Irradiation of the dinucleotide TpBU at all wavelengths from 240 to 295 m/u produces a debrominated photoproduct and two minor products. The main compound has an absorption maxi­ mum exactly at the same wavelength as the parent compound, but with approximately half the value of the extinction coefficient. It cannot be reverted by short wavelengths, such as 240 m/j,. Consistent with our observat...

reactions of 1 ,zdihydropyridines (la-c) and 1,4-dihydropyridines (2a-c) in the presence of benzyne (3) under thermal conditions, and in the case of (2c) under photochemical conditions, have been investigated. benzyne acts as an oxidizing agent to convert dihydropyridine (la) and (2a) to the corresponding pyridine (4) or adds as a dienophile to (lb-c).

Light availability is considered a key factor regulating the thermal sensitivity of reef building corals, where excessive excitation of photosystem II (PSII) further exacerbates pressure on photochemical pathways already compromised by heat stress. Coral symbionts acclimate to changes in light availability (photoacclimation) by continually fine-tuning the photochemical operating efficiency of P...

The effects of temperature, pressure, solvent, and substrate concentration upon several enantioand diastereodifferentiating photochemical reactions have been investigated and discussed in detail. These entropy-related external factors, which manipulate the weak electronic and steric interactions in the excited state, dynamically control the stereochemical outcome of asymmetric photochemical rea...

As an important precursor of hydroxyl radical, nitrous acid (HONO) plays a key role in the chemistry of the lower atmosphere. Recent atmospheric measurements and model calculations show strong enhancement for HONO formation during daytime, while they are inconsistent with the known sources in the atmosphere, suggesting that current models are lacking important sources for HONO. In this article,...

The principal objective of this work has been to assess the quantitative importance of homogenous and heterogeneous photochemistry as a sink of pollutants in the aquatic environment. Using a combination of chemical trapping techniques, steady-state and time-resolved spectroscopic methods and product analysis, we have examined the mechanisms and magnitude of the photochemical production of stron...

that the longer the wave-length (the lower the frequency) of the exciting radiation, the greater the amount of energy associated with the same photochemical change in the glass. The straight line relation of the data, indicated in figure 2, is suggestive and requires further investigation. This method of portraying the observations is not entirely free from shortcomings. However, if further res...

Halogens produced by ocean biological and photochemical processes reach the tropical tropopause layer (TTL), where cold temperatures and the prevailing low ozone abundances favor the diurnal photochemical enhancement of halogen atoms. Under these conditions atomic bromine and iodine are modeled to be the dominant inorganic halogen species in the sunlit TTL, surpassing the abundance of the commo...

CDOM is the most important sunlight-absorbing dissolved substance in the sea and a critical component of the global carbon cycle. Irradiated CDOM produces reactive species that interact in the ocean in a complex series of photochemical and electron transfer reactions that impact the color and oxidative capacity of surface waters, the growth of marine biota, and the production of volatile gases ...