title: Organomanganese compounds in organic synthesis

authors: Prasad, Narendra Jai

subjects: cyclomanganated chalcones

abstract: This thesis describes the preparation and reactions of some cyclomanganated chalcones, dienones and aryl ketones. Investigation has previously been undertaken into the reaction of cyclomanganated chalcones and dienones with alkynes to give both pyranyl and cycloheptadienyl Mn(CO)₃ complexes. In the current study, the reaction was further investigated with a cyclomanganated dienone derived from a cyclic ketone which gave only the (pyranyl)Mn(CO)₃ complex (2-6) and not the cycloheptadienyl product as consistent with a mechanism previously proposed. Also extended in the current study was previous work involving the methylmanganese pentacarbonyl-mediated transformation of enynes to cyclopropanated bicyclic compounds and cyclopentanes bearing an exocyclic double bond. In the current study, benzylmanganese pentacarbonyl was used instead of methylmanganese pentacarbonyl under similar conditions. In the current study however, the type of product that formed in diethyl ether (3-4) was the one dominant in acetonitrile in the MeMn(CO)₅ study, and that formed in acetonitrile (3-5) was the dominant product type in diethyl ether (3-4). There was no apparent explanation for this reverse reactivity. Ferrocenyl pyrylium salts of the type 5-5 have been prepared using a new route to ferrocenyl pyrylium from cyclomanganated chalcones and ferrocenylethyne. UV-visible and electrochemical properties of the pyrylium salts have been investigated. The ferrocenyl pyrylium salt (5-5) was obtained by the oxidation of [2-ferrocenyl-4,6-diphenyl-ɳ₅]-pyranyltricarbonylmanganese (5-6). The crystal structure of 5-6 was also determined.

text: Organomanganese compounds in organic synthesis This thesis describes the preparation and reactions of some cyclomanganated chalcones, dienones and aryl ketones. Investigation has previously been undertaken into the reaction of cyclomanganated chalcones and dienones with alkynes to give both pyranyl and cycloheptadienyl Mn(CO)₃ complexes. In the current study, the reaction was further investigated with a cyclomanganated dienone derived from a cyclic ketone which gave only the (pyranyl)Mn(CO)₃ complex (2-6) and not the cycloheptadienyl product as consistent with a mechanism previously proposed. Also extended in the current study was previous work involving the methylmanganese pentacarbonyl-mediated transformation of enynes to cyclopropanated bicyclic compounds and cyclopentanes bearing an exocyclic double bond. In the current study, benzylmanganese pentacarbonyl was used instead of methylmanganese pentacarbonyl under similar conditions. In the current study however, the type of product that formed in diethyl ether (3-4) was the one dominant in acetonitrile in the MeMn(CO)₅ study, and that formed in acetonitrile (3-5) was the dominant product type in diethyl ether (3-4). There was no apparent explanation for this reverse reactivity. Ferrocenyl pyrylium salts of the type 5-5 have been prepared using a new route to ferrocenyl pyrylium from cyclomanganated chalcones and ferrocenylethyne. UV-visible and electrochemical properties of the pyrylium salts have been investigated. The ferrocenyl pyrylium salt (5-5) was obtained by the oxidation of [2-ferrocenyl-4,6-diphenyl-ɳ₅]-pyranyltricarbonylmanganese (5-6). The crystal structure of 5-6 was also determined.

year: 2009

title: Sediment aluminium content of Lake Okaro: 2021 monitoring survey

authors: Tempero, Grant Wayne

abstract: The application of aluminium salts such as polyaluminium chloride and aluminium sulphate has been widely used to assist in the remediation of eutrophic freshwater ecosystems. Aluminium binds to phosphorus, reducing its availability for phytoplankton growth, with the additional benefit that sediment phosphorus is reduced under anoxic lake conditions. Since 2013, alum (aluminium sulphate) has been applied twice per year to Lake Okaro to reduce dissolved reactive phosphorus availability. The lake’s annual Trophic Lake Index has decreased from 5.5 in the early 2000s to 4.5 in 2020. Alum dosing has resulted in the addition of 3.8 t of aluminium to the lake, however, the spatial distribution and sediment accumulation rate of alum derived aluminium has not been investigated.

