oxygen by photosynthetic systems in anaerobic atmospheres under flow conditions. Time‐dependent photosynthetic quotients (PSQ) have bccn obtained. A detailed description of the instrument, including how it was constructed, calibrated and uscd for photosynthesis measurements, is presented. An important factor in the measurements was a clear understanding of the response time of the instrument. As with any flow system, flow rate, forward void volume and relative position of the O2 and CO2 sensors in the gas train were crucial to performance. Response time was measured by step‐function calibrations mimicking PSQ of unity. Oxygen was generated using an in‐line electrolysis cell driven by a programmable constant current source. Carbon dioxide assimilation was mimicked with the use of a programmable electronic gas blending system. Simultaneous step functions of these two key photosynthetic parameters fully characterized the response time and sensitivity of the instrument. In this report, time‐dependent PSQ for spinach leaf disks and the microalga Scenedesmus D3 are reported. It is explicitly demonstrated that the transient approach to steady state is different for the two systems. Whereas the time‐dependent PSQ for spinach depended on illumination history and reached a steady‐state value less than 1, this was not the case for Scenedesmus.