User:Scohen23/sandbox

Above is a rotating view of a BPA molecule that I have made to satisfy the CxC tech credit I petitioned for. It has been added to the introduction.

Uses
Bisphenol A is used primarily to make plastics, and products using bisphenol A-based plastics have been in commercial use since 1957. It is commonly found in reusable drink containers, food storage containers, canned foods, children's toys, and even receipts from stores. At least 3.6 million tonnes (8 billion pounds) of BPA are used by manufacturers yearly. However, it is estimated that the global annual output of BPA 6.8 million tonnes. It is a key monomer in production of epoxy resins and in the most common form of polycarbonate plastic. Bisphenol A and phosgene react to give polycarbonate under biphasic conditions; the hydrochloric acid is scavenged with aqueous base:

Environmental Risk:
In 2010, the U.S. Environmental Protection Agency reported that over one million pounds of BPA are released into the environment annually. BPA can be released into the environment by both pre-consumer and post-consumer leaching. Common routes of introduction from the pre-consumer perspective into the environment are directly from chemical plastics, coat and staining manufacturers, foundries who use BPA in casting sand, or transport of BPA and BPA-containing products. Post-consumer BPA waste comes from effluent discharge from municipal wastewater treatmennt plants, irrigation pipes used in agriculture, ocean-borne plastic trash, indirect leaching from plastic, paper, and metal waste in landfills, and paper or material recycling companies. Despite a rapid soil and water half-life of 4.5 days, and an air half-life of less than one day, BPA's ubiquity makes it an important pollutant. BPA has a low rate of evaporation from water and soil, which presents issues, despite it's biodegradability and low concern for bio-accumulation. BPA has low volatility in the atmosphere and a low vapor pressure between 5.00 and 5.32 Pascals. BPA has a high water solubility of about 120 mg/L and most of its reactions in the environment are aqueous. An interesting fact is that BPA dust is flammable if ignited, but it has a minimal explosive concentration in air. Also, in aqueous solutions, BPA has shown absorption of wavelengths greater than 250 nm.

The ubiquitous nature of BPA makes the compound an important pollutant to study as it has been shown to interfere with nitrogen fixation at the roots of leguminous plants associated with the bacterial symbiont Sinorhizobium meliloti. A 2013 study also observed changes in plant health due to BPA exposure. The study exposed soybean seedlings to various concentrations of BPA and saw changes in root growth, nitrate production, ammonium production, and changes in the activities of nitrate reductase and nitrite reductase. At low doses of BPA, the growth of roots were improved, the amount of nitrate in roots increased, the amount of ammonium in roots decreased, and the nitrate and nitrite reductase activities remained unchanged. However, at considerably higher concentrations of BPA, the opposite effects were seen for all but an increase in nitrate concentration and a decrease in nitrite and nitrate reductase activities. Nitrogen is both a plant nutritional substance, but also the basis of growth and development in plants. Changing concentrations of BPA can be harmful to the ecology of an ecosystem, as well as to humans if the plants are produced to be consumed.

The amount of absorbed BPA on sediment was also seen to decrease with increases in temperature, as demonstrated by a study in 2006 with various plants from the Xiangjiang River in Central-South China. In general, as temperature increases, the water solubility of a compound increases. Therefore, the amount of sorbate that enters the solid phase will lower at the equilibrium point. It was also observed that the adsorption process of BPA on sediment is exothermic, the molar formation enthalpy, ΔH°, was negative, the free energy ΔG°, was negative, and the molar entropy, ΔS°, was positive. This indicates that the adsorption of BPA is driven by enthalpy. The adsorption of BPA has also been observed to decrease with increasing pH.

A 2005 study conducted in the US had found that 91–98% of BPA may be removed from water during treatment at municipal water treatment plants. A more detailed explanation of aqueous reactions of BPA can be observed in the Degradation of BPA section below. Nevertheless, a 2009 meta-analysis of BPA in the surface water system showed BPA present in surface water and sediment in the US and Europe. According to Environment Canada in 2011, "BPA can currently be found in municipal wastewater. […]initial assessment shows that at low levels, bisphenol A can harm fish and organisms over time.

BPA affects growth, reproduction, and development in aquatic organisms. Among freshwater organisms, fish appear to be the most sensitive species. Evidence of endocrine-related effects in fish, aquatic invertebrates, amphibians, and reptiles has been reported at environmentally relevant exposure levels lower than those required for acute toxicity. There is a widespread variation in reported values for endocrine-related effects, but many fall in the range of 1μg/L to 1 mg/L.

A 2009 review of the biological impacts of plasticizers on wildlife published by the Royal Society with a focus on aquatic and terrestrial annelids, molluscs, crustaceans, insects, fish and amphibians concluded that BPA affects reproduction in all studied animal groups, impairs development in crustaceans and amphibians and induces genetic aberrations.

Photodegradation
Photodegradation is BPA's main method of natural weathering in the environment, via the Photo Fries rearrangement. Experimentally, BPA has been shown to photodegrade in reactions catalyzed by zinc oxide, titanium dioxide, and tin dioxide, as methods of water decontamination procedures. The Photo Fries degradation is a complex rearrangement of the aromatic carbonate backbone of BPA into phenyl salicylate and dihydroxybenzophenone derivatives before the energized ring releases carbon dioxide. In aqueous solution, BPA shows UV absorption of wavelengths between 250nm and 360nm, and the Photo Fries degradation occurs at wavelengths less than 300nm. The reaction begins by an alpha cleavage between the carbonyl carbon and the oxygen in the carbonate linkage, with the subsequent Photo Fries rearrangement of the products. Below is the mechanism of the photodegradation of BPA by the Photo Fries reaction:

Combustion of BPA
Hydroxyl radicals are powerful oxidants that transform BPA into different forms of phenolic group compounds. The advanced photocatalytic oxidation of BPA, using compounds like sodium hypochlorite, NaOCl, as the oxidizing agent, can accelerate the degradation efficiency by releasing oxygen into the water. This decomposition occurs when BPA is exposed to UV irradiation. This release of oxygen, another strong oxidant, also causes BPA disintegration in aqueous conditions to produce carbon dioxide and water. The dissolved carbon dioxide in the water results in an increase of carbonic acid, therefore causing an acidification of the water.

Oxidation of BPA by Ozone
During water treatment, BPA can be removed through ozonation. A 2008 study has identified the degradation products of this reaction, through the use of liquid chromatography and mass spectrometry. The reaction of BPA and ozone is seen below: Solutions of BPA and water decreased in pH after the ozonation process was completed. pH drops from 6.5 to 4.5 pH units were observed. This is likely because of the formation of carboxylic acids. These products were produced when the solution was 20±2°C. The products have high molecular weight. Also, ozone is electrophilic, so reactions were between ozone and aromatic rings by electrophilic substitution.

Kinetics of BPA Degradation
In 1991, the first explanation of the rate of BPA degradation through ozonation was determined.

$$-{d[BPA] \over dt} = k_apparent[BPA][O_3]$$

This relates the concentration of BPA to time by the apparent dissociation constant, concentration of BPA, and the concentration of ozone.