The University of Waikato was contracted by the Bay of Plenty Regional Council to survey sediment aluminium concentrations in Lake Okaro to determine the distribution and accumulation of alum derived aluminium. In addition to sediment total aluminium content, the proportion of amorphous (non-crystalline) aluminium was assessed. Amorphous aluminium is the fraction of total aluminium able to adsorb dissolved phosphorus, sequestering it from uptake by phytoplankton. It was assumed that increased proportions of amorphous aluminium were primarily derived from alum dosing.

text: Sediment aluminium content of Lake Okaro: 2021 monitoring survey The application of aluminium salts such as polyaluminium chloride and aluminium sulphate has been widely used to assist in the remediation of eutrophic freshwater ecosystems. Aluminium binds to phosphorus, reducing its availability for phytoplankton growth, with the additional benefit that sediment phosphorus is reduced under anoxic lake conditions. Since 2013, alum (aluminium sulphate) has been applied twice per year to Lake Okaro to reduce dissolved reactive phosphorus availability. The lake’s annual Trophic Lake Index has decreased from 5.5 in the early 2000s to 4.5 in 2020. Alum dosing has resulted in the addition of 3.8 t of aluminium to the lake, however, the spatial distribution and sediment accumulation rate of alum derived aluminium has not been investigated.

The University of Waikato was contracted by the Bay of Plenty Regional Council to survey sediment aluminium concentrations in Lake Okaro to determine the distribution and accumulation of alum derived aluminium. In addition to sediment total aluminium content, the proportion of amorphous (non-crystalline) aluminium was assessed. Amorphous aluminium is the fraction of total aluminium able to adsorb dissolved phosphorus, sequestering it from uptake by phytoplankton. It was assumed that increased proportions of amorphous aluminium were primarily derived from alum dosing.

year: 2023

title: Estimated catchment loads of nitrogen and phosphorus to the Rotorua Te Arawa Lakes

authors: McBride, Chris G.

abstract: The Rotorua Te Arawa Lakes are central to the identity of their region, of immense historical and cultural importance, and provide ecosystem services that underpin biodiversity, conservation and socioeconomic aspirations of the community. The diversity of water quality in the lakes reflects their catchments, which are diverse in topography, hydrogeology and intensity of land use, ranging from the largely undeveloped land around lakes Tikitapu and Okataina, to highly developed forestry and pastoral land around lakes Rerewhakaaitu, Rotorua and Okaro. Lake water quality is strongly linked to nutrients received by each lake from surface flows and groundwater springs. It therefore follows that management of lake water quality requires a good understanding of nutrient loads derived from the landscape, as does the assessment or prediction of the in-lake effects of catchment-based management initiatives aimed at improving lake water quality.

text: Estimated catchment loads of nitrogen and phosphorus to the Rotorua Te Arawa Lakes The Rotorua Te Arawa Lakes are central to the identity of their region, of immense historical and cultural importance, and provide ecosystem services that underpin biodiversity, conservation and socioeconomic aspirations of the community. The diversity of water quality in the lakes reflects their catchments, which are diverse in topography, hydrogeology and intensity of land use, ranging from the largely undeveloped land around lakes Tikitapu and Okataina, to highly developed forestry and pastoral land around lakes Rerewhakaaitu, Rotorua and Okaro. Lake water quality is strongly linked to nutrients received by each lake from surface flows and groundwater springs. It therefore follows that management of lake water quality requires a good understanding of nutrient loads derived from the landscape, as does the assessment or prediction of the in-lake effects of catchment-based management initiatives aimed at improving lake water quality.

year: 2